Should Starship (BFS) have a launch escape system?

[hkultala]

Bump this thread due to all the BFR abort discussion triggered by the Soyuz accident, such as this:

It shows the importance of having a launch escape system. They may only ever be used on rare occasions but when they do they save a crew's life! After this, I don't think NASA will certify BFR for astronaut transport and will demand Dragon 2 be kept online for the foreseeable future.

Don't be silly. NASA isn't in the process of certifying BFS for use by NASA astronauts. And BFS was never going to replace Crew Dragon for ISS crew rotation missions. BFS is way too massive for that. The docking-loads, imparted on the aging ISS structure, alone were a showstopper for "BFS-to-ISS".

It does bring up a good point though, not having a launch abort system is a critical flaw in BFS.

I think what is missing from the discussion is that the Soyuz escape tower was already jettisoned when the abort occurred, so the spacecraft basically aborted by itself, just like BFS is supposed to do in case the BFB has an issue.

Why people assume only 1st stage will fail on BFR, upper stage has same engines and fuel, both are capable RUD. Even in 1st stage RUD, upper stage is useless as it can't power up and boost away from exploding 1st stage in time.

Often the first stage failure is NOT a spontaneous explosion of the whole rocket.

Often it's single engine failure - which doesn't even cause LOM for BRF.

Or it might be multiple engines failure (one breaking engine breaking others), still without causing an explosion.

Typically we see explosions on engine failures because the launch abort system self-destructs the rocket when it's off-course.

In case the first stage goes out of control, the self-destruct mechanism can be delayed by something like 10 seconds to allow BFS to get away from it.

For example todays soyuz failure looks such fail that BFS would not have have any trouble escaping that.

[Torbjorn Larsson, OM]

Bump this thread due to all the BFR abort discussion triggered by the Soyuz accident, such as this:

It shows the importance of having a launch escape system. They may only ever be used on rare occasions but when they do they save a crew's life! After this, I don't think NASA will certify BFR for astronaut transport and will demand Dragon 2 be kept online for the foreseeable future.

Don't be silly. NASA isn't in the process of certifying BFS for use by NASA astronauts. And BFS was never going to replace Crew Dragon for ISS crew rotation missions. BFS is way too massive for that. The docking-loads, imparted on the aging ISS structure, alone were a showstopper for "BFS-to-ISS".

It does bring up a good point though, not having a launch abort system is a critical flaw in BFS.

I think what is missing from the discussion is that the Soyuz escape tower was already jettisoned when the abort occurred, so the spacecraft basically aborted by itself, just like BFS is supposed to do in case the BFB has an issue.

Why people assume only 1st stage will fail on BFR, upper stage has same engines and fuel, both are capable RUD. Even in 1st stage RUD, upper stage is useless as it can't power up and boost away from exploding 1st stage in time.

I am reminded of Hans Koenigsmann on reusability. 'what other 50 MUSD design is used once and then thrown away'. Same question here would be, what other vehicle design has a LAS system?

The ejection seat was invented for military crafts, was it not? Nothing else, from submarines over cars and trains to planes has LAS or even escape systems, except large leaking boats or submarines, or large crash landed planes. I guess the idea is that a rocket is not a plane, but this rocket is - and the Shuttle and Buran was - designed as a plane. Which gets us back to Hans recent note on reuse and its ability to rapidly increase reliability. And - since this seems to be an old thread - to the recent redesign with 7 sea level Raptors on BFS, so upping landing redundancy on the 1st gen design.

The riskiest modern mass transportation is city walking. When - I am fairly certain it is a "when" - SpaceX get their systems down to equivalent risk numbers they will be unassailable. Same as for the radiation risk of a Mars trip, I think the estimates are closing in on something like a 3 % lower life expectancy when city living - which now the majority of the global population has chosen - globally and currently decrease life expectancy with 10 %. (I expect the city numbers will drop rapidly as air pollution [not walking  ] is the main problem and fossil fuels are going the way of non-reusable vehicles.)

EDIT: Added in the large submarines, I was thinking of deep dive research crafts during 1st draft.

[GalacticIntruder]

It is silly season. BFS does not need a escape system.

BFS is meant for large numbers of humans to be in space, like up to 100 humans. Abort options are not worth the effort; complexity or mass and costs and testing and qual etc. That is the paradigm SpaceX wants to change. Planes crash, people die, albeit rarely, given the large numbers of planes and passenger-miles per year. Rocket fail, people die. Obviously a BFS with 100 people crashing would be tragedy and it will happen sooner or later. And the media hysteria and Congress Critters and Bureaucrats and hand wavy experts, Monday morning QBs, keyboard warriors, will go psycho, but that is life. Hopefully people who go to the Moon or Mars will not be naive.

[Rocket Science]

It is silly season. BFS does not need a escape system.

