Atlas & BOMI: Weapons for a new frontier

At the dawn of the space age, there appeared to be two viable routes to spaceflight, each with their roots firmly in German wartime research. On one hand there was the ballistic missile and on the other, the winged spaceplane.

The famed Peenemünde group led by von Braun and working for the German Army had created the world’s first practical ballistic missile, the A4, but by the latter years of the war had also begun to look at extending the missile’s range through the addition of wings. Independently of the Peenemünde group, Austrian scientist Eugene Sänger and his mathematician partner Irene Bredt were working on concepts for a rocket boosted Antipodal bomber for the German Air Ministry.

As the two global superpowers emerged in the immediate aftermath of World War II, these aerodynamic and ballistic concepts as well as the key protagonists behind their creation became the subject of huge military interest on both sides of the Iron Curtain. While the initial desire for exoatmospheric vehicles was based squarely around a requirement for long range weapons systems, the vehicles and techniques that resulted from these initial development programmes helped lay the groundwork for the space launch systems of the future.

Two contemporary advanced weapons projects carried out for the United States Air Force during the 1950s, namely BOMI and Atlas, illustrate these differing approaches well but endured very different fortunes.

The birth of a giant
The success of von Braun’s Peenemünde group in deploying an operational ballistic missile during the closing stages of World War 2 had been a wake up call to the US military. Whereas rocketry had previously been seen as having limited utility beyond short-range bombardment, missiles now seemed to hold promise as a long-range weapon, perhaps even rivaling the role of the bomber in the delivery of newly developed nuclear weapons. Following the allied invasion of Europe, captured research became available and German scientists were spirited into the US under Operation Paperclip. During October 1945 the US Army Air Technical Service Command began seeking design proposals from the aviation industry for both winged cruise missiles and ballistic missiles with ranges between 20 and 5000 miles.

One company who enthusiastically heeded the Air Force’s call was Consolidated Vultee. The San Diego based firm put forward proposals for both jet powered cruise missiles and a longer range ballistic missile designed by a group headed by one of the great unsung heroes of post-war American rocketry, the Belgian-born engineer Karel J. Bossart.

While von Braun began setting up an experimental operation test flying recovered A4s for the US Army at White Sands, Bossart developed a ballistic missile design featuring several revolutionary features which he believed would improve on the shortcomings of the German missile. While Consolidated Vultee lost out in the competition for cruise missiles to other manufacturers (including North American Aviation with their ramjet powered Navajo) they were granted a contract in early 1946 to develop the MX-774 High-Altitude Rocket (Hiroc) as a testbed technologies that could later be applied to a proposed longer range vehicle. While appearing superficially similar to the A4, the Hiroc featured a number of Bossart’s new ideas including monocoque single-wall tanks, where propellant pressure helped provide the structural strength of the body, and a warhead that would separate from the missile during flight. Bossart also included a gimballed Reaction Motors XLR35-RM-1 engine on the Hiroc seeing a gimballed engine as an improvement on the carbon steering vanes used by von Braun. The result was a far lighter missile with the promise of greatly improved accuracy.

Unfortunately for Bossart, many within the Air Force viewed missiles as a threat to their ‘main business’, the bomber. Although the design showed considerable promise, the Air Force cancelled MX-774 in July 1947 shortly before it reached the flight testing stage. Fortunately Convair (as Consolidated Vultee was now known) had enough funding remaining from the original contract to finish three of the ten vehicles originally ordered and the Air Force granted permission for these to be flown. The first flight took place in July 1948 and the remaining vehicles were flown in September and December the same year. Although engine problems meant that none of the flights were entirely successful, Bossart’s innovations were judged to have been effective and he continued to work on his ideas for a larger missile using company funds. Among the new ideas under development were the ‘one-and-a-half’ stage concept whereby booster engines used during the launch and boost phase could then be discarded leaving only a sustainer engine to carry the now considerably lighter missile towards its target.

Bossart soon got a new opportunity to put his ideas into practice as the Air Force again looked to develop a long-range missile capability in the light of the Korean War and the realisation that the Soviet Union now also possessed the means to create atomic weapons. Convair were awarded a development contract in January 1951 and Bossart’s new long-range design was designated the MX-1593, but became more commonly known as Atlas. Although originally more modestly funded than the more favoured cruise missile projects, the promise of the ICBM earned Atlas the Air Force’s highest priority ‘crash program’ status in response to worries about Soviet missile developments and funding began to flow more freely.

