07 February 2016

The End of the Line for Curtiss Aircraft

XP-87 Blackhawk prototype
(USAF Museum)
In the summer of 1945 the US Army Air Force was in the process of outlining its combat aircraft needs in the post-war world. For fighter aircraft, there were three classes of aircraft that the USAAF wanted- an all-weather offensive fighter, a point-defense interceptor, and a long-range penetration fighter. It was expected that because of the state of the technology of the day that the all-weather offensive fighter would be the biggest of the three. On 28 August 1945 the USAAF issued its RfP (Request for Proposals) for the all-weather offensive fighter- a speed of 525 mph at 35,000 feet, 12 minutes to reach 35,000 feet and a 600-mile combat radius. It was thought at the time that piston engines would be necessary, but a refinement of the USAAF requirements a few months later laid out the service's desire for an aircraft that could seek out and destroy both enemy aircraft and ground targets in all weather conditions, day or night. Bell, Consolidated (Convair), Curtiss, Douglas, Goodyear, and Northrop submitted entries; Bell, Convair, and Goodyear were eliminated quickly due to performance deficiencies. Curtiss submitted a large four jet design based on the XA-43 attack jet design they had been working on for a different ground attack specification. Douglas submitted a land-based version of their F3D Skyknight, and Northrop submitted three designs- a refined version of the P-61 Black Widow, one based on the XP-79 flying wing fighter, and an all-new twinjet design. 

The political winds of change meant that the USAAF favored Curtiss heavily for the reasons that the previously dominant aircraft manufacturer had no contracts to sustain it in the postwar period and no civilian designs readily available for the growing passenger market. What was left of the funding for the XA-43 project was used to contract with Curtiss for prototypes of their design to be designated the XP-87. But the USAAF was sufficiently interested in Northrop's all-new twinjet design to contract for prototypes of that design as well to be designated XP-89. The USAAF also contracted with Martin Aircraft for a nose mounted turret that would allow the cannons to be swiveled to off-center targets that was to be fitted to both the XP-87 and XP-89. 

The XA-43. Note the differences from the XP-87 design.
(The Unwanted Blog at up-ship.com)
The designation XA-43 is often and mistakenly used interchangeably with the XP-87 designation- they were in fact two different aircraft that only resembled each other in basic layout. The XA-43 had a tandem cockpit, oval cross-section nacelles that were mounted inline with the wing, and was 65% larger than the XP-87 which had a side-by-side cockpit, rectangular nacelles under the wing. The XA-43's horizontal tail was low set and the design also featured a tail gun. The fact that the first XP-87 prototype was contracted with XA-43 funding led to the confusion that still is seen to this day. The XA-43 was ordered in November 1944 for a jet-powered ground attack bomber but it soon outgrew its proposed powerplants. By the time of the all-weather fighter RfP, the USAAF had lost interest in the XA-43 and allowed Curtiss to redirect its XA-43 efforts to the XP-87. But since policy of the time dictated two prototype aircraft in case of the loss of one, the original XA-43 contract was amended to allow for the construction of a second XP-87 prototype. In August 1946 Curtiss requested to name the XP-87 the Bat, but as there was already a US Navy glide bomb called the Bat, the request was turned down and a month later the XP-87 was given the name Blackhawk. 

By 1947 a review was underway to determine which of the fighters under development at the time might be suitable as a tactical reconnaissance aircraft- due to the size and carrying capacity of the XP-87, it was decided that it would also be developed into a reconnaissance version designated the RP-87. In order to not slow down the development, Curtiss was to complete both prototypes as all-weather fighters and then convert the second aircraft into the reconnaissance configuration at the completion of the prototype flight tests. In June 1947 Curtiss raised concerns with the USAAF on the power output of using four Westinghouse J34 engines in the paired nacelles and suggested changing to the Allison J33 as a single J33 engine had the power of two J34s not to mention the simplification of maintenance having only two engines instead of four. The change was approved for the production model but the prototypes would be completed with the four J34 engines. 

Only the XP-87 prototypes were to have four paired engines
(USAF Museum)
The first prototype was built at Curtiss' production facility in Columbus, Ohio, that once housed wartime production of the SB2C Helldiver. Taxi testing and ground tests took place at Columbus, but the USAAF wanted all flight testing to occur at Muroc AAF (later renamed Edwards AFB) in California. The first XP-87 was partially disassembled and loaded onto a trailer for transport to California- on going under the first highway overpass near the Columbus plant, the height was misjudged and the vertical fin hit the overpass, resulting in significant damage. With the damaged fin removed, he convoy headed out again and outside of Tulsa, Oklahoma got into an accident that damaged the nacelle for the left two engines. It was felt repairs could be made at Muroc and after month, the convoy reached the base where a new vertical fin and a team of  engineers were waiting to repair the prototype. The first flight was finally made on 1 March 1948 on a reasonably uneventful 58-minute maiden flight. The next several flights discovered buffeting in the tail due to it having a lower critical Mach number than the rest of the aircraft. Curtiss proposed a redesigned swept empennage for the production aircraft that was also duly approved by the USAAF. A total of 55 contractor test flights were made with the Blackhawk prototype and the flights confirmed the need to change to the Allison J33 on the production fighter- the Westinghouse J34s were unreliable and needed constant repair and replacement. By the time of the next series of flights with service test pilots, the USAAF was now the US Air Force and the first USAF flights were made on 3 June 1948. A week later the USAF placed a preliminary order for 57 P-87B Blackhawks (J33 engines and swept empennage were features of the production "B" version) and 30 RP-87B photo-recon aircraft. The following day the USAF switched from P-for-pursuit to F-for-fighter, the Blackhawk becoming the XF-87.

The now-designated XF-87 from the rear
(USAF Museum)
After 19 USAF test flights, a recommendation was made to Curtiss for a slightly larger wing to help reduce the stall speed and it was agreed that the second prototype XF-87 under construction would have the larger wing, the J33 engines, the swept empennage and reconnaissance modifications and would be designated XF-87C. In October 1948 the USAF held a fly-off evaluation with the XF-87 Blackhawk prototype, the Northrop XF-89 which got the name Scorpion, and a borrowed Navy F3D Skyknight to represent the Douglas submission as it was felt the Douglas design was close enough to the production Skyknight that it could act as a stand-in. With pilots of the Air Defense Command participating, while the XF-87 Blackhawk and F3D Skyknight had their strong points (side-by-side seating being one of the strongest suits of both designs in the opinion of the ADC pilots), the Northrop XF-89 Scorpion came out overall ahead in the evaluation and it was selected for production as having the best development potential. 

It was a crushing blow for Curtiss-Wright as the XF-87 was its only postwar jet design to take to the air. The Navy had canceled the XF15C mixed-propulsion fighter a few years earlier after only three examples were built. The company, in effect, was betting its future as an aircraft manufacturer on the XF-87 Blackhawk. The first prototype was ferried to Wright-Patterson AFB in Ohio in December 1948 and was eventually scrapped by 1950. The second unfinished prototype was never completed and what was done got parted out for other projects that the company was attempting. With no other designs in advanced development, Curtiss-Wright was forced to shut down its Airplane Division and its assets were sold to North American Aircraft and the Columbus plant would be used for the manufacture of the F-86 Sabre. Curtiss-Wright's propeller division remained active into the 1960s and was responsible for the X-19 radial lift test aircraft. Some feel the X-19 was Curtiss' last aircraft design, but in reality it was the XF-87 Blackhawk that represented the end of the line for Curtiss-Wright Aircraft, a company that just ten years earlier was one of the dominant aircraft manufacturers of the United States. 

Source: Experimental & Prototype U.S.Air Force Jet Fighters by Dennis R. Jenkins and Tony R. Landis. Specialty Press, 2008, p95-101. 



