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A recent Government Accountability Office (GAO) report has cast doubts on the ability of the Orion MPCV to meet its requirements on its already excessive budget. Orion has been in development since 2006 and will likely continue until 2023 with costs in excess of \$20 B before crew fly on it.

As I understand the commercial crew contracts SpaceX is to receive up to \$2.6 B and Boeing is to receive up to \$4.2 B for design development and testing of the Dragon 2 and Starliner. So what I am wondering is what modifications would be needed to be made to these spacecraft to let them fly beyond LEO say to cis-lunar space. Necessary modifications I can think of include: life support systems to allow longer missions, radiation protection for crew and radiation hardened electronics, larger heat shield to allow for much faster reentry, and more robust structures for greater g-loads upon entry. Would it be possible to modify the current designs to include these requirements or would these changes require the the development of an entirely new spacecraft which would be about as expensive as the Orion?

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    $\begingroup$ The answer here space.stackexchange.com/questions/8307/… says that the heat shield of a Dragon 2 could resist reentry from a lunar mission. I would say that it will be much more easier and a lot less costly to modify them than starting new projects with new spacecrafts. $\endgroup$ – Mark777 Aug 1 '16 at 22:53
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The ISS crew cargo craft do not have real facilities for long term stays. There is no washroom for example.

Of course any serious beyond-LEO mission in a capsule will likely include a hab module of some kind which is not something CST-100 or Dragon is excluded from.

Gwynne Shotwell in discussing Red Dragon mentioned that deep space communication systems was one of their big issues.

SpaceX claims their heat shield is over designed for LEO reentry with sufficient margin for higher energy return missions. How high, I am sure they will experiment to find out on some mission.

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  • $\begingroup$ Yes, but how is this any different from the Orion. $\endgroup$ – SpacePaulZ Aug 2 '16 at 13:26
  • $\begingroup$ The ISS crew cargo craft do not have real facilities for long term stays - that is if you exclude Soyuz. It's been on successful manned multi-week missions long before ISS was created. $\endgroup$ – SF. Oct 28 '17 at 7:54
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It is the volume problem that must be solved to leave LEO. LEO means you can be resupplied and abort back to Earth in an emergency. With Cis lunar or farther you have a series of non-linear scaling problems that go in a step-wise fashion that greatly increase mass and volume required to "bring everything with you". Neither of these can be expanded in a way that is meaningful, regardless of the good points on limitations the comments point out like radiation shielding. In order to solve the volume and mass problem, given the rocket equation and the limitations it places on launches and mass to orbit on each launch, there is basically no way to build a deep space capable craft without making it in section and assembling it in LEO just like the ISS. Once the parts are all together and proven to function, more supplies and fuel need to be sent up, along with an second propulsion module because one failure that leads to total loss of propulsion that far away leads to total loss of crew, which is unacceptable. Same goes for other critical functions, so you must bring spare parts and the tools and expertise to replace them. On the ISS they remove and replace, sending back to Earth for repair, not an option for far beyond LEO. Estimates for a 900 day journey (to allow the planets to align and use reasonable fuel) requires about eight fully loaded Cygnus extended capacity missions, which carry 3500 KG and are 25 m^3 each all connected together. This means that even if the Boeing or SpaceX capsules could be connected together in this way, they would need about the same of them 8-10 all connected together. This does NOT allow for MARS habitats on the ground or ascent/descent vehicles. Lets say we almost DOUBLE the mass and volume needed for that. That makes 8-9 missions sent three years in advance to pre-position in Mars orbit THEN 10 launches assembled in LEO to go with a crew of 6. So, NO, they cannot be expanded in a meaningful way to allow the occupants to live beyond LEO without another 10 missions all connected together to support.

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  • $\begingroup$ Can you add some links (to the 900 day journey estimate, for instance)? $\endgroup$ – Hobbes Oct 28 '17 at 7:36
  • $\begingroup$ I don't have a link because it is copywritten. It is from my SYS-635 Class. The reference is from the Orbit Design Module of Human Spaceflight Mission Analysis and Design, by Dr. Wiley Larson, ISBN 978-0-07-236811-6, chapter 9, table 9-12 through 9-15. Phasing of planetary orbits make it such that there are only launch windows 7 times every 26 months in repeating 15 year cycles. Table 9-12 show the lowest delta V requirement is average 8.5 Km/sec and requires a long mars stay on the next launch date of 7/27/20 with outbound duration of 207 days, Mars stay of 517 days and 203 day return. $\endgroup$ – Joe B Oct 28 '17 at 15:54
  • $\begingroup$ Using the same launch years Table 9-13 shows 12.515 Km/sec Delta V with a total duration of 864 days launching on 8/20/20. Table 9-14 shows 450 mission days with a mars stay of 40 days and 15.943 Km/sec. This is the shortest possible mission duration. One mission option is a Venus gravity assist to lower the delta V back down to 10,832 Km/sec but the mission duration is still 594 days with a launch date of 6/9/20. $\endgroup$ – Joe B Oct 28 '17 at 15:54

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