Boeing's X-20 Dyna-Soar Hypersonic Space Bomber
Updated: Jul 26, 2023
The Boeing X-20 Dynamic Soarer, or Dyna-Soar, was a manned spaceplane developed by the United States Air Force for reconnaissance, space bombing, space rescue, and satellite intercepting and maintenance. Since it was reusable, it was a more advanced concept than other spacecraft of the time, such as the American Mercury and Soviet Vostok capsules. It was also the earliest manned space program to result in development contracts. The X-20 is best remembered as the predecessor to spaceplanes of the modern era, particularly the Space Shuttle Orbiter, Sierra Nevada Dream Chaser, and Boeing X-37B.
Artist's depiction of the X-20 with Transtage during flight (USAF)
The fundamental concept of the X-20 was developed by German engineers Eugen Sänger and Irene Bredt during World War II. It was part of the Silbervogel proposal, a study of a rocket-powered bomber capable of launching from Germany and landing in the Pacific. Its wings would generate lift and pull the craft up into a new ballistic trajectory, exiting the atmosphere. During Operation Paperclip, some German scientists with knowledge of this concept came to the United States. Two of them in particular went to work for Bell Aircraft where they proposed a vertical launch version of Silbervogel known as Bomi. Bomi was a series of rocket powered vehicles with the ability to travel long distances by being boosted to a high speed and altitude using a rocket and gliding back down. The booster would place the vehicle on a suborbital trajectory and instead of a full reentry and landing, like the ballistic capsules of the Space Age would undertake, it would use the lift generated from its wings to redirect its glide angle upward, giving the illusion of flight. This way, the vehicle would be bounced back up into space again and continue its journey. This method was called skip-glide and would repeat until the speed of the spaceplane was low enough for the pilot to land it.
Image of the Silbervogel taken from A Rocket Drive for Long Range Bombers
(Public Domain)
In 1956, Bomi had gained enough interest that it was split into three different sections: Robo (ROcket BOmber) was an updated version of Bomi. Brass Bell was a long-range reconnaissance vehicle. Hywards (HYpersonic Weapons Research and Development Supporting system) was a small prototype used to develop and test the technologies needed for Robo and Brass Bell. A few days after the launch of the Soviet Sputnik in 1957, the US Air Force Air Research and Development Command (ARDC) merged those three studies into the Dyna-Soar project, or Weapons System 464L. It drew together the boost glide proposals into a single vehicle that was designed to carry out bombing and reconnaissance tasks for the military. It held the confidential description "Hypersonic Glide Rocket Weapon System", the confidential nickname "Dyna-Soar", and the unclassified title "Hypersonic Strategic Weapon System."
Dyna-Soar program patch (spacefacts.de)
In March 1958, nine aerospace companies competed for the contract to develop and construct Dyna-Soar. In the end, Martin-Bell, the designer of the original Bomi vehicle, was up against Boeing-Vought, and despite Bell's experience, the contract was awarded to Boeing in June of 1959. Martin would stick around to develop the Titan boosters used for launch.
Dyna-Soar had a length of 35.34 feet (10.77 meters), a height of 8.5 ft (2.6 m), and a wingspan of 20.8 ft (6.3 m). Completely empty, its weight was 10,395 pounds (4,715 kg). Its maximum takeoff weight was 11,386 pounds (5,165 kg). The Dyna-Soar's maximum speed was 17,500 miles per hour (28,200 km/h). The airframe had a low wing delta shape and was made from René 41 super alloy. The vehicle had winglets on the back of the wings rather than a conventional tail. The heat shield on the underside of the craft consisted of molybdenum sheets placed over René 41. The nose cone, which was also susceptible to extreme heat during reentry, was made from graphite and zirconia. The vehicle passed the design review on October 27, 1960 and the Air Force signed a contract with Boeing ordering ten "production" spacecraft.