02 February 2016

Amidst Internal Turmoil, TWA Orders the Boeing 727

Trans World Airlines' first Boeing 727-100 and 727-200
(The Chicken Works: The Aviation Art of JP Santiago)
TWA launched its first jet services on 25 January 1959 between New York Idlewild-San Francisco with the Boeing 707 in competition with American Airlines' launch of 707 services between New York Idlewild and Los Angeles. Howard Hughes pushed TWA's finances to the limit to get into jets and while the arrival of the Jet Age to TWA marked the beginning of its zenith, it also laid the groundwork for Howard Hughes' eventual exit from TWA despite the near-limitless capital that he could access from his own parent company, Hughes Toolco. In February 1956 he ordered eight Boeing 707-120s, then followed in June 1956 with an order for 30 Convair 880s, and then 25 more Boeing 707s in May 1957. The value of these three orders was $300 million for the 63 jets, quite a large sum for those days. TWA raised additional funds with a one-to-one stock offering underwritten by Hughes Toolco that also gave Hughes 77% control of the airline. But the money raised from the stock offer wasn't enough and it looked like TWA couldn't meet its payroll obligations for the first quarter of 1958- Hughes borrowed $12 million from the banks, but at this point, one of TWA's original 1945 backers, Equitable Life, wanted a long term financing plan for the 63-jet order as it was getting nervous about Hughes' borrowing to meet basic costs like payroll. 

To ease the creditors, Hughes had Toolco accept the obligations for the jet order who in turn would lease the aircraft to TWA. Aircraft orders were swapped with Pan American (something that pained Hughes to have to approach his rival Juan Trippe to help TWA out) and the Convair order was cut to 20 aircraft. It still wasn't enough and some of Hughes' banks cut off his credit in March 1960. With the other creditors, a short term financing plan was arranged to allow TWA to keep operating provided Toolco assumed all financial liabilities for the airline as long as there was a change in management at TWA. To further put the brakes on Hughes, his shares in TWA were put into a voting trust which essentially (and controversially for the day) locked out Hughes from the airline. While a financing plan agreeable to all the parties was eventually settled upon at the end of 1960, Hughes still found himself shut out of TWA and for six years lawsuit and countersuit after another were filed as he tried to regain control of TWA. He would finally give up in 1966 when in May of that year Hughes Toolco sold off its entire share of TWA stock and he was out of the airline business for the time being - four years later he bought Air West, but that's a topic for a future article!

Despite the legal battle over leadership and control over TWA, the airline still held gravitas in the airline market and with the traveling public, managing to overtake Pan Am in 1969 in numbers of passengers flown across the Atlantic. Despite Hughes' virtual ouster in 1960, TWA's managers realized they had something that rival Pan Am didn't- a domestic route network and it was high time on the heels of the launch of 707 services to bring short haul jet service to TWA's network. In 1961 TWA had ordered 10 Sud-Aviation Caravelles that would have been powered by GE aft fan CJ805 engines, but that order was canceled in May 1962 when Boeing's 727-100 offered greater promise; in fact, TWA had already ordered the Boeing 727-100 (10 aircraft) in March 1962 while it still had the Caravelle order in place. The airline's first two Boeing 727-100s were delivered on the same day, N850TW and N851TW which were delivered on 29 April 1964 with the first 727-100 services started on 1 June 1964 with two daily round trips between New York JFK and Indianapolis with services expanding to Boston, St. Louis, and Kansas City on 5 June. On 1 July 1964, TWA returned to New York La Guardia with four 727 flights per day. By the end of 1964, the 100th jet aircraft in TWA's fleet was in fact a Boeing 727-100 which the airline dubbed the "Jetennial" plane. By the end of 1964, TWA already had sixteen 727-100s in service. 

TWA's 100th Jet was a Boeing 727-100
(TWA Skyliners Collection)
N850TW along with N851TW were TWA's first 727 jets
(The Chicken Works: The Aviation Art of JP Santiago)
The delivery of the Boeing 727-100s allowed TWA to finally retire its last passenger Lockheed Constellations on 6 April 1967 and become the first all-pure jet major airline in the United States. The last cargo Constellations were retired in the following month (12 May) with the introduction of six examples of "quick change" 727-100QC variant in the airline's fleet. The -100QCs were ordered in 1965. 
N12301 was TWA's first Boeing 727-200
(The Chicken Works: The Aviation Art of JP Santiago)
With the 727-100 and the new Douglas DC-9 now flying short/medium jet services, in March 1968 TWA added the larger Boeing 727-200 to its fleet, the first -200 being N12301, delivered on 6 March 1968. Over its history, TWA's 727s were a vital backbone of its fleet with a total of 36 727-100s and 78 727-200s operated total- in fact, the 727 served longer with TWA than any other aircraft type used on a continuous basis by the airline. The Lockheed Constellation family, from the short body L-749 to the L-1649 Starliner, served for about 20 years. The Boeing 707s nearly served 25 years. The 727 at TWA outlasted the Lockheed L-1011 Tristar by nine years and the Boeing 747 by about seven years. The last 727 service at TWA took place on 30 September 2000, a remarkable 36-year history with the venerable trijet with the airline. 

Related reading: 


The TWA Starstream 727 print can be seen in more detail here. Contact me at thechickenworks@gmail.com for details. 

Sources: TWA Skyliner Collection, The State Historical Society of Missouri. TWA: An Airline and Its Aircraft 75 Years of Pioneering Progress by R.E.G. Davies. Palawdr Press, 2000, p75-81. 


28 January 2016

The Short Brothers' Empire Flying Boats

When the three Short brothers Eustace, Oswald, and Horace established the Short Brothers company to design and build aircraft in 1908, there was a difference of opinion in the early days of the company's history about getting into the flying boat business. Oswald and Eustace were keen to get into flying boats which were becoming popular during the First World War, but Horace, the eldest of the three, thought flying boats were "nonsense". When Horace passed away in 1917, the other two Short brothers wasted no time in securing a contract from the Admiralty to license build flying boats to gain experience before flying their own design, the Short N.3 Comarty in 1921. Over the next 15 years, Short Brothers designed and built progressively larger flying boats for both the Royal Navy and Imperial Airways for its far-flung routes throughout the British Empire. By 1932, Eustace had passed away, leaving Oswald Short in charge of the whole enterprise. Imperial Airways flying boat requirements called for progressively larger and more capable designs as the passenger demand as well as mail and freight shipments on the Empire routes continued to grow. In a bid to regain world leadership in aviation, the Empire Air Mail Scheme was established in 1934 that essentially shifted all first-class mail to air mail aboard Imperial Airways' flying boats. As a result of the EAMS, Imperial Airways needed more capable flying boats particularly on its trunk routes to South Africa, the Middle East, and Australia. 

In 1935, Imperial Airways approached Oswald Short for a vastly more capable flying boat than the previous large biplane designs Short had produced for the airline. The specification called for the transport of 24 passengers in comfort with 1 1/2 tons of mail and freight over a distance of 800 miles. but as far as 2,000 miles with a smaller payload. Short placed his chief designer, Arthur Gouge on the project. After seeing the entrants to the 1934 MacRobertson Air Race the prior year, particularly KLM's Douglas DC-2, Gouge had been considering a monoplane layout for his next flying boat design and the Imperial Airways requirement was the perfect opportunity. Designated the S.23, the preliminary design was shown to Imperial Airways who decided to skip the construction of two prototypes that had been originally planned and proceed with a production order of fourteen S.23 flying boats. Shortly afterwards, Imperial Airways upped their order to an unprecedented 28 aircraft- prior Short production runs for the airline had been in small numbers as low as three aircraft. 

Oswald Short was rightly apprehensive about the new terms despite the company's long pedigree of solid designs. He insisted on at least a single prototype, but Imperial Airways, seeing the growing competition from the Americans across the Atlantic,  felt time was of the essence and duly reminded Oswald Short this was the biggest contract yet for Short Brothers. He ultimately relented and put Arthur Gouge in charge to bring the S.23 or "C-Class" flying boats to production. The leap in performance and technology the new aircraft promised resulted in their more common name "Empire Boats" in reference to their importance the Empire Air Mail Scheme. 
Canopus G-ADHL, the first Short Empire flying boat
(Profile Publications)
Using as his staring point the specified cubic capacity per passenger laid down by Imperial Airways to insure comfortable accommodations and space for mail and freight, Gouge adopted a two deck layout that faired the wing neatly into the fuselage for drag reduction. In addition, the fuselage for the first time on a production Short design didn't flare out at the planing bottom of the hull like older designs. Instead, the fuselage sides were near vertical to the waterline which gave the Empire Boat a large internal volume. The new planing bottom developed for the hull cut down on water drag and gave the large aircraft a relatively short water run at takeoff. To further improve the takeoff and landing performance of what was one of the largest production aircraft of the day, Gouge invented a new type of flap called the Gouge flap. Similar to a Fowler flap that translates aft before pivoting down, the Gouge flap used a curved track to curve downward while translating aft that was mechanically simpler than a Fowler flap. A Short Scion Senior aircraft was converted to a near half-scale prototype for the Empire Boat to prove the water characteristics of the new hull design. 

