Author Topic: Using a cargo spacecraft as a rescue spacecraft for crew  (Read 3258 times)

Offline yg1968

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I am pretty sure this has been discussed before but I am having a hard time finding the prior discussions on it.

Here is the question: in an emergency, could a cargo Dragon 1 or 2 or a cargo DC be used as a rescue spacecraft (for the descent from ISS to Earth) without any modifications to it?

I imagine that it could be done if the astronauts used a spacesuit of some kind.

Offline Coastal Ron

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Re: Using a cargo spacecraft as a rescue spacecraft for crew
« Reply #1 on: 05/20/2018 04:18 pm »
I am pretty sure this has been discussed before but I am having a hard time finding the prior discussions on it.

Here is the question: in an emergency, could a cargo Dragon 1 or 2 or a cargo DC be used as a rescue spacecraft (for the descent from ISS to Earth) without any modifications to it?

I imagine that it could be done if the astronauts used a spacesuit of some kind.

Elon Musk has stated that a Drago Cargo vehicle could be used, and I think his point was that the return-to-Earth profile of a Dragon Cargo vehicle would not be injurious to humans.

No doubt you'd need an air supply and something soft to lay on, but in an emergency you have to work with what you have.
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Offline yg1968

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Re: Using a cargo spacecraft as a rescue spacecraft for crew
« Reply #2 on: 05/20/2018 04:22 pm »
Would you have to use an EVA suit?

Offline brihath

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Re: Using a cargo spacecraft as a rescue spacecraft for crew
« Reply #3 on: 05/20/2018 04:25 pm »
I would be surprised if the Dragon 1 and DC cargo vehicles have an environmental life support system configured to support crew.  Anyhow, the ISS VV schedule is built to have enough vehicles to act as life boats for all crew members.

Offline geza

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Re: Using a cargo spacecraft as a rescue spacecraft for crew
« Reply #4 on: 05/20/2018 04:28 pm »
I am pretty sure this has been discussed before but I am having a hard time finding the prior discussions on it.

Here is the question: in an emergency, could a cargo Dragon 1 or 2 or a cargo DC be used as a rescue spacecraft (for the descent from ISS to Earth) without any modifications to it?

I imagine that it could be done if the astronauts used a spacesuit of some kind.
Spacesuit is useless w/o a  compatible life-support system. Suit support is usually integral to the s/c, so you cannot find one for the cargo Dragon in emergency. On the other hand, if the Dragon deorbits soon after hatch closing, cabin air (probably) will be sufficient w/o life support and no need for suit. Lack of seats makes the g-s inconvenient...

Offline SweetWater

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Re: Using a cargo spacecraft as a rescue spacecraft for crew
« Reply #5 on: 05/20/2018 04:43 pm »
I was going to suggest that astronauts might get knocked around quite a bit without some kind of restraint system; however, I remembered reading that Story Musgrave stood up on the orbiter flight deck during the re-entry of STS-80, so I guess lack of restraints wouldn't necessarily be an issue.

Wearing spacesuits might not be practical depending on the type of emergency. I know that the American ones use pure oxygen at relatively low pressure for a breathing gas. Since the station uses normal air (oxygen/nitrogen/argon) mix at normal pressure, some period of pre-breathing is needed to prevent the astronaut getting the bends when they switch to the low pressure pure O2 in the suit. I believe standard practice for American spacewalks is currently for astronauts to 'camp out' in the airlock to gradually make the switch overnight before a spacewalk. I'm sure that timeframe could be compressed in an emergency, but I don't know how far.

As others above have noted, I don't think cargo-only craft have environmental systems added. I'm sure in an emergency astronauts could use bottled oxygen (if available) to replenish what they breathe and use up. Not sure how you would go about scrubbing CO2, but that might not be an issue depending on how much air was available and how many people were using it.
« Last Edit: 05/21/2018 07:36 am by Chris Bergin »

Offline IRobot

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Re: Using a cargo spacecraft as a rescue spacecraft for crew
« Reply #6 on: 05/20/2018 07:29 pm »
You could use oxygen candles but that would increase the pressure inside. Unless you could reduce pressure to a minimum before detaching.
There was a big discussion more than a year ago regarding this topic and if I recall correctly, the main issue was that Dragon v1 cannot undock/un-berth without internal command from ISS, so somebody would have to stay behind.

Offline johnfwhitesell

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Re: Using a cargo spacecraft as a rescue spacecraft for crew
« Reply #7 on: 05/20/2018 09:50 pm »
Would you have to use an EVA suit?

I believe that has been SOP on every mission since the time the cosmonauts died.

