Dragon 2, from information I have found, has a dry mass of 6,350 kg and carries a total prop mass of 1815 kg including the abort propellant. At an ISP of 300s for the Draco thrusters that's 0.74 km/s bone dry no payload. Well short of returning from anywhere other than L2.Now adding a kick stage of sorts or trunk based propulsion is well within possibility, but not within the scope of the vehicle as designed.
And why not stage from L2? The gateway will be in a similar energy orbit.Just because Apollo used LLO doesn't mean that we should or that it's ideal. Even Orion cannot use LLO unless it leaves LEO with a lander (or similar) attached, which tends to necessitate an expendable lander.I think EML1,2, or a similar energy orbit would be more appropriate for staging as we already have multiple current or near-term vehicles that would be capable of reaching it with minimal modifications (Orion, Dragon, Starliner, Soyuz, possibly even Shenzhou, on top of SLS, Falcon Heavy, Vulcan Heavy or Vulcan with distributed lift, New Glenn, two launch Delta IV Heavy, Proton/Angara, Long March 5, etc).As far as having enough room, Gemini was tiny and the two astronauts spent 2 weeks in LEO. 3 or so days transit (longer for a more efficient trajectory) is not a huge constraint. Dragon has much more room per crew than Gemini. Plenty for cislunar. Same with Starliner.Also, LLO is terrible for staging anywhere but the Moon.
As far as having enough room, Gemini was tiny and the two astronauts spent 2 weeks in LEO. 3 or so days transit (longer for a more efficient trajectory) is not a huge constraint. Dragon has much more room per crew than Gemini. Plenty for cislunar. Same with Starliner.
Cygnus, definitely. Dream chaser... I think so, with some work.
Quote from: Robotbeat on 07/31/2017 11:56 pmCygnus, definitely. Dream chaser... I think so, with some work.Cygnus is probably the easiest commercial vehicle to modify for BLEO use.