No aircraft the size of the Empire Boat had ever been built by the British aircraft industry at the time. The wing spar had to be machined in sections that were then joined. Short engineers had to design many of their own tools and jigs to build the aircraft. The slab sided fuselage not only provided more internal volume, it also proved easier to produce than earlier Short designs that used more complex hull shapes. The fuselage interior was 17-feet deep and allowed for two decks- behind the cockpit (called the "bridge" by Short) was a long upper deck compartment that could carry as much as 3,000 lbs of mail and freight. Below the cockpit on the lower deck was the marine compartment that carried all the necessary water and mooring equipment. Behind the marine compartment was the forward passenger compartment followed by a long hallway to the middle passenger compartment. On one side of the lower deck hallway were the toilets and on the other side was the galley. Behind the middle passenger compartment was a spacious promenade cabin followed by the aft passenger compartment. Behind the aft compartment was another cargo space that extended nearly to the tail. 

1936 ... Short 'Empire' flying boat
Interior configuration of the Short Empire flying boat
(Flickr)


The first Empire Boat to fly was Canopus G-ADHL on 4 July 1936. The flight test program revealed few issues with test pilots from Short and Imperial Airways pleased with the design. Canopus was delivered to Imperial Airways later that summer with the first commercial taking place 22-25 October (longer due to bad weather) on the London-Marseilles route. The second Empire Boat was Caledonia G-ADHM, first flying on 15 September 1936 and delivered to Imperial Airways on 4 December 1936. She had increased fuel tankage that allowed her to become the first Empire Boat to cross the Atlantic on 5 July 1937, beating the time of a Pan American Sikorsky Clipper by 34 minutes. From September 1936 onward, Short completed the Empire Boats at the rate of one a month. Such was the need to put them into service that subsequent aircraft were delivered to Imperial Airways after each airframe's maiden flight! The last Empire Boat of the original 28-aircraft order was Coorong G-AEVI, delivered on 26 February 1938. With the two Empire Boats that preceded it on the production line, Coogee G-AEUG and Corio G-AEUH, those last three aircraft were delivered to QANTAS for operation on the Australian portion of the Empire Air Mail Scheme. 
The predecessor to Air New Zealand, Tasman Airways had three Empire boats
(Air New Zealand)
Imperial Airways was so pleased with the Empire Boats that in 1937 another eleven aircraft were ordered from Short. The 39 aircraft total was the largest single order for British commercial aircraft at the time. The first three of the second order were built to the same production standard as the original 28-aircraft order- those three aircraft, Carpenteria, Coolangatta, and Cooee, were delivered to QANTAS to bring their fleet of Empire Boats up to six. The rest of the second production block were built to S.30 standard which involved a change to the Bristol Perseus engine (890 hp) versus the Bristol Pegasus (920 hp) used on the S.23 version. Though lower in horsepower and an increased weight from structural beef up in the hull, the S.30 versions had near-identical performance thanks to drag reduction. Champion G-AFCT was the first S.30 boat laid down, but it was Cabot G-AFCU that flew first as it was needed by Shorts for flight testing. The last three Empire Boats from this second order were delivered to Tasman Airways for use on the Sydney-Auckland portion of the Empire Air Mail Scheme. 

A single S.30 Empire Boat was ordered in 1939, Cathay G-AFKZ was delivered to Imperial Airways in March 1940 just before the airline was renamed British Overseas Airways Corporation or BOAC. Three more Empire Boats were ordered after Cathay was ordered, but those three aircraft reverted back to the original Bristol Pegasus engine and were designated S.33. Only two of those aircraft were completed and delivered in April and May 1940, Clifton G-AFPZ and Cleopatra G-AFRA. The third planned S.33 aircraft was never built. 

S.26/G-Class Empire Boat Golden Hind
(Profile Publications)
As the S.30/S.33 production began to wind down as most of the British aircraft industry turned its attention to wartime production and Short devoted more resources to the Sunderland program, a final development of the Empire Boats was ordered. The G-Class or S.26, was a scaled up variant of the original S.23/S.30/S.33 design that incorporated some of the Sunderland's design features. First to fly was Golden Hind G-AFCI on 14 July 1939 followed by Golden Fleece G-AFCJ on 8 July 1940 and finally the last Empire Boat built, Golden Horn G-AFCK on 21 January 1940. The larger size of these  three G-Class aircraft would have allowed nonstop trans-Atlantic services to Canada and the United States, but wartime demands had all three of these aircraft put into RAF service as VIP transports armed with defensive turrets. Only Golden Hind survived the Second World War. Used by the Ministry of Aviation postwar, she was returned to BOAC in 1948 but the airline wasn't in too much of a hurry to put her back in service as she was damaged during a 1954 storm and scrapped soon afterwards. 

No discussion of the Short Empire Boats would be complete without taking a look at the Short-Mayo Mercury/Maia composite piggyback aircraft, but that will be the subject of a future article!

There's a common misconception that the Short Sunderland was a military derivative of the Empire Boat. The aircraft were developed in parallel to two different but broadly similar specifications that allowed Short to share some design elements between the two designs. The Short Sunderland was the result of Air Ministry Specification R.2/33 issued on 23 September 1933 for a large four-engined flying boat for the Royal Air Force to use in the maritime patrol and anti-submarine role. Imperial Airways had started its discussions with Short but had not formalized anything until the 1934 passage the Empire Air Mail Scheme. This accounts for why work on the first Empire Boat went so smoothly and quickly from the 1935 to the first flight of Canopus the following year- Short had done plenty of *similar* engineering work on the Sunderland program already. While there was no Empire Boat prototype, much of the work already done on the Sunderland undoubtedly helped. The first Sunderland prototype flew 16 October 1937, about 15 months after the first flight of the Empire Boat Canopus

Sources: Sunderland: The RAF's Legendary Protector of the Sea Lanes, Aeroplane Icons, February 2012. "Sunderland Story" by Martyn Chorlton, pp 6-17. "The Short Empire Boats" by Geoffrey Norris. Profile Publications, No. 84, 1966. 

23 January 2016

What Your Kitchen Refrigerator and Ballistic Missiles Have in Common: Freon


Minuteman II test launch
(National Park Service/Minuteman Missile NHS)
While liquid-fueled rocket engines have been the mainstay for the satellite launch industry, the long road of technological development in solid-fuel rockets have also benefited the aerospace industry. Often times unique solutions were needed in the development of solid-fuel rockets. One of the more unusual ones was the use of liquid freon to direct the exhaust flame from solid-fueled rockets. That's right. Liquid. Freon. How? I'll get to that.

In the 1950s the conventional wisdom in ICBM development was that only liquid-fueled engines had the power to lift the heavy nuclear warheads of the day. The two main ICBMs in development, the Atlas and the Titan, used liquid-fueled engines. But the US Navy, seeking to put ICBMs on nuclear submarines as a sea-based strategic deterrent, considered liquid-fuels on a submarine wholly impractical and not just for safety reasons. As a result, the engineers who were developing the Polaris SLBM focused their efforts on solid-fuel rocket motors for the missile. They were storable and could be quickly fired. In addition, with enough right mix of solid propellants, the missile could be much smaller than a comparable liquid-fueled missile.

The advantages of a storable propellant and rapidity of launch made solid-fuel an attractive option for a land-based ICBM as well. In the US Air Force, General Bernard Schriever was in charge of the Air Force's ICBM development effort as the head of the Western Development Division. While he initially believed that liquid-fueled engines were the only way to power an operational ICBM, he was ably convinced by several of his engineers to look at solid-fuels as an alternative. That tangent then took on an important priority equal to that of the Atlas and Titan programs, becoming the Minuteman ICBM which was developed in the same time frame as the Navy's Polaris missile. The two weapons shared many similar characteristics due to their solid-fuel rocket engines. The first variant of the Minuteman, the LGM-30A Minuteman I, became operational at Malmstrom AFB in Montana in 1962. 

