Author Topic: Human rating the BFS  (Read 24290 times)

Offline Nomadd

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Re: Human rating the BFS
« Reply #120 on: 03/12/2018 05:46 PM »
 BFS passengers might not be professional astronauts, but they're also not tourists on their way to Disneyland. Going to live on Mars will always be higher risk than flying to Anaheim for the weekend, both on planet and getting there. But, it will be informed risk. Compared to riding a chunk of wood across the ocean to your new home, a pretty minimal risk. Pioneers are a different class of people. Anybody who insists on absolute safety can stay behind, forever limit themselves to getting no closer to space than their NSF handles and clog up serious threads with their ranting.

Offline Kansan52

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Re: Human rating the BFS
« Reply #121 on: 03/12/2018 06:01 PM »
If memory serves, Soyuz was accepted by NASA as human rated based on the Soyuz record. If NASA ever feels the need of BFS then the number of flights may give NASA the same insight and approval.

Offline ulm_atms

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Re: Human rating the BFS
« Reply #122 on: 03/12/2018 06:24 PM »
If memory serves, Soyuz was accepted by NASA as human rated based on the Soyuz record. If NASA ever feels the need of BFS then the number of flights may give NASA the same insight and approval.

Well if that is the case wouldn't Atlas V fit then(at least on the booster side/2nd stage)?  And also, NASA didn't really have a choice to not rate Soyuz "humanable".  It's the only way they could get to the ISS after the shuttle.

I am willing to bet a quarter that Soyuz does not meet the same requirements that NASA is asking for the CC providers.

Offline woods170

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Re: Human rating the BFS
« Reply #123 on: 03/12/2018 06:30 PM »
If memory serves, Soyuz was accepted by NASA as human rated based on the Soyuz record. If NASA ever feels the need of BFS then the number of flights may give NASA the same insight and approval.

Well if that is the case wouldn't Atlas V fit then(at least on the booster side/2nd stage)?  And also, NASA didn't really have a choice to not rate Soyuz "humanable".  It's the only way they could get to the ISS after the shuttle.

I am willing to bet a quarter that Soyuz does not meet the same requirements that NASA is asking for the CC providers.


In fact it doesn't. LOC for CCP is 1-in-270. Current LOC for Soyuz, based on flight-history, is a lot lower, somewhere around 1-in-120.

Offline AncientU

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Re: Human rating the BFS
« Reply #124 on: 03/12/2018 06:41 PM »
If memory serves, Soyuz was accepted by NASA as human rated based on the Soyuz record. If NASA ever feels the need of BFS then the number of flights may give NASA the same insight and approval.

Well if that is the case wouldn't Atlas V fit then(at least on the booster side/2nd stage)?  And also, NASA didn't really have a choice to not rate Soyuz "humanable".  It's the only way they could get to the ISS after the shuttle.

I am willing to bet a quarter that Soyuz does not meet the same requirements that NASA is asking for the CC providers.


In fact it doesn't. LOC for CCP is 1-in-270. Current LOC for Soyuz, based on flight-history, is a lot lower, somewhere around 1-in-120.

And for shuttle, it was something like 1-in-90.
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Re: Human rating the BFS
« Reply #125 on: 03/12/2018 07:44 PM »
If memory serves, Soyuz was accepted by NASA as human rated based on the Soyuz record. If NASA ever feels the need of BFS then the number of flights may give NASA the same insight and approval.

Well if that is the case wouldn't Atlas V fit then(at least on the booster side/2nd stage)?  And also, NASA didn't really have a choice to not rate Soyuz "humanable".  It's the only way they could get to the ISS after the shuttle.

I am willing to bet a quarter that Soyuz does not meet the same requirements that NASA is asking for the CC providers.


In fact it doesn't. LOC for CCP is 1-in-270. Current LOC for Soyuz, based on flight-history, is a lot lower, somewhere around 1-in-120.

And for shuttle, it was something like 1-in-90.

And for Apollo? Let's assume LEO, so Apollo 7/Skylab missions/ASTP? I'm not sure how you would measure that but perhaps there is a number out there...
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Offline CorvusCorax

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Re: Human rating the BFS
« Reply #126 on: 03/12/2018 10:20 PM »
I see way too much policy based discussion here, and not nearly enough technical suggestion how a "save" BFR/BFS could look like.

