Author Topic: Should Starship (BFS) have a launch escape system?  (Read 53929 times)

Online cppetrie

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Re: Should the ITS have a launch escape system?
« Reply #60 on: 10/06/2017 07:59 PM »
Current rockets arenít as safe as airliners. They intend to demonstrate safety on the order of airliners. If itís fully reuseable and can be flown for a couple million in fuel and ops costs, then they could afford to fly it empty just for the purpose of building flight history similar to how new airplane models are certified. They fly numerous times essentially empty to build flight history as part of the cost of development and certification.

Edit: typo
« Last Edit: 10/06/2017 07:59 PM by cppetrie »

Offline DJPledger

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Re: Should the ITS have a launch escape system?
« Reply #61 on: 10/06/2017 08:26 PM »
Early crewed flights won't have 100 people. They'll have much smaller crews for either Luna on Mars exploration and base construction. No need for an escape system because crews can be transferred in LEO via a Dragon or two and there's nowhere to go if there's a problem on Luna or Mars.
What if the BFR booster explodes on the pad or shortly after liftoff? I am afraid it will be LOC without a LAS so a LAS is a must if SpX are even contemplating putting crew on this thing.

Online RonM

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Re: Should the ITS have a launch escape system?
« Reply #62 on: 10/06/2017 08:38 PM »
Early crewed flights won't have 100 people. They'll have much smaller crews for either Luna on Mars exploration and base construction. No need for an escape system because crews can be transferred in LEO via a Dragon or two and there's nowhere to go if there's a problem on Luna or Mars.
What if the BFR booster explodes on the pad or shortly after liftoff? I am afraid it will be LOC without a LAS so a LAS is a must if SpX are even contemplating putting crew on this thing.

I see you missed the part about using Dragon to transfer crew in LEO. In this small crew scenario, the BFR launches from Earth without the crew.

Offline Lar

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Re: Should the ITS have a launch escape system?
« Reply #63 on: 10/06/2017 08:48 PM »
Early crewed flights won't have 100 people. They'll have much smaller crews for either Luna on Mars exploration and base construction. No need for an escape system because crews can be transferred in LEO via a Dragon or two and there's nowhere to go if there's a problem on Luna or Mars.
What if the BFR booster explodes on the pad or shortly after liftoff? I am afraid it will be LOC without a LAS so a LAS is a must if SpX are even contemplating putting crew on this thing.
Why is it a "must"? It's been explained why SpaceX has decided not to do it but that apparently doesn't satisfy you.

Rather than repeating yourself, give some reasons beyond "it's a must".
"I think it would be great to be born on Earth and to die on Mars. Just hopefully not at the point of impact." -Elon Musk
"We're a little bit like the dog who caught the bus" - Musk after CRS-8 S1 successfully landed on ASDS OCISLY

Offline DJPledger

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Re: Should the ITS have a launch escape system?
« Reply #64 on: 10/06/2017 08:59 PM »
Early crewed flights won't have 100 people. They'll have much smaller crews for either Luna on Mars exploration and base construction. No need for an escape system because crews can be transferred in LEO via a Dragon or two and there's nowhere to go if there's a problem on Luna or Mars.
What if the BFR booster explodes on the pad or shortly after liftoff? I am afraid it will be LOC without a LAS so a LAS is a must if SpX are even contemplating putting crew on this thing.
Why is it a "must"? It's been explained why SpaceX has decided not to do it but that apparently doesn't satisfy you.

Rather than repeating yourself, give some reasons beyond "it's a must".
Launching crew is still a high risk activity which is why all current crewed launches have a LAS. I think SpX needs to get the LOC risk down to around 1 in 100,000 to 1,000,000 for the BFR to be deemed safe enough to not have a LAS. This safety factor for BFR may be possible a long way down the road but unlikely to be achieved during the first few years of BFR service life.

Just one LOC event could kill SpX.
« Last Edit: 10/06/2017 09:00 PM by DJPledger »

Offline Lar

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Re: Should the ITS have a launch escape system?
« Reply #65 on: 10/06/2017 09:01 PM »
Why is it a "must"? It's been explained why SpaceX has decided not to do it but that apparently doesn't satisfy you.