First SLBM launch, 23 July 1960.
Polaris A1 from the USS George Washington
(US Navy)
The first solid rockets used tabs that jutted into the exhaust stream to deflect the plume for directional control. It was the simplest system but to provide effective control and deflection, the tabs had to be of a size that inevitably cut into the exhaust stream's total velocity. The next solution was what the Polaris team called "jetevators". The exhaust cone of the solid rocket had an extension at the bottom of the cone that was in effect, a gimbaled extension of the skirt (rather than moving the whole nozzle assembly) and small actuators moved the whole extension. Jetevators were used on the first versions of the Polaris SLBM, the A1 and A2 variants. The main disadvantage of jetevators was they added technical complexity to the solid rocket motor as well as weight. Small jetevators could only provide slight corrections but to provide more significant directional control, larger and heavier jetevators would be needed.

Both the early versions of Polaris and Minuteman used jetevators on each of the three stages of the missiles, with the first and second stages of both missiles having four nozzles that could be differentially vectored to provide control. By 1962, however, the next versions of the missiles were already in development- for Polaris it was the A3 version (third version) and for the Minuteman it was the Minuteman II (second version, obviously). In both missiles a range increase was desired and one way to get it was to lighten the missile itself. For both new versions, the second stage switched from four nozzles with jetevators to a single nozzle that used what was called "liquid injection thrust vectoring control". For both the LGM-30B Minuteman II and the UGM-27C Polaris A3, a bigger second stage with the new liquid injection thrust control got the range increases needed. 

1964 patent diagram for liquid
injection thrust vectoring control.
(Google Patents)
Around the perimeter of the nozzle about 1/2 the way up were a series of four ports that angled slightly upward. Liquid freon was injected into one of the ports and as it did, it created a shockwave in the nozzle that pushed the exhaust stream in a direction up to 7 to 10 degress opposite from the port the freon entered. The freon didn't react with the hot plume, it merely created a thermal shockwave that pushed the plume one direction. By injecting freon into the various ports, directional control could be achieved for a lot less weight than traditional actuator-driven control mechanisms. 

On the Minuteman II, the second stage carried 262 pounds of freon in a rubber bladder to use for thrust vectoring. The Minuteman II and Polaris A3 weren't the first missiles to use this novel method of control. That honor goes to the Lance short-range battlefield missile that was used by the US Army until the 1960s. The knowledge gained from the Minuteman II and Polaris A3 in liquid injection thrust vectoring control would be used to its fullest on the large solid rocket boosters used on the Titan III and Titan IV launchers, long the mainstay of US expendable heavy-lift vehicles. Both boosters on the Titan launchers used liquid injection thrust vectoring control. If you look at a picture of a Titan III/IV at launch, you'll notice a small external tank attached to the core rocket's base, one for each booster. That's the reservoir for the liquids used for the thrust vectoring system of the solid rocket boosters.
From left to right: Polaris A1, Polaris A2, Polaris A3, Poseidon C3, Poseidon C4, Trident D5
(Federation of American Scientists)
The Polaris was superseded in the Navy's strategic deterrent by the Poseidon, which was followed by  the current missile, the Trident. The Minuteman II was retired from service and the land-based ICBM deterrent for the United States relies on the Minuteman III.

Further reading: 

Martin, the Titan I and the Titan II Ballistic Missiles
One of the Most Important Missions of the Douglas C-133 Cargomaster: Transporting ICBMs


Source: To Reach the High Frontier- A History of US Launch Vehicles, edited by Roger D. Launius and Dennis Jenkins. The University Press of Kentucky, 2002, p262-266.

18 January 2016

The Bomber Career of the Douglas A-3 Skywarrior, 1955-1968

Douglas ad for the A-3 Skywarrior
The origins of the Douglas A-3 Skywarrior lay in a 1948 Navy requirement for a jet-powered, carrier-based, nuclear attack bomber. Even though at the time, the Navy's first purpose-built carrier bomber capable of nuclear attack, the North American AJ Savage, was in the midst of flight testing, the Navy had set its eyes on a more capable successor aircraft that could carry a 10,000 lb nuclear bomb over a combat radius of 2,000 miles. The planned operating weights of the new jet bomber would limit its use to the new 61,000-ton super carrier USS United States as it was too large to operate off the Essex-class carriers and even the much larger Midway class carriers. The program was seen as the most challenging of the Navy's postwar aircraft programs and the VAX(H) Program only received two formal submissions- one from Douglas and the other from Curtiss-Wright. Headed by the legendary designer Ed Heinemann who was already widely regarded for his work on the SBD Dauntless and the AD Skyraider, the Douglas team emphasized that a smaller aircraft was possible that could meet the stringent requirements of the VAX(H) specification. Heinemann championed a smaller aircraft that could also operate safely from the 45,000-ton Midway class carriers as well as even the smaller 29,000-ton Essex class carriers and still accommodate a notional 10,000 lb nuclear weapon. 

The preliminary Douglas designs were for a twin jet aircraft that was less than half the planned operating weight limit set by the Navy's Bureau of Aeronautics. BuAer felt that the nuclear attack mission required an aircraft of 200,000 lbs weight but Ed Heinemann felt that he could meet the mission requirements with an aircraft only 70,000 lbs at maximum operating weight. Naturally his design was met with considerable skepticism within the Navy but Heinemann's planning for a more flexible design not limited to super carriers was validated with the 1949 cancellation of the USS United States. Given that the Douglas submission could also operate off smaller carriers made it the winner of the VAX(H) competition. 

VAH-4 Skywarrior pilot. Note the set back B/N console.
(Wikipedia)
The prototype A3D Skywarrior took the air for the first time on 16 September 1953. Initially low-powered with the troublesome Westinghouse J40 turbojet, the Navy wisely switched the more powerful and widely used Pratt & Whitney J57 engine. A three year flight test program ensued and proved the Skywarrior able to safely operate not just off the super carrier decks of the United States' replacement, the Forrestal class, but also the Midway and Essex classes as well that had been duly upgraded with angled decks and steam catapults. The crew of three consisted of the pilot on the left side, the bombardier/navigator (B/N) on the right side and slightly more aft than the pilot, and the plane captain/navigator who sat behind them facing aft who controlled the twin 20mm cannon in the tail. The cannons proved to be a maintenance nightmare and were all removed from the Skywarrior flight between 1960 and 1961 and replaced with a dovetail or "duck butt" fairing that contained electronic warfare gear. 

The first production Skywarriors weighed in at 43,000 lbs empty, the maximum weight for a catapult launch was 73,000 lbs, and the maximum landing weight was 50,000 lbs. In 1959 an A3D-2 was catapulted from the USS Saratoga with a weight of 84,000 lbs, setting a record that still stands for the heaviest aircraft to be catapulted from an aircraft carrier. 

The first Skywarrior squadron was Heavy Attack Squadron ONE (VAH-1) established on 1 November 1955 a NAS Jacksonville, followed by VAH-3 on 1 June 1956. "Heavy One" went to sea first aboard the USS Forrestal in October 1956, followed by a Mediterranean deployment in January 1957. "Heavy Three" went to sea next, embarked aboard the USS Franklin D. Roosevelt for a Mediterranean cruise in July 1957. Getting used to operating the A3D took a lot of work given it's size which gave it its nickname "Whale". In the first full year of fleet deployments, there were seven flight deck accidents that cost the lives of nine crew. One of the main issues with the high accident rate was that many A3D crew came from the land-based patrol community as it was assumed they were most experienced at handling large aircraft. Turns out, it was carrier experience that was needed as well as more standardized training. As new Skywarrior squadrons were established, they were assigned to NAS Jacksonville to pool experience and training. Eventually Heavy Attack Wing ONE moved to NAS Sanford north of Orlando. By 1958, the accident rate was dropping significantly with the influx of personnel experienced in carrier jet operations. Previously the Navy preferred to keep its carrier air wings united at a single base, but the Skywarrior community set the pattern for the future, for the first time the Navy based all of one aircraft type together at a single base at NAS Sanford. 

With the new A3D-2 variant entering service to replace the earlier A3D-1, a second Skywarrior base for the Pacific Fleet was established at NAS Whidbey Island in Washington. Heavy Attack Wing TWO was set up in Washington, having previously been based at NAS North Island when its heavy attack squadrons flew the AJ Savage. Even numbered VAH squadrons were with the Pacific Fleet, odd numbered VAH squadrons were with the Atlantic Fleet in Florida. The first Pacific Fleet deployment was carried out by VAH-2 aboard the USS Bon Homme Richard in July 1957. Interestingly at the time, there were no Forrestal class carriers assigned to the Pacific Fleet, so nearly all of the Pacific Fleet Skywarrior cruises at the time were done aboard the small Essex-class carriers.