Cutaway of the Dyna-Soar (Public Domain)
Dyna-Soar would sit a single pilot in the front with an equipment bay behind him, housing data collection equipment, weapons, and reconnaissance equipment. A Martin-Marietta Transtage upper stage attached to the aft of the spacecraft would allow orbital maneuvers and launch abort capability. It would be jettisoned before reentry and descent. The Transtage was what the Air Force called the upper stage of the Titan III rocket. Opaque heat shields would protect the windows at the front of the craft and would be jettisoned after aerobraking so the pilot could see outside and land. Dyna-Soar did not have wheels because rubber tires would burn during reentry. Instead, Goodyear Tire & Rubber Company developed retractable skids made from the same René 41 alloy as the vehicle's airframe.
For most of the program's duration, there was uncertainty over which booster would be used for orbital flight. Boeing wanted to use the Atlas-Centaur but Martin wanted its Titan family of launch vehicles. Even though Titan was confirmed by the Air Force in November 1959, the Titan I was not powerful enough to launch the vehicle into orbit. The next option was Titan II and in January 1961, the rocket was approved for orbital launches. Over the next year, though, the Dyna-Soar would continue to increase in weight. A more powerful rocket was needed to efficiently put the spacecraft in orbit. The two choices were the Titan IIIC or the Saturn C-I, which would later become the Saturn I used for early tests of the Apollo program. The Titan IIIC was chosen on December 28, 1961. This was primarily due to the fact the rocket allowed for minimal design changes to the Dyna-Soar since the launch vehicle was essentially a Titan II with a pair of solid rocket boosters. Additionally, the Titan IIIC included the Transtage needed for orbital flight.
Dyna-Soar atop the three different Titan launch vehicles (Reuben Barton via Wikipedia)
Dyna-Soar had advantages over both traditional ICBMs and unmanned spy satellites. Unlike ICBMs, it could attack enemy targets from any direction and could be recalled or retargeted at any point during the mission. This also meant its orbit could not be predicted like traditional satellites, making it harder for the enemy to track it or even know it was there at all. It was also able to pass over enemy targets at a lower altitude than reconnaissance satellites and provide better-quality images. Furthermore, the data acquired would be ready for analysis within a matter of hours, eliminating the long wait involved with capsule reentry, payload recovery, and deliverance of the information.
There were three phases or stages of the Dyna-Soar program. Dyna-Soar I was an unmanned suborbital hypersonic research vehicle. It would have consisted of air-drop flights beginning in March 1963 and single-stage booster flights in 1964. A modified B-52 Stratofortess would have been used for the drop tests of the spacecraft and the Titan I would have been used for launch. Next was Dyna-Soar II, a manned suborbital hypersonic reconnaissance vehicle. It was previously the Brass Bell designed in 1956. Its pilot would monitor automated reconnaissance systems that consisted of a side-looking radar and high-resolution camera. However, it was found that high speeds and high temperatures experienced by the spacecraft would cause problems for the operation of the sensors. Drop tests would have begun in January 1966 with boost tests by the end of 1967. Last was Dyna-Soar III, a manned hypersonic strategic bombardment and reconnaissance system that would have been fully operational by 1974. It was previously the RoBo designed in 1956 as well.
In April 1960, seven astronauts were secretly chosen to pilot the new spaceplane. Their names were Neil Armstrong, Bill Dana, Henry Gordon, Pete Knight, Russell Rogers, Milt Thompson, and James Wood. All of them were part of the X-15 program with the exception of Thompson, who was a civilian at NASA who had previously been part of the program. Armstrong and Dana were also NASA civilian. In mid-1962, Armstrong left the program to join NASA's second class of astronauts. Dana left as well. The Air Force chose Al Crews, who later joined the first class of Manned Orbiting Laboratory astronauts, as their replacement. On September 19, 1962, only two days after Armstrong was announced a NASA astronaut, the names of the six Dyna-Soar astronauts were made public. A few months prior on June 19, Dyna-Soar was given the designation X-20 and an unveiling ceremony in Las Vegas, Nevada.