From Silverbirds to Bomber Missiles
As Bossart’s group responded to the Air Force call for missiles, von Braun’s team continued work on A4 derived designs under the auspices of the US Army. Their former commanding officer Dr. Walter Dornberger hadn’t come to the US with the original group but, following his release from British custody he began working as a consultant for the United States Air Force Air Materiel Command in 1947. In 1950 Dornberger moved from the military into industry, working with the Bell Aircraft Company on various missile projects and soon began to examine the potential offered by winged rocket systems as characterised by Sänger’s Antipodal ‘skip-glide’ Silbervogel (Silver Bird) bomber.

Sänger had been working on his ideas for a spaceplane since the mid 1930s. As Europe moved towards war, his theories came to the attention of the German military who funded further research. Sänger proposed a system whereby a winged craft would be accelerated along a track by rockets before flying free and igniting it’s own rocket motor to push it beyond the atmosphere in a ballistic arc. On descent the vehicle would ‘skip’ off the denser layers of the upper atmosphere in a series of ever smaller arcs like a stone skipping across water. Flying outside of the vast majority of the atmosphere and using the skipping technique, Sänger’s vehicle would be extremely fast and have unparalleled range. If the techniques could be applied to a weapons system, it could cruise beyond the reach of any existing defences and deliver weapons to intercontinental targets such as North American cities. Though much theoretical work was done during the war years, support was withdrawn from the project in 1942 as the Reich concentrated resources behind other more promising weapons such as von Braun’s A4. Following the war, Sänger chose to settle in France but copies of his research attracted interest in both the United States and Soviet Union.

A 1946 report by the RAND organisation had concluded that a winged orbital vehicle would be feasible for human spaceflight in the near future and Dornberger began to examine the potential for an intercontinental bomber along similar lines to those proposed by Sänger. He was aided in his new endeavours by another of the former Peenemünde engineer, Krafft Ehricke. Between them they devised an updated rocket propelled exoatmospheric bomber, a concept that became known as the BOmber MIssile or BOMI and Bell approached the Air Force’s Wright Air Development Center (WADC) with a proposal based on this work in April 1952. In its earliest incarnation BOMI was a two stage vehicle consisting of a large winged booster stage with a smaller winged bomber mounted on top. By the early 1950s research had shown that Sänger’s skip-glide technique would be largely impractical (although Bell included skip-glide trajectories in their proposals for some time), as it was recognised that these may create excessive heating and structural loads on the vehicle as well as being less suitable for certain missions. It was far more likely that BOMI would use a refined technique known as Boost-Glide, whereby the combined vehicle would launch vertically with the booster propelling the bomber to speeds in excess of Mach 4 and altitudes in excess of 100,000ft. Both vehicles would be piloted with the booster returning to base after its job was done. The bomber would then coast to a range approaching 3,500 miles, dropping its payload on a target before descending to land horizontally at a friendly base. Although hugely ambitious given the technology of the day, Bell Aircraft felt that their experience on the X-1 and X-2 experimental rocketplanes placed them in a position to take on the considerable technological challenges BOMI posed. Dornberger apparently also tried to recruit Sänger and Bredt to the project at this stage, but they declined preferring to remain in France where Sänger was involved in ramjet research.

By April 1953 WADC judged the initial BOMI design to be lacking sufficient range for an effective intercontinental system, and highlighted the many technical unknowns inherent in the design. Undeterred, Bell doggedly stuck to their belief that the proposal was worthy of further examination and in September of the same year briefed the Air Research and Development Command (ARDC), winning a 1 year $250,000 development contract to refine the BOMI concept. The revised design that emerged from this contract featured a piloted winged first stage booster, an uncrewed non-recoverable second stage booster and a piloted winged bomber as the third stage. Known as MX-2276 it had a far greater range of over 10,000 miles, with a range to target of 5000 miles. Ehricke also carried out a study of alternative trajectories for BOMI to allow it to circumnavigate the globe or even make multiple orbits.

The 1954-55 vintage MX-2276 BOMI shows an obvious design influence from Sänger’s 1940s era Silbervogel designs with the first stage winged booster featuring a low wing and tapered, flat based body, although it also featured a smaller canard wing on the forward fuselage. Featuring four 150,000lb plus four 75,000lb thrust rocket motors, the first stage would provide much of the initial thrust at launch, but would also cross-feed propellants to the second stage ensuring this had a full fuel load at separation. The second stage was a far simpler design sharing a similar fuselage shape to the first stage but without wings or any other empennage. This stage also would also fire at launch and featured 8 engines with a total thrust of 300,000lbs.

