Author Topic: Should Starship (BFS) have a launch escape system?  (Read 231854 times)

Offline KelvinZero

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Re: Should the ITS have a launch escape system?
« Reply #80 on: 10/07/2017 11:55 am »
There are a list of reasons to conclude this design can at least be safer than the shuttle by a significant margin.

Also, unlike the shuttle, it looks to me like we will have a good long time (or many launches) to establish the safety of the BFS architecture before committing to manned launches.

As to it's ultimate safety, I know nobody knows.. but we can know we will know before we need to know :-)

Re: Should the ITS have a launch escape system?
« Reply #81 on: 10/07/2017 03:27 pm »
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).

Expendable rockets fly once; all the world's rockets are expendable less one.
Rocketry as an industry is in its infancy.
Yeah and that's a thing overlooked by some that still think expendable small launcher will be competitive with RLV. Reusability is not only about cost: it's the only way to take rocket reliability to the next level. When you can fly affordably and frequently you can also test and improve reliability in a way not possible before. Putting your payload on a rocket that has never flown before and whose reliability is calculated on less data points by orders of magnitude will be like putting it in the hands of a shaman. And that will also apply to ULA.
Failure is not only an option, it's the only way to learn.
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Offline Lee Jay

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Re: Should the BFR have a launch escape system?
« Reply #82 on: 10/07/2017 05:30 pm »
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.

What you just said is that this rocket is going to be at least 100 times safer than any rocket before it, but that any LAS the same company builds won't be any safer than historical LAS's.

Makes zero sense.

Offline Lee Jay

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Re: Should the BFR have a launch escape system?
« Reply #83 on: 10/07/2017 05:31 pm »
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.

Those two things are in direct conflict.

Aircraft are required to be as safe as they are by entities like the FAA.  Why would they allow a far less safe vehicle to be in "routine commercial operations" when they don't for airliners?

Offline Robotbeat

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Re: Should the BFR have a launch escape system?
« Reply #84 on: 10/07/2017 05:34 pm »
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.

Those two things are in direct conflict.

Aircraft are required to be as safe as they are by entities like the FAA.  Why would they allow a far less safe vehicle to be in "routine commercial operations" when they don't for airliners?
Because this isn't an airliner. Regulations can change. FAA already was planning to allow routine commercial operations for space tourism.
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

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Offline Robotbeat

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Re: Should the BFR have a launch escape system?
« Reply #85 on: 10/07/2017 05:39 pm »
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.

What you just said is that this rocket is going to be at least 100 times safer than any rocket before it, but that any LAS the same company builds won't be any safer than historical LAS's.

Makes zero sense.
Sure it makes sense. LASes (and similar things like ejection seats) are never tested as often as launches are. By their very nature they are often destructive and not amenable to reuse. The whole reason BFR might get 100 times as safe is not because SpaceX is magic but because they can afford to fly it a thousand times to prove it's safe.

You have a choice. Spend resources on a LAS, which would halve the number of people you can carry while also G costing billions to develop, or you focus on safety of the vehicle and getting costs down and flight rate up enough to become safer WITHOUT a LAS than existing systems WITH a LAS.
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

Offline TomH

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Re: Should the ITS have a launch escape system?
« Reply #86 on: 10/07/2017 07:36 pm »
There are a list of reasons to conclude this design can at least be safer than the shuttle by a significant margin.

Also, unlike the shuttle, it looks to me like we will have a good long time (or many launches) to establish the safety of the BFS architecture before committing to manned launches.

As to it's ultimate safety, I know nobody knows.. but we can know we will know before we need to know :-)

And add to that the fact  that BFR/BFS will function far more as a traditional rocket than STS. STS had some fatal design flaws, each of which led to LOV/LOC.
-Massive segmented solid boosters
-A fragile, TPS sitting downhill from falling ice and brittle foam.

Obviously, new technology comes with unknown risks. At the same time, basic rocket engineering has now had 80 years to mature. CAD troubleshooting and 3D printing were not available in the past. This rocket will have no COPVs, no LH2, none of STS's fatal flaws. So from the starting line, this rocket will begin its engineering design with a lot of advantages not available in the past. Just as a new car design today would assume crumple zones, impact absorbing composites, seat belts, air bags, radar detection/avoidance, ABS, telescoping steering collumns, etc., BFR starts off with innumerable lessons from history already built in. How many original Atlas rockets failed? How many Atlas V have failed? You learn from mistakes on past rockets and apply those lessons to new rockets.