BFS is meant for large numbers of humans to be in space, like up to 100 humans. Abort options are not worth the effort; complexity or mass and costs and testing and qual etc. That is the paradigm SpaceX wants to change. Planes crash, people die, albeit rarely, given the large numbers of planes and passenger-miles per year. Rocket fail, people die. Obviously a BFS with 100 people crashing would be tragedy and it will happen sooner or later. And the media hysteria and Congress Critters and Bureaucrats and hand wavy experts, Monday morning QBs, keyboard warriors, will go psycho, but that is life. Hopefully people who go to the Moon or Mars will not be naive.

You might have missed this when I posted it a while back. There was a escape concept for MCT...Looked interesting...

[Tulse]

There was a escape concept for MCT...Looked interesting...

I think that carrying the escape motors and their propellant with you well past their need poses a risk in itself, especially since the rockets are pointed directly into a crewed section of the vehicle.

[Rocket Science]

There was a escape concept for MCT...Looked interesting...

I think that carrying the escape motors and their propellant with you well past their need poses a risk in itself, especially since the rockets are pointed directly into a crewed section of the vehicle.

Unless they dump the prop after they are no longer needed could be an option I guess...

[Lars-J]

It is silly season. BFS does not need a escape system.

BFS is meant for large numbers of humans to be in space, like up to 100 humans. Abort options are not worth the effort; complexity or mass and costs and testing and qual etc. That is the paradigm SpaceX wants to change. Planes crash, people die, albeit rarely, given the large numbers of planes and passenger-miles per year. Rocket fail, people die. Obviously a BFS with 100 people crashing would be tragedy and it will happen sooner or later. And the media hysteria and Congress Critters and Bureaucrats and hand wavy experts, Monday morning QBs, keyboard warriors, will go psycho, but that is life. Hopefully people who go to the Moon or Mars will not be naive.

You might have missed this when I posted it a while back. There was a escape concept for MCT...Looked interesting...

That was some random artist concept, nothing official. It does not make sense.

[Rocket Science]

It is silly season. BFS does not need a escape system.

BFS is meant for large numbers of humans to be in space, like up to 100 humans. Abort options are not worth the effort; complexity or mass and costs and testing and qual etc. That is the paradigm SpaceX wants to change. Planes crash, people die, albeit rarely, given the large numbers of planes and passenger-miles per year. Rocket fail, people die. Obviously a BFS with 100 people crashing would be tragedy and it will happen sooner or later. And the media hysteria and Congress Critters and Bureaucrats and hand wavy experts, Monday morning QBs, keyboard warriors, will go psycho, but that is life. Hopefully people who go to the Moon or Mars will not be naive.

You might have missed this when I posted it a while back. There was a escape concept for MCT...Looked interesting...

That was some random artist concept, nothing official. It does not make sense.

What would you do different?

[lamontagne]

It is silly season. BFS does not need a escape system.

BFS is meant for large numbers of humans to be in space, like up to 100 humans. Abort options are not worth the effort; complexity or mass and costs and testing and qual etc. That is the paradigm SpaceX wants to change. Planes crash, people die, albeit rarely, given the large numbers of planes and passenger-miles per year. Rocket fail, people die. Obviously a BFS with 100 people crashing would be tragedy and it will happen sooner or later. And the media hysteria and Congress Critters and Bureaucrats and hand wavy experts, Monday morning QBs, keyboard warriors, will go psycho, but that is life. Hopefully people who go to the Moon or Mars will not be naive.

You might have missed this when I posted it a while back. There was a escape concept for MCT...Looked interesting...

That was some random artist concept, nothing official. It does not make sense.

That was a 2015 concept by Richard Heidmann, who worked on Ariane and is a french propulsion scientist.
Hardly a random artist, this was one of the best precursor designs for the BFR.
http://planete-mars.com/mars-colonization-transport-rumeurs-avant-revelation-du-projet/

OF course, he got it wrong, as we all did :-)

[lamontagne]

I find it interesting that the new 2018 BFR with 7 engines now has enough thrust to take off on its own from a BFB, or separate during flight with a bit of acceleration.
I also think the new landing legs give it a lot of flexibility for landing in case of a flight abort.  I would expect the BFS to carry a map of all the possible landing fields along its flight path.

Landing on water would be a problem though.  Although even that was shown to be possible when a Falcon 9 booster failed to break up after a water landing.  Would it be a case of abandon ship, or a case of stay with the ship?

I don't really see the point of an escape system with this configuration.  And since it can be tested without a crew, there can be any number of flights and tests done with no risk to crew and passengers.