The bomber itself featured a single vertical fin, a short low-mounted double-delta wing and a long pointed fuselage. Bell recognised the difficulties involved in providing a glassed cockpit canopy given the dynamic and thermal loads, so it was proposed that a periscope system would be used for forward vision.  The 4,200lb nuclear weapon would be carried in the rear of the vehicle between its two 25,000lb thrust rocket engines and ejected rearwards in a similar fashion to the North American Aviation A-5 Vigilante jet bomber. To cope with the thermal challenges of the flight regime the bomber would feature a double walled construction with an outer aerodynamic shell made of Inconel X and insulation between the walls protecting the main structure. The outer wall would feature regular expansion joints to prevent buckling as the vehicle endured the extremely high temperatures of hypersonic flight and reentry. Interestingly although MX-2276 was highly classified at the time, much of Bell’s thinking on thermal protection, aerodynamics and reaction control for BOMI carried over into their unsuccessful May 1955 proposal for the Air Force’s Project 1226 which later became the X-15. It was suggested that a standard USAF partial pressure suit would provide the pilot with sufficient protection within the pressurised cockpit and interestingly, given the contemporary trends of the time, Bell chose not to install an escape capsule instead recommending that the pilot should attempt to stay with the bomber stage until it reached a suitable speed and altitude for ejection.

While MX-2276 still bore the name BOMI, by the mid fifties much attention was being given to the system’s potential as a reconnaissance vehicle with the ability to quickly overfly enemy territory beyond the reach of all known defences and rapidly return the results to friendly territory. Bell also went to great pains in their proposals to the Air Force to stress the superiority of a piloted vehicle over ‘automatic missile systems’ in terms of accuracy, reliability and the ability to be recalled after launch. But even as Dornberger and Ehricke continued to refine their ideas for WADC, Convair’s Atlas was already under development providing competition for BOMI’s proposed inter-continental bombing mission.

Atlas takes shape
With the Air Force’s highest level of priority assigned to it, Atlas was developing quickly and whereas hypersonic boost-glide still seemed a somewhat distant prospect, General Bernard Schriever now headed up the Western Development Division of ARDC with the aim of getting ICBMs deployed by 1960. Bossart’s MX-1593 design had continued to develop throughout the early fifties and now advances in the miniaturisation of atomic weapons meant that only 2 two jettisonable XLR43-NA-5 booster engines would be needed rather than the 4 originally envisioned saving weight and adding to the reliability of Atlas. A single gimballed XLR43-NA-5 would act as the sustainer after booster jettison as well as providing directional control for the missile. The basic Atlas design was frozen in December 1954. It was time to test the design.

Construction and static testing of 8 Atlas-A prototypes continued throughout 1955 and 1956 with the first vehicle ready for launch at Cape Canaveral on June 11th 1957. Unfortunately the first two flights were cut short as the missiles departed from their planned trajectories and were destroyed by the range safety officer. Before a third flight could be made, the world was rocked by the news that the Soviet Union had successfully launched Sputnik 1 on October 4th 1957. While this event marked the start of the space-age, it also proved the Soviets had a heavy lift missile capable of intercontinental flight adding extra urgency to Atlas’s development. Concerns over a missile gap between the Soviet Union and the United States gave renewed urgency to the fledgling ICBM programme. On December 17th, the third Atlas-A flew over 600 miles across the Florida Missile Test Range before falling into the Atlantic. In total four of the eight test flights were judged to have been successful proving the validity of Bossart’s basic design. Now the entire system needed to be tested over intercontinental range to prove that Atlas could become a viable and deployable weapon system.

Ever changing fortunes for Boost Glide
As Atlas’s development moved forward with the aim of spearheading America’s strategic nuclear deterrent, BOMI’s fortunes were somewhat different. The project now entered a slightly confusing phase of multiple overlapping Air Force requirements which would continue for many years. Although Dornberger’s team had continued to refine the vehicle’s design under Bell’s own funding, attention soon began to move more towards BOMI’s potential reconnaissance role, something that missiles and satellites were currently not capable of performing (although Project Feedback, a nascent spy satellite development programme was by now underway). As the Air Force began to examine its options for future advanced reconnaissance systems under the new designation 118P, additional funding became available for BOMI in September 1955 as its suitability for this role was assessed.

