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SpaceX Vehicles and Missions => SpaceX BFR - Earth to Deep Space => Topic started by: Pipcard on 07/24/2017 11:42 PM

Title: Should the BFR have a launch escape system?
Post by: Pipcard on 07/24/2017 11:42 PM
The STS, better known as the Space Shuttle, was assumed during its development to be so reliable that it did not need any launch abort capabilities. The Challenger disaster of 1986 led to the questioning of this notion. However, they could not retrofit the Shuttle due to complexity, weight, and cost concerns.

Some people assume that the ITS is going to operate like an airliner, such that it won't need any form of LES, but will SpaceX have trouble getting proper safety certifications for the ITS in order for it to launch people?

How many test flights would take place before such a vehicle can be deemed safe to carry humans? For example, the Japanese SSTO concept Kankoh-maru (designed for large-scale space tourism) was thought to have required 1200 test flights (http://www.cthisspace.com/ftl/features/spacehotel.html).

edit: changed title to BFR.
Title: Re: Should the ITS have a launch escape system?
Post by: IanThePineapple on 07/24/2017 11:48 PM
Its LES is pretty much the engines on the bottom of the ship, you can't have an escape system that large.
Title: Re: Should the ITS have a launch escape system?
Post by: Robotbeat on 07/24/2017 11:49 PM
Well, if ITS doesn't have a LAS, it probably will at least have a docking port. So can always launch crew in Dragon. That could also be one of QuantumG's payload subscale BFRs, too.

So, annoying but definitely no showstopper. Musk mentioned a crew (LEO) transport transferring people to interplanetary ITS if refueling takes too long, so presumably you could fit an LAS onto this other ITS if Dragon is deemed too expensive.

That would be when you want to send lots of people. It need not happen until there's a LOT of infrastructure already prepared on Mars or the Moon, i.e. 2030s or 2040s.
Title: Re: Should the ITS have a launch escape system?
Post by: Lars-J on 07/25/2017 12:08 AM
Not this topic again.  ;D This has been discussed a lot on this forum, look at old ITS threads to see every possible argument in favor and against launch escape systems.
Title: Re: Should the ITS have a launch escape system?
Post by: spacenut on 07/25/2017 12:45 AM
I predict the first humans to Mars will only have between 6-18 crew.  Six can be brought up at a time on Dragon capsules.  They will dock with ITS.  ITS will be in orbit until it is refueled, and if necessary add cargo.  It could launch empty and cargo brought up by another ITS making refueling easier with only one or two tanker ITS.  A couple of unmanned ITS could go to Mars before hand and set up refueling operations etc.   

Later manned only ITS taking colonists can still be loaded not only by Dragons, but CTS-100's or Soyuz or even Chinese or whoever else wants to send.  Six with one Dragon, 4 with one CTS-100, 3 with Soyuz and 3 maybe with Chinese, that is 16 and all can dock and load their colonists within a day of each other.  By then India may have a capsule.  Even another provider like Blue Origin.  Europeans may want to pay for flights.  People don't have to be launched on ITS.  It is for in space use mostly for humans, and for earth launches of cargo.   
Title: Re: Should the ITS have a launch escape system?
Post by: stcks on 07/25/2017 02:33 AM
Look, if you're going to hop in the ITS and make a propulsive landing on another heavenly body then you are already trusting your life to a system without a dedicated abort system. At that point you might as well take the ride out of Earth's atmosphere too.
Title: Re: Should the ITS have a launch escape system?
Post by: Kenp51d on 07/25/2017 02:57 AM
Look, if you're going to hop in the ITS and make a propulsive landing on another heavenly body then you are already trusting your life to a system without a dedicated abort system. At that point you might as well take the ride out of Earth's atmosphere too.
Agreed
 At least for a fair number of years, if you abort on Mars you are still toast. The toaster just pops up a bit later.
A second or third ship might make me wrong though, that's a good thing indeed.

Sent from my XT1565 using Tapatalk

Title: Re: Should the ITS have a launch escape system?
Post by: Robotbeat on 07/25/2017 03:10 AM
I don't know if I think ITS should have an abort capability or not, but:

The idea that abort on Mars would be pointless is a dumb myth that needs to die. There's no reason that need necessarily be true, and there are several strategies to ensuring survival for those who abort.

Down-range placement of supplies or rover.

Survival equipment on the capsule.

Mars aircraft sent for pickup or supply delivery.

Small orbital caches sent to the surface.

Suborbital hoppers.

Backup ITS used to rescue stranded survivors.

Fast rovers.

Escape capsule maneuvering.

A combination of the above concepts.


Seriously, you might think it's not worth it. I haven't decided myself. But to say aborting crew would necessarily be toast is incredibly small-minded.
Title: Re: Should the ITS have a launch escape system?
Post by: Kenp51d on 07/25/2017 03:46 AM
I don't know if I think ITS should have an abort capability or not, but:

The idea that abort on Mars would be pointless is a dumb myth that needs to die. There's no reason that need necessarily be true, and there are several strategies to ensuring survival for those who abort.

Down-range placement of supplies or rover.

Survival equipment on the capsule.

Mars aircraft sent for pickup or supply delivery.

Small orbital caches sent to the surface.

Suborbital hoppers.

Backup ITS used to rescue stranded survivors.

Fast rovers.

Escape capsule maneuvering.

A combination of the above concepts.


Seriously, you might think it's not worth it. I haven't decided myself. But to say aborting crew would necessarily be toast is incredibly small-minded.
You just might be right on some of those options.
Every effort to save a crew is worth while. We certainly try very hard to save people here on Earth. Even great efforts are spent too save animals that are trapped, hurt whatever. Many fire units are even equipped with mask to save a dog or cat. I applued all of that. Life is very precious.
You had valid points that I was not aware of as options. But your rebuttal would have been just as evective if delivered without harshness, meant that way or not.
I have generally found honey first, then the vinager has a higher success rate with people.
No offense meant with my reply. I have usually read your posts a little closer.

Sent from my XT1565 using Tapatalk

Title: Re: Should the ITS have a launch escape system?
Post by: Robotbeat on 07/25/2017 04:18 AM
I don't know if I think ITS should have an abort capability or not, but:

The idea that abort on Mars would be pointless is a dumb myth that needs to die. There's no reason that need necessarily be true, and there are several strategies to ensuring survival for those who abort.

Down-range placement of supplies or rover.

Survival equipment on the capsule.

Mars aircraft sent for pickup or supply delivery.

Small orbital caches sent to the surface.

Suborbital hoppers.

Backup ITS used to rescue stranded survivors.

Fast rovers.

Escape capsule maneuvering.

A combination of the above concepts.


Seriously, you might think it's not worth it. I haven't decided myself. But to say aborting crew would necessarily be toast is incredibly small-minded.
You just might be right on some of those options.
Every effort to save a crew is worth while. We certainly try very hard to save people here on Earth. Even great efforts are spent too save animals that are trapped, hurt whatever. Many fire units are even equipped with mask to save a dog or cat. I applued all of that. Life is very precious.
You had valid points that I was not aware of as options. But your rebuttal would have been just as evective if delivered without harshness, meant that way or not.
I have generally found honey first, then the vinager has a higher success rate with people.
No offense meant with my reply. I have usually read your posts a little closer.

Sent from my XT1565 using Tapatalk
Good point.
Title: Re: Should the ITS have a launch escape system?
Post by: Jim on 07/25/2017 01:44 PM
Look, if you're going to hop in the ITS and make a propulsive landing on another heavenly body then you are already trusting your life to a system without a dedicated abort system. At that point you might as well take the ride out of Earth's atmosphere too.

Not really.  Earth orbital launch is completely different than a martian orbital launch.  The delta V and atmosphere make for two different vehicles.  Martian orbital launch launch vehicle is a small SSTO.  Earth orbital launch will be a large multistage vehicle.
Title: Re: Should the ITS have a launch escape system?
Post by: stcks on 07/25/2017 01:55 PM
Look, if you're going to hop in the ITS and make a propulsive landing on another heavenly body then you are already trusting your life to a system without a dedicated abort system. At that point you might as well take the ride out of Earth's atmosphere too.

Not really.  Earth orbital launch is completely different than a martian orbital launch.  The delta V and atmosphere make for two different vehicles.  Martian orbital launch launch vehicle is a small SSTO.  Earth orbital launch will be a large multistage vehicle.

I understand that. But that doesn't really change anything. Once you hit Mars atmosphere you're committed. What use is some fancy abort pod in that regime? You're not making it back to earth. (And yes, fine, if some existing base is already on Mars with proper emergency vehicles and whatever in place already, maybe you survive, but im not talking about that).

If the booster fails on ascent from Earth, you rely on the ship to abort. If something fails inbound to Mars, you also rely on the ship. It just seems odd to me to ferry passengers to LEO on a separate ship when their lives will depend entirely on the integrity of the interplanetary ship anyway.

