Boeing X-20 DynaSoar
Conceived in 1957 as a follow-on programme to the X-15, the theory behind the Boeing X-20A Dyna Soar in fact had its origins much earlier. In Germany in the 1930’s Dr Eugene Sanger had begun work developing a ‘regenerativley cooled’ liquid fuelled rocket engine which eventually produced an exhaust velocity of 10000 feet per second (fps), considerably better than the rocket engine which powered the V2 that only produced an exhaust velocity of 6560fps. After the start of WW2 Sanger proposed that his powerful rocket engine propel a development of his Silverbird manned, winged vehicle which he hoped could eventually reach orbit.
The new vehicle would be called the ‘Amerika Bomber’ and would take-off by being propelled down a 1.9 mile long monorail track by a rocket powered sled that could deliver 600 tons of thrust for 11 secs and propel the vehicle to Mach 1.5. After take-off the ‘Amerika Bomber’ would fire its main engine for 8 mins burning 90 tons of fuel before reaching a speed of 13,700 mph and a altitude of 90 miles. Then, after descending under the pull of gravity, the aircraft would ‘skip’ back up to a higher orbit and it was hoped a series of these skips would allow the vehicle to cover over 14,000 miles – giving it sufficient range to bomb New York. However, Germany’s defeat put paid to any chance of this very advanced concept ever entering service.
Whether the ‘Amerika Bomber’ would have worked will never be known, but I suspect that the concept was way too far ahead of available technology to have had much chance of success, particularly in terms of avionics. Indeed, post-war analysis of the Silverbird design uncovered a mistake in the calculation of the effect of aerodynamic heating during re-entry - in fact had the Silverbird design ever made it into orbit it would almost certainly had burned up during re-entry. Furthermore, Germany would certainly have needed to develop an atomic bomb to make the attack worthwhile and, even if he survived the very high ‘G’ forces on take-off and the re-entry, the pilot would certainly be on a one-way mission, so the ‘Amerika Bomber’ was in reality a highly-advanced kamikaze vehicle. Nevertheless, when WW2 ended, both the Russians and the Americans studied Sanger’s research with great interest.
After the end of WW2 the Commanding General of the Army Air Force (AAF), ‘Hap’ Arnold created the Research and Development (RAND) corporation and the Scientific Advisory Board (SAB) to ensure that the AAF would still benefit from the very best scientific research US scientists could provide. The SAB, headed by Dr Theodore von Karman, also suggested that the new USAF create their own Air Research and Development Centre (ARDC) and these organisations eventually led to the new USAF embracing the concept of ballistic missiles. As well as realising that using these new ballistic missiles to orbit satellites would create an excellent communications relay, the USAF considered other possibilities, particularly the Sanger concept of a boost-glide vehicle that could act as both as an intercontinental bomber and reconnaissance vehicle. After various feasibility studies, such as Hywards, Brass Bell and Rocket Bomber (ROBO), on 10 Oct 57 the boost-glide concept resulted in a formal proposal for the X-20 Dyna-Soar program – Dyna-Soar was a contraction of the terms Dynamic Ascent and Soaring Flight. Nine companies responded to this proposal: Boeing-Vought, Convair, Douglas, Lockheed, McDonnell, North American, Northrop, Martin Bell and Republic.
After thorough evaluation of various proposals, it was announced on 16 Jun 58 that Martin Bell and Boeing were finalists in the X-20 Dyna-Soar program and each company were awarded $9 million for additional studies and development work. In Jun 59, despite Bell having completed six years worth of research into the project, it was announced that the contract for the spaceplane was actually being awarded to Boeing, a decision that must have been very hard Bell, particularly as the final Boeing design bore a very close resemblance to the Bell design.
The X-20 Dyna-Soar program was planned in three stages: Dyna-Soar I would be a research vehicle that would undergo 20 air-launched test flights from a modified B-52 starting in Jun 63, followed by five unmanned sub-orbital test flights, boosted by a Titan I rocket, starting in Nov 63. The final part of the first stage would involve 11 manned flights from Cape Canaveral, landing at a variety of different locations, including Brazil. Dyna-Soar II missions would be used to gather data on operations in orbit and eventually result in a reconnaissance vehicle which would also have the ability to inspect satellites. Dyna-Soar III would be the operational system and as well as reconnaissance duties, it would be able to act as an intercontinental nuclear bomber.
All the X-20 Dyna-Soar vehicles would be launched on top of various versions of the Titan rocket booster and would enter low earth orbit achieving a speed of 17,500 mph at around 530,000ft. The X-20 Dyna-Soar would initially be crewed by a single pilot, but behind the cockpit was a payload bay that could carry a 450kg payload or additional crew members. The first glide tests of the Dyna-Soar I were planned for 1963, with powered flights commencing the next year. It was hoped that the complete X-20 Dyna-Soar III system would be operational by 1974.
However, as development of the Dyna-Soar continued, so did a secret US programme for unmanned reconnaissance satellites. In addition, both the Eisenhower and Kennedy administrations wanted to avoid initiating a space weapons race with Russia and the offensive capability of the Dyna-Soar would send the wrong message and almost certainly result in the Russians orbiting an offensive weapons system in retaliation. In the end the programme was a casualty of the administrations diplomatic negotiations which were incompatible with the military objectives of the Dyna-Soar. Eventually on 10 Dec 63, the Secretary of State for Defence, Robert S McNamara, announced the Dyna-Soar programme would be cancelled.
However, the concept of lifting bodies ‘skipping’ of the earths atmosphere continued and today the US is developing the ‘HyperSoar’ which will use exactly this technique. Using a scramjet engine, the HyperSoar is planned to achieve Mach 10 and climb to 130,000ft where the engine would be switched off, then the HyperSoar would slowly descend back into the atmosphere where the engine would be re-ignited for a further ‘skip’. Even today this concept is at the very limit of current technology and it will be many years before a full scale HyperSoar ever enters operational service, if it ever does. It says something about the about the advanced thinking and engineering ability of Dr Eugene Sanger that he could envisage a system in the 1930’s which, despite all the huge advances in aviation and space technology that have taken place over the last 75 years, still remains many years from actual fruition.