Rather than repeating yourself, give some reasons beyond "it's a must".
Launching crew is still a high risk activity which is why all current crewed launches have a LAS. I think SpX needs to get the LOC risk down to around 1 in 100,000 to 1,000,000 for the BFR to be deemed safe enough to not have a LAS. This safety factor for BFR may be possible a long way down the road but unlikely to be achieved during the first few years of BFR service life.

Just one LOC event could kill SpX.
Proof by assertion..., isn't.

This still is of the form "it's a must". Airliners do not have LAS, and didn't even back in the 1930s. Nor are passengers issued parachutes. Shuttle didn't have LAS. Just saying "well I don't care, BFS has to have one because everyone else does" isn't convincing.
« Last Edit: 10/06/2017 09:02 PM by Lar »
"I think it would be great to be born on Earth and to die on Mars. Just hopefully not at the point of impact." -Elon Musk
"We're a little bit like the dog who caught the bus" - Musk after CRS-8 S1 successfully landed on ASDS OCISLY

Offline DJPledger

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Re: Should the ITS have a launch escape system?
« Reply #66 on: 10/06/2017 09:07 PM »
Why is it a "must"? It's been explained why SpaceX has decided not to do it but that apparently doesn't satisfy you.

Rather than repeating yourself, give some reasons beyond "it's a must".
Launching crew is still a high risk activity which is why all current crewed launches have a LAS. I think SpX needs to get the LOC risk down to around 1 in 100,000 to 1,000,000 for the BFR to be deemed safe enough to not have a LAS. This safety factor for BFR may be possible a long way down the road but unlikely to be achieved during the first few years of BFR service life.

Just one LOC event could kill SpX.
Proof by assertion..., isn't.

This still is of the form "it's a must". Airliners do not have LAS, and didn't even back in the 1930s. Nor are passengers issued parachutes. Shuttle didn't have LAS. Just saying "well I don't care, BFS has to have one because everyone else does" isn't convincing.
Airliners are so safe they don't need LAS. Shuttle not having LAS was a huge mistake with two LOC events. Safety factor of future crew launch systems including BFR needs to be around 3 orders of magnitude higher than Shuttle to do away with the LAS.

Offline Lee Jay

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Re: Should the ITS have a launch escape system?
« Reply #67 on: 10/06/2017 09:20 PM »
An airliner is safe not because it doesn't fail, but because it has such a wide variety of intact abort modes.  Not having an abort system on a crewed vessel is a show-stopper.
It has redundancy and large safety margins but not an escape system. Thereís no parachutes onboard for all passengers. Any passengers actually.

I didn't say anything about an escape system.

Offline Lee Jay

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Re: Should the ITS have a launch escape system?
« Reply #68 on: 10/06/2017 09:24 PM »
Current rockets arenít as safe as airliners. They intend to demonstrate safety on the order of airliners.

Being as safe as an airliner means it has to be able to tolerate multiple failures and still land intact.  Last week an A380 had an uncontained engine failure and still landed intact with no people injured.  I was aboard an airliner with a control-systems failure.  We landed without issue.  This sort of thing happens all the time.  That's the reason airline travel is so safe - because the vast majority of failures, even dramatic ones, don't result in a crash.

Offline DJPledger

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Re: Should the ITS have a launch escape system?
« Reply #69 on: 10/06/2017 09:29 PM »
Current rockets arenít as safe as airliners. They intend to demonstrate safety on the order of airliners.

Being as safe as an airliner means it has to be able to tolerate multiple failures and still land intact.  Last week an A380 had an uncontained engine failure and still landed intact with no people injured.  I was aboard an airliner with a control-systems failure.  We landed without issue.  This sort of thing happens all the time.  That's the reason airline travel is so safe - because the vast majority of failures, even dramatic ones, don't result in a crash.
BFR needs to be made as fault tolerant as airliners for it to be safe enough not to need a LAS. Hopefully EM has this in mind for BFR design.

Online cppetrie

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Re: Should the ITS have a launch escape system?
« Reply #70 on: 10/06/2017 10:05 PM »
Current rockets arenít as safe as airliners. They intend to demonstrate safety on the order of airliners.

Being as safe as an airliner means it has to be able to tolerate multiple failures and still land intact.  Last week an A380 had an uncontained engine failure and still landed intact with no people injured.  I was aboard an airliner with a control-systems failure.  We landed without issue.  This sort of thing happens all the time.  That's the reason airline travel is so safe - because the vast majority of failures, even dramatic ones, don't result in a crash.
And why canít that be true for BFR?