[Robotbeat]

Landing on the water may actually work with some powerful methane oxygen thrusters in the nose to cushion the vehicle as it falls over into the water after a vertical landing in the water. Might need such powerful nose thrusters for landing on unprepared sites on Mars anyway, and Musk mentioned thrusters with 10 tons of thrust, so like 3 of those would be enough.

[Robotbeat]

A giant, whole-vehicle parachute might work if you are coming down empty.  Parachute only needs to weigh about 5% dry mass. For 80 ton dry, that’s 4 tons of parachute. Might be worth it.

[RonM]

In a water landing, the large landing leg fins will be underwater. That might cause enough drag to slow down tipping over to a safe speed. Also depends on BFS buoyancy. Problem would be payload mass at the top. Flooding the lower propellant tank might allow BFS to bob like a buoy. Many options waiting for simulation.

[KelvinZero]

Wouldn't a BFS pretty much always have the delta-v to either get back to land or forwards to land, depending where it abandons the 1st stage? Maybe you could also have a fairly permanent floating landing pad that could serve occasional high delta-v missions and as a "just in case" abort option halfway between back and forwards options.

[RonM]

Wouldn't a BFS pretty much always have the delta-v to either get back to land or forwards to land, depending where it abandons the 1st stage? Maybe you could also have a fairly permanent floating landing pad that could serve occasional high delta-v missions and as a "just in case" abort option halfway between back and forwards options.

Assuming the abort worked as planned BFS could get back to a pad, but it's always a good idea to plan for the worst. What if BFS comes in short of the floating landing pad? Need a contingency plan for a water landing.

[JonathanD]

Assuming the abort worked as planned BFS could get back to a pad, but it's always a good idea to plan for the worst. What if BFS comes in short of the floating landing pad? Need a contingency plan for a water landing.

Your seat is also a flotation device

[speedevil]

Landing on water would be a problem though.  Although even that was shown to be possible when a Falcon 9 booster failed to break up after a water landing.  Would it be a case of abandon ship, or a case of stay with the ship?

A properly functioning ship landing in the water can do a very modified hoverslam.
The vehicle normally falls mostly downwards, terminating at some 100m/s and 800m.

The modification is to somewhere at around that altitude, pick a suitable direction along with the wind, using the RCS, or both, so as to end up at a body attitude of some 45 degrees nose-up near the sea, moving backwards at significant speed with respect to the sea surface.

It then lights the main engines, and does the majority of vertical deceleration with the body at 45 degrees, before the main body tilts down to some 15 degrees and the acceleration ramps up, for a final phase before contact with the water at near zero forward velocity.
The very final portion is at a total acceleration of some 5G, 1.2G vertical deceleration.

A headwind may help quite a lot.

This means, as the engines cut out, the vehicles base is touching the ocean, at near zero velocity, and the cargo compartment is 'only' 13m above the waves.

RCS will help a little to a lot to slow this impact into the water, a lot if empty.

I note in principle that the velocities shortly before (minutes) landing are quite comparable to normal skydiver egress speeds at ~100m/s.

One can also imagine bouncy castles deployed from near the passenger lock, at the moment of impact to cushion touchdown.

[Zed_Noir]

<snip>
Landing on water would be a problem though.  Although even that was shown to be possible when a Falcon 9 booster failed to break up after a water landing.  Would it be a case of abandon ship, or a case of stay with the ship?
<snip>

Think the BFS is nose heavy after a ditching with most of the propellant vented or expended. Maybe some pop-out inflatable flotation devices will keep the BFS somewhat level and afloat.

Getting out of the BFS in high sea states will be tricky. Wave actions around a ditched BFS will make ingress and egress interesting. So likely the crew will stay aboard until recovery arrives unless the BFS is in danger of breaking up.

Would need something like a LSD amphibious landing ship as part of the recovery operation to hauled the BFS into the well deck. Then getting in and out of the BFS will be a lot easier.

With some preparation could also pop off the main cargo hatches and deployed enclosed lifeboats. If there are lifeboats aboard. Similar to deploying a lifeboat from a gas/oil production platform. Think such deployment can do done just before or after ditching, unless the lifeboat is equipped with a parachute. Of course a lifeboat with a parachute is in effect an escape pod that can be ejected at altitude.

[Rocket Science]

I suppose for a pad abort something like a launch cabin that separates just aft of the forward fins with external abort motors similar to the SD on Dragon is possible (think JSC Shuttle II). Fins could add to stability... The launch cabin then can descend on chutes...
http://spaceflighthistory.blogspot.com/2017/02/nasa-johnson-space-centers-shuttle-ii.html

[envy887]

A giant, whole-vehicle parachute might work if you are coming down empty.  Parachute only needs to weigh about 5% dry mass. For 80 ton dry, that’s 4 tons of parachute. Might be worth it.

Worked for the Shuttle SRBs, kinda. Those were in the same mass ballpark, though the landing velocity was a bit high.