Offline Robotbeat

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Re: Should the BFR have a launch escape system?
« Reply #87 on: 10/07/2017 08:15 pm »
Interestingly, Shuttle only managed like 8 or 9 launches per year at its peak, whereas SpaceX has already down 13 this year and hopes to get to a total of 20 plus another 30 next year. And it looks likely they'll get close to those numbers.

Since BFR is primarily just a replacement for Falcon in the early days, that means it will be entering into a demand position much better than Shuttle.
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

Offline Lee Jay

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Re: Should the BFR have a launch escape system?
« Reply #88 on: 10/08/2017 12:10 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.

Those two things are in direct conflict.

Aircraft are required to be as safe as they are by entities like the FAA.  Why would they allow a far less safe vehicle to be in "routine commercial operations" when they don't for airliners?
Because this isn't an airliner. Regulations can change. FAA already was planning to allow routine commercial operations for space tourism.

Taking 6 people paying a quarter million each to space for a couple minutes on a sub-orbital mission, all of them likely having signed a massive waiver isn't the same thing at all as commercial, economy-fare point-to-point travel of thousands of average folks each day.

This idea of using this vehicle for rapid, volume, point-to-point travel of average people paying airline economy fares is about as far fetched as FTL and propellantless propulsion.  It will be thousands of times less safe than the average airliner.

The Concorde was the safest airliner in the world until one crash.  That one made it the least safe (and by a wide margin - the 707 was five times safer).  This is because of its low flight rate.  1 crash in about 50,000 flights is a terrible record for an airliner.  1 crash in 100 flights is world-class for rockets.  The fatal accident rate for airliners over the past 10 years is about 1 in 4 million, including the entire world.  For just the US and Canada, it's better than 1 in 10 million.

So, how do you expect SpaceX to get from 1 in 100 (world class for rockets) to 1 in 10,000,000 - a five order of magnitude improvement?  Or do you expect average folks to accept an accident rate that's thousands of times worse than an airliner?

Offline Robotbeat

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Re: Should the BFR have a launch escape system?
« Reply #89 on: 10/08/2017 12:23 am »
So you're saying people shouldn't be allowed to take measures risks?

Should we go back in time and stop people from taking airline flights in the 50s just because they don't meet current airline standards?

I say if the FAA is doing their job, they'll make sure people understand the risks involved, take reasonable steps that ensure as much safety as possible without making it out of reach of normal people, and then just let people take those risks.

We don't ban people from riding motorcycles even though it's very unsafe.
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

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Offline Robotbeat

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Re: Should the BFR have a launch escape system?
« Reply #90 on: 10/08/2017 12:28 am »
If SpaceX gets reliability to just 99.995% reliability, they will be superior to regular airlines in average lifetime saved. Saving 12 hours of your useful life is worth it at that point.
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

Offline cppetrie

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Re: Should the BFR have a launch escape system?
« Reply #91 on: 10/08/2017 12:29 am »
People do risky things literally on a daily basis by driving to work. It doesn’t need to demonstrate equal risk to airliners, just sufficiently low risk to warrant not sitting on a plane for 18 hours, where you have a not insignificant chance of suffering a DVT that could result in death, and instead fly by rocket and be where you’re going in a couple hours instead (couple hours includes transport from dock to launch platform and back).

Offline Robotbeat

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Re: Should the BFR have a launch escape system?
« Reply #92 on: 10/08/2017 12:47 am »
I don't think we should get rid of regular airlines. People should still be allowed to take them, obviously.

And by the way: Concorde still flew paying passengers for years after the accident. That means you don't have to achieve a safety record equal to today's airlines to be allowed to fly passengers. Bush pilots in Alaska fly passengers all the time and the general aviation crash rate is very high.

If you drive in a car the same distance as BFR would travel on a long distance trip, you have about a 0.01% chance of dying. In my opinion, that's a pretty reasonable standard, equal to 99.99% reliability. Do we outlaw driving (or taking a bus or train) cross-country just because flying in a jet is safer? Obviously not.

And yeah, I think it's pretty reasonable for BFR to achieve 99.99% reliability long-term, provided it can get anywhere near the cost figure it's shooting for. And I think that's a reasonable level for the FAA to require for mass long distance transit. More waivers required before that level is achieved.

Higher reliability can come later.
« Last Edit: 10/08/2017 12:48 am by Robotbeat »
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

Offline TomH

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Re: Should the BFR have a launch escape system?
« Reply #93 on: 10/08/2017 03:19 am »
Perhaps we should examine a different metric. Maybe we should examine the total human miles flown on all US space craft flights and divide that by 14 to determine the average number of miles traveled per fatality. Then compare that to the number of miles traveled per fatality in cars.