Special nuclear storage facilities were set up on the carriers where the nuclear weapons were stored, guarded by special Marine detachments. Alert aircraft on the carrier deck were also guarded by Marines. Essex class carriers carried three A3D-2s, nine to eleven A3D-2s were embarked on the Midway class and full twelve-aircraft squadrons were sent aboard the Forrestal class decks when they were finally assigned to the Pacific Fleet.  While tanking and conventional bombing were routinely practiced, they were considered secondary to the nuclear deterrent mission. At any given time, a carrier with Skywarriors aboard had at least one or two aircraft armed and on alert for immediate launch. Alert Skywarriors were sometimes kept in the hangar deck near an elevator for immediate movement to the flight deck. The Skywarrior's preferred nuclear attack profile was to make the run into the target at low level at 520 knots. Once the B/N had the target on his radar, the A3D would pull up at 2.5Gs at full throttle, pitching up to 60 degrees climb to release the weapon. After release, the Skywarrior would roll 120 degrees, still pulling 2.5Gs, and hit the deck to egress the target area to escape the nuclear blast. 

By 1960, NAS Whidbey Island was home to five A3D Skywarrior squadrons- four operational squadrons and one training squadron. The last of the Skywarriors were delivered in January 1961, from a production run of 283 aircraft. The zenith of Skywarrior operations was in mid-1961 when there were 227 aircraft in service. With the entry into service of the Polaris sea-launched ballistic missile (SLBM) in 1961, the nuclear deterrent mission of the Skywarrior and its replacement, the supersonic North American A3J (designated A-5 after 1962) Vigilante, was soon to end. The Skywarrior units with the Atlantic Fleet based at NAS Sanford transitioned to the Vigilante, the first fleet deployment taking place in 1963 aboard the USS Independence. By 1965-1966, there were no more Skywarriors with the Atlantic Fleet as all the squadrons in Florida had converted to the Vigilante, leaving NAS Whidbey Island in Washington as the center of the Skywarrior's world with four operational squadrons, VAH-2, -4, -8, and -10, with VAH-123 acting as the training squadron. 

VAH-4 Skywarrior in a shallow dive bombing run
(Skywarrior Association)
On the night of the Tonkin Gulf incident on 2 August 1964 that set in motion the long US involvement in the Vietnam War, VAH-4 had three A-3B Skywarriors embarked on the USS Ticonderoga and twelve A-3Bs with VAH-10 aboard the USS Constellation. The A-3B (as the A3D-2 was redesigned after 1962) could carry up to 8,000 lbs of conventional bombs. Usually the high drag box fin Korea-era bombs were carried as most could fit in the A-3B's bomb bay. The low drag Mark 82 series bombs were reserved for aircraft that had to carry their bomb loads externally. The first bombing missions by Skywarriors in Vietnam were carried out by VAH-2 in 1964 which was uniquely split between two aircraft carriers, the USS Ranger and the USS Coral Sea. Many Skywarrior missions going into 1965 were level bombing runs at night using radar. Most Skywarriors did dual roles, both tanking and bombing. During VAH-2's marathon 331-day deployment 1964-1965, the unit's A-3Bs flew 4900 hours, dropped over 400,000 lbs of bombs, and offloaded over 4 million pounds of fuel. 

During 1966-1967, many of the targets in the North weren't good radar targets for the Skywarrior. Driven as well by concerns about the A-3B's survivability in the increasingly lethal air defenses of North Vietnam, Skywarrior squadrons shifted Viet Cong targets in South Vietnam as well as missions against the Ho Chi Minh Trail in Laos. But there was a problem. If the juicy targets in North Vietnam weren't very good radar targets, how much better was a target somewhere in the jungles of South Vietnam and Laos? The Skywarrior crews adopted dive bombing, attacking in 30-degree dives. While it wasn't anything new as it had been done in exercises in the past, the A-3B lacked an optical sight for dive bombing. Skywarrior pilots resorted to grease pencil marks on the windscreen, some used the refueling probe as an improvised aim point in their dive attacks. The pilots began their attack runs at 8,000 to 10,000 feet, pulling out at 3,000 feet to avoid light caliber anti-aircraft guns and to avoid over stressing the aircraft. More enterprising units resorted to bolting gunsights from A-1 Skyraiders to the glare panel and one unit even got its hands on some gunsights from A-4 Skyhawks. Some Skywarrior missions involved leading groups of A-4 Skyhawks on level bombing runs, the Skyhawks dropping on command from the A-3B's B/N. 

A steeper bombing attack by the Skywarrior over Vietnam
(Skywarrior Association)
A usual A-3B bombing mission involved both bombing and tanking. A Skywarrior would launch, refuel aircraft in the departing strike package, then go on its own bombing mission. On return to the carrier, it would refuel the next outgoing strike package before recovering. When not loaded with bombs or a tanker package, the bomb bay could carry critical spare parts, mail and other high priority items. It was common for a spare A-3B to be sent to NAS Cubi Point in the Philippines for critical aircraft spare parts or get sent to Japan to pick up combat pay for the ship's crew. 

The Skywarrior's role in Vietnam as a bomber began to wind down in late 1967 as it was deemed that its air refueling role was a more vital mission and that more capable, more survivable attack aircraft like the Grumman A-6 Intruder and Vought A-7 Corsair were available. The last bombing missions were carried out in 1968. But there is an oft-repeated apocryphal story amongst Skywarrior veterans of Vietnam that General William Westmoreland, commander of US forces in Vietnam, himself ordered an end of A-3 bombing missions. The story goes that he was shocked when visiting an aircraft carrier that Skywarriors were providing close air support to Army troops "without the benefit of a proper gunsight". 

Nearly every aircraft carrier that participated in Vietnam had A-3 Skywarriors aboard, mostly as tankers, bombers until 1968, and later in the war, in reconnaissance and electronic warfare roles. Just in the bomber/tanker roles, Skywarrior squadrons made 62 combat cruises in Southeast Asia, ranging from three-aircraft detachments on the Essex class to full twelve-aircraft squadron deployments on the larger super carriers. Sixteen different aircraft carriers operated Skywarriors in Vietnam, only the USS Intrepid and USS Saratoga never operated Skywarriors during the war. Six Skywarriors were lost in combat, twelve were lost to operational accidents in the theater, and 35 crew were lost. 

Related reading:


Sources: A-3 Skywarrior Units of the Vietnam War by Rick Morgan. Osprey Combat Aircraft No. 108, Osprey Publishing, 2015, pp8-30. Strike From the Sea: US Navy Attack Aircraft from Skyraider to Super Hornet 1948-Present by Tommy Thomason. Specialty Press, 2009, p75-87.

13 January 2016

The Japanese Spruce Goose: The Kawanishi H11K Soku

Profile of the H11K from the Anigrand 1/144 scale kit
(Anigrand Craftswork)
By 1944, the US Navy's unrestricted submarine warfare against Japanese shipping had reached its highest totals in terms of shipping sunk and it was taking its toll on Japanese industry. As an island nation with few natural resources, Japan was dependent upon shipping for the importation of raw materials and oil for not just its industry but also for it military forces. The Imperial Japanese Army Air Force looked at using transport gliders to bring oil from Sumatra to Japan, but the fuel costs to do so outweighed the volume of oil brought in. The Imperial Japanese Navy, however, with its experience in operating large seaplanes, asked Kawanishi to develop a large transport seaplane to make up for the shipping losses. Kawanishi had already designed and put into production two large flying boats, the H6K (Allied code named "Mavis") and the H8K (Allied code named "Emily"). The H8K in particular was avery well-regarded flying boat design, even by the Allies. Kawanishi had also modified its production flying boats for the transport role as well. The transport version of the H8K was designated H8K-2L Seiku ("Calm Sky") and the company had built 36 for the IJN for transport duties aside from the prototype which was converted from a front line H8K. Most of the defensive positions were deleted to save weight save a 13mm machine gun position in the nose and a 20mm cannon in the tail position. The fuselage fuel tanks were reduced in size to allow for more cargo volume. An H8K-2L could carry up to 62 fully-equipped troops.

Overall configuration of the H11K Soku
(Airwar.ru)
The earlier H6K also had a transport version. It didn't have the space or load carrying capability of the larger and later H8K, but 20 aircraft designated H6K4-L were built and another two were converted from former front line H6K4 flying boats. And earlier production run of 18 aircraft designated H6K2-L were primarily passenger aircraft used by Japan's wartime airline, Dai Nippon Kokku. As passenger transports, they could accommodate 18 passengers and had sleeper berths.