What are the largest threat to humans while riding on BFR/BFS:

1. Being burnt and blown to pieces in a RUD
2. Impacting the ground at unsurvivable velocity
3. Impacting the ground and then not making it out (burning/exploding) (This is the main cause of death in civil aviation)
4. Suffocating/Freezing in orbit or high altitude flight.
5. Ripped to shreds during vehicle breakup (loss of control at high Mach speeds, for example during reentry)

How did shuttle address these issues:
1. Not addressed
2. Shuttle could glide to a landing (but only if intact -> Challenger (after RUD))
3. Shuttle had multiple emergency landing strips, but there were gaps
4. Shuttle crew had space suits
5. Not addressed (Columbia)

How does Soyus/Crew dragon address this
1. LAS
2. Redundant Parachutes
3. No/Not much fuel left at landing/touchdown
4. Spacesuits (but were not enough in some Soyus cases!)
5. Passively aerodynamically stable capsule design (Soyus repeatedly survived non-detached "trunks" )

BFR BFS ?
1. BFS could (possibly) LAS away from malfunctioning BFR
2. BFS can propulsively land (if intact!)
3. can BFS crew compartment survive a crash-landing?
4. Spacesuits?
5. ???

Both BFR and BFS have multi engine out capability, and SpaceX has demonstrated in the past that they have engine failures very well under control (aka contained, see CRS-1) All mission losses SpaceX had were due to tank failures. I would (especially because of the large carbon fibre tanks) consider tank rupture to be more dangerous than engine failure, as even multi engine failures would not lead to LOC unless they also affect tankage.

At launch, or shortly after, BFS can likely LAS away from a malfunctioning BFR. If it has >1.0 TWR, it could then hover for a while at save distance to shed propellant, and transfer to a save landing spot in the vicinity of the launch complex.

Bigger problems arise in the advanced stage of flight. If the booster fails at or around MaxQ , BFS is in thick atmosphere but also already at significant downrange distance and supersonic speed. BFS might not be able to turn retrograde without breaking apart if its moving too fast in too thick an atmosphere. In such a situation, the BFS might actually have to burn prograde for a while to make it high enough up to use RCS for reorientation and boostback.

Similarly, for LAS in late 1st stage flight, BFS would need to boost-back to the launchsite while possibly lofting the trajectory.

The big question is, if after an emergency LAS boost, plus possibly apogee rising and boostback, if there's enough propellant left for propulsive landing. There should be, as BFS isn't getting anywhere near orbital speeds and should literally have kilometers per second of deltaV spare.

A RUD of BFS might be survivable in the crew compartment, if the latter's pressure vessel is sturdy enough and the cargo section in between can absorb some damage. Even Challenger's pressure vessel initially survived the explosion. Biggest issue is the aerodynamics/ loss of control and subsequent risk of breakup.

This would also rule out propulsive landing, so if crew is not killed at breakup like in the Columbia incident, they would die on impact, like the crew of Challenger did.

I would suggest the following modifications to the vehicle design:

1. A "break-point" which allows the entire nose including crew compartment to detach from the rest of BFS cleanly if aerodynamic (or overpressure) stresses become too great.
2. A relatively strong pressure vessel shaped such, that it would self stabilize after such an event even at hypersonic speeds
3. ... And in such a way that heat shielding is still effective enough to survive the then non-steered ballistic reentry
4. Parachutes, big enough to slow this detached pressure vessel to survivable impact speeds on both land and water

But no additional propulsive escape (beyond BFS itself that is)

This survival section could possibly be a subsection of the entire crew compartment, but the entire crew would have to be in it during launch, so for larger crews it would likely not make sense to subcompartmentalise the crew compartment.

As an additional bonus, the survival section could be deliberately jettisoned, if BFS is technically intact but cannot make it to a save landing site or has insufficient power/fuel/thrust - to then save the crew by parachute.

This likely would eat up tons of BFS payload capacity, but would only be needed for LEO crew ferries, not for cargo, and not for mars ships (those could launch without crew and get boarded from a LEO ferry after being fueled in orbit. Parachutes are useless on Mars, so not much point in equipping the Mars transporter with them. Returning ships from Mars could worst case aerocapture into LEO and transfer back to a ferry for save(r) crew landing - if there's a large crew contingent and if this is really needed.

Offline Lar

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Re: Human rating the BFS
« Reply #127 on: 03/12/2018 10:45 PM »
Thanks for a great post. Maybe it will help refocus things a bit?
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Offline John Alan

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Re: Human rating the BFS
« Reply #128 on: 03/12/2018 10:51 PM »
Human Rating the BFS/BFR system....  ???

Who decided the Wright Flyer was human rated?
They did... they built it after all...  ;)

Turn it around... who decides something is NOT human rated...  ???
Answer... when NO human on the planet will get in the thing?...  :P
No... when MOST people will not get in the thing...  ;)

Famous examples of things that humans got into once... but in time lost all market share...
Ford Pinto (fuel tank fires)
DC-10 (engine fell off, Chicago)

As was posted up above.... the FAA is ok with basically using an experimental classification for human spaceflight.
While this seems wrong to many... it's a practice that goes back years for airplanes...