You could use oxygen candles but that would increase the pressure inside. Unless you could reduce pressure to a minimum before detaching.
There was a big discussion more than a year ago regarding this topic and if I recall correctly, the main issue was that Dragon v1 cannot undock/un-berth without internal command from ISS, so somebody would have to stay behind.

Couldn't they just vent the excess air?

Offline speedevil

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Re: Using a cargo spacecraft as a rescue spacecraft for crew
« Reply #8 on: 05/21/2018 12:32 am »
Would you have to use an EVA suit?
The internal volume of the dragon 1 is 10m^3.
For six astronauts, that is 1.6m^3 each or so.
You can breath that amount of air for four hours and on average only have breathed it once.
At the end of this time, it is going to become quite unpleasant.

First 'nasty' effects perhaps an hour afterwards.
On some nominal dragon flights, six crew would have probably survived, if they could open the door at landing.
However, if you can pick the appropriate time so you are landing in range (more or less) of emergency recovery forces, there is no good reason to take more than an hour - landing happens around 40 min after the entry burn.


Offline brihath

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Re: Using a cargo spacecraft as a rescue spacecraft for crew
« Reply #9 on: 05/21/2018 12:52 am »
Would you have to use an EVA suit?
The internal volume of the dragon 1 is 10m^3.
For six astronauts, that is 1.6m^3 each or so.
You can breath that amount of air for four hours and on average only have breathed it once.
At the end of this time, it is going to become quite unpleasant.

First 'nasty' effects perhaps an hour afterwards.
On some nominal dragon flights, six crew would have probably survived, if they could open the door at landing.
However, if you can pick the appropriate time so you are landing in range (more or less) of emergency recovery forces, there is no good reason to take more than an hour - landing happens around 40 min after the entry burn.



After the Soyuz 11 Cosmonauts died, the Russians started using the Sokol pressure suits for ascent and reentry.  They are not EVA suits, but rather pressure suits designed to keep the crew members alive in the event of a depressurization.  The Shuttle Launch and Entry suits were designed for the same purpose, as well as to mount parachutes in case of a bail out through the shuttle hatch.  EVA suits are far more robust and most likely would not be a practical alternative  due to the pressure differential as mentioned earlier.

Offline Patchouli

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Re: Using a cargo spacecraft as a rescue spacecraft for crew
« Reply #10 on: 05/21/2018 05:16 am »


One solution might be use the scrubber EVA suit backpacks or send up CO2 absorber curtains like those used for emergencies on mines and on submarines.

DC probably would be better to use than Dragon since it has cross range and can land at any airport that can handle jumbo jets so it would be able to return immediately vs waiting for it's orbital track to line up with a suitable landing site.

« Last Edit: 05/21/2018 07:37 am by Chris Bergin »

Offline IRobot

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Re: Using a cargo spacecraft as a rescue spacecraft for crew
« Reply #11 on: 05/21/2018 08:12 am »

You could use oxygen candles but that would increase the pressure inside. Unless you could reduce pressure to a minimum before detaching.
There was a big discussion more than a year ago regarding this topic and if I recall correctly, the main issue was that Dragon v1 cannot undock/un-berth without internal command from ISS, so somebody would have to stay behind.

Couldn't they just vent the excess air?
Unsure if Dragon V1 has that capability. What would be the purpose of it, for a normal mission?

Offline deruch

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Re: Using a cargo spacecraft as a rescue spacecraft for crew
« Reply #12 on: 05/21/2018 10:01 am »
I am pretty sure this has been discussed before but I am having a hard time finding the prior discussions on it.

Here is the question: in an emergency, could a cargo Dragon 1 or 2 or a cargo DC be used as a rescue spacecraft (for the descent from ISS to Earth) without any modifications to it?

I imagine that it could be done if the astronauts used a spacesuit of some kind.

They wouldn't have a way to detach from the station without someone inside unbolting them from the CBM.  The ground robotics operators could move them away from the station and release the capsule without ISS crew involvement.  But that could only happen once Dragon was free from the bolts, which require physical interaction with live crew member on station to release.

When they transport rodents in the Dragon, they use LiOH for CO2 scrubbing.  So, if they are doing it for the mice, I would guess that the much larger humans might face a serious challenge without some for of MacGuyvered ECLSS.
Shouldn't reality posts be in "Advanced concepts"?  --Nomadd

Offline Archibald

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Re: Using a cargo spacecraft as a rescue spacecraft for crew
« Reply #13 on: 05/21/2018 06:36 pm »
Back in 2003-2004 there were studies of an ATV as an "in orbit lifeboat".
Han shot first and Gwynne Shotwell !

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