Jim, I'm curious how you would see an abort capability working.
Title: Re: Should the ITS have a launch escape system?
Post by: JamesH65 on 07/26/2017 10:49 AM
I look on it as if you were trying to make an launch abort system for a small airliner carrying say 100 people. Some way of getting everyone to safety if it fails in flight.

And I cannot think of a way of doing that...
Title: Re: Should the ITS have a launch escape system?
Post by: Arb on 07/26/2017 10:05 PM
If you were going to do it the obvious way would be to cram the launch-and-landing-couches into the ship's nose and make that section a separable, large capsule. It would need enough propellant to abort in earth gravity (plus parachutes to land). On mars and the moon it'd need enough propellant to abort and land.

Lot's of trades to be done to determine if feasible and at what cost in $ and lost cargo/passenger capacity.

I quite like the idea of everyone on board being in close proximity for launch and landing (those short but dangerous phases of flight); it feels right somehow.
Title: Re: Should the ITS have a launch escape system?
Post by: Patchouli on 07/26/2017 10:27 PM
Two ways to solve it you either make the systems able to handle multiple failures during launch and able to make an emergency landing if needed like an airliner or you launch it uncrewed and then once it's on orbit have a vehicle that is inherently safer such as a capsule,small space plane or even a HOTOL like Skylon carry up the crew and passingers.

Dealing with T+ 0 failures is lot easier for a HOTOL as like an airliner they don't fall back on the pad if thrust to weight drops below 1 to 1 which is why I suggest it as a solution.

Plus having ITS launch uncrewed removes some of the time constraints to get it refueled and not having 50 to 100 people and all their luggage on board  would save a lot of mass on the hardest leg of the trip.
Title: Re: Should the ITS have a launch escape system?
Post by: livingjw on 07/27/2017 02:21 AM
Two ways to solve it you either make the systems able to handle multiple failures during launch and able to make an emergency landing if needed like an airliner or you launch it uncrewed and then once it's on orbit have a vehicle that is inherently safer such as a capsule,small space plane or even a HOTOL like Skylon carry up the crew and passingers.

Dealing with T+ 0 failures is lot easier for a HOTOL as like an airliner they don't fall back on the pad if thrust to weight drops below 1 to 1 which is why I suggest it as a solution.

Plus having ITS launch uncrewed removes some of the time constraints to get it refueled and not having 50 to 100 people and all their luggage on board  would save a lot of mass on the hardest leg of the trip.

- Disagree. If you loose all propulsion in an airliner you will most likely die.
- There are no HTOL systems that can accomplish SSTO. They will have to be TSTO. This includes Skylon.
- HTOL launchers are more complex than VTOL rockets and use advanced technology (lower TRLs, higher risk).
- As Patchouli said, you need to be able to handle failures and still get down safely. Some obvious things that could be done are:
           - robust landing rockets and fuel separate from main propulsion.
           - main propellant dump system to empty tanks quickly (and sequentially)
           - landing on its side instead of upright
Just some ideas.

John

Title: Re: Should the ITS have a launch escape system?
Post by: CuddlyRocket on 07/27/2017 04:18 AM
If you loose all propulsion in an airliner you will most likely die.

That's not true. In many such cases the pilots manage to re-start an engine. Where they do not, most successfully glide to the nearest runway (the record is 65 miles). Even when they can't reach a runway, many successfully land elsewhere or ditch on water (e.g. Captain Sully on the Hudson river).
Title: Re: Should the ITS have a launch escape system?
Post by: su27k on 07/27/2017 04:57 AM
I look on it as if you were trying to make an launch abort system for a small airliner carrying say 100 people. Some way of getting everyone to safety if it fails in flight.

And I cannot think of a way of doing that...

Some examples:
https://encrypted.google.com/patents/EP1110861A1?cl=en
https://www.google.com/patents/US20110233341

These do not make much sense for airplane because air travel is very safe, but I think they're definitely needed if we're going to send 50 people on top of BFR. One advantage of rocket travel is the launch itself only lasts a very short time, so you can pack people like sardines into a much smaller space.
Title: Re: Should the ITS have a launch escape system?
Post by: pathfinder_01 on 07/27/2017 06:31 AM
It just seems odd to me to ferry passengers to LEO on a separate ship when their lives will depend entirely on the integrity of the interplanetary ship anyway.


There are advntages and disadvantages of ferring in a seperate ship.

The ITS bound for mars could take a less human safe trajectory (g forces and location where an abort system would land a crew)into orbit which could allow for greater amounts of cargo to get to orbit. Humans would retain the safety of abort system.

It would relax the time constraints with regard to refueling the ITS before departure.

Also although Elon plans to depart from LEO, LEO isn't the only place he could depart from.

I rather doubt that any human carring spacecraft will attempt to go without a escape system for quite some time(i.e. so long as crews are small.)
Title: Re: Should the ITS have a launch escape system?
Post by: Pipcard on 09/21/2017 01:36 AM
I just found out that this question was already answered last year, after the presentation livestream.
https://www.youtube.com/watch?v=-PQNL9ZpCfY

The points made by Musk were:
- Spaceship is meant to be its own abort system during Earth launch
(but don't launch escape systems, including that of Crew Dragon, need to have a high TWR? Or engines that can start as soon as possible?)
- A separate LES on Mars is pointless: "if you're not taking off, you're not taking off" and "parachutes don't work too well."
- An specialized LES for 100 people is not feasible.
- Key is focusing on reliability and "redundancy in the engines, high safety margins," and lots of testing "like a commercial airliner."

Martianspirit on r/spacex (https://www.reddit.com/r/spacex/comments/558g5i/discussion_what_would_you_change_about_the_its/d89kizh/) speculated about putting the passengers on a tanker (therefore, not requiring the use of partially expendable Falcon 9 + Dragon).
Quote
Elon Musk has mentioned the possibility to launch the passengers late into the refuelled vehicle. It would be quite inefficient to use a full ITS for that purpose. Take a tanker and cut off the nose. Replace it with an abort capsule. For 100 passengers it may have a weight of 60t and would not reduce the tanker capacity too much. The capsule would be crammed but it would only be for a few hours.

Or maybe splitting the crew between five tankers? And making it an SSTO when doing LEO tourism? (Robotbeat thinks a modified tanker would have enough delta-v margin for smaller payloads - is it carbon fiber that makes this possible?)

A few have mentioned that going to Mars is already risky enough. But what if someone just wants to be a tourist in LEO? Having an LES may make it more attractive to more potential customers.
Title: Re: Should the ITS have a launch escape system?
Post by: matthewkantar on 09/21/2017 03:02 AM
Maybe SpaceX could give the passengers a choice, letting those individuals pick from a menu. Earth surface to Mars on a single vehicle with no LES would cost $500,000. If you want go up on a falcon and transfer to ITS, the additional cost might be $3,000,000, or one seventh of a twenty or so million dollar F-9 launch.

I know what I would choose.

Matthew
Title: Re: Should the ITS have a launch escape system?
Post by: MATTBLAK on 09/21/2017 03:31 AM
If the big(gest) ITS could eventually show a loss-of-mission safety ratio about one-third that of a busy, commercial airliner - that would be more than good enough for me. But we would be waiting some years for that to happen...
Title: Re: Should the ITS have a launch escape system?
Post by: GORDAP on 09/21/2017 12:04 PM
I've always wondered just what is wrong with the BFS being its own LES. 

I know that it doesn't have high T/W ratio, and that the turbopumps take a few seconds to spin up, but it's not like you're going to outrun a true detonation event in the booster anyway, no matter how quickly a human 'pod' can skedaddle out of there.  It seems that it should only be required to outrun a conflagration of the booster, right?

Can anyone point to a realistic booster failure scenario in which a traditional LES would save the passengers, but in which the planned BFS LES would not?
Title: Re: Should the ITS have a launch escape system?
Post by: envy887 on 09/21/2017 01:51 PM
I've always wondered just what is wrong with the BFS being its own LES. 

I know that it doesn't have high T/W ratio, and that the turbopumps take a few seconds to spin up, but it's not like you're going to outrun a true detonation event in the booster anyway, no matter how quickly a human 'pod' can skedaddle out of there.  It seems that it should only be required to outrun a conflagration of the booster, right?

Can anyone point to a realistic booster failure scenario in which a traditional LES would save the passengers, but in which the planned BFS LES would not?

Any launch where the vehicle fails to control its angle of attack in the atmosphere (like Ariane 501 or the Challenger breakup) would be much easier to survive in a capsule than an integrated stage/capsule. I'm not sure the ship will be designed to survive a high AoA at max-Q pressures, and a clean separation is also very tricky.

