CRS2 vehicles as lifeboats for ISS

[J-V]

Both Dragon 2 and Dreamchaser have variants that can - and probably will - use docking for CRS2. Would it be possible to use these cargo crafts as lifeboats for ISS in a case of emergency? Or maybe the correct question would be what kind of modifications would be required to use them in such a way. Seats? Software changes? Life support?

I'm not saying that these should be used as primary evacuation vehicle, but would it make (economic) sense to prepare them for such role also?

[Jim]

no and no

[J-V]

no and no

That's what I thought, but can you elaborate a bit what are the biggest reasons why not?

[rocx]

My guess is that they will not officially have this role, because making spacecraft human-rated takes a lot of time and money. But my guess is that there are some NASA engineers who, sanctioned or not, do some calculations on scenarios where for some reason Soyuz is unavailable and astronauts need to be evacuated quickly.

[rpapo]

And the CRS-2 vehicles will not be outfitted with passenger needs, like seats... and life support.

Even if they use a Dragon 2 or a CST-100 as a cargo vehicle, because they will likely be volume limited for cargo I can't see them flying with seats when flying cargo.  Seats take up space.  Just look at what they do to a jetliner when they are in cargo service.

[J-V]

Are seats needed for a lifeboat? Is something like inflatable cushions and some straps enough? And what is the level of life support needed for just returning to earth? I assume thermal control is there already. How much you oxygen/CO2 scrubbing/moisture control is need?

[Jim]

1.  Are seats needed for a lifeboat? Is something like inflatable cushions and some straps enough?

2.  And what is the level of life support needed for just returning to earth?

3.  I assume thermal control is there already.

4. How much you oxygen/CO2 scrubbing/moisture control is need?

1.  No, need real seat for gloads
2.  Full, deorbit may not happen right away
3.  Not enough
4.  A few hours up to 1/2 day or so

[J-V]

Thanks for the information. Space is hard and humans are soft...

[tva]

I may be wrong but I think Dragon needed assistance of the CanadArm to move away from the station to a safe distance before it could commence any separation burn. Not exactly a lifeboat.

[J-V]

I may be wrong but I think Dragon needed assistance of the CanadArm to move away from the station to a safe distance before it could commence any separation burn. Not exactly a lifeboat.

IIRC this is true for berthing vehicles, but not for docking ones.

[tva]

"SpaceX Dragon completes CRS-6 mission with splashdown"
http://www.nasaspaceflight.com/2015/05/crs-6-dragon-departs-iss-homecoming/

"SpaceX’s CRS-6 Dragon unberthed from the International Space Station (ISS) and was released from the grip of the Station’s “Big Arm” on Thursday"

[J-V]

"SpaceX Dragon completes CRS-6 mission with splashdown"
http://www.nasaspaceflight.com/2015/05/crs-6-dragon-departs-iss-homecoming/

"SpaceX’s CRS-6 Dragon unberthed from the International Space Station (ISS) and was released from the grip of the Station’s “Big Arm” on Thursday"

http://forum.nasaspaceflight.com/index.php?topic=29416.msg1476914#msg1476914

Lindsey: with both docking and berthing options, can go to any port on the station, offer NASA flexiblity in traffic management.
https://twitter.com/jeff_foust/status/688063473570414594

http://www.nasaspaceflight.com/2016/01/nasa-awards-crs2-spacex-orbital-atk-sierra-nevada/

SpaceX – yet to release a statement on the CRS2 award – will utilize its Dragon spacecraft, in two configurations, during CRS2, with both the berthed Dragon spacecraft – as currently being employed during CRS1 – and the upgraded Dragon 2, which can dock directly with the ISS.

[Hotblack Desiato]

My guess, it could be done, but it's the very last chance if everything else fails. There are no seats, and the interior isn't outfitted for humans in non-zero-g environment, and no life support. So something needs to be done, at least a lot of used clothes as a cushion (would be still a very bumpy ride).

There needs to be an emergency landing at a coastline, coast guards anywhere in the world should be able to rescue astronauts from a landed Dragon capsule (DC-cargo should be able to land on any airport, that's easier).

But that's not the worst problem:

For berthed vehicles, we need a hero. Somebody who stays behind in the station and performs unberthing, and in case of not having another opportunity like Soyuz, Dragon2 or CST-100 (why else would someone risk to fly with a cargo craft), that person is done. I don't think, that anyone at NASA would (openly) support such a procedure. It would be a disaster.

[J-V]

For berthed vehicles, we need a hero. Somebody who stays behind in the station and performs unberthing, and in case of not having another opportunity like Soyuz, Dragon2 or CST-100 (why else would someone risk to fly with a cargo craft), that person is done. I don't think, that anyone at NASA would (openly) support such a procedure. It would be a disaster.

In the opening post I mentioned that Dragon2 and Dreamchaser are also flying with docking ports in CRS2. I wouldn't bother even trying with berthed vehicles.

[RonM]

No need to use cargo vehicles for lifeboats. The vehicles the crew arrived in will still be there.

[J-V]

No need to use cargo vehicles for lifeboats. The vehicles the crew arrived in will still be there.

One motivation to start this thread was to understand if there was a cheap way to use the docking CRS2 vehicles as redundant lifeboats in case the actual crew vehicles are not operational for some reason.

[RonM]

No need to use cargo vehicles for lifeboats. The vehicles the crew arrived in will still be there.

One motivation to start this thread was to understand if there was a cheap way to use the docking CRS2 vehicles as redundant lifeboats in case the actual crew vehicles are not operational for some reason.

1.  Are seats needed for a lifeboat? Is something like inflatable cushions and some straps enough?

2.  And what is the level of life support needed for just returning to earth?

3.  I assume thermal control is there already.

4. How much you oxygen/CO2 scrubbing/moisture control is need?

1.  No, need real seat for gloads
2.  Full, deorbit may not happen right away
3.  Not enough
4.  A few hours up to 1/2 day or so

As you can see from Jim's response, there is no cheap way to do it. Sure, it can be done, but at a loss of cargo space and then the need for more flights to resupply ISS. That would be expensive.

A scenario resulting in abandoning ISS and having one of the crew vehicles non operational is extremely unlikely.

Now if a docking CRS2 Dragon is just a reused crew Dragon stuffed with cargo bags, then it might not be a big deal to leave the seats in and have the life support ready. But what are the odds a scenario resulting in abandoning ISS and having one of the crew vehicles non operational and having a CRS2 docked at the same time? Now that's really a stretch.

[Jim]

One motivation to start this thread was to understand if there was a cheap way to use the docking CRS2 vehicles as redundant lifeboats in case the actual crew vehicles are not operational for some reason.

This has been discussed ad nauseum for the existing Dragon.  There isn't much difference other than docking.

[rayleighscatter]

For berthed vehicles, we need a hero. Somebody who stays behind in the station and performs unberthing, and in case of not having another opportunity like Soyuz, Dragon2 or CST-100 (why else would someone risk to fly with a cargo craft), that person is done. I don't think, that anyone at NASA would (openly) support such a procedure. It would be a disaster.

Actually, is there a function of unberthing that can't be done from the ground?

[rpapo]

I can easily imagine a scenario where the ISS has lost power and the bolts that hold the berthed capsule cannot be withdrawn, since they are driven from the ISS side.  AFAIK, the docking hardware was designed to deal with such situations.

Or do I misunderstand the berthing port design?

[abaddon]

You can come up with a contrived scenario where something like this might be possibly useful as a last-gasp effort.  But realistically it's probably more likely useful for getting a body back for burial rather than having it floating around in space or burning up on reentry.

I could use it for a Hollywood script but it wouldn't have much use in the real world.