SpaceX Falcon 9/Dragon COTS Demo (C2+) GENERAL DISCUSSION

[Lobo]

I would also assume that they would want to get a few successful propulsive landings under their belt before trying it with a human crew.

(I sense that this is going off-topic for this mission-specific discussion thread.  Hey, I think I'm starting to get the hang of this place!   )

Agreed on both.  THat's right, the latter F9 will have more margin to handle the additional propellant mass.
And I would think returning COTS Dragon capsules would be a great way to "real-world" test the propulsive landing system.  And they get it that test flight basically for free, as the capsule will be going up on a mission paid for by NASA anyway, so they don't have to have dedicated unmanned test missions.  And if the first one goes "splat" on a dry lake bed at EAFB, it's not a costly issue in terms of either money or lives.  I'd think they'd probably want to be doing that for awhile to build up a record of success before they try it with a crew.  If that record has not been established by the time the first crew is ready to fly on crew-Dragon, then I imagine they'll return via a water landing and recovery until such a time when that record is established and everyone feels comfortable with landing a crew propulsively. 
I wonder if there is a problem in the propulsive descent, if they can switch to backup parachutes?  I would imagine anything above maybe 1000 ft would be enough time for the parachutes to deploy, but even if they do, will the crew be able to survive a non propulsive parachute landing over land?
If SPaceX can figure out a way to design that suvivability into crew-dragon (maybe shock absorbers in the couches, or a crumple zone in the bottom of Dragon, or something?) then I think that would get crews landing propulsively sooner. 

[JNobles]

Since any Dragon with Superdracos will be riding on v.1.1 or later, it's likely that they'll have more margin to work with.  I agree that it makes sense to only have one recovery method.

Didn't they already say they were going to keep the chutes (at least for manned flights) as a backup?

[Jason1701]

Since any Dragon with Superdracos will be riding on v.1.1 or later, it's likely that they'll have more margin to work with.  I agree that it makes sense to only have one recovery method.

Didn't they already say they were going to keep the chutes (at least for manned flights) as a backup?

Yes, of course. The point was that it will increase commonality and reduce costs if both Crew and Cargo Dragons have SuperDracos and nominally attempt a propulsive landing.

[JNobles]

Didn't they already say they were going to keep the chutes (at least for manned flights) as a backup?

Yes, of course. The point was that it will increase commonality and reduce costs if both Crew and Cargo Dragons have SuperDracos and nominally attempt a propulsive landing.

Okay, yes.  I always assumed they would prove out propulsive landing on the cargo flights and then that would become the operating standard for both cargo and manned. 

I am wondering about landing areas though.  So far they've really only talked about VAFB seriously.  If putting up a sign means they are serious.  I guess trucking Dragon back to Hawthorne for refurbishment won't cost that much.

I'm wondering about the first and second stages though.  Are they thinking of landing them on the west coast, refurbishing them there, and trucking them to Texas and then Florida I wonder.  Or are they thinking of landing them on the east coast and doing the refurbishment there?

I'm trying to figure out how all this works with their announced goal of rapid reusability.  I guess we'll find out at a later date.

[rickl]

Didn't they already say they were going to keep the chutes (at least for manned flights) as a backup?

I think they have to, since the Super Dracos are also the launch escape system.

[AS-503]

The parachutes on crewed Dragon are not going away.

If the Dragon aborts how else could it land?

They are integral to the system not optional.

Even if SpaceX perfects propulsive landing with the abort system, the chutes will always be needed to land after the Super Dracos have completed the abort.

[cro-magnon gramps]

one small detail, I think SpaceX will need to ask for NASAs and the ISS Partners permission to experiment with a new landing system, as it is there down mass that will go "SPLAAAAAAT" if there is any problems

[jongoff]

The parachutes on crewed Dragon are not going away.

If the Dragon aborts how else could it land?

They are integral to the system not optional.

Even if SpaceX perfects propulsive landing with the abort system, the chutes will always be needed to land after the Super Dracos have completed the abort.