Also any failures that happen on or near the launch pad, like AMOS-6 or the Proton nosedive in 2013, would not leave the ship with enough altitude and velocity to get away with it's low TWR at sea level. Not an issue with a capsule.
Title: Re: Should the ITS have a launch escape system?
Post by: GORDAP on 09/21/2017 03:16 PM
I've always wondered just what is wrong with the BFS being its own LES. 

I know that it doesn't have high T/W ratio, and that the turbopumps take a few seconds to spin up, but it's not like you're going to outrun a true detonation event in the booster anyway, no matter how quickly a human 'pod' can skedaddle out of there.  It seems that it should only be required to outrun a conflagration of the booster, right?

Can anyone point to a realistic booster failure scenario in which a traditional LES would save the passengers, but in which the planned BFS LES would not?

Any launch where the vehicle fails to control its angle of attack in the atmosphere (like Ariane 501 or the Challenger breakup) would be much easier to survive in a capsule than an integrated stage/capsule. I'm not sure the ship will be designed to survive a high AoA at max-Q pressures, and a clean separation is also very tricky.

Also any failures that happen on or near the launch pad, like AMOS-6 or the Proton nosedive in 2013, would not leave the ship with enough altitude and velocity to get away with it's low TWR at sea level. Not an issue with a capsule.

Hmm, are you saying the BFS would have a TWR less than 1 at sea level?  I think that's hard to imagine with all 9 engines screaming at full thrust (yes, I realize that 6 of these would be overexpanded at sea level, but it seems this would be acceptable for a small amount of time during a dire emergency).

It appears you are saying that a capsule with appropriate LES had a much better chance of survival than a vehicle that depends upon aerodynamics during this critical phase, right? (correct me if I'm wrong.)  But I'm not suggesting that the BFR fly like an airplane during an abort, I'm suggesting that if flies, then lands as a rocket ship in the same mode as its final decent on Mars and Earth.  Sure, it will have to hover for a good while to burn off fuel, but that shouldn't be an issue. 

I'm still not seeing why a capsule with LES would be inherently safer than a BFS, unless one can make a credible argument that getting away from a disintegrating booster underneath you - in a great hurry - is critical.
Title: Re: Should the ITS have a launch escape system?
Post by: RonM on 09/21/2017 04:14 PM
I'm still not seeing why a capsule with LES would be inherently safer than a BFS, unless one can make a credible argument that getting away from a disintegrating booster underneath you - in a great hurry - is critical.

Look at Apollo, Orion, Soyuz, Shenzhou, Starliner, and Dragon. Somebody thinks it's critical.
Title: Re: Should the ITS have a launch escape system?
Post by: GORDAP on 09/21/2017 05:01 PM
I'm still not seeing why a capsule with LES would be inherently safer than a BFS, unless one can make a credible argument that getting away from a disintegrating booster underneath you - in a great hurry - is critical.

Look at Apollo, Orion, Soyuz, Shenzhou, Starliner, and Dragon. Somebody thinks it's critical.

Ron, I fully understand that getting away is critical.  I underlined the 'great hurry' part to distinguish the argument that a few seconds delay and/or slower acceleration is somehow an important differentiator.  I'm asking for someone to explain how/why this would make the difference between success and loss of life.
Title: Re: Should the ITS have a launch escape system?
Post by: RonM on 09/21/2017 05:27 PM
I'm still not seeing why a capsule with LES would be inherently safer than a BFS, unless one can make a credible argument that getting away from a disintegrating booster underneath you - in a great hurry - is critical.

Look at Apollo, Orion, Soyuz, Shenzhou, Starliner, and Dragon. Somebody thinks it's critical.

Ron, I fully understand that getting away is critical.  I underlined the 'great hurry' part to distinguish the argument that a few seconds delay and/or slower acceleration is somehow an important differentiator.  I'm asking for someone to explain how/why this would make the difference between success and loss of life.

Look at some old rocket explosion videos. It should become obvious. An emergency on the pad or early in flight require a high gee acceleration to escape. Later in the flight, more gentle aborts will work. That's why Apollo, Orion, Soyuz, and Shenzhou jettison their LAS before reaching orbit; it's no longer needed.

Even high gee LAS won't save the crew all of the time. If there's no indication of a problem before a massive explosion, no LAS is going to do the job.

There will always be a chance the crew will be killed. That's ok for daring astronauts on exploration missions, but what about 100 passengers wanting a new start at a Mars colony? If there isn't a LAS on ITS spacecraft, then the booster better be as reliable as a modern aircraft. Either that or the passengers need to be well informed about the danger.
Title: Re: Should the ITS have a launch escape system?
Post by: AncientU on 09/21/2017 05:37 PM
I'm still not seeing why a capsule with LES would be inherently safer than a BFS, unless one can make a credible argument that getting away from a disintegrating booster underneath you - in a great hurry - is critical.

Look at Apollo, Orion, Soyuz, Shenzhou, Starliner, and Dragon. Somebody thinks it's critical.

Ron, I fully understand that getting away is critical.  I underlined the 'great hurry' part to distinguish the argument that a few seconds delay and/or slower acceleration is somehow an important differentiator.  I'm asking for someone to explain how/why this would make the difference between success and loss of life.

Look at some old rocket explosion videos. It should become obvious. An emergency on the pad or early in flight require a high gee acceleration to escape. Later in the flight, more gentle aborts will work. That's why Apollo, Orion, Soyuz, and Shenzhou jettison their LAS before reaching orbit; it's no longer needed.

Even high gee LAS won't save the crew all of the time. If there's no indication of a problem before a massive explosion, no LAS is going to do the job.

There will always be a chance the crew will be killed. That's ok for daring astronauts on exploration missions, but what about 100 passengers wanting a new start at a Mars colony? If there isn't a LAS on ITS spacecraft, then the booster better be as reliable as a modern aircraft. Either that or the passengers need to be well informed about the danger.

People by the millions flew on commercial aircraft 30-40 years ago when they were a fraction as safe as 'modern aircraft.'  People by the millions (billions) do all sorts of crazy things today that aren't as safe as 'modern aircraft,' like driving to work, or skiing, or jumping out of airplanes that aren't on fire...

Inform passengers of the risk, have them sign on the dotted line, and get on with it. 

Don't go if your standard is as safe as 'modern aircraft'... won't happen.


Title: Re: Should the ITS have a launch escape system?
Post by: envy887 on 09/21/2017 06:23 PM
Look at some old rocket explosion videos. It should become obvious. An emergency on the pad or early in flight require a high gee acceleration to escape. Later in the flight, more gentle aborts will work. That's why Apollo, Orion, Soyuz, and Shenzhou jettison their LAS before reaching orbit; it's no longer needed.

Even high gee LAS won't save the crew all of the time. If there's no indication of a problem before a massive explosion, no LAS is going to do the job.

The high acceleration is mainly to get away from any debris thrown during a booster breakup that might damage the capsule, as well as the potential overpressure wave and thermal damage. Not every booster failure results in debris, pressure, or thermals that threaten the crew vehicle, and there are situations where the low thrust and delayed start of the upper stage Raptors would be sufficient to save the crew.

Hmm, are you saying the BFS would have a TWR less than 1 at sea level?  I think that's hard to imagine with all 9 engines screaming at full thrust (yes, I realize that 6 of these would be overexpanded at sea level, but it seems this would be acceptable for a small amount of time during a dire emergency).

It appears you are saying that a capsule with appropriate LES had a much better chance of survival than a vehicle that depends upon aerodynamics during this critical phase, right? (correct me if I'm wrong.)  But I'm not suggesting that the BFR fly like an airplane during an abort, I'm suggesting that if flies, then lands as a rocket ship in the same mode as its final decent on Mars and Earth.  Sure, it will have to hover for a good while to burn off fuel, but that shouldn't be an issue.

The ITS ship as presented at IAC 2016 would definitely have a TWR very near 1, because the overexpanded vacuum nozzles reduce the available thrust from those engines. That design might change to something more useful for a pad abort.

The biggest issue with using the Raptors for abort is the potential loss of control during the delay for startup, especially near Max-Q. That stage is going to have a much tougher time flying sideways at Mach 1 than a capsule would. Perhaps the RCS system and/or body flaps could be used for control while the Raptors spin up.
Title: Re: Should the ITS have a launch escape system?
Post by: spacenut on 09/21/2017 06:25 PM
The 9m ITS will probably send 5-10 unmanned cargo ships to Mars first with equipment, habitats, solar panels, etc.  One ship will make fuel for return.  These will probably be sent in one synod.  Then the next synod, humans will go.  To begin with I say a small crew, no more than say 30 on the smaller ITS.  So ITS while refueling can easily have 2-3 Dragons or other spacecraft dock and transfer their people.  One Dragon (6), one CTS-100 (4), Soyuz (3), the Chinese craft (3), That is 16, maybe others on their spacecrafts.  So I don't see ITS having a LES, probably ever.  Docking for fueling will probably be done from the sides.  Docking for visiting spacecraft transfering people can be done from the nose while it is refueling for a trip to Mars.  These early ships will be a mix of crew and cargo.  Maybe even husband-wife astronauts or specialists in botony, or mining, or chemistry. 
Title: Re: Should the ITS have a launch escape system?
Post by: GORDAP on 09/21/2017 09:17 PM
Look at some old rocket explosion videos. It should become obvious. An emergency on the pad or early in flight require a high gee acceleration to escape. Later in the flight, more gentle aborts will work. That's why Apollo, Orion, Soyuz, and Shenzhou jettison their LAS before reaching orbit; it's no longer needed.