The following December, Bell presented its revised BOMI concept to meet requirement 118P. The winged booster stage was abandoned and replaced by expendable rocket boosters and the shape of the vehicle itself changed considerably as it was recognised that the original design had been hugely optimistic in terms of its ability to cope with the thermal and dynamic loads it would have to endure. Now a delta-shaped dart, the vehicle would carry a crew of two at speeds reaching Mach 15 and a maximum altitude of 165,000ft. The NACA also examined Bell’s BOMI proposal at this stage and judged it to be generally feasible, although a research programme was recommended to build-up towards an operational vehicle. As 1956 dawned, Bell were again in need of funding if they were to continue their research and again the Air Force proved accommodating. An additional Operational Requirement now directed Bell to work on an advanced reconnaissance vehicle to be available by 1959. The new vehicle, designated Reconnaissance System 459L but was more commonly known as Brass Bell. In their 1957 submission Brass Bell was a dart shaped glider with a clear evolutionary lineage from the earlier MX-2276 design to satisfy 118P. Bell proposed a two-stage booster (solid or liquid propellant options for the first stage were both documented) which would launch the vehicle to an altitude in excess of 170,000ft and a range of over 5000 miles.

While Brass Bell moved the boost-glide concept away from the bomber role, ARDC had issued yet another requirement (SR-126) in December 1955 for a crewed hypersonic Rocket propelled Bomber – shortened to RoBo. Nine aerospace companies including Bell, Convair and Boeing were invited to bid for SR-126 and, seeing an obvious synergy with their previous work, Bell proposed a more advanced version of their previous 118P BOMI design. They now offered the Air Force the option of a full-size recoverable crewed or a smaller expendable uncrewed system. A Global System allowing orbital flight via the use of larger boosters was also outlined.

Recognising that hypersonic boost-glide projects such as Brass Bell and RoBo would require a great deal of experimental data that currently did not exist, the Research and Target Systems Division of ARDC proposed that an experimental interim vehicle was needed to help speed up the development of these weapons systems. By November 1956 this new requirement, System 455, became known as the Hypersonic Weapons Research and Development Supporting System (HYWARDS). With Brass Bell (459L), RoBo (SR-126) and HYWARDS (455) all moving forward with the aim of creating hypersonic boost-glide weapons systems, Air Force Headquarters directed that these programmes should be brought together under a single designation and in October 1957 the were consolidated as System 464L. At this stage a new term, ‘Dynamic-Soaring’, was introduced to replace boost-glide. This was popularly, but slightly unfortunately, shortened to Dyna Soar and would encompass various stages representing flight research (HYWARDS), reconnaissance (Brass Bell) and Orbital Bombing (RoBo).

Having worked on boost-glide proposals and accrued a wealth of research since the early 1950s Bell looked well placed to win the Dyna Soar development contract, but in 1959 the contract eventually went to Boeing finally ending Dornberger’s dreams of creating a winged hypersonic bomber. The multitude of overlapping requirements which had characterised the development of BOMI did not end with the consolidation of the programme under its new name. Dyna Soar was under constant pressure throughout its relatively short life as the Air Force struggled to define a role for the expensive new system in a world where satellites and ICBMs could perform reconnaissance and weapons delivery. When Eisenhower had concluded that America’s space programme should be run by a civilian agency and signed NASA into existence with the National Aeronautics and Space Act in July 1958, the Air Force also lost what it saw as its natural role in furthering its mastery of the skies into the new frontier of space. As NASA raced forward propelled by Kennedy’s 1961 Moon promise, the need for unique and costly crewed space systems for the Air Force came under increased pressure. Eventually Dyna Soar was cancelled by Secretary of Defense MacNamara in 1963 without hardware ever flying. It was recommended that the Air Force could participate in NASA’s upcoming Gemini programme to gain initial manned experience before moving on to a Manned Orbiting Laboratory, also utilising Gemini hardware, later in the decade. Following Dyna Soar’s cancellation Boeing presented Dornberger with a large painting of Dyna Soar which adorned his office wall at Bell. The inscription read “Dyna Soar, Born 1954, Walter Dorngerger: Died 1963, Mac the Knife”.

Atlas comes good
While the boost-glide efforts became the troubled and ill-defined Dyna Soar, Atlas was officially designated as the B-65 (B referring to Bomber – this designation was later changed to SM-65 for Strategic Missile) and moved ever closer to demonstrating its potential. Following the relative success of the Atlas-A tests a second test vehicle, originally designated X-12 but now referred to as Atlas-B, was now produced to expand the flight envelope beyond what Atlas-A had achieved. The Atlas-B would feature the sustainer engine and the detachable warhead and, if successful, would allow Atlas to move forward to the first production model and deployment. The first flight took place on July 19th 1958 and on November 28th of the same year an Atlas-B flew over 6000 miles, thus demonstrating intercontinental range.

