Space Onion: Chrysler Single-Stage Earth-Orbital Reusable Vehicle (SERV)

The Single-Stage Earth-Orbital Reusable Vehicle (SERV) was a conceptual reusable vertical takeoff and landing (VTOL) vehicle developed by the Chrysler Space Division for NASA's Space Shuttle program in the late 1960's. It consisted of a single-stage to orbit (SSTO) booster that could reach orbit, deploy a crew or cargo vehicle, and return to Earth ballistically to land at its original launch site.

Artist's depiction of the SERV during launch (Chrysler Corporation)

Unlike other Space Shuttle proposals of the time, Chrysler's did not consist of a winged orbiter. At least, not really. The first version was developed in November 1969 and submitted to NASA during Phase A of the agency's shuttle competition. Known for their automobiles, Chrysler also built the Redstone rockets used by NASA to send the first two Americans into space as well as the S-IB, the first stage of the Saturn IB rocket at the Michoud Assembly Facility in New Orleans, Louisiana. Now that the facility was no longer constructing Saturn boosters as a result of the Apollo program winding down, the corporation could use it to build the SERV. The company's Space Division last participated in spaceflight in 1975 when one of its Saturn IB rockets launched the American segment of the Apollo-Soyuz Test Project.

The Manned Upper-Stage Reusable Payload (MURP) was a manned orbiter to be constructed by McDonnell Douglas. It had no real cargo capacity and was to be used mostly for crew. It was a winged spacecraft based on the HL-10 lifting body NASA had been working on since 1966. It also came in two different sizes— the D-34 had about 279 cubic feet (85 cubic meters) of internal space while the smaller D-10 had only 16.4 cubic feet (5 cubic meters) with a cylinder at its end for more space. Both could carry a crew of two and up to ten passengers. It used only a small amount of fuel since the SERV would do most of the heavy-lift work. For heat protection, the MURP would be covered with a spray-on silicone ablative skin that could be peeled off and re-sprayed after every trip. It would also be able to land at virtually any landing strip if long enough.

NASA's HL-10 lifting body in 1966 (NASA)

The SERV was an SSTO booster with an enormous cargo bay. The MURP would sit on top of the SERV. Once in low Earth orbit (LEO), the booster would separate from the MURP and return ballistically to Cape Canaveral, Florida, where the whole process would start over again another 99 times. It would have been only 126 feet (38.5 m) tall by 92 feet (28 m) wide. For comparison, the Space Shuttle stack was 169.3 feet (51.6 m) tall. Since it returned to Earth ballistically, it had the same blunt end shape as the Apollo spacecraft. Its underside was made of a similar silicone ablative material embedded in a metal honeycomb framework like the Gemini B spacecraft that would have been used for the Air Force's Manned Orbiting Laboratory program. With this method, worn-out or damaged sections could be swapped out for repair and refurbishment like tiles on the Space Shuttle Orbiter.

The SERV also would have used the undeveloped aerospike nozzle. Typical exhaust nozzles on rocket engines are bell-shaped and lose efficiency if burning at a higher or lower altitude than what they are specifically tuned for. Aerospike engines had inverted bell shapes and therefore operated at a much higher efficiency. Additionally, they would have had a combined 32 kilonewtons (kN) of force compared to the three Space Shuttle Main Engines that produced only 1.9 kN. The Energia rocket RD-170 engines, the most powerful liquid fuel engines ever actually built, produced 7.9 kN. The SERV could lift 39 tons of payload to LEO. Chrysler pointed out that the SERV had the potential to be a suborbital "space airline" between major cities but ticket prices reflected the price of fuel per flight.

Drawings of the SERV in action (reddit)

For Phase B of the Shuttle proposals in 1971, Chrysler added more modules that could be mated to the top of the SERV. One was a ballistic passenger capsule similar in shape and size to the Apollo spacecraft but smaller than the D-10 version of the MURP. Another was a nuclear-rocket launched upper stage for heavier moon and Mars trips.

One problem it faced was not having an accurate enough landing system. On ballistic reentry it could aim for an area about 9.3 miles (15 km) in diameter but NASA needed it to be more precise. Chrysler decided to put a ring of 28 jet engines underneath the spacecraft so it could get within 246 feet (75 meters) of its aim point. Two special landing pads would have been built at Cape Canaveral next to the vehicle's maintenance buildings on the shore of the Banana River.

Schematic diagram of the SERV with MURP on top (NASA)

If awarded the contract on January 1, 1973, Chrysler predicted the first test flight of the SERV would take place at the end of 1977. The first operational flight of the entire system would occur in the first few months of 1978. The total cost of flying four SERVs with three MURPs would have been $10.01 billion.

Although the SERV and MURP had a number of advantages over other spaceplanes submitted to NASA and did make it through both proposal phases, it was never seriously considered by the agency. Its main failing point was its lack of support— most people at NASA agreed a traditional spaceplane was the way to go. Astronauts did not appreciate how it could fly unmanned cargo missions while engineers were concerned about its SSTO characteristics and aerospike engine. It also failed to meet NASA's required engine characteristics and needed technology that was not ready at the time. The Space Shuttle went years over time and a billion dollars over-budget as it was, and the SERV was even more complex and expensive. Another factor was NASA's years of studies with other spaceplanes like ASSET, the X-15, and the HL-10 (see: Hidden Histories: X-20 Dynamic Soarer).

What ultimately made the SERV fail was its audacity. Like many impressive space vehicle concepts of the era, it was too complex and technologically ahead of its time. However, Chrysler's final space proposal has not entirely been lost to the sands of time— remnants can be seen in SpaceX's Starship. To most people, though, the SERV is no more than an odd-looking drawing on the back of a Kennedy Space Center exhibit.

The SERV depicted on the back of the glass case that holds the first Space Shuttle Orbiter model constructed by Max Faget in 1969 at KSC's Atlantis building (Aeryn A.)

Author's Note: Thanks for reading and be sure to like and share this post!

---

Bibliography

• Drye, Paul. “SERV/MURP: Chrysler's Space Truck.” False Steps, 7 Sept. 2012, falsesteps.wordpress.com/2012/08/18/servmurp-chryslers-space-truck/.

• Reindl, JC. “Chrysler Tried to Build a Better Space Shuttle; NASA Said 'No'.” Detroit Free Press, 9 Mar. 2019.