Even high gee LAS won't save the crew all of the time. If there's no indication of a problem before a massive explosion, no LAS is going to do the job.

The high acceleration is mainly to get away from any debris thrown during a booster breakup that might damage the capsule, as well as the potential overpressure wave and thermal damage. Not every booster failure results in debris, pressure, or thermals that threaten the crew vehicle, and there are situations where the low thrust and delayed start of the upper stage Raptors would be sufficient to save the crew.

Hmm, are you saying the BFS would have a TWR less than 1 at sea level?  I think that's hard to imagine with all 9 engines screaming at full thrust (yes, I realize that 6 of these would be overexpanded at sea level, but it seems this would be acceptable for a small amount of time during a dire emergency).

It appears you are saying that a capsule with appropriate LES had a much better chance of survival than a vehicle that depends upon aerodynamics during this critical phase, right? (correct me if I'm wrong.)  But I'm not suggesting that the BFR fly like an airplane during an abort, I'm suggesting that if flies, then lands as a rocket ship in the same mode as its final decent on Mars and Earth.  Sure, it will have to hover for a good while to burn off fuel, but that shouldn't be an issue.

The ITS ship as presented at IAC 2016 would definitely have a TWR very near 1, because the overexpanded vacuum nozzles reduce the available thrust from those engines. That design might change to something more useful for a pad abort.

The biggest issue with using the Raptors for abort is the potential loss of control during the delay for startup, especially near Max-Q. That stage is going to have a much tougher time flying sideways at Mach 1 than a capsule would. Perhaps the RCS system and/or body flaps could be used for control while the Raptors spin up.

I've seen clips of many rockets failing during ascent, and they seem to fall into 3 general categories:  A) Violent explosions (rare), B) Gradual (relatively speaking) disintegration, and C) Quickly moving 'conflagrations' (i.e. Shuttle).

There seems to be agreement that no LES designs will survive type A, with high speed debris and the over pressure wave.  I think both BFS and a capsule would survive type B.  That leaves type C - a rapidly expanding conflagration.  Because of its orientation, the shuttle was instantly in the middle of the fireball, plus sandwiched between the two solids (not a good place to be).   Is there a good reason to believe that a BFS would not survive a 'typical' conflagration type event of the booster (other than the momentary aerodynamic issue raised above)?

I just suspect that when someone runs the actual numbers for failure scenarios, they'd find something like, yeah, a capsule plus traditional LES survives 80% of the failures, and the BFS will only survive 75%.  If this is the case, the "You can't launch 100 civilians without traditional LES" argument is revealed to be too simplistic. 
Title: Re: Should the ITS have a launch escape system?
Post by: whitelancer64 on 09/21/2017 09:40 PM
I've seen clips of many rockets failing during ascent, and they seem to fall into 3 general categories:  A) Violent explosions (rare), B) Gradual (relatively speaking) disintegration, and C) Quickly moving 'conflagrations' (i.e. Shuttle).

There seems to be agreement that no LES designs will survive type A, with high speed debris and the over pressure wave.  I think both BFS and a capsule would survive type B.  That leaves type C - a rapidly expanding conflagration.  Because of its orientation, the shuttle was instantly in the middle of the fireball, plus sandwiched between the two solids (not a good place to be).   Is there a good reason to believe that a BFS would not survive a 'typical' conflagration type event of the booster (other than the momentary aerodynamic issue raised above)?

I just suspect that when someone runs the actual numbers for failure scenarios, they'd find something like, yeah, a capsule plus traditional LES survives 80% of the failures, and the BFS will only survive 75%.  If this is the case, the "You can't launch 100 civilians without traditional LES" argument is revealed to be too simplistic.

LES systems are designed for your category A. LES systems can react faster than the blink of an eye. A crewed Dragon v2 on top of Amos-6 would have gotten clear of the explosion easily, for example.
Title: Re: Should the ITS have a launch escape system?
Post by: Norm38 on 09/22/2017 05:43 PM
LES systems are designed for your category A. LES systems can react faster than the blink of an eye. A crewed Dragon v2 on top of Amos-6 would have gotten clear of the explosion easily, for example.

I have a question about that, regarding the g-forces on the human body. At launch the astronauts are strapped in, facing forward, braced and ready for the acceleration.
Now I supposed that the astronauts will have to be already strapped in before fueling starts, but they won't be braced for an unexpected high g abort.  So they've got their arms about, their head up, looking around, then are suddenly slammed back at several g.  What happens?
Title: Re: Should the ITS have a launch escape system?
Post by: cppetrie on 09/22/2017 08:30 PM
LES systems are designed for your category A. LES systems can react faster than the blink of an eye. A crewed Dragon v2 on top of Amos-6 would have gotten clear of the explosion easily, for example.

I have a question about that, regarding the g-forces on the human body. At launch the astronauts are strapped in, facing forward, braced and ready for the acceleration.
Now I supposed that the astronauts will have to be already strapped in before fueling starts, but they won't be braced for an unexpected high g abort.  So they've got their arms about, their head up, looking around, then are suddenly slammed back at several g.  What happens?
For Dragon 2, at least, fueling will take approximately 75 minutes. During that time the passengers would be strapped in tightly with little room to move. They wonít be able to move their heads much and there would be little reason to be reaching about in the capsule as everything is automated or controlled from the ground. At most they might be reading something off a display and relating it to ground but even that is probably unnecessary. They will mostly just be confirming they are go for launch when the time comes. The same will be true during ascent. A sudden high-G maneuver could result in injury if they were moving around or not secured properly, but neither should be the case.
Title: Re: Should the ITS have a launch escape system?
Post by: eriblo on 09/22/2017 08:42 PM
LES systems are designed for your category A. LES systems can react faster than the blink of an eye. A crewed Dragon v2 on top of Amos-6 would have gotten clear of the explosion easily, for example.

I have a question about that, regarding the g-forces on the human body. At launch the astronauts are strapped in, facing forward, braced and ready for the acceleration.
Now I supposed that the astronauts will have to be already strapped in before fueling starts, but they won't be braced for an unexpected high g abort.  So they've got their arms about, their head up, looking around, then are suddenly slammed back at several g.  What happens?
For Dragon 2, at least, fueling will take approximately 75 minutes. During that time the passengers would be strapped in tightly with little room to move. They wonít be able to move their heads much and there would be little reason to be reaching about in the capsule as everything is automated or controlled from the ground. At most they might be reading something off a display and relating it to ground but even that is probably unnecessary. They will mostly just be confirming they are go for launch when the time comes. The same will be true during ascent. A sudden high-G maneuver could result in injury if they were moving around or not secured properly, but neither should be the case.
I agree with cppetrie and my basic-physics guess is that worst case scenario is a dislocated/broken arm or two and strained neck muscles. The initial g-force is about 6 g in the best possible direction ("eyeballs in") which is comparable to at most a 8 m/s (29 kph, 18 mph) rear end collision (assuming equal weight cars and 1 m ideal crumple zone). The acceleration will of course continue for much longer but then you have time to tense up and use your muscles.
Title: Re: Should the ITS have a launch escape system?
Post by: docmordrid on 09/22/2017 10:11 PM
For comparison, the highst G coaster is the 'Tower of Terror' at Gold Reef City, South Africa

6.3G

http://entertainmentdesigner.com/news/top-seven-most-thrilling-roller-coasters-in-the-world/
Title: Re: Should the ITS have a launch escape system?
Post by: Norm38 on 09/23/2017 04:05 AM
Okay, so in the equation of whether I as a paying passenger want an LES or not;
The choice is airline like operations at higher risk, or astronaut level precautions.

One way colonists may tolerate that. But there's some frequency limit to that.
Title: Re: Should the ITS have a launch escape system?
Post by: cppetrie on 09/23/2017 05:09 AM
LES systems are designed for your category A. LES systems can react faster than the blink of an eye. A crewed Dragon v2 on top of Amos-6 would have gotten clear of the explosion easily, for example.