Not necessarily. It's possible that's the way the trades will work out, but if you're not using parachutes, you don't need as much total impulse for a worst case abort, so having it have enough propellant for the escape and for the propulsive landing may very well be viable. I mean, you may have some sort of insider information, but if you don't, I'd say let's see which way they decide to go, instead of jumping to conclusions.

~Jon

[SiameseCat]

An abort will likely resulting in landing in the Atlantic, not on land. I suspect parachutes might work better than propulsive landing, even if the propellant is available.

[Jorge]

The parachutes on crewed Dragon are not going away.

If the Dragon aborts how else could it land?

They are integral to the system not optional.

Even if SpaceX perfects propulsive landing with the abort system, the chutes will always be needed to land after the Super Dracos have completed the abort.

Not necessarily. It's possible that's the way the trades will work out, but if you're not using parachutes, you don't need as much total impulse for a worst case abort, so having it have enough propellant for the escape and for the propulsive landing may very well be viable. I mean, you may have some sort of insider information, but if you don't, I'd say let's see which way they decide to go, instead of jumping to conclusions.

~Jon

They've publicly stated they're keeping the chutes for crewed launches, no insider information required.

[Lobo]

Didn't they already say they were going to keep the chutes (at least for manned flights) as a backup?

I think they have to, since the Super Dracos are also the launch escape system.

Yea, that'd make for s pretty rough launch abort with no chutes.

[kkattula]

Dragon would need enough propellant for OMS/RCS and propulsive landing.

Abort is high thrust but not a lot of delta-v, so there ought to be plenty left over for landing.

Keeping the chutes as a backup is just sensible, not necessarily mandatory.


Look at it this way: If you've got both chutes and landing engines, wouldn't you still want both to be available after an abort? One or the other might be damaged by shock or debris during the abort. Hopefuilly not both.

[JimOman]

Didn't they already say they were going to keep the chutes (at least for manned flights) as a backup?

I think they have to, since the Super Dracos are also the launch escape system.

I don't recall where, but I remember seeing a SpaceX animation that showed the Dragon riding down on the chutes until around a few thousand feet, then dropping and firing the Draco's for a smooth vertical landing.

[cro-magnon gramps]

this might help people to understand what the narrator on the NTV feed is saying about the various burns;

[sojourner]

I mised it, why are the burns 1 hour behind?

[MP99]

The parachutes on crewed Dragon are not going away.

If the Dragon aborts how else could it land?

They are integral to the system not optional.

Even if SpaceX perfects propulsive landing with the abort system, the chutes will always be needed to land after the Super Dracos have completed the abort.

Not necessarily. It's possible that's the way the trades will work out, but if you're not using parachutes, you don't need as much total impulse for a worst case abort, so having it have enough propellant for the escape and for the propulsive landing may very well be viable. I mean, you may have some sort of insider information, but if you don't, I'd say let's see which way they decide to go, instead of jumping to conclusions.

Would hypergol exhaust in the area be safe in the event of an abort splash landing?

Thinking of Shuttle environment on the runway after a landing.

cheers, Martin

[Lars_J]

Would hypergol exhaust in the area be safe in the event of an abort splash landing?

Thinking of Shuttle environment on the runway after a landing.

I think the toxicity of hypergol exhaust will be quite low on the worry-scale, after having aborted off an exploding LV.

[cro-magnon gramps]

NASA Narrator has been giving time for CE-2 burn as 5:33 am ET, here is correction tweet

NASA ‏@NASA

Correction: Co-elliptic burn at 4:43amET for @SpaceX #Dragon capsule, 2.5km below and 40km behind station, marking beginning of fly under.

[AJA]

Is the Dragon performing attitude changes between HA and CE burns? And an extension of the question - are the thrust vectors for the two kinds of burns orthogonal to each other, or are they both along the r or v-bars?

[Jorge]

Is the Dragon performing attitude changes between HA and CE burns?

Yes, for solar array tracking.

And an extension of the question - are the thrust vectors for the two kinds of burns orthogonal to each other, or are they both along the r or v-bars?

They are both along the +Vbar, more or less.