(back to front) Crews, Gordon, Wood, Thompson, Rogers, Knight with a Dyna-Soar mockup
(image source: spacefacts.de)
1963 was the defining year for the X-20 program. On March 26, Boeing was awarded a $358 million contract to manufacture and test the Dyna-Soar up until its first orbital flight. In June, Edwards Air Force Base in California, Holloman Air Force Base in New Mexico, and Wendover Air Force Bace in Utah were chosen as the vehicle's main landing sites. On September 18, the Air Force launched the first of its ASSET test vehicles. ASSET stood for Aerothermodynamic Elastic Structural Systems Environmental Tests and tested the heat shield of the X-20 prior to launch. All six test articles were launched from Launch Complex 17B on Cape Canaveral in Florida. Later that month, the Air Force announced the development of a new spacesuit at Wright-Patterson Air Force Base in Ohio that was to be worn by astronauts during flight.
Preserved ASSET vehicle at the USAF museum in Dayton, Ohio (US Air Force)
The termination of the X-20 program is mostly attributed to its lack of a clear goal. The original purpose of the project was to combine aerospace research with weapons systems development. However, once it was determined NASA would be responsible for manned spaceflight, people questioned the necessity of the Air Force having its own manned space program as well. The Air Force placed a good deal of emphasis on its development of controlled reentry, which NASA was unable to achieve (only for the time being— the first controlled reentry was performed during Gemini 3 in 1965). Some saw the X-20 as an expensive alternative to other manned systems, particularly NASA's Gemini. On January 19, 1963, Secretary of Defense Robert McNamara told the Air Force to instigate a study to determine whether Gemini or Dyna-Soar was the more feasible approach to a space-based weapons system. He later determined the Air Force had been placing too much emphasis on controlled reentry and had no real objectives for orbital flight. The program was also expensive— costing $410 million dollars in total— and was years away from its first manned flight. Unable to justify the its continuation, the X-20 Dyna-Soar program was cancelled on December 10, 1963, eight months before the first B-52 drop test. The Manned Orbiting Laboratory program was announced the very same day.
ASSET would continue to study reentry heating for high-lift reentry vehicles, particularly for the Winged Gemini concept. The research done for the X-20 program contributed a great deal to the spaceplanes that followed it, specifically Martin's X-23 PRIME, the European Space Agency's Hermes, and of course, the Space Shuttle.
Artist's rendition of ESA's Hermes spaceplane (European Space Agency)
The X-20 Dyna-Soar would also leave its mark on pop culture of the time. In 1959, an early episode of The Twilight Zone, "And When the Sky was Opened", made a reference to the X-20 with a vehicle of the same name and profile that could carry a crew of three. Donald Wollheim released the fifth book in his Mike Mars series, Mike Mars Flies the Dyna-Soar, in 1962. John Berryman wrote the short story "The Trouble with Telstar" in 1963 in which a Dyna-Soar was used to repair a satellite. Perhaps most notable was featured in the 1969 movie Marooned. In the film, a rescue craft called the X-RV, modeled after the X-20, is launched to recover astronauts from their crippled Apollo command module in Earth orbit.
Book cover of Mike Mars Flies the Dyna-Soar (lwcurrey.com)
The Air Force's X-20 Dyna-Soar was a conceptual manned spaceplane that would have been used for a variety of missions, including everything from reconnaissance to strategic bombing. It came about during a period of time when no agency or government power knew what steps to take in space exploration and is one of numerous "whacky" proposals of the early space age. It is one of the most famous rejected manned space concepts and the extent of its impact is evident in the spaceplanes of the modern age. Was the X-20's cancellation a major loss to the space program or was it inevitable? Feel free to tell me your thoughts in the comments and remember to like and share this post. Thanks for reading!
Bibliography
Dorr, Robert F. "X-20 Dyna-Soar Spaceplane was Decades Ahead of its Time." Defense Media Network, 19 Sept 2018, https://www.defensemedianetwork.com/stories/what-might-have-been-x-20-dyna-soar/
LePage, Andrew. “The Future That Never Came: The X-20 Dyna Soar Aerospace Plane.” Drew Ex Machina, 1 May 2019, www.drewexmachina.com/2016/04/10/the-future-that-never-came-the-x-20-dyna-soar-aerospace-plane/.
Wade, Mark. Dynasoar, astronautix.com/d/dynasoar.html.
“X-20 Dyna-Soar - NasaCRgis.” NASA, NASA, 2015, crgis.ndc.nasa.gov/historic/X-20_Dyna-Soar.
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