So all this talk of LAS and other stuff is basically a lot of hand waving in my opinion...
BFS does not need trained pilots to fly it... it's all automated... as it should be (again my opinion)
And if something goes wrong, it either saves itself or crashes... period...

What it will do someday, (hopefully) is take human 'cargo' along with all the other cargo it hauls here and there...
Those humans will sign their names on a release form and take their chances... (I would)

And if enough BFS's crash... nobody will get on one... and we are then back to square one...
Stuck on this blue marble, because we are too scared to fix it and try again?
Humans don't give up, when we set our minds to something... do we?...  ;)

« Last Edit: 03/12/2018 11:00 PM by John Alan »

Offline CorvusCorax

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Re: Human rating the BFS
« Reply #129 on: 03/13/2018 07:00 AM »
Human Rating the BFS/BFR system....  ???

Who decided the Wright Flyer was human rated?
They did... they built it after all...  ;)

Turn it around... who decides something is NOT human rated...  ???
Answer... when NO human on the planet will get in the thing?...  :P
No... when MOST people will not get in the thing...  ;)

Famous examples of things that humans got into once... but in time lost all market share...
Ford Pinto (fuel tank fires)
DC-10 (engine fell off, Chicago)

As was posted up above.... the FAA is ok with basically using an experimental classification for human spaceflight.
While this seems wrong to many... it's a practice that goes back years for airplanes...

So all this talk of LAS and other stuff is basically a lot of hand waving in my opinion...
BFS does not need trained pilots to fly it... it's all automated... as it should be (again my opinion)
And if something goes wrong, it either saves itself or crashes... period...

What it will do someday, (hopefully) is take human 'cargo' along with all the other cargo it hauls here and there...
Those humans will sign their names on a release form and take their chances... (I would)

And if enough BFS's crash... nobody will get on one... and we are then back to square one...
Stuck on this blue marble, because we are too scared to fix it and try again?
Humans don't give up, when we set our minds to something... do we?...  ;)

This is not a valid comparison. The wright flier was inherently save. It had wings and could glide to a save landing on the beach in case of propulsion failure. And even if a wing fell off, the wright brothers would likely have surcived the crash since it was going at low speeds.

On faster airplanes that are experimental or prototypes, test pilots, who are willing to accept the risks of an untested airframe, are regularly wearing personal parachutes, and ever since world war II, craft that go too fast to eject have ejection seats.

These have saved thousands of lives over the decades.

General aviation (sports) planes are nowadays equipped with emergency systems where the entire craft can land on parachute in case of loss of control.

Only large passenger planes ( like the mentioned DC10 ) have no safety system for individual passengers, but these are offset by triple redundancy in control systems, decades of safety lessons in daily operation learned and implemented, andeven an airliner can glide powerless and make a save emergency landing ( for example in the Hudson )

It would need decades of daily passenger flights until rockets could even hope to achieve that level of operational safety.

And rockets are inherently more unsafe :
1: they carry oxidizer which in case of hull rupture makes the entire vehicle a giant bomb with several kilotons TNT equivalent yield.
2: in case of SpaceX propulsive landing approach, a loss of power becomes completely unsurvivable.

Yes, a few daredevils might be willing to sit in these things without safety systems. Just like some people strap jet engines to a wing suit and pretend to be a fighter jet, go proximity flying at low altitudes in the mountains, or make a survival trip on their own through the Australian Outback.

Nasa had no problems finding a willing crew for the shUttle, despite its risks. But when they died it was a drama of not only National but world wide scale. These are the heroes that are going to expand mankinds final frontier and bring civilisation to Mars. Mars alone is deadly enough, no one would want to see these perish in a launch mishap.

It would be catastrophic for SpaceX image and later ability to sell tickets on commercial rides.

Rocket explosion blooper reels are cool - but not if there are people aboard!

And once commercial tickets are sold on a largerscale, be.iteatth to earth or earth to Mars, the FAA woild require the design to be inherently save, not a flying death trap.

A propulsively landing vehicle that cannot glide, auto-rotate like a helicopter, or deploy emergency parachutes IS a deathtrap. The FAA would never approve that for commercial passenger service, even if its not loaded with 100 tons of explosive propellant mixture.

No matter how reliable the individual  engines are. They still all rely on the same fuel pressurization system. Every passenger airliner has a RAM air turbine in case of complete propulsion loss. BFS will need the equivalent!



