SpaceX COTS Demo 1 Updates

[Lars_J]

Possibly... Although I think we are moving off topic for this "COTS Demo 1" thread. This discussion should probably move to the general SpaceX discussion thread.

[Lars_J]

What do people give odds for successful reentry and recovery of COTS Demo 1 Dragon, assuming it gets to orbit?

90% would be my odds... But what do I know!  Parachute deployment seems like the biggest risk element to this uninformed observer. 

[hop]

I thought all systems on a "man rated" spacecraft had to be triple failure tollerant, so, are there already backup chute systems designed into Orion/Soyuz today?

Soyuz has a backup chute. IIRC it's a bit smaller than the main, so the landing won't be gentle. And as always with reserve chutes, you better hope the main is out of the way.

[savuporo]

And as always with reserve chutes, you better hope the main is out of the way.

Which, IMO, again makes the case for personal parachutes, rather than a backup capsule chute.
Well known technology, proven every day by thousands of people all over the world, and quite safe. Especially because every rig ( save for base-jumping ones ) comes with a reserve.

Increases the chances of individual survival for the entire crew, IMHO.

[SpacexULA]

Which, IMO, again makes the case for personal parachutes, rather than a backup capsule chute.
Well known technology, proven every day by thousands of people all over the world, and quite safe. Especially because every rig ( save for base-jumping ones ) comes with a reserve.

Increases the chances of individual survival for the entire crew, IMHO.

Up to 6 people, out of a hole no more than 2x2 feet wide, while wearing pressure suits, out of a possibility wildly gyrating, supersonic capsule, into a pressure bubble which would be located at the top of the capsule....

From the time the chutes attempt to deploy to impact with the water would be what?  2-3 minutes?  Given some time for attempts at redeployment and the speed the capsule would be falling, and how long it will take for them to unfasten themselves and get out the hole, I just don't know how any of them would survive the attempt.

[jimvela]

And as always with reserve chutes, you better hope the main is out of the way.

Which, IMO, again makes the case for personal parachutes, rather than a backup capsule chute.
Well known technology, proven every day by thousands of people all over the world, and quite safe. Especially because every rig ( save for base-jumping ones ) comes with a reserve.

Increases the chances of individual survival for the entire crew, IMHO.

How many of those thousands of jumpers per day have spent six months in zero gravity before attempting the jump?

If it were my butt in the capsule, I'd want a reserve on the capsule along with a robust, redundant way to cut the primary and deploy the secondary.  I wouldn't want to try and bail out after extended zero G exposure.

[Lars_J]

Exactly... Trying to add personal parachutes and hope that people can get out is just a non-starter.

There's a reason why no capsule since Vostok has implemented such a scheme. (or were Gemini crew capable of ejecting if the parachute failed?)

[simonbp]

And the first three shuttle missions...

[savuporo]

Previous zero-g exposure is a valid point. I probably wouldn't be keen on jumping after floating around that long either, otherwise it would be a nice thrill.

But then, we are talking about last resort, all else failed attempt with the only alternative of hitting water at 300kph.
Note : reserve parachute of a capsule does not get tested every day, while i standard gear from Performance Designs and the like does, and ( almost ) never fails.

[Lars_J]

And the first three shuttle missions...

Yes, but the question was about capsules. The Shuttle has no main parachute that can fail.

[corrodedNut]

The Vostok ejection seat wasn't just for emergencies, it was used on nominal decents.

SpaceX uses three mains for the same reason Apollo and Orion did/will; only two are needed the third is the redundant/backup.

[mduncan36]

7 skydivers can exit a plane in 2-3 seconds. Even with this being more difficult in freefall, if you start jumping at 15000feet ( regularly considered safe jumping altitude ) that gives you quite a bit of time to get out.

Yes, but those skydivers are standing in an open doorway. They don't have to climb over each other and squeeze out of a pressure hatch after six months of zero gravity. In the Dragon you would have a difficult time just getting two people to the door at the same time. Much better to put your backup chute on the capsule. Dragon has three and only needs two for a safe landing. A single open chute would probably make for a survivable if not entirely healthy landing on water. Apollo 15 landed with only two good parachutes and the impact wasn't even severe enough to dislodge the Hassleblad camera that Jim Irwin was gripping between his knees at the time. That is a risk I would much rather take than any attempt at a bailout from a spinning, rapidly descending, crowded, capsule.

[go4mars]

7 skydivers can exit a plane in 2-3 seconds. Even with this being more difficult in freefall, if you start jumping at 15000feet ( regularly considered safe jumping altitude ) that gives you quite a bit of time to get out.

Yes, but those skydivers are standing in an open doorway. They don't have to climb over each other and squeeze out of a pressure hatch after six months of zero gravity. In the Dragon you would have a difficult time just getting two people to the door at the same time. Much better to put your backup chute on the capsule. Dragon has three and only needs two for a safe landing. A single open chute would probably make for a survivable if not entirely healthy landing on water. Apollo 15 landed with only two good parachutes and the impact wasn't even severe enough to dislodge the Hassleblad camera that Jim Irwin was gripping between his knees at the time. That is a risk I would much rather take than any attempt at a bailout from a spinning, rapidly descending, crowded, capsule.

But as back up number 3, If the main chute fails, and the reserve chute gets tangled in the main chutes or something, it would sure feel good to have a 24V sawsall and a backpack parachute.   Personal parachute is an interesting idea, and bears consideration since they are relatively small and light.  Like landing habs on Mars.  Save the powered decent for just the people, and land the habs, etc. at higher gforce, built tougher.

[someguy]

I don't really get this whole discussion. Sometimes there are just unrecoverable situations. At a certain point you have as much redundancy as can be reasonably added, beyond which you don't really get more safety. I think personal parachutes are beyond this point, especially due to the difficulty of ever being able to reasonably use them.

[butters]

I suppose it wouldn't be too difficult to implement a parachute deploy system that runs on its own dedicated battery and altitude/velocity instruments.  Skydivers use a similar system. 

If everything else fails during entry, then all that has to work for a survivable landing is the parachute system, so why not make it completely independent of the main avionics systems?

For all we know, this could be what SpaceX is doing.  Did the drop test Dragon capsule contain flight-spec rechargeable batteries and flight computers, or was it just a mass simulator with a simple independent parachute system like I describe?

[Chandonn]

Guys, we need to get this thread back on topic and take the discussion to teh SpaceX Discussion thread...

http://forum.nasaspaceflight.com/index.php?topic=22769.msg653494

[Toner Soprano]

Guys, we need to get this thread back on topic and take the discussion to teh SpaceX Discussion thread...

http://forum.nasaspaceflight.com/index.php?topic=22769.msg653494

Another SpaceX music video posted:  http://spacex.com/multimedia/videos.php?id=54

It looks like the Dragon drop test put to music. 

[Robotbeat]

Guys, we need to get this thread back on topic and take the discussion to teh SpaceX Discussion thread...

http://forum.nasaspaceflight.com/index.php?topic=22769.msg653494

Another SpaceX music video posted:  http://spacex.com/multimedia/videos.php?id=54

It looks like the Dragon drop test put to music. 

It looks a lot like the chutes are stored in the ring outside the pressure vessel but just above the heat shield.

[ugordan]

It looks a lot like the chutes are stored in the ring outside the pressure vessel but just above the heat shield.

Hasn't that fact been established a long time ago?

[Robotbeat]

It looks a lot like the chutes are stored in the ring outside the pressure vessel but just above the heat shield.

Hasn't that fact been established a long time ago?

Probably, but I didn't realize it.