I have a question about that, regarding the g-forces on the human body. At launch the astronauts are strapped in, facing forward, braced and ready for the acceleration.
Now I supposed that the astronauts will have to be already strapped in before fueling starts, but they won't be braced for an unexpected high g abort.  So they've got their arms about, their head up, looking around, then are suddenly slammed back at several g.  What happens?
For Dragon 2, at least, fueling will take approximately 75 minutes. During that time the passengers would be strapped in tightly with little room to move. They wonít be able to move their heads much and there would be little reason to be reaching about in the capsule as everything is automated or controlled from the ground. At most they might be reading something off a display and relating it to ground but even that is probably unnecessary. They will mostly just be confirming they are go for launch when the time comes. The same will be true during ascent. A sudden high-G maneuver could result in injury if they were moving around or not secured properly, but neither should be the case.
I agree with cppetrie and my basic-physics guess is that worst case scenario is a dislocated/broken arm or two and strained neck muscles. The initial g-force is about 6 g in the best possible direction ("eyeballs in") which is comparable to at most a 8 m/s (29 kph, 18 mph) rear end collision (assuming equal weight cars and 1 m ideal crumple zone). The acceleration will of course continue for much longer but then you have time to tense up and use your muscles.
A traumatic brain injury is possible if it is possible for the passenger to flex forward enough to create sufficient gap that upon activation of the abort system the head was accelerated back towards some sort of headrest. But why would they even permit that level of movement? There is no need for it. The passengers should be restrained almost to the point of being immobile so as to virtually eliminate the possibility of injury from abort system activation. I would think even passengers on ITS would be largely constrained in some sort of restraint system akin to a mix between 5 point racing harness and roller coaster restraints. So long as the ship itself remained intact I would think severe injuries would be very unlikely.
Title: Re: Should the ITS have a launch escape system?
Post by: octavo on 09/23/2017 08:02 AM
For comparison, the highst G coaster is the 'Tower of Terror' at Gold Reef City, South Africa

6.3G

http://entertainmentdesigner.com/news/top-seven-most-thrilling-roller-coasters-in-the-world/
It's a really short duration though. I've ridden it several times in a row on a quiet day - great fun, but, whoosh and it's over.
Title: Re: Should the ITS have a launch escape system?
Post by: meekGee on 09/24/2017 01:48 AM
I really like the idea of five 20-person escapable capsules, one on each tanker flight.
Title: Re: Should the ITS have a launch escape system?
Post by: su27k on 09/24/2017 03:21 PM
I've always wondered just what is wrong with the BFS being its own LES. 

Full size BFS has a propellant load higher than Falcon Heavy, even a subscale BFS would probably have propellant load higher than Falcon 9, it itself represents a danger to the crew. Remember both catastrophic failure of Falcon 9 happened on the upper stage.
Title: Re: Should the ITS have a launch escape system?
Post by: docmordrid on 09/24/2017 11:19 PM
I've always wondered just what is wrong with the BFS being its own LES. 

Full size BFS has a propellant load higher than Falcon Heavy, even a subscale BFS would probably have propellant load higher than Falcon 9, it itself represents a danger to the crew. Remember both catastrophic failure of Falcon 9 happened on the upper stage.

And both of those failures involved the helium system, which BFS, of full or ITSy size, will not have.
Title: Re: Should the ITS have a launch escape system?
Post by: John Alan on 09/25/2017 12:24 AM
I really like the idea of five 20-person escapable capsules, one on each tanker flight.

Agreed... Much smaller system mounted near the nose or front top side... only able to safely save the strapped in crew and capsule system at any point UNTIL S2 fires normally in a earth launch situation...
At that point... it transitions to a primary S2 based "try and fly it home" as the velocities are getting a bit much to build something that survives suborbital reentry...
If S2 makes it to orbit and then goes bang... I guess in theory the escape capsule could do short term till help arrives lifeboat on orbit duty...

Trying to launch the entire S2 off a failing S1 is just silly crazy in an emergency... Just my opinion on topic...
Title: Re: Should the ITS have a launch escape system?
Post by: spacenut on 09/25/2017 02:08 AM
Liquid methane and liquid oxygen can self pressurize with boil off, no need for helium.  ITSy at 9m diameter will be much larger than FH.  So an ITSy tanker will also have to be made to fill. 
Title: Re: Should the ITS have a launch escape system?
Post by: drzerg on 09/25/2017 02:32 AM
you could use separate ship just for transfering people from earth to orbit. so it will be like:

1 ITS MARS - cargo + people and all needs for long term to mars and back to earth
2 ITS CARGO LEO - just cargo any including comersial
3 ITS TANKER LEO - just fuel
4 ITS PEOPLE TO LEO - cargo + full abort support with capsules. possible more sealevel engines (up to 15) for higher T/W



Title: Re: Should the ITS have a launch escape system?
Post by: DreamyPickle on 09/26/2017 09:57 AM
How about building small escape pods into the walls of the ship? They would be shaped like Soyuz or Dragon except with the engines pointing the other way. In case of danger the crew enters those pods through hatches. If something goes wrong the engines fire and they "pop" right out at an angle.

These pods would have heat-shields normally facing outwards through what are structurally "windows" through the hull. They would be small, barely large enough that people can fit while strapped in. This could also work from orbit, they would just have to linger until on top of a suitable splashdown location for reentry.

The problem with such a system is that it would be still quite large and require a lot of work to develop and test properly.
Title: Re: Should the ITS have a launch escape system?
Post by: Athrithalix on 09/26/2017 10:59 AM
In the event of an emergency during a launch, it seems unlikely that there would be time for passengers to climb into individual escape pods and strap themselves in, and you would probably want each escape pod to hold as many people as possible for efficiency's sake. Imagine the mass and cost penalty for adding hundreds of capsules, engines, parachutes, life support and re-entry protection systems.
Title: Re: Should the ITS have a launch escape system?
Post by: DreamyPickle on 09/26/2017 12:01 PM
In the event of an emergency during a launch, it seems unlikely that there would be time for passengers to climb into individual escape pods and strap themselves in, and you would probably want each escape pod to hold as many people as possible for efficiency's sake. Imagine the mass and cost penalty for adding hundreds of capsules, engines, parachutes, life support and re-entry protection systems.

You can just require everybody to strap in and close the hatches whenever you're firing the engines. You only allow passengers to move around when safely in orbit or landed. Commercial airliners already require wearing seatbelts for landing and takeoff so it's not a big deal.

The mass/cost penalty will indeed be quite large but:

* Special seats are required for high-G maneuvers anyway, might as well place them in escape pods.
* Escape pods only need emergency life support for a few days. This can serve double duty as backup for the main ECLSS.
* Maybe you can start from a Dragon v2 to cut down on development costs?
* The escape pods would fit multiple people with Soyuz-like packing and barely any room to move around:

(https://www.nasaspaceflight.com/wp-content/uploads/2017/02/2017-02-26-023105-350x232.jpg)
Title: Re: Should the ITS have a launch escape system?
Post by: su27k on 09/26/2017 12:31 PM
How about building small escape pods into the walls of the ship? They would be shaped like Soyuz or Dragon except with the engines pointing the other way. In case of danger the crew enters those pods through hatches. If something goes wrong the engines fire and they "pop" right out at an angle.

These pods would have heat-shields normally facing outwards through what are structurally "windows" through the hull. They would be small, barely large enough that people can fit while strapped in. This could also work from orbit, they would just have to linger until on top of a suitable splashdown location for reentry.

The problem with such a system is that it would be still quite large and require a lot of work to develop and test properly.

This is similar to my thoughts, instead of one big escape pod, use multiple smaller ones, much easier to manufacture and test. And obviously the crew will need to sit inside the escape pod during ascend, just pack them like sardines. The difference is I think the pods can be put inside launch tubes like SSBNs, with tube opening on the opposite side of the main heat shield (BFS enters side ways, so only one side needs strong heat shield). For pod propulsion I think you'll probably want to go with solids, like the New Shepard, since it's probably not a good idea to have tons of hypergolic fuel inside BFS. The solid propulsion section would be like the service section of CST-100, it drops off once expended, leaving the capsule to land on parachutes.
Title: Re: Should the ITS have a launch escape system?
Post by: RonM on 09/26/2017 02:18 PM
Once you add 10 to 20 small escape pods there will be little mass left over for cargo. It isn't practical.
Title: Re: Should the ITS have a launch escape system?
Post by: envy887 on 09/26/2017 03:22 PM
Once you add 10 to 20 small escape pods there will be little mass left over for cargo. It isn't practical.

Agree that it's not practical, but more likely due to complexity and cost and not mass. Soyuz and Dragon 2 mass about 1,000 kg per person, so a 100-person ITS would have 100 tonnes of escape capsules. On the 2016 ITS that leaves 200 tonnes for cargo.

IMO separating the entire crew cabin would be considerably simpler, cheaper, and more reliable, if an abort system is required.
Title: Re: Should the ITS have a launch escape system?
Post by: su27k on 09/27/2017 04:27 AM
Once you add 10 to 20 small escape pods there will be little mass left over for cargo. It isn't practical.