Online cppetrie

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Re: Should the ITS have a launch escape system?
« Reply #71 on: 10/06/2017 10:18 PM »

Airliners are so safe they don't need LAS. Shuttle not having LAS was a huge mistake with two LOC events. Safety factor of future crew launch systems including BFR needs to be around 3 orders of magnitude higher than Shuttle to do away with the LAS.
A LAS would only have maybe prevented one of the LOC events. It is irrelevant for Columbia which was lost on re-entry not launch. That would have required an ejection system to eject crew from the vehicle at hypersonic speeds during atmospheric re-entry. Iím not sure how such a system could even work.

Online envy887

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Re: Should the ITS have a launch escape system?
« Reply #72 on: 10/06/2017 10:29 PM »
...
Safety factor of future crew launch systems including BFR needs to be around 3 orders of magnitude higher than Shuttle to do away with the LAS.

Probably higher than that, actually. But plausible to demonstrate with 1000s of launches in a high launch rate, low cost per launch architecture.

Online envy887

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Re: Should the ITS have a launch escape system?
« Reply #73 on: 10/06/2017 11:37 PM »
From past examples, a LAS offers about a 10-fold improvement in reliability: that is, a system that's 97% reliable (Shuttle) becomes 99.7% reliable.

I don't think it's plausible to design a LAS that allows a vehicle with reliability substantially short of "airliner-like" to become "airliner-like". Any zero-altitude, zero-velocity LAS is going to have the same highly-stressed rocket components as the booster and upper stage, and is going to add lots of new non-benign failure modes.

Perhaps a better question would be, could the BFS be designed to have fewer catastrophic failure modes? Every other form of transportation doesn't take the "get the hell outta there" form of reacting to a failure.

Offline Robotbeat

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Re: Should the ITS have a launch escape system?
« Reply #74 on: 10/07/2017 12:57 AM »
...Safety factor of future crew launch systems including BFR needs to be around 3 orders of magnitude higher than Shuttle to do away with the LAS.
Absolutely, utterly false. AT BEST, a LAS only buys you a SINGLE order of magnitude.

An escape system is NOT a guarantee of survival. All it does is take care of about nine out of ten launch vehicle failures AT BEST.

So, existing rockets are about 95 to at best 99% reliable. A LAS gets you AT BEST to 99.5 to 99.9% reliable. And probably worse than that as it doesn't improve entry or in-space safety.

The solution to this is to just fly and recover BFR 200 to 1000 times in a row safely (or technically, 100 to 500 flights would probably do it especially if you included some near-miss analysis). That shouldn't take too long. And it wouldn't even cost more: if BFR has a marginal cost per launch of $2 million, that means you can do all those launches for $400 million to $2 billion, and they can serve double-duty. Orion's LAS alone probably cost more than $2 billion.
« Last Edit: 10/07/2017 01:08 AM by Robotbeat »
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Offline Lee Jay

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Re: Should the ITS have a launch escape system?
« Reply #75 on: 10/07/2017 03:00 AM »
Current rockets arenít as safe as airliners. They intend to demonstrate safety on the order of airliners.

Being as safe as an airliner means it has to be able to tolerate multiple failures and still land intact.  Last week an A380 had an uncontained engine failure and still landed intact with no people injured.  I was aboard an airliner with a control-systems failure.  We landed without issue.  This sort of thing happens all the time.  That's the reason airline travel is so safe - because the vast majority of failures, even dramatic ones, don't result in a crash.
And why canít that be true for BFR?

Because it's not inherently flyable and because the energy levels are so much higher.

Could it land in an all engines out situation?  Airliners can and have.  They have to be certified to do so.

It is safe in a catastrophic rupture of the cabin?  Airliners have landed safely after such an event.

Can it land safely in a lake, river or ocean?  People have survived that occurrence many times.

Almost everything will have to go right for this thing to be safe to ride on.

At the very least, the upper stage (or spacecraft, if you prefer) needs to be able to separate from a failing first stage and fly itself to safety.  However, as I understand it, that isn't possible.  Did I misunderstand that part?

