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Oct 14, 2013

Inflatable Life Capsule - "Space Lifeboat"

Based on the NASA's latest Inflatable Heat Shield (IHS) innovation it is now rather straight forward to figure out how an inflatable Space Lifeboat (SLB / ISLB) or an Inflatable Life Capsule (ILC) should look like and how it should be used.

Video: HIAD or IHS Re-entry (Hypersonic Inflatable Aerodynamic Decelerator, Inflatable Heat Shield)

An IHS might also be called a HIAD (Hypersonic Inflatable Aerodynamic Decelerator).

An Inflatable Life Capsule is similar to a lifeboat in an ocean ship.

In picture 1 we see an ILC connected to some space vehicle (ISS, a rocket or similar). The idea behind an ILC is similar to a lifeboat in a ship. A lifeboat is a boat carried for emergency evacuation in the event of a disaster aboard a ship. In case of an ILC it is attached to a space ship.

A Futuristic Space Ship

NASA has been experimenting with X-38 Crew Return Vehicle (CRV) which can carry 8 persons back to Earth. More about that is in link 7.

Lets see what parts an ISLB is made of (see picture 1).

1) Portable Life Suppoort System (PLSS), space suit, space man (or a doll for testing)
2) Seat pan, seat belts and the support for side packs and RCS jets.
3) Inflatable heat shield IHS or HIAD (See IRVE 3 for an example)
4) Parachute System (See BRS Parachutes for an example)
5) RCS fuel packs including RCS jets on both sides, not shown, similar to pack 4 (see picture 4 for details)

Picture 1: Initial condition - a space man needs to be rescued to Earth

The sequence from space to Earth is shown in pictures 1 to 7.

When a space man needs a transport to Earth he first takes the ILC out of its container (picture 1). Then he binds him self to the seat pan with seat belts and moves it to some distance from the vehicle (picture 2).

Picture 2: Fasten seat belts.

Now he inflates the heat shield (or HIAD) (picture 3.). At the same time the parachute system (under legs) and fuel packs (on both sides) turn to their reentry position.

Picture 3: Inflate the heat shield and turn side packs to their position. The parachute pack and 2 RCS fuel and jet packs will turn.

Before reenter you usually need to do some adjustment to your speed and/or attitude.  This is done by firing the RCS (Reaction Control System) jets as required (picture 4).

Picture 4: Start return - fire jets so that the attitude and speed is correct for the reentry. In this picture the fuel packs with RCS jets are shown. There are 4 jets altogether. To go "forward" you fire all 4 jets at the same time.

Now starts the reentry phase which may take some time (picture 5.

Picture 5: Reentry - during reentry keep the attitude using RCS jets.

During the reentry period the ILC must be kept in right attitude and stabilized (not spinning etc.). The atmospheric drag will take care of the deceleration which is relative to the size of the HIAD and weight of the whole space lifeboat and its passenger.

Picture 6: Shoot the parachute - at some low altitude open the parachute so that the landing is smooth.

At 25000 meters or so the parachute is shot out of its container (see PRS Parachutes video for an example) (picture 6).

Picture 7: Splashdown - activate the radio beacon to be sea rescued

Splashdown should be rather smooth since a real parachute is used for the final phase (picture 7). The IRVE-3 test for an example did not use any parachute at the final phase and had higher speed at the end. One possibility might be to use a bit larger shield (HIAD) and use that partially as a parachute and have somewhat harder splashdown compared to the parachute version.

Note that in case of stormy sea the PLSS should be able to support the life for some time even under water. Hopefully until the rescue is made. And the HIAD of course keeps the lifeboat floated.

An inflatable life raft is very similar to an ILC.

Here is the flat ILC or space lifeboat and its parts again in 3-view.

Inflatable Space Lifeboat

Here is a typical life raft open sequence which is very much similar but of course the device is more simple since it only have to handle the on Earth environment.

Typical on Earth life raft open sequence.


/1/ YouTube inflatable heat shield NASA IRVE

/2/ Shootable parachutes BRS Aviation

/3/ Wikipedia PLSS and space suits

/4/ Wikipedia Atmospheric reentry and Skip reentry

/5/ YouTube HIAD video

/6/ MIT/NASA Science Reporter video: PLSS Part

/7/ YouTube Video: NASA X-38 Crew Return Vehicle (CRV)

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