Agree that it's not practical, but more likely due to complexity and cost and not mass. Soyuz and Dragon 2 mass about 1,000 kg per person, so a 100-person ITS would have 100 tonnes of escape capsules. On the 2016 ITS that leaves 200 tonnes for cargo.

IMO separating the entire crew cabin would be considerably simpler, cheaper, and more reliable, if an abort system is required.

The unstated assumption here is that this BFS with LES is for LEO access only, there's no point dragging the escape pods to Moon/Mars where they will be useless anyway, so if you're going to Moon/Mars, the BFS-LES will take you to LEO to meet up with the fully refueled Moon/Mars BFS and transfer the crew. But BFS-LES' day job would be taking space tourists to LEO for joyrides. In this scenario the cargo capability for BFS-LES is not that important.

As for which solution is better, obviously no way to know, I'm just guessing here. But the reasoning is similar to why BFR has multiple engines instead of one big engine. One big engine is inherently difficult to design due to combustion instability, it's more costly to test since you need a super big test stand, and it's more costly to manufacture since you won't have a production line. It's also less flexible, for example you won't be able to use it on 2nd stage. All these reasoning can be applied to escape system in one way or another, for example the first thing you'll have trouble with one big escape cabin is what propulsion system to use.
Title: Re: Should the ITS have a launch escape system?
Post by: Norm38 on 09/29/2017 12:53 PM
There isn't going to be any LES, over and done. Nowhere in the architecture are there detachable capsules or escape pods.  Musk said repeatedly they're going for airliner level reliability and relying on redundancies.
Anyone who isn't happy with that can stay home.  Time to focus on other things.
Title: Re: Should the ITS have a launch escape system?
Post by: woods170 on 09/29/2017 01:12 PM
There isn't going to be any LES, over and done. Nowhere in the architecture are there detachable capsules or escape pods.  Musk said repeatedly they're going for airliner level reliability and relying on redundancies.
Anyone who isn't happy with that can stay home.  Time to focus on other things.
Agreed. Any continued discussion regarding to subject of this thread is pretty much pointless now that ITS, and the refined BFR, both have been shown as having no Launch Escape System but other means of ensuring crew safety.
Title: Re: Should the ITS have a launch escape system?
Post by: Lee Jay on 10/06/2017 07:32 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.

Edit/Lar: Rump thread, posts from https://forum.nasaspaceflight.com/index.php?topic=43923 that were debating escape vs. no escape are here, for a bit, then will be deleted. If you  ned yours moved back PM me.
Title: Re: Should the ITS have a launch escape system?
Post by: cppetrie on 10/06/2017 07:33 PM
I believe Elon on this one. It simply wonít. The added cost, complexity and weight make it technically and economically infeasible and perhaps less safe. If the system isnít safe enough to not need one, it just doesnít work.

Also, what good is an escape system while landing on Mars or moon? Now youíre marooned and will die slowly from lack of supplies. Honestly, I think Iíd rather just go quickly incinerated or at impact, but thatís just me. YMMV.
Title: Re: Should the ITS have a launch escape system?
Post by: cppetrie on 10/06/2017 07:43 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.
Title: Re: Should the ITS have a launch escape system?
Post by: DJPledger on 10/06/2017 07:44 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.
If SpX kill 100 people due to BFR system not having a LAS will mean the end of SpX. BFR needs a LAS to prevent loss of life should a BFR fail and it may just save SpX as well.
Title: Re: Should the ITS have a launch escape system?
Post by: DJPledger on 10/06/2017 07:47 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.
This is because airliners are so safe but rockets aren't anywhere near the safety levels of them. BFR needs a LAS because it will likely be several orders of magnitude less safe than airliners. Should only drop the LAS from a manned LV design when it's safety factor is getting close to that of airliners.
Title: Re: Should the ITS have a launch escape system?
Post by: cppetrie 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
Title: Re: Should the ITS have a launch escape system?
Post by: DJPledger 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.
Title: Re: Should the ITS have a launch escape system?
Post by: RonM 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.
Title: Re: Should the ITS have a launch escape system?
Post by: Lar 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".
Title: Re: Should the ITS have a launch escape system?
Post by: DJPledger 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.
Title: Re: Should the ITS have a launch escape system?
Post by: Lar 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.
Title: Re: Should the ITS have a launch escape system?
Post by: DJPledger 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.
Title: Re: Should the ITS have a launch escape system?
Post by: Lee Jay 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.
Title: Re: Should the ITS have a launch escape system?
Post by: Lee Jay 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.
Title: Re: Should the ITS have a launch escape system?
Post by: DJPledger 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.
Title: Re: Should the ITS have a launch escape system?
Post by: cppetrie 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?
Title: Re: Should the ITS have a launch escape system?
Post by: cppetrie 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.
Title: Re: Should the ITS have a launch escape system?
Post by: envy887 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.
Title: Re: Should the ITS have a launch escape system?
Post by: envy887 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.
Title: Re: Should the ITS have a launch escape system?
Post by: Robotbeat 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.
Title: Re: Should the ITS have a launch escape system?
Post by: Lee Jay 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?
Title: Re: Should the ITS have a launch escape system?
Post by: Robotbeat 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.
Title: Re: Should the ITS have a launch escape system?
Post by: AbuSimbel 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).
Title: Re: Should the ITS have a launch escape system?
Post by: jded 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?
Title: Re: Should the ITS have a launch escape system?
Post by: AncientU 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).

Expendable rockets fly once; all the world's rockets are expendable less one.
Rocketry as an industry is in its infancy.
Title: Re: Should the ITS have a launch escape system?
Post by: KelvinZero 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 :-)
Title: Re: Should the ITS have a launch escape system?
Post by: AbuSimbel 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.
Title: Re: Should the BFR have a launch escape system?
Post by: Lee Jay 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.
Title: Re: Should the BFR have a launch escape system?
Post by: Lee Jay 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?
Title: Re: Should the BFR have a launch escape system?
Post by: Robotbeat 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.
Title: Re: Should the BFR have a launch escape system?
Post by: Robotbeat 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.
Title: Re: Should the ITS have a launch escape system?
Post by: TomH 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.
Title: Re: Should the BFR have a launch escape system?
Post by: Robotbeat 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.
Title: Re: Should the BFR have a launch escape system?
Post by: Lee Jay 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?
Title: Re: Should the BFR have a launch escape system?
Post by: Robotbeat 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.
Title: Re: Should the BFR have a launch escape system?
Post by: Robotbeat 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.
Title: Re: Should the BFR have a launch escape system?
Post by: cppetrie on 10/08/2017 12:29 AM
People do risky things literally on a daily basis by driving to work. It doesnít 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 youíre going in a couple hours instead (couple hours includes transport from dock to launch platform and back).
Title: Re: Should the BFR have a launch escape system?
Post by: Robotbeat 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.
Title: Re: Should the BFR have a launch escape system?
Post by: TomH 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.
Title: Re: Should the BFR have a launch escape system?
Post by: Lee Jay 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.
Title: Re: Should the BFR have a launch escape system?
Post by: CuddlyRocket 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.
Title: Re: Should the BFR have a launch escape system?
Post by: Hog 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.
Title: Re: Should the BFR have a launch escape system?
Post by: pathfinder_01 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.
Title: Re: Should the BFR have a launch escape system?
Post by: Norm38 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?
Title: Re: Should the BFR have a launch escape system?
Post by: rklaehn 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.
Title: Re: Should the BFR have a launch escape system?
Post by: Robotbeat on 10/08/2017 10:17 PM
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.
Yes, because I expect BFR to fly >500x as many times as Falcon 9.

And by reasonable, I meant that it'd be reasonable for the FAA to give that kind of requirement before putting passengers on for point to point.

For spaceflight, the bar should be lower, more like 99.5-99.9%, as that's comparable to a regular rocket (95-99%) with a LAS (catches at most one out of ten rocket failures).
Title: Re: Should the BFR have a launch escape system?
Post by: Oli on 10/08/2017 10:35 PM
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.
Yes, because I expect BFR to fly >500x as many times as Falcon 9.

You're talking about ~10k flights per year, how should that happen if BFR doesn't prove to be extremely reliable and cheap beforehand?

Title: Re: Should the BFR have a launch escape system?
Post by: Robotbeat on 10/09/2017 04:49 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.
Yes, because I expect BFR to fly >500x as many times as Falcon 9.

You're talking about ~10k flights per year, how should that happen if BFR doesn't prove to be extremely reliable and cheap beforehand?
I expect it to do so. More like 1000 per year for many years.