Offline Robotbeat

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Re: Should the ITS have a launch escape system?
« Reply #76 on: 10/07/2017 03:08 AM »
Meh, I disagree with your whole shpiel. A lot of people died in the 1950s in aircraft. But people still flew, and if SpaceX gets to that reliability level, they'll be fine even for point to point due to lifetime saved in getting to destination faster.

People are treating LAS as if it's magic and saves you in all instances. It ain't magic. It'll fail to save you 1 time out of 10, and that's just on the way up. And such systems can kill you all by themselves even if the rocket is fine: http://www.dailymail.co.uk/news/article-2548135/Coroner-slams-ejector-seat-manufacturer-failing-warn-RAF-defects-led-death-Red-Arrows-pilot.html

A LASless BFR that has flown and been recovered 2000 times safely is a lot safer than Orion or Soyuz will ever be.
« Last Edit: 10/07/2017 03:10 AM by Robotbeat »
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Re: Should the ITS have a launch escape system?
« Reply #77 on: 10/07/2017 09:50 AM »
I' with Robotbeat here: it's possible that rockets fundamentally cannot reach modern aircrafts levels of safety, but I fail to see how they couldn't reach acceptable reliability for routine commercial operations. And, not being an engineer thus not understanding the technicalities as robotbeat does, the thing I can comment on is how irrational it seems to draw similar pessimistic conclusions when talking about rockets, machines that fly less then 100 times per year and are still in their infancy vs airliners. That will change with BFR and full reusability. Instead of making assumptions we should wait and see (or try and see, if you are an aerospace company: the sad thing is that after the Shuttle we had to wait for SX and BO for someone to do this).
« Last Edit: 10/07/2017 09:53 AM by AbuSimbel »
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Offline jded

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Re: Should the ITS have a launch escape system?
« Reply #78 on: 10/07/2017 10:12 AM »
Current rockets arenít as safe as airliners. They intend to demonstrate safety on the order of airliners.

Being as safe as an airliner means it has to be able to tolerate multiple failures and still land intact.  Last week an A380 had an uncontained engine failure and still landed intact with no people injured.  I was aboard an airliner with a control-systems failure.  We landed without issue.  This sort of thing happens all the time.  That's the reason airline travel is so safe - because the vast majority of failures, even dramatic ones, don't result in a crash.
And why canít that be true for BFR?

Because it's not inherently flyable and because the energy levels are so much higher.

Could it land in an all engines out situation?  Airliners can and have.  They have to be certified to do so.

It is safe in a catastrophic rupture of the cabin?  Airliners have landed safely after such an event.

Can it land safely in a lake, river or ocean?  People have survived that occurrence many times.

Almost everything will have to go right for this thing to be safe to ride on.

At the very least, the upper stage (or spacecraft, if you prefer) needs to be able to separate from a failing first stage and fly itself to safety.  However, as I understand it, that isn't possible.  Did I misunderstand that part?

I agree. I can believe that SpaceX will be reasonably sure that BFR will not explode violently on pad and will not provide any measures against this, just like airplanes don't. But I can't see them putting people in a craft that would just slowly drop to its doom if BFR fails to provide just-enough dV for orbit for any reason.

At the very least they should have enough software flexibility in BFS to bo able to separate (even with thrust/weight <1 it still can separate), and take a path allowing to burn down fuel and land in some safe spot eventually- at least for a part of the flight envelope (not immediately after liftoff, obviously)...

Can we determine, with currently available data, how high/fast would the stack need to be for this to be possible?
« Last Edit: 10/07/2017 10:18 AM by jded »

Offline AncientU

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Re: Should the ITS have a launch escape system?
« Reply #79 on: 10/07/2017 11:16 AM »
I' with Robotbeat here: it's possible that rockets fundamentally cannot reach modern aircrafts levels of safety, but I fail to see how they couldn't reach acceptable reliability for routine commercial operations. And, not being an engineer thus not understanding the technicalities as robotbeat does, the thing I can comment on is how irrational it seems to draw similar pessimistic conclusions when talking about rockets, machines that fly less then 100 times per year and are still in their infancy vs airliners. That will change with BFR and full reusability. Instead of making assumptions we should wait and see (or try and see, if you are an aerospace company: the sad thing is that after the Shuttle we had to wait for SX and BO for someone to do this).

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