Capsules are heavy, but necessary.
Or at least, they are necessary for launch, landing, and stays in space lasting more than an hour or two.

But it is possible to imagine situations where cosmonauts would want to move quickly from one location to another, with a high relative velocity, where both the origin and the destinations have shelters. An example would be boarding an interplanetary cycler as it flies by.

For a "taxi" spacecraft, mass could be saved by eliminating the crew capsule. "The crew dresses up in EVA suits and grabs on to the rocker".

Understandably, no mission profiles to date have been suitable for such spacecraft. Almost all manned traffic is up and down to LEO, which requires a capsule. The exception would be Apollo, but there were no shelter infrastructure for it to take advantage of, instead minimizing risk by flying everything in a single stack.

The Lunar Escape System was such a capsule-free proposal, but it was only considered for emergency use.

Has such a capsule-free spacecraft ever been seriously proposed for regular use?

  • $\begingroup$ What about the MMU? Would that satisfy your criteria? (And subsequently, SAFER?) $\endgroup$
    – Polygnome
    Oct 22, 2020 at 17:41
  • $\begingroup$ @Polygnome Not really, since they are neither high impulse, nor intended to reach some other destination. But good point. $\endgroup$ Oct 22, 2020 at 17:44
  • $\begingroup$ I have to wonder just how ridiculous a chemical-power MMU would be. $\endgroup$
    – ikrase
    Oct 22, 2020 at 19:27
  • $\begingroup$ Two notes: first, can't EVAs last a lot longer than 2 hours? Second, how high is high relative velocity? Most descriptions of these vehicles I've seen (pressurized or no) have been fairly low delta-V (hundreds) and intended more to cover moderate distance than to handle relative velocity. Of course you do see insanity in science fiction like Alistair Reynolds' nuclear thermal rocket taxi. $\endgroup$
    – ikrase
    Oct 22, 2020 at 19:31
  • 6
    $\begingroup$ About 20 years ago, a design for an open style Lunar transport platform was being proposed by one of the bigs for crew travel across the Moon's surface. I can remember John Young railing against the concept - he did not like the idea of a space suit being the only thing between a crew member and an MMOD hit. Trouble was, old John was usually right... $\endgroup$
    – Digger
    Oct 22, 2020 at 19:35

1 Answer 1


What you are describing is pretty much a space tug. Examining that web page, those which were proposed during the Apollo era had a proper crew compartment, and during the Shuttle era and later were uncrewed. So the answer appears to be "no".


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