Kawanishi's design for a large purpose-designed transport flying boat was designated H11K Soku ("Blue Sky"). Since metal alloys were desperately needed in the production of fighters for homeland defense, Kawanishi's H11K would have been made of wood wherever possible- making it in a sense a Japanese counterpart to the Hughes HK-1 "Spruce Goose". Starting out by scaling up the H8K but having a nearly identical fuselage keel, the H11K was powered by the same four Mitsubishi MK4Q Kasei 22 1,850-hp radial engines, each engine driving a large four-bladed propeller 14 feet in diameter. By comparison, the large Martin JRM Mars had 16 foot, 8 inch four bladed propellers. Most of the wings and fuselage made of wood. Under each wing was a fixed float for water stabilization. The fuselage had two decks- the upper deck had not just the flight deck but also quarters for the crew of five. The lower main deck could accommodate over 80 fully equipped troops, vehicles or an equivalent volume of cargo. To speed loading and unloading operations, the nose had split clamshell doors. Three machine gun positions were located in the fuselage for self-defense. 

The H11K mockup with its nose clamshell doors
(RC Groups Forum)
After presentation of the H11K proposal to the Imperial Japanese Navy, full design work began in 1944 with Kawanishi building a full-scale mockup of the H11K for inspection and review by the IJN at one of its facilities on the west coast of Japan. However, the deteriorating war situation meant that  the full-scale mockup which was nearly completed on was destroyed along with most of the Kawanishi facilities in a bombing attack on 1 April 1945. No further work was attempted on the H11K Soku after the attack.

Some comparisons with other large Second World War-era flying boats to give you an idea of the Soku's size:




Dimensions
Span: 47.97m 157.4ft
Length: 37.70m I23.7ft
Height: 12.55m 41.2ft
Wing area: 289.95m2 3,121ft2
Wing loading: 156.72kg/m2 32.1 lb/ft2

Weights
Empty: 26,405kg 58,213lb
Loaded: 45,550kg 100,420 Ib
Useful load 19,095kg 42,097b

Performance
Max speed: 470km/h 292mph at 5,000m at 16,404ft
Cruise speed: 369km/h 229mph
Landing speed: 144km/h 89mph
Range: 3,890km 2,417 miles
Climb: 11 min 30 sec to 3,000m (9,842ft)

Source:  Japanese Secret Projects: Experimental Aircraft of the IJA and IJN 1939-1945 by Edwin M. Dyer, III. Midland Publishing/Ian Allan Publishing, Ltd, 2009, p63-64.

08 January 2016

Project Thunderstorm: Storm Chasing with P-61 Black Widows

P-61 crew with their hail damaged aircraft
(NOAA History)
In the immediate postwar period the Civil Aeronautics Authority (CAA, the predecessor organization in the United States to the current FAA) began to gear up several research efforts in order to establish guidelines for the regulation of the anticipated boom in civilian flying. One of the areas that the CAA placed emphasis on was understanding the dynamics of severe thunderstorms which were all too common across many of the trunk routes of the United States. In 1945, the U.S. Congress authorized $250,000 to the U.S. Weather Bureau (which would become the National Weather Service in 1970) to study severe thunderstorms with specially-instrumented Northrop P-61 Black Widow fighters. Cooperating with the U.S. Weather Bureau were a number of organizations- the U.S. Army Air Forces, the Naval Research Laboratory of the U.S. Navy, the National Advisory Committee for Aeronautics (NACA, the predecessor organization of NASA), the Meteorology Department of the University of Chicago, the Physics Department of the University of New Mexico, the Electronics Department of the Massachusetts Institute of Technology, and the Soaring Society of America. With the U.S. Weather Bureau as the coordinating agency, University of Chicago meteorologist Dr. Horace Byers was appointed director of the Project Thunderstorm. 

The P-61's SCR-720 radar
(Wikipedia)
With the Second World War having ended just weeks prior to the Dr. Byers' appointment, there was a ready surplus of aircraft, pilots, and personnel to undertake the project. In addition, the CAA anticipated a rapid increase in postwar civilian flying. A spate of weather related accidents in the summer of 1945 also provided additional impetus to the endeavor. While other aircraft would be used in the study, the main storm penetration flights would use the P-61 Black Widows that once belonged to an Alaska-based USAAF weather reconnaissance unit. The aircraft were large with good range for multiple storm penetrations and were known to be tough. Pilots and crews were all volunteer and briefed in advance of the hazardous nature of the flights. The Black Widow in addition carried an onboard radar, the SCR-720. The radar was a joint development between Bell Laboratories and MIT as an improvement over previous airborne intercept radars which had a limited range of only five miles. Compared to previous AI units, the SCR-720 had a longer range (twenty miles in good conditions) and would be the primary AI night fighter radar of the Allies during the Second World War. One of the early problems of AI units in those days was attenuation and blocking of the radar beams by heavy precipitation- for Project Thunderstorm, though, this limitation was useful as it allowed the P-61's radar operator to get radar images of the thunderstorms at multiple levels. 

The pilots were selected from the Air Materiel Command's All-Weather Flying Division and were scrutinized closely for their skills and aptitude for the missions. The radar operators were all highly-trained and experienced individuals from the Navy and USAAF and the third member of the P-61 crew was a weather observer would would be responsible for collecting a variety of measurements during the storm penetration flights. 

The Soaring Society of America provided three Pratt-Read TG-32 two-seat gliders and pilots. The gliders were used to gather data on cumulus clouds before they had developed into thunderstorms as well as to make study flights on the storm periphery. Approximately 141 glider flights were made for the US Weather Bureau- one pilot, Paul Tuntland, got caught inside a thunderstorm updraft and was carried from 4,000 feet to 22,000 feet, setting a new national altitude record for gliders!

P-61s and a single F-15 Reporter getting ready to sortie
(NOAA History)
The first phase of Operation Thunderstorm took place over a sixty-square mile instrumented range near Orlando, Florida. Aircraft were based at Pinecastle Army Air Field, Florida (today's Orlando International Airport) using Black Widows fitted out with data recorders and weather instruments. Two seat glider aircraft were also used to gather data on the periphery of the storms as they entered the test range area. Microwave radar stations were set up around the Orlando area for early warning- as a storm was detected, the P-61s sortied and would penetrate the storm cell five aircraft at a time at 5,000-foot intervals from 5,000 feet to 25,000 feet. The same radar stations would also vector the P-61s into and around the the storms on their missions. Fifty ground based stations also were used to collect atmospheric data at ground level. Three radiosonde stations were also used to release multiple weather balloons into the storms in the test range. The test flights took place between 29 June and 18 September of 1946. The second phase took place at Clinton Army Air Field near Wilmington, Ohio (today's DHL Airborne Airpark), only this time there were 13 of the specially-instrumented Black Widows used plus four Northrop F-15s (the reconnaissance version of the Black Widow) owned by Northrop and single P-61 that was being used by Trans World Airlines for its own weather research. Starting on 1 May 1947, the aircraft would make storm cell penetrations every time a severe weather front passed through the area. 

SCR-720 radar image of a thunderstorm
(YouTube)
Pilots made their penetration flights with the trim set for straight and level flight. Once in the storm, they were to do their best to minimize control inputs as sensors would record not just the pilot's instrument panel, but also the power settings, control surface movements as well as the aircraft's motion as it was buffeted by the storm. Aircraft routinely landed after their missions with damage from hail and lightning strikes. Despite the punishment of the storms and the hazardous nature of the penetration flights, over the course of 1,362 missions, not a single aircraft or crew member was lost. In recognition of their skill and bravery, all the crews were awarded the Distinguished Flying Cross. 

By 1949, the study ended and the meteorology department of the University of Chicago was given responsibility for analyzing the data from both phases. One of the most prominent severe weather researchers came from the University of Chicago's department having had his start with the Operation Thunderstorm data- Theodore Fujita, who would later become one of the world's foremost experts on mesoscale systems and tornadoes- and who developed the Fujita Scale for tornadoes used today as the Enhanced Fujita (EF) Scale. 

Operation Thunderstorm contributed a large body of data that not only increased the safety of civil aviation, but also set the stage for improvements in severe weather forecasting. The use of the Black Widow's SCR-720 radar also led to the development of airborne weather avoidance radar by commercial aircraft. 