Offline archae86

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Some have RAT, some do not
« Reply #130 on: 03/13/2018 12:22 PM »
Every passenger airliner has a RAM air turbine in case of complete propulsion loss.
Actually not all models do.  Boeing 737 and Boeing 747 are two that generally do not.  And on some other models they are an option.  So there are many, many thousands of passenger airliners flying every day without a RAT.

The point is--these things are carried in order to meet safety criteria in specific scenarios--not just because some checklist somewhere says they have to be there.  A rational approach to safety systems does not start with a "got to have" list.

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Re: Human rating the BFS
« Reply #131 on: 03/13/2018 01:19 PM »
This is not a valid comparison. The wright flier was inherently save. It had wings and could glide to a save landing on the beach in case of propulsion failure. And even if a wing fell off, the wright brothers would likely have surcived the crash since it was going at low speeds.

The wright brothers were not the first to try manned winged flight. They were just the first to succede.

They INVENTED "gliding to a safe landing," as everyone before them rolled and fell out of the sky.

Offline CorvusCorax

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Re: Some have RAT, some do not
« Reply #132 on: 03/13/2018 01:25 PM »
Every passenger airliner has a RAM air turbine in case of complete propulsion loss.
Actually not all models do.  Boeing 737 and Boeing 747 are two that generally do not.  And on some other models they are an option.  So there are many, many thousands of passenger airliners flying every day without a RAT.

The point is--these things are carried in order to meet safety criteria in specific scenarios--not just because some checklist somewhere says they have to be there.  A rational approach to safety systems does not start with a "got to have" list.

Well researched, but completely beyond the point.
Indeed, 737 and 747 use a battery powered hydraulic pump to provide basic flight control, if both main engines and APU fail (fuel starvation). They have large batteries to provide 60 minutes of emergency power, instead of many other planes where small batteries and hydraulic reservoirs only bridge a few seconds until a RAT has deployed.

Some very old planes (pre 1970s) as well as smaller planes have neither. Instead these still have mechanical control wires to actuate control surfaces in this case.

Nevertheless there's always an emergency system in place for the rare but significant event of complete power failure, that lets the pilot glide the plane to an at least potential safe landing.

More importantly, despite all precautions, these events do happen at a measurable rate! If you look at https://en.wikipedia.org/wiki/List_of_airline_flights_that_required_gliding there was only one flight listed that had no survivors. Helios flight 522 - and that was because almost everyone was already dead at the time of impact due to pressurization loss at high altitude - they didn't wear spacesuits.

To get this back on topic, I think to human rate a craft it is necessary that.

The operator/manufacturer has countermeasures for all known failure modes that
 1. involve a single system failing (edit: with its potential additional failures as logical consequences...)
 2. would result in loss of life.

AKA there mustn't ever be any single thing that if it happens - dooms the passengers/crew.

Murphies law says that everything that can fail will eventually fail. SpaceX will eventually have an engine failure. SpaceX will eventually have an electrical systems problem, SpaceX will eventually have a tank pressurization system failure, and SpaceX will eventually have a tank rupture. In fact they already had all of the above, and they will have it again.

SpaceX task to make their vehicles save for human flight is to make sure that in every single one of these events, the crew has at least a conceivable chance of survival. If more things go wrong, you can attribute it to a bad day (for example LAS during RUD followed by parachute failure) and try to improve systems afterwards.

But if a forseeable event (such as loss of thrust) dooms the crew because the craft can no longer land, and you know beforehand you will potentially have this vehicle full of people tumbling towards the ground, and then impact and kill everyone while they nor anyone else can do nothing about it. Then this is a flaw that needs to be mitigated before crew is allowed on board.

The question is, how likely does a system failure have to be in order to mandate mitigation. Does one always need to have a backup system? Or is it enough, if - to stay with aircraft examples - the main wing spar is rated to 3 times the maximum flight load before it breaks, and then you don't need a spare set of emergency wings/parachutes?

If SpaceX can proof that they have sufficient margin and redundancy in all systems needed to savely bring the vehicle to the ground to fight any single system failure - if the fuel pressurization still works if the heat exchanger main valve failed, if enough engines still get enough fuel even if one of them had a RUD and the main tank is leaking. If the craft can still land if the main electric bus supplying avionics has a short - that might be sufficient.

This is the approach taken by airliners. Margins upon margins, very well understood technology and redundant systems.