While the Air Force pressed on to rush the operational version of the missile, the Atlas-D, into production and deployment, Atlas got an early opportunity to demonstrate a role in which it would ultimately become more famous. One of the 13 ‘B’ test missiles, Atlas 10B, was launched on December 18th 1958 carrying the SCORE communications payload. SCORE (standing for Signal Communications by Orbiting Relay Equipment) is regarded as the world’s first communications satellite but actually consisted of the entire first stage of the Atlas B.

Conclusion
Atlas missiles went on operational alert as early as October 1959, but the first full squadron deployment took place in 1960. Atlas wasn’t a perfect weapon by any means. The missiles were stored horizontally in concrete ‘coffins’, then erected and fuelled when needed. This meant that response time was far from instant and soon the Air Force looked to replace Atlas with silo-based missiles with storable or solid propellants such as the Titan II and Minuteman. In this regard Atlas had much in common with its Soviet counterpart, Korolev’s R-7. But like the ‘Semyorka’, Atlas proved to be an effective launch vehicle, carving out a major role in mankind’s early planetary explorations. The Atlas-D also carried the first Americans into orbit in the guise of the modified LV-3B used in Project Mercury.

The family line of boost-glide designs first developed in wartime Germany and carried through Dornberger’s efforts with Bell into Dyna Soar never bore fruit in quite the same way as the ballistic missile. There were simply too many unknowns regarding the materials required and the hypersonic flight environment at the time to have made the designs truly practical without a great deal of prior experimental research. Even as BOMI morphed through its various guises, many within NASA and the Air Force began to see lifting bodies as a far more practical direction than winged space gliders. But by the 1970s many of the ideas underpinning both Sänger’s Silbervogel and Dornberger’s BOMI did eventually come to pass in the form of NASA’s space shuttle. It also looked like the Shuttle would finally give the Air Force the spaceplane they had longed for since the early 1950s, but even by the time it first flew in 1981 Defence Chiefs were beginning to raise serious doubts about the Space Transportation System and although the Air Force’s own launch facilities at Vandenberg AFB in California were almost complete, the Challenger accident in 1985 marked an end for the Air Force’s interest in operating the shuttle. More recently the uncrewed and secretive X-37B reusable spaceplane has flown long-duration missions and while little has been publicly acknowledged about the nature of its missions, it seems reasonable to regard it as the distant descendent of the 1950s spaceplane designs.

One final footnote that ties BOMI and Atlas together is Kraft Ehricke’s move from Bell to Convair where he worked with Bossart to create the D-1 Centaur, the world’s first high-energy cryogenic upper stage. The Centaur was used successfully with the Atlas up until 2004 as well as providing a high energy kick for planetary payloads when used with other launchers such as the Titan III. The legacy of both Atlas and Centaur continues to this day under the auspices of United Launch Alliance (ULA).

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Author’s Note
I’d like to thank Allen at Fantastic Plastic models for allowing me to use some of the images of BOMI featured on his site. You can see the Fantastic Plastic model of MX-2276 here

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Sources
The Need For Speed: Hypersonic Aircraft and the Transformation of Long Range Airpower – Kenneth F. Johnson, Thesis 2005

The Day of the Atlas – Stewart M. Powell, Air Force Magazine, October 2009

History of the X-20A Dyna-Soar – Clarence J. Geiger

The Rise and Fall of the Dyna-Soar: A History of Air Force Hypersonic R&D – Major Roy F. Houchin

Bell BOMI Parts 1&2 – Scott Lowther, Aerospace Projects Review Volume 2, Numbers 2&3

MX-2276 Advanced Strategic Weapon System – Various reports dated 1954-55, Bell Aircraft

BRASS BELL: Reconnaissance Aircraft Weapon System, Summary Report (D143-945-055) – August 1957, Bell Aircraft

The X-Planes: X-1 to X-45 (Third Edition) – Jay Miller

Hypersonic: The Story of the North American X-15 – Dennis R. Jenkins & Tony R. Landis

Space Shuttle: The History of the National Space Transportation System – Dennis R. Jenkins

Secret Projects: Military Space Technology – Bill Rose