Further reading: 


Sources: Wings of Fame, Volume 15. AIRtime Publishing, 1999, "Northrop P-16 Black Widow" by Warren E. Thompson, p91. "Thunderstorm Research Project" from In the Breeze Vol. 2, No. 12, January 10, 1946, pp1-2, accessed via NOAA History. "Project Thunderstorm" by Steve Zuger, Aviation History, July 2015, pp30-33.

03 January 2016

Martin, the Titan I, and the Titan II Ballistic Missiles

Titan I ICBM elevated out of its silo for laugh
(USAF Museum)
When George M. Bunker took over the reins of Martin Aircraft from Glenn Martin in 1952, Bunker wanted to diversify Martin which up to that point had produced only aircraft. With an able group of lead engineers that Glenn Martin had literally hand picked in the years prior to his retirement from his company, Bunker moved some of Martin's engineering and research efforts into the rocket and missile arena that bore first fruit with the Viking research rocket and the Vanguard light satellite launcher built for the Navy. While many in the growing rocket and missile division were focusing their efforts on the Vanguard program, it was Jess Sweetser, Martin's VP for Sales and Requirements, who pushed the company to bid for the second USAF ICBM contract. At the time, General Bernard Schriever was heading the Western Development Division (WDD) in Los Angeles which directed the ICBM effort that started off with the Atlas ICBM built by Convair. Schriever wanted a second ICBM system fielded as a backup to the Atlas and the WDD issued a requirement that spelled out the range, guidance and throw weight (the payload of the missile, which was the nuclear warhead). Left up to the contractors would be the missile configuration, liquid vs. solid propellants, staging and number of engines.

Sweetser got to know General Schriever so well they became golfing buddies* in their free time and as a result, he was able to anticipate the need for a second ICBM program from his conversations with the general. As a result, when the WDD issued the requirement, Martin's team of engineers was already doing preliminary work in addition to their work on the Vanguard launcher for the Navy. It became clear from further directions from the Western Development Division as well as the operator of the ICBMs, the Strategic Air Command, that not just a backup ICBM was wanted, but one that was a true alternative to the Atlas ICBM and if possible, more advanced. With both Boeing and Lockheed in the competition for the alternative ICBM contract, George Bunker split the rocket and missiles team into two parts- one group stayed on the East Coast and worked on the Vanguard launcher, the other group set up shop in Los Angeles next to the WDD to work on their ICBM design. Martin's design was based on work that had been already done for the Vanguard launcher- instead of the thin, pressurized balloon skin arrangement used on the Atlas, the Martin proposal used two liquid propellant stages made of a rigid framework of copper-aluminum alloy with the tank wall integral to the rocket walls for weight savings as had been done on the Vanguard. The first stage would use two powerful 150,000 lb thrust engines and the second stage used a single 80,000 lb thrust engine that would be ignited in zero-gravity in near-space, a first for such a large engine. The Vanguard had proved that near-space ignition of the second stage was possible, but this would be the first large-scale application. 

In addition, Martin's ICBM design would be modular, allowing the design to be enlarged over time for heavier payloads. The sweetener of the proposal that would win the USAF contract for Martin in December 1955 was the creation of an all-new development, testing, and production facility in one location at the base of the Rocky Mountains in Littleton, Colorado. This was chosen for two reasons- first, the valleys in some of the mountains could house engine test stands with the mountains acting as natural sound insulators for the surrounding area, and secondly, Martin pointed out that a mid-continent facility was furthest away from the coasts which could be vulnerable to Soviet submarine missile launches and bomber attacks. Ground was broken on the Littleton facility outside of Denver in February 1956 for the missile that the USAF christened the Titan. As a result of the USAF's requirement that everything that went into the Titan missile be thoroughly tested, the first facilities built were the test stands, some of which replicated full size launch pads were complete Titan missiles could be tested. 

Just three years after the start of construction on the facility itself, the first Titan I missile was flight tested from Cape Canaveral on 6 February 1959. The second, third, and fourth test flight were a success, unprecedented in a new rocket or missile program. The fifth and sixth flights were failures with explosions on the launch pad, but the seventh flight was a success and by 1960 Martin had 11 more successful Titan I test flights. Out of 18 test flights, only two Titan I test flights failed, a success rate that was stunning and groundbreaking given the technology of the time. 

Titan I 3x3 ICBM base layout
(USAF Museum)
The first Titan I silos were built in 1959 in the Lowry AFB gunnery range just east of Denver. The first Titan I ICBMs went on nuclear alert on schedule in August 1962 at Lowry AFB. As the Titan I used liquid oxygen as an oxidizer, the missiles were kept the silos until the launch order was given. At this point a massive elevator lifted the Titan I out its silo to an above ground position where it was fueled for launch. All of the necessary facilities were deep underground, even the propellant storage tanks. Each ICBM squadron had nine Titan Is in groups of three. Each group of three missiles were part of a single launch complex. Once the missiles were fueled, the radio guidance domes also were elevated from their own silos. The radio guidance system tracked the missiles after launch and fed the necessary course corrections, much like the guidance system used on the Atlas ICBMs. 

With advances in Soviet ICBMs, though, while the Titan I flight test program was taking place, Martin's engineers were already working on a successor, Titan II. Titan II had an even bigger warhead and the modularity of the Titan design paid off as the engineers merely had to fatten the second stage to the same diameter as the first stage and then lengthened both stages for a bigger missile. To replace the radio guidance system on the Titan I, AC Delco and MIT created a new inertial guidance system that set the standard for ICBMs. No longer would radio signals from the launch site be necessary, minimizing the Titan II's vulnerability to a counterstrike. The liquid oxygen was also replaced as the oxidizer and Titan II now had non-cryogenic storable liquid propellants- Aerozine-50, which was a mix of hydrazine and unsymmetrical dimethylhydrazine (UDMH) and dinitrogen tetroxide as the oxidizer. As a result, no fueling process was needed. 

Titan II silo "hot launch"
(USAF Museum)
The simplification of the Titan II launch complexes compared to the Titan I was dramatic. Major underground structures dropped from 42 to just 18 structures, 6,000 feet of service tunnels were reduced to just 945 feet, the power requirements dropped from 12,000 kilowatts per squadron to just 2,700 kilowatts. Only half the wiring connections were needed and the need for periodic checkout of missile systems dropped by an astounding 90%.  As a result, the silos could be more widely dispersed. With a formal contract awarded in 1960, the Titan II flight test program went smoothly- of 33 test launches, 25 were successful- in fact, the last 13 test launches were so successful and reliable, the Titan II was selected by NASA to be the launcher for Project Gemini. 

With this reliability came the need to solve the basing issue. The Titan I was housed in silos, but it was lifted out of the silo for launch. Martin's engineers argued that it was possible to launch the Titan II right out of its silo, dramatically reducing its response time. Significant debate ensued about the feasibility let alone the safety of launching the 110-foot Titan II with its 430,000 lbs of first stage thrust right out of a silo. On 19 February 1963, a test Titan I was successfully launched from a Titan II test silo at Vandenberg AFB in California, validating the concept so clearly that the USAF had Boeing incorporate silo-launch on its Minuteman ICBM. The first Titan II missiles went on nuclear alert in 1963 just one year after the first Titan I missiles went on alert! 

The Titan I missile squadrons were operational from 1962 to 1965 at Lowry AFB in Colorado, Ellsworth AFB in South Dakota, Beale AFB in California, Larson AFB in Washington, and Mountain Home AFB in Idaho. Only Lowry AFB was home to two Titan I missile squadrons while the other bases only hosted a single squadrons. The Titan II missile squadrons were grouped three squadrons to a missile wing and were operational from 1963 to 1987 at McConnell AFB in Kansas, Little Rock AFB in Arkansas, and Davis-Monthan AFB in Arizona. The modularity of the Titan design, though, made it a versatile heavy-lift space launcher. Not only did the Titan II launch the manned Gemini missions, but it was also used as a satellite launcher until 2003. Titan III and Titan IV were exclusively space launchers, with the last Titan IV launch in 2005. In 1995, when Lockheed merged with Martin Marietta, the Colorado facility became part of the Lockheed Space and Missiles Division. Since the retirement of the Titan IV launcher, the Littleton facility is now the headquarters of United Launch Alliance, the joint venture of Lockheed Martin and Boeing for the Delta and Atlas launch vehicles. Although no production takes place there any longer, ULA still has its mission control, testing and engineering facilities at the same location that was the birthplace of the Titan missile when ground was broken over fifty years ago.