If - like in a military jet or in a stunt plane - you don't have the margins because of weight/performace/expense requirements - then it might make more sense to add an ejection seat+parachute - or in case of spacecraft - a LAS

But if you do neither, you might kill someone.
« Last Edit: 03/13/2018 02:46 PM by CorvusCorax »

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Re: Human rating the BFS
« Reply #133 on: 03/13/2018 02:16 PM »
Don't confuse paperwork saying something is safe with something actually being safe. It is possible to have one without the other.

And vise versa.

I am not a native English speaker but the wording seems to imply exactly that.

Offline John Alan

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Re: Human rating the BFS
« Reply #134 on: 03/13/2018 04:00 PM »
BFS has one advantage, no commercial passenger or cargo aircraft has used in testing, to date (that I could find)...

It will fly unmanned from first flight, till it's deemed safe enough for some human occupancy... 

I suggest some of you think on that for a while...  ;)



« Last Edit: 03/13/2018 04:01 PM by John Alan »

Re: Human rating the BFS
« Reply #135 on: 03/13/2018 04:29 PM »
BFS has one advantage, no commercial passenger or cargo aircraft has used in testing, to date (that I could find)...

It will fly unmanned from first flight, till it's deemed safe enough for some human occupancy... 

I suggest some of you think on that for a while...  ;)
This is what I've been trying to say for a long time.
Many think BFR is about SpaceX trying to achieve a main goal: some focus on reusability, some on low cost, some on heavy lift capability.
This is not true: this design is optimized to reach multiple goals, in an interconnected way.

These goals are: -Full reusability, -Low cost operations, -Unprecedented safety and reliability, -Very high cadence, -Heavy lifting capacity.

The rocket's design is crafted in such a way that reaching each one of these goals both builds upon the others and furthers the others. It's a remarkably organic and synergistic approach. Every step towards meeting one of these goals also increases the probability of meeting the others. It's a (to me wonderfully crafted) self reinforcing design path.

And it makes it likelier that, if BFR manages to fly, they'll be able to accomplish all of these goals.
« Last Edit: 03/13/2018 04:46 PM by AbuSimbel »
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Offline tchernik

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Re: Human rating the BFS
« Reply #136 on: 03/13/2018 04:43 PM »
BFS has one advantage, no commercial passenger or cargo aircraft has used in testing, to date (that I could find)...

It will fly unmanned from first flight, till it's deemed safe enough for some human occupancy... 

I suggest some of you think on that for a while...  ;)

True. And according to its stated capabilities, it seems its first interplanetary trips (to the Moon and back) could be fully unmanned too. Which will be a remarkable feat, I concur.

Martian trips and landings can happen automatically as well, but the return trip would require some external help (for checking the refuel process works OK), that is, people on the surface.

When humans get on-board for the first time, BFR should have several full mission profile tests already.
« Last Edit: 03/13/2018 06:23 PM by tchernik »

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Re: Human rating the BFS
« Reply #137 on: 03/13/2018 05:56 PM »
Another consideration for HR is the potential to use BFS for perhaps space tourism, both suborbital and orbital.

Perhaps one of the reasons for not HR FH is ... that there's a better first step into building a HSF business, possibly doing so in grander style, bigger windows, more at a flight ... than NS? Interesting.

Offline envy887

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Re: Some have RAT, some do not
« Reply #138 on: 03/13/2018 06:03 PM »
If SpaceX can proof that they have sufficient margin and redundancy in all systems needed to savely bring the vehicle to the ground to fight any single system failure - if the fuel pressurization still works if the heat exchanger main valve failed, if enough engines still get enough fuel even if one of them had a RUD and the main tank is leaking. If the craft can still land if the main electric bus supplying avionics has a short - that might be sufficient.

This is the approach taken by airliners. Margins upon margins, very well understood technology and redundant systems.

If - like in a military jet or in a stunt plane - you don't have the margins because of weight/performace/expense requirements - then it might make more sense to add an ejection seat+parachute - or in case of spacecraft - a LAS

But if you do neither, you might kill someone.

SpaceX has already made it rather clear that they are choosing Option A. You get airliner-like reliability with airliner-like redundancy.

Plus a LAS is pretty pointless during a reentry, or a launch from another planet, while redundancy is much more useful.
« Last Edit: 03/13/2018 06:03 PM by envy887 »

Offline Lar

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Re: Human rating the BFS
« Reply #139 on: 03/13/2018 06:43 PM »
Don't confuse paperwork saying something is safe with something actually being safe. It is possible to have one without the other.

And vise versa.

I am not a native English speaker but the wording seems to imply exactly that.
My wording implied "and vice versa" since I didn't reference either thing specifically, but I didn't think it was important enough to comment back to AncientU.  Or to go fix the original post to add those words...  I don't think we need to belabor the point further.
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