In article ,
says...

On 2020-01-04 10:40, Jeff Findley wrote:

No, because that propellant is needed in case of a launch abort.

I was asking on whether propellant used for abort = propelland needed
for propulsive landing. Aka: had SpaceX been allowed propulsive landing,
would the fuel tanks for the super dracos have been bigger?

No. I clearly explained this in detail, but here it is again:

If the propellant is used for abort, there is none left for propulsive
landing. Which doesn't matter anyway, because an abort puts Dragon 2
over the ocean anyway. So in an abort, you'd use parachutes and splash
down in the ocean.

With regards to landing gear: I have to wonder if that might not have
been the show stopper for NASA. Mechannically deployed landing legs seem
like a accident begging to happen if one fails to deploy/lock.

It wasn't.

BTW, did the shuttle crew have cranks to manually lower the landing
gears like on planes at some point in time? Or is the time between
landing gear deployment and touching ground so short that it was
pointless to add manual gear deploy cranks?

No. In a contingency (e.g. no hydraulic power to lower the landing
gear), there were pyros which would operate what amounted to pneumatic
cylinders which would force the gear down. Clearly "one time use", but
in an emergency, it's better than crashing into the runway without
landing gear.

Note that the orbiters could NOT safely belly land due to the thermal
tiles literally "digging into the runway" and creating way too much
friction. Simulations indicated this would cause the orbiter to
pinwheel out of control and off the runway. So if all three landing
gear did not deploy *and* lock, it was a "very bad day" (loss of orbiter
and crew).

a propulsive landing. In the event of a launch abort, Dragon 2 would
have used parachutes to splash down in the ocean.

Can Starliner launch over land if after an abort, the combination of
parachutes and inflatable mattress lets it land anywhere?

Doesn't matter because Atlas V would never be allowed to launch over
land. Dropping stages on land is something that only Russia and the
Chinese do. All other countries drop their expendable stages in the
ocean.

insertion propellant. And in the case of a complete failure of
Starliner to perform that orbital insertion burn, it will simply reenter
as Atlas V puts it into an orbit whose low point is within the earth's
atmosphere.

So in the context of the recent Starliner test launch, how long after it
detached from Atlas and failed to activate orbit insertion engines,
would Starliner have re-entered? a few orbits or at the next perigee?

As I said, the low point of the orbit was *inside* the atmosphere. So
it would reenter without really completing that single orbit.

Just curious how close to re-entry the ship was at the time ground
control re-established contact with it and started to "fix" it. I take
it a "confused" ship left to its own devices would have re-entered with
its service module still attached and not have realised it was
re-entering and not deployed parachutes?

(since its software seems so based on a timer).

In retrospect, the decision to have Atlas V *not* put Starliner into a
"stable orbit" was a bad one. But, it was a trade based on all the
possible failure scenarios and it automatically put the Centaur upper
stage on a destructive reentry so that there was zero chance it would
not destructively reenter.

Jeff
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