But really: I shouldn't say "expect." What I'm describing is what I think is the best possible outcome that could still happen. I don't really expect it to be that good.
Title: Re: Should the BFR have a launch escape system?
Post by: intrepidpursuit on 10/10/2017 05:20 AM
There are really two cases here. Risk of LOC (LOP loss of passengers?) on a mission to Mars, a planet 34 million miles away that we could never reach otherwise, and a LOP on a "mission" from LA to Shanghai that could have been done on a plane if you are the type of person who can be patient and kind for 18 hours straight.

For the mission to mars, comparison to Shuttle or upcoming CC vehicles is apt. Shuttle had the main engines attached to the crew compartment, so at the design table traditional abort would have been kind of pointless. It did turn out to lose crew because of its various required appendages and just one close call from its own engines. The BFR will fly many times with the human rated propulsion system before humans ever get on. At least a dozen and maybe 100 launches of the propulsion system before we put people on it. A simple propulsion system (single fuel type, autogenous pressurization, all throttleable and testable engines, no dangly bits) abort modes after the first minute or so of flight, thorough testing, lot of redundancies and engineering led launch team I think can get BFR to Dragon 2 levels of reliability and beyond even without a LES. 1 failure in 370 launches wouldn't put people on that launch.

For a mission to save a business day, the rules are different. Airplanes are scary but are safer than cars. There are hundreds of people on every single flight and it would fly at least hundreds of times a year. The level of safety necessary here is WAY higher. I don't think SpaceX could market this a general transportation until they found some way to make its safety comparable to planes. Whether I would do it or not, regulators would not let a company make money on a system that sacrifices lives for time. Of course, this problem wouldn't actually be solved by a LES, which only helps and does not solve the safety problem.

From a higher level perspective, if a BFS fails after the first few launches, they will probably have a hard time getting buy in. If the operators of the Hindenburg 2 started handing out parachutes for the next flights people still wouldn't get on the thing. This is a spacecraft that will be more valuable than its payloads. It really needs to not blow up; LES or not.
Title: Re: Should the BFR have a launch escape system?
Post by: Patchouli on 10/10/2017 06:09 AM
Near term BFR probably should have a LAS of sorts though if the spaceship is upgraded to have more then a 1 to 1 thrust to weight ratio without shredding the vacuum engine nozzles and the ability to dump propellant you'd gain much of the benefits of having one except for a scenario where there's a catastrophic failure of the booster on the pad or early in flight.
It might be possible to design the nose of it to be able to detach and survive reentry but this would eat up a lot of mass probably reducing the payload by a third.
I  wonder would having several escape pods based on Dragon's be the way to go on early versions.
As for talks of it flying thousands of times per year and competing directly with airliners I dismiss this as mostly fantasy with the first version of BFR as it's air frame and engines are much higher stressed than an airliner so they will be subject to more wear and tear and need more frequent inspection.

Title: Re: Should the BFR have a launch escape system?
Post by: JamesH65 on 10/10/2017 09:57 AM
Loads of people saying it should have a LAS, but no suggestions on how it could actually be done? Presumably because no-one has yet thought of a way of doing it? Is it even physically possible? All very well saying it should have one, but if having one means the craft never gets made because its either impossible or so hugely expensive, or make the craft useless for its intended purpose, then making it s a requirement is pointless.

Musk has said it won't have one. I guess he may have thought it through.
Title: Re: Should the BFR have a launch escape system?
Post by: KelvinZero on 10/10/2017 10:48 AM
Loads of people saying it should have a LAS, but no suggestions on how it could actually be done? Presumably because no-one has yet thought of a way of doing it? Is it even physically possible? All very well saying it should have one, but if having one means the craft never gets made because its either impossible or so hugely expensive, or make the craft useless for its intended purpose, then making it s a requirement is pointless.

Musk has said it won't have one. I guess he may have thought it through.
This thread has been specifically separated off from the thread discussing how it could be done, because that was being continually derailed by people posting on the thread who only wanted to say the thread was a dumb idea. :)

http://forum.nasaspaceflight.com/index.php?topic=43923.0
Title: Re: Should the BFR have a launch escape system?
Post by: guckyfan on 10/10/2017 10:56 AM
Musk has said it won't have one. I guess he may have thought it through.

I guess he completely goes for reliability of the system. It has to be extremely reliable to work for a very large number of reuses. So he puts engineering for reliablity ahead of a LAS.

I can only think of one reasonable way to have a LAS for the whole crew of 100. Carrying a LAS all the way to Mars is not an option IMO, too much of a weight penalty. So have a separate vehicle, probably a tanker with a capsule on top that crams in 100 people and has its own abort propulsion. That tanker may lose up to 100t of propellant capacity but it would be enough to top off the tanks and bring the passengers. Maybe another launch but launches are cheap. That way the ship can be mostly fueled before passengers arrive.
Title: Re: Should the BFR have a launch escape system?
Post by: Robotbeat on 10/10/2017 11:49 AM
Seems everyone's assuming a LAS is free.

Giving BFS a LAS would cost billions of dollars and would dramatically reduce the payload in crewed configuration. Better to put those resources to use in improving reliability and a proven flightrate.
Title: Re: Should the BFR have a launch escape system?
Post by: KelvinZero on 10/10/2017 02:32 PM
Pulled in from another thread, discussing BFS+Dragon2
In the medium term a Dragon has no place in a BFS architecture. It means carrying a vehicle with plenty of hypergolic propellant. If they want a mobile pod for local actions they would build one based on the BFS RCS-thrusters, maybe a smaller version. It runs on methalox and can be refueled from the BFS main tanks. A Dragon would not be a good match. Such a vehicle needs an airlock. Dragon is designed around the ability to reenter. It has a quite small internal volume due to the cone shape.
I think a dragon, for LAS plus other possible purposes, does have a place in the BFS architecture, in short, medium, and long terms.

Short term:
I think the first BFS produced will be a cargo version. I have heard that the Crew version will be a lot more expensive. Also it may not be allowed near NASA assets for various reasons. I can think of various scenarios where a Dragon on top of and external to a Cargo BFS, instead of continuing with F9, might be considered.

Medium term:
I define medium term as after the Cargo BFS has matured, and the final decisions on the Crew version, based on lessons from the cargo version, must be made. Musk has stated a clear plan for the Crew BFS but I believe that he will prepare for lessons or mistakes from the Cargo BFS to change that plan. He may really want for a Crew version yet not have achieved the safety margins he had hoped for.. yet.

Long term:
Long term I think there is a good reason for a third variant (the debate is simply how significant a variant it must be.. maybe it will end up a trivial modification of the Crew variant. That third variant is *Space Shuttle on steroids variant.* It is quite different from the Crew ( *passengers as cargo* ) variant. Like the shuttle it has a small team actually there to do work and  a large cargo bay with large doors that could take entire satellites on board.

I think a Dragon 2 could give you 100x more safety for many missions, because it is not just a LAS, it duplicates practically everything that you need to survive a trip to space and back. If you think you do not need a 100x more safety, perhaps you should turn that around and ask if you can be doing missions a hundred times more extreme for the same safety.

Asteroid missions could be a good example. Unlike passengers to Mars, you will not have people or even cargo waiting for you. They also do create specific new threats to your heatshield so there is very good reason to want a backup option for that too.
Title: Re: Should the BFR have a launch escape system?
Post by: KelvinZero on 10/10/2017 10:09 PM
In the medium term a Dragon has no place in a BFS architecture. It means carrying a vehicle with plenty of hypergolic propellant.
Please have that conversation here instead: https://forum.nasaspaceflight.com/index.php?topic=43438.0

...in fact I will quote it there and reply to it there now.

Why there? I am in no way talking about a LES-system but my understanding was that Dragon could become a utility vehicle around BFS. I argued that Dragon is not good for that purpose.
Because you said "In the medium term a Dragon has no place in a BFS architecture. It means carrying a vehicle with plenty of hypergolic propellant."

Therefore your argument is based on dismissing the worth of the BFS having a dragon for a LAS+lifeboat. Obviously the only reason to consider including a heatshield and massive superdraco engines is because these uses are considered as part of the worth of including a crew dragon.
Title: Re: Should the BFR have a launch escape system?
Post by: guckyfan on 10/11/2017 07:35 AM
I emphasized that this vehicle is not a LES system but a utility vehicle. My understanding was that this is what was talked about. A Dragon is a poor match for that purpose.
Title: Re: Should the BFR have a launch escape system?
Post by: Lobo on 10/11/2017 11:33 PM
Musk has said it won't have one. I guess he may have thought it through.

I guess he completely goes for reliability of the system. It has to be extremely reliable to work for a very large number of reuses. So he puts engineering for reliablity ahead of a LAS.

I can only think of one reasonable way to have a LAS for the whole crew of 100. Carrying a LAS all the way to Mars is not an option IMO, too much of a weight penalty. So have a separate vehicle, probably a tanker with a capsule on top that crams in 100 people and has its own abort propulsion. That tanker may lose up to 100t of propellant capacity but it would be enough to top off the tanks and bring the passengers. Maybe another launch but launches are cheap. That way the ship can be mostly fueled before passengers arrive.

