David Masten wrote:
The suspicion that an incident during the ascent of Columbia contributed
to its demise during re-entry leads to a few things that a successful
private space transportation system must address. (NASA should also
address these things, but I won't hold my breath.)
1. The vehicle must be simple enough to fix "in the field", or at least
jury-rig something that will get them to safety.
I suspect this would be a byproduct of, and perhaps a more measurable
(during design) milestone of, keeping it simple to keep design and
manufacturing costs down.
2. The crew should have the ability to get out and do a visual and
tactile inspection.
Include, as standard equipment for each crew member, EVA suits that are
normally worn at all times. (This would be more suitable for shorter
missions, say no more than three orbits/four and a half hours,
especially if used instead of life support equipment that covers the
entire manned volume.) Also an airlock, with places to clip safety
tethers on the outside (or, if EVA-capable suits are always worn, a
simple hatch, with tether mount points for the suits inside the bird).
I've been mulling a hardsuit like NASA's discontinued AX-5, or the
marine "Newt Suits", but with proper hands - but such things would not
be usable to us until we start sending people up, which won't be for
quite a while yet, so mulling is all I've done on this. (Such suits
would need to be adjustable for the passengers; fortunately, the AX
series had a provision for just that - though the extremely small, or
the extremely large in any of the three dimensions, would have trouble.)
3. The crew should have the tools and parts to do simple repairs (such
as patching/replacing thermal tiles).
Determine what these tools and parts are, and bring along a patch kit.
Possibly include a 3D printer, if you can find or make one that can
operate in orbit (in vacuum, if the vehicle is not pressurized) and can
handle the ship's structural materials, to fabricate oddly-shaped pieces
of hull, or just make most of the hull parts standardized enough that
only a few spares are needed (though I think this might be very
unlikely, given the other, more important constraints on the hull).
4. There should always be another vehicle ready for (and capable of) a
rescue mission.
A natural consequence of an RLV program: cost per unit manufactured
matters a lot more if you build a lot of birds than if you just build
one. It makes economic and safety sense to have more birds than you
have customers for (if one breaks down, send up your customer on one
that isn't broken instead of waiting for the fix). It would be a huge
PR boost to send up one of our craft to bail NASA, or whomever else, out
when theirs breaks down in orbit - though this would hopefully be a rare
event. (If nothing else, if we do wind up rescuing them a lot, why not
just use our vehicles to begin with?)
How practical is it for a future space transport system to have these
capabilities? How practical is it to not have these capabilities?
A bit leading, but obviously NASA thought it was practical not to have
them. However, it's more than sheer practicality that would drive such
things. Consider a commercial spinoff of ERPS vs. a competitor that
doesn't bother with such safety systems: "Statistically, you are much
less likely to die if you ride with us than if you ride with them, and
here's why." Somehow, I just see that really mattering to most space
tourists, you know? ^_-
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