[SHB] The Return of the Apollo Shape

[Orionid]

The Return of the Apollo Shape
Posted by David S. F. Portree on 5/25/2022


An Apollo-derived crew module lands in the desert at the end of a 1975 piloted Mars flyby mission in this NASA concept art from 1967. To save weight and volume, this design would have used solid-propellant rocket motors to cushion landing. Image credit: NASA

As I type this, we're 10 minutes past Starliner's return to Earth at the end of Orbital Flight Test-2 (OFT-2). The six-day Starliner mission to the International Space Station (ISS) marks a big step in the triumphant return of the iconic broad conical shape last employed for piloted spaceflight in the United States in July 1975, when the last Apollo spacecraft splashed down in the Pacific Ocean at the end of the Apollo-Soyuz Test Project (ASTP) mission.

Mind you, the OFT-2 Starliner spacecraft is not the first Apollo-shaped capsule to fly since ASTP. I'll describe a little-known non-U.S. example at the end of this post.

OFT-2 was, as its designation indicates, Starliner's second flight. Its first flight, OFT-1 in December 2019, was, however, a disappointment; software trouble meant it failed to reach ISS. If OFT-2 turns out to have been as successful as it appears, Starliner will become the first Apollo-shaped spacecraft since ASTP to carry a crew later this year.

Another U.S. Apollo-shaped capsule flew briefly nearly eight years ago. Orion orbited Earth twice without a crew for about four and a half hours and splashed down in the Pacific in December 2014. An Orion spacecraft is expected to swing around the Moon during an automated test flight as early as this year. Orion could carry a crew around the Moon by 2025.

We have a lot of data on the behavior of the Apollo shape, so it's a natural choice for an advanced piloted capsule. In fact, if NASA had been given the opportunity, it almost certainly would not have abandoned the Apollo shape. In the form of Apollo-derived spacecraft, it might have been used to return crews from a second Skylab mission, additional lunar missions, or from planetary missions. It might even have been scaled up to make a piloted Mars lander if NASA's 1960s piloted Mars mission plans had gone ahead. For a time in the 1980s, it was the preferred shape for a U.S.-built Space Station lifeboat.

I wrote a post about using the Apollo shape as the basis for a family of piloted crew and automated cargo Mars landers:

http://spaceflighthistory.blogspot.com/2015/09/the-martian-adventure-gumdrops-on-mars.html

If NASA had been given the opportunity, modified Apollo capsules would have set down on land in the Apollo Applications Program (AAP) in the late 1960s and 1970s. In fact, most advanced missions NASA studied that used the Apollo shape assumed a switch from splashdowns to land landings.

Cost played a major part in that choice. A land landing would not need a large recovery fleet, so would be cheaper. Not dunking the capsule in salt water would reduce corrosion, making money-saving reusability easier. NASA Associate Administrator for Manned Space Flight George Mueller discussed land landing and salt corrosion in this post I wrote about the state of AAP in January 1967:

https://spaceflighthistory.blogspot.com/2015/07/before-fire-nasas-26-january-1967.html

It's worth noting that the Apollo-Soyuz Test Project mission was not the last time before the December 2014 Orion test that a conical capsule with Apollo proportions flew in space. The Soviet Union began development of the TKS spacecraft in 1964 as part of its Almaz space station program. The TKS included an Apollo-shaped crew capsule attached to a space station module.

TKS capsules flew in pairs without crews in December 1976, March 1978, and May 1979. A TKS capsule attached to a space station module first reached orbit during the Cosmos 929 mission in July 1977; the capsule, without a crew, performed a land landing in central Asia the following month.

The TKS capsule never became an operational part of the Soviet space program. The space station module component, by contrast, became the basis for space station modules that docked with Salyut 6, Salyut 7, Mir, and the International Space Station.


The Apollo-shaped Boeing Starliner capsule approaches the International Space Station for the first time during Orbital Flight Test-2 on 20 May 2022. Image credit: NASA

Source: http://spaceflighthistory.blogspot.com/2022/05/the-return-of-apollo-shape.html