Historical tangent: 

I had mentioned above how Martin Aircraft's VP for Sales and Requirements Jess Sweetser, had become a golfing buddy of USAF General Bernard Schriever. Before he came to work for Martin Aircraft, Jess Sweetser was a championship golfer in the 1920s. While a student at Yale, Sweetser had won the National Intercollegiate Championship in 1920, placed 11th at the US Open the following year despite his youth, and won the Metropolitan Championship  in 1922 in his junior year at Yale. He then won the US Amateur Championship that same year and then became the first American to win the British Amateur Championship in 1926 despite having the flu. He played on the first Walker Cup team (a trophy for amateur golfers in the United States, Great Britain and Ireland) in 1922 and five more teams in years following. After graduation from Yale, he worked as a stockbroker and played golf on weekends. His first job in aviation was with Curtiss-Wright before he came to Martin Aircraft. 

Source: Raise Heaven and Earth: The Story of Martin Marietta People and Their Pioneering Achievements by William B. Harwood. Simon and Schuster, 1993, p299-325

29 December 2015

The First American Covert Overflights of the Soviet Union

1st Lieutenant Bryce Poe II, USAF
(Gathering of Eagles Association)
The introduction of nuclear weapons at the end of the Second World War had a profound influence in many combat doctrines and none nowhere else as much as that of airborne reconnaissance. In November 1945, General Henry "Hap" Arnold of the US Army Air Forces warned the US government that in the future, American leaders would require "continuous knowledge of potential enemies, including all aspects of their political, social, industrial, scientific and military life" if the United States was to avoid a surprise attack with nuclear weapons. Traditional reconnaissance doctrines had the use of airborne assets in support of ongoing combat operations. General Arnold and many of his contemporaries at the dawn of the Cold War recognized that airborne reconnaissance was needed to provide an assessment and early warning of potential enemies, namely the Soviet Union that was rapidly tightening its grip on Eastern Europe. The start of the Berlin Blockade in June 1948 pressed the issue further that up-to-date reconnaissance was needed of the Soviet Union should tensions escalate to an all-out conflict. Interestingly while the highest levels of the US government tried to determine the best way to make such an assessment, the United States Far East Air Forces (FEAF) based in Japan took the initiative to begin its own assessment of Soviet forces in their region in response to the rising tensions during the Berlin Blockade. The commander in chief of the US FEAF, Major General George Stratemeyer, ordered the 8th Tactical Reconnaissance Squadron and its Lockheed RF-80 Shooting Stars to begin a series of covert overflights of the Soviet Far East. Based at Yokota Air Base, Stratemeyer ordered the 8th TRS to deploy to Misawa AB on the northern Japanese home island of Hokkaido. Two pilots were selected with 1st Lieutenant Bryce Poe as the primary pilot for the secret missions to assess Soviet air strength in the region. The RF-80s were modified with larger wingtip tanks for longer range. Poe was instructed that if the coastline was free of clouds, dash into Soviet airspace, photograph the targets and dash back out and head back to Misawa as fast as possible. 

The first reconnaissance overflight (and USAF jet reconnaissance mission) of the Soviet Union took place on 10 May 1948 with 1Lt. Poe departing Misawa AB to overfly targets on Kuril Islands. Missions were flown to photograph targets on Sakhalin Island as well further to the north. The first overflight of the Soviet mainland took place on 10 March 1950 to photograph bases around the port of Vladivostok. Most of the airfields Poe had photographed were full of not just only Lend-Lease Bell -39 Airacobras and P-63 Kingcobras, but also late model Lavochkin piston fighters like the La-9 and La-11. Although jet powered, the RF-80s had increased drag and lower speeds with the larger external tanks needed for the recon missions which cut down on the performance margin over the Lavochkin fighters which often tried to give chase to the missions. 

Lockheed RF-80 with the enlarged camera nose section
(Wikipedia)
What was impressive about these first overflights is that they were done at the initiative and discretion of General Stratemeyer without any prior clearance from Washington and they were done in the face of significant technical and logistical obstacles. The reconnaissance cameras used on the RF-80 were designed for piston-engined aircraft and lacked the capability to do stereo images in a high speed aircraft like the RF-80. Spare parts were in constant short supply and given that Misawa at the time was on the far northern part of a still rebuilding Japan, insuring even basic food rations for the 8th TRS personnel deployed north proved challenging. Many F-80 units based in Japan at the time found themselves the subject of "moonlight parts acquisitions" so the secret overflights could continue. 

Despite the failure of the Berlin Blockade which was finally lifted on 11 May 1949 and the formation of NATO, tensions remained high with the first detonation of a Soviet atomic bomb on 29 August 1949 followed by Mao Tse-Tung's Communist victory in China on 1 October 1949 over the Nationalists. With Stalin feeling more confident about the Soviet posture on the world stage, on 25 June 1950, the North Korean Army smashed across the DMZ on the Korean Peninsula, igniting the Korean War. In order to prevent further escalation the conflict, American reconnaissance pilots were instructed to avoid Chinese and Russian air space, however, the advance of North Korean forces meant that 1st Lt. Bryce Poe was called upon again by General Stratemeyer to begin a new set of secret overflights. In August 1950, he was called to FEAF HQ to again deploy out of Misawa and fly a series of missions against Soviet airfields in the region. While Soviet fighters tried more aggressively to intercept the RF-80s, none came close to getting shot down. By this point, the intelligence from Poe's flights was deemed critical by the Joint Chiefs of Staff and on 28 July 1950, the JCS requested official permission from the Secretary of Defense, Louis Johnson, for overflights of Chinese bases on the coasts adjacent to the Korea. Just four days later, President Truman gave his approval and again, because of his prior expertise, 1st Lt. Bryce Poe flew the missions against Chinese coastal targets and additional missions by other pilots were flown against Chinese ports opposite of Taiwan to make sure no amphibious assault preparations were underway to move against Taiwan. 

By the summer of 1950 discussions had been taking place at the Pentagon about using the more-capable North American RB-45 Tornado for overflight missions of Chinese and Soviet targets, but the aircraft being a bomber, it was felt at the time to be too politically risky, particularly as the Pentagon was seeking authority for overflights of Soviet targets in Europe as well as in the Far East. By this point Allied fortunes in the Korean War had improved following the landings at Inchon. Poe was once again called to FEAF HQ for a third set of covert overflights but the other pilot that he had been working with on the prior sets of overflights had been killed in action, so for this next set of missions, Bryce Poe would be the only pilot flying. Due to the secrecy of the missions, Poe did all his own flight planning. He was told by General Douglas MacArthur and General Stratemeyer what information they needed and Poe himself figured out the targets, routes, photographic equipment, times and altitudes. Despite the ongoing war in Korea, Poe found that the defensive posture of the Soviet airfields had only modestly increased, but as a precaution, F-80 Shooting Star fighters would meet Poe on his outbound leg to make sure no Soviet fighters were trying to tail him. 

Major General Bryce Poe II before retirement
(USAF)
Once he landed, the film was developed by one warrant officer and Poe himself did all the photo interpretation work and then hand carried the imagery to brief General MacArthur as well as General Stratemeyer and his FEAF deputy. It was a remarkable degree of authority given to a 1st lieutenant! Stratemeyer felt only barest minimum of individuals needed to be involved in the secret overflights. Bryce Poe rotated back to the United States in January 1951 after making nineteen secret overflights of Chinese and Soviet territory as well as 90 unclassified tactical reconnaissance missions in support of operations in Korea. After Korea, Poe flew as an exchange pilot with several NATO nations before serving as the executive officer to General Bernard Schriever at the Western Development Division where ICBM development was taking place. He then served as an Atlas ICBM missile officer with the Strategic Air Command before returning to reconnaissance in time for Vietnam. As vice-commander of the 460th Tactical Reconnaissance Wing, he flew 213 recon missions in the RF-4C Phantom in Vietnam. He later commanded the 26th Tactical Reconnaissance Wing with the United States Air Forces Europe. Following his USAFE assignments, he assumed command positions with the Ogden Air Logistics Center in Utah and at Wright Patterson AFB in Ohio. He retired in 1981 as a very decorated four-star general and veteran of two wars, flying west on 20 November 2000. 

Sources: Shadow Flights: America's Secret Air War Against the Soviet Union by Curtis Peebles. Presidio Press, 2000, pp 4-39.