Offline Lee Jay

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Re: Should the BFR have a launch escape system?
« Reply #94 on: 10/08/2017 03:46 am »
And yeah, I think it's pretty reasonable for BFR to achieve 99.99% reliability long-term, provided it can get anywhere near the cost figure it's shooting for.

Sure...only 500 times better than F9 with 10 times the complexity.

Offline CuddlyRocket

Re: Should the BFR have a launch escape system?
« Reply #95 on: 10/08/2017 03:57 am »
Aircraft are required to be as safe as they are by entities like the FAA.  Why would they allow a far less safe vehicle to be in "routine commercial operations" when they don't for airliners?

The FAA and other regulators don't set safety standards for airliners based on some theoretical assessment; they base them on the fact that they already know airliners can be built to meet such standards. If they couldn't then the safety standards would be lower, as they were in the past. (And 'can be built' also includes 'can be built at a price that enables economic operation'.)

Not all aircraft in routine commercial operations have to meet the same safety standards as airliners. In fact, safety standards for airliners varies with size. Then there are aircraft like helicopters, which are allowed to operate because they can do things and go places airliners cannot.

In short, the FAA is highly unlikely to impose safety standards on rocket powered passenger craft so onerous that they couldn't operate at all. Much more likely is that they'll impose safety standards that they know such craft can meet.

Offline Hog

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Re: Should the BFR have a launch escape system?
« Reply #96 on: 10/08/2017 04:29 pm »
Perhaps we should examine a different metric. Maybe we should examine the total human miles flown on all US space craft flights and divide that by 14 to determine the average number of miles traveled per fatality. Then compare that to the number of miles traveled per fatality in cars.
What if Columbia or Challenger were carrying the proposed Shuttle Passenger Module?  The Rockwell proposed SPM would carry 78 humans.
Compare this to another launch system that utilizes 3 crewmembers/launch that fails 20 times. It would appear to be safer based on the metric you propose.(assuming the same travelled distance for each system).

A system where 85 humans perish in 2 out of 135 missions is "safer" than another system where 60 perish, in 20 out of 135 missions, even though the total deaths in the latter system were less.
« Last Edit: 10/08/2017 04:36 pm by Hog »
Paul

Offline pathfinder_01

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Re: Should the BFR have a launch escape system?
« Reply #97 on: 10/08/2017 08:43 pm »
I think that for any near term realistic manned mission the BFR  should have a LES or the crew be launched in a system that does. While it isn't practical to have a LES and launch hundreds of people. I don't think that near term this thing will  be sending hundreds anywhere. The most likely first users of the system will be Space X test pilots and NASA astronauts.

I can not imagine NASA(a source of funding) allowing it's crews to use a system without a LES nor can I imagine a need to send hundreds anywhere in the solar system developing for just a bit of time.

Offline Norm38

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Re: Should the BFR have a launch escape system?
« Reply #98 on: 10/08/2017 09:08 pm »
Or do you expect average folks to accept an accident rate that's thousands of times worse than an airliner?

If they want to get to Mars in their lifetime they absolutely will accept more risk than an airline. Or they don't go. Those are the options.
There will not be a shortage of willing colonists. And if NASA stays home, so what?

Offline rklaehn

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Re: Should the BFR have a launch escape system?
« Reply #99 on: 10/08/2017 09:34 pm »
I don't think BFS should have a LES.

First of all, it does not need to be as reliable as a commercial airliner. A business traveller flies commercial airliners dozens of times per year, hundreds of times in a lifetime. A typical BFS passenger flying to mars would launch exactly once.

So even if it is a factor 10 less reliable than commercial airliners, it would still be acceptable for most people. The chances of dying during launch would still be much lower than the chances of dying during the 20 years of business travel while you make the money for the ticket...  :)

Second, BFS passengers bound for mars engage in other risky activities after the launch. So as long as the risk of launch is significantly lower than the other risks of the voyage to mars, minimising launch risk by reducing the capabilities of the vehicle might even be a net increase in risk for the entire voyage.

Imagine you have a LES that significantly reduces the launch capability, and because of it you have less redundancy or fewer spares for your life support system, less margin in your heat shield, etc.

Now of course somebody will argue that you could just reduce the number of passengers by half, and thus double the price. But if the price is too high, the entire mars settlement project does not work since there are not enough people willing and able to go.

By the way: I am sure there are some metrics such as risk per passenger mile where a mars-bound BFS could easily be vastly safer than a commercial airliner doing short trips.

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