Back when I was working with the design team that was working on concepts of what the Mars Transportation System might look like, before Musk unveiled the ITS system a year ago, the issue of an LAS was debated.  We eventually came up with a biconic design as well as a Super Dragon Capsule type of design that sat on a reusable 2nd stage.
The Super Dragon Capsule design was easier to put an LAS on, as it sat on a 2nd stage and was launch unfueled.  So it only had enough propellant for abort, and then would be refueled in orbit.  But it had other drawbacks like door in the heat shield for the engines, as well as both pressure fed fast fire abort engines and pump fed normal propulsion engines.  And it was 3 pieces instead of just 2 like the biconic concept.

I'd always favored a 2-piece biconic design overall for simplicity and capability, and eventually I won out with that in the team.  But the rest of the team still thought it would have an LAS, so we worked one into it.  But I still never thought SpaceX's design would have one.  And that has turned out to be correct. 
The main reasons are there's a lot of design compromises.  The ship is already going to be very complex without introducing more failure modes and complexity into it.  While an LAS would help with launch, it becomes a liability in cost and capacity, and even an extra point of failure after that, with no real benefits.

The way I saw it, early on, the crews would be small.  Probably no more than 7, which Dragon 2 could take up as it would already be flying and available to do so, and it has an LAS.  If you wanted 14, you could do two Dragon 2 launches for the crew.  With reusable boosters and spacecraft, that's really not that prohibitive.  After that, BFR should have established a flight track record.  As it would have redundant engines, and tolerate an engine out at any point during launch, that really reduces the failure modes for a liquid rocket.  There could still be a complete explosion on the pad or lift off, which would result in the loss of crew, but barring that, it should be able to tolerate most other issues with a safe abort mode.

But even so, if the customer still demand an LAS system, a modified ship could be built that would have an LAS, and be used as a crew taxi to take a full crew of 100 up just before departure from orbit.  It would sacrifice it's payload for that LAS system but it would be just a reusable crew taxi, and that would be it's only job.  If an LAS was a must, then that was the way to do it rather than to try to integrate it into the interplanetary ship.  It'll already have enough jobs that it must do.
But...it will be a long time before the crews would be anywhere near that big.  You need to have a lot of infrastructure on the Moon or Mars to support adding 100 new people on a single mission, so that's a long time down the road, and Falcon/Dragon can handle the smaller crews in the mean time.




Title: Re: Should the BFR have a launch escape system?
Post by: Robotbeat on 10/12/2017 01:44 PM
By the way, a LAS would add its own risk factors. For instance, if the LAS on Orion fails to separate, the crew dies.
And commercial airlines are so safe that if you added a LAS or ejection seats to them, the extra risks would greatly outweigh the abort advantages, and you'd REDUCE overall safety.

Again, for those in the back:
If BFR is as reliable as Musk wants it to be, adding a LAS would REDUCE safety.
Title: Re: Should the BFR have a launch escape system?
Post by: AncientU on 10/12/2017 04:26 PM
I can't believe that someone is building a NOVA-class, fully reusable launcher and all this focus on a friggin' launch escape system.
Get over it...
Title: Re: Should the BFR have a launch escape system?
Post by: Semmel on 10/12/2017 04:47 PM
Robotbeat, I agree with you. However the question is not based purely on statistics but also on human nature. If you have a LOC event, it's a big difference in public opinion if it reads "despite the LAS, the failure was so severe that no one survived." or "no one survived and the rocket didn't even have an ejection seat.". At this point it does not matter if a LAS would have caused the failure and didn't save the crew. In the mind of the public, a LAS makes you seem to try harder even if the engineering said otherwise. As an engineer, it huts me to say this but here are some examples..

In the US, many more people are scared of terrorism than car crashes, despite the fact that it is far more likely to die in a car than by a terrorist attack. And there are no anti car laws put in place. Jet we see legislation after legislation giving advanced rights to the police to counter the terrorist threat. That is just an example of how nonsensical public perception can be. And the same will happen to a BFR with or without a LAS. This can mean life and death of SpaceX.

Also, I am not arguing in favor of a LAS here. I share your concern that a LAS can make BFR less safe. But I want to point out that we can't restrict the discussion on the engineering aspects.
Title: Re: Should the BFR have a launch escape system?
Post by: Norm38 on 10/12/2017 06:49 PM
A big difference in human nature deals with private vs. public spending.  When astronauts are government employees and national heroes and they are killed in an accident, every citizen feels they are a stakeholder, that it was their money being spent, and why oh why wasn't more done.

Change that over to the same number of people killed while flying an experimental aircraft on their dime, and the public shrugs it off. People are allowed to risk their lives with their money.
We need to get to commercial operations where people who accept the risks are buying their own tickets.  At that point governments will put their crew on it, just like government employees fly commercial and don't all fly in military transports strapped into ejection seats.

Airliners like TWA 800 have exploded with great loss of life, far more than 14 people.  And no one asked why 747s don't have escape capsules, and Boeing hasn't redesigned the 747 to add them.  Passengers still fly, because there's no other way to get to their destination. If people want to go to Mars, they will accept the risks that come with the trip.

The only way that we are going to get to airliner level operations and reliability is to simply just do it that way.
Title: Re: Should the BFR have a launch escape system?
Post by: Semmel on 10/12/2017 07:11 PM
I dont want to defend how the public opinion often works. I find it quite nonsensical my self. But look how the reaction was to the first Tesla autopilot death. It got way more attention than it should have. Way more than any other car accident got. Now imagine this wasnt a self driving car with a guy not paying attention where he should have, but maybe one of the first BFR point to point flights. I dont think my self that accidents should be a deciding factor. But public opinion should at least go into the equation. I agree, it should not dominate it.
Title: Re: Should the BFR have a launch escape system?
Post by: KelvinZero on 10/12/2017 10:02 PM
By the way, a LAS would add its own risk factors. For instance, if the LAS on Orion fails to separate, the crew dies.
And commercial airlines are so safe that if you added a LAS or ejection seats to them, the extra risks would greatly outweigh the abort advantages, and you'd REDUCE overall safety.

Again, for those in the back:
If BFR is as reliable as Musk wants it to be, adding a LAS would REDUCE safety.
Do you have a reference for that? I assumed it was cost, but I can imagine it being true.
Title: Re: Should the ITS have a launch escape system?
Post by: yg1968 on 10/12/2017 11:47 PM
Its LES is pretty much the engines on the bottom of the ship, you can't have an escape system that large.

It's similar to the crewed Dream Chaser's abort system.
Title: Re: Should the ITS have a launch escape system?
Post by: Lars-J on 10/13/2017 04:55 AM
Its LES is pretty much the engines on the bottom of the ship, you can't have an escape system that large.

It's similar to the crewed Dream Chaser's abort system.

...Which they were having problems with, even at Dreamchasers much smaller scale. When DC was dropped from commercial crew, they were in the middle of evaluating new propulsion ideas to replace it. (It was a hybrid system) The cargo DC has no such system.
Title: Re: Should the BFR have a launch escape system?
Post by: pathfinder_01 on 10/13/2017 09:03 AM
By the way, a LAS would add its own risk factors. For instance, if the LAS on Orion fails to separate, the crew dies.
And commercial airlines are so safe that if you added a LAS or ejection seats to them, the extra risks would greatly outweigh the abort advantages, and you'd REDUCE overall safety.

Again, for those in the back:
If BFR is as reliable as Musk wants it to be, adding a LAS would REDUCE safety.

Ejection seats are not practical on any commercial airline because of the wide variation between passengers(300 pound man, baby, elderly woman), number of passengers on a plane(hundreds) and the fact that the passengers would need training. Nobody would think of designing an experimental craft , bomber or a fighter jet without some consideration of escape.

In this time period and age BFR is closer to an experimental aircraft than anything else and If the shuttle had lived up to it's safety claims Columbia and Challenger would not have occurred.


The first BFR flights will not  have such a number of people that it is impossible to put in an LES. In fact I don't think you could find as many people as Elon hopes to travel to the moon, mars or LEO at the price he is offering on any regular bias. The most likely paying passenger at the moment for better or worse is going to be NASA and not private citizens.
Title: Re: Should the BFR have a launch escape system?
Post by: JamesH65 on 10/13/2017 10:42 AM
By the way, a LAS would add its own risk factors. For instance, if the LAS on Orion fails to separate, the crew dies.
And commercial airlines are so safe that if you added a LAS or ejection seats to them, the extra risks would greatly outweigh the abort advantages, and you'd REDUCE overall safety.

Again, for those in the back:
If BFR is as reliable as Musk wants it to be, adding a LAS would REDUCE safety.

Ejection seats are not practical on any commercial airline because of the wide variation between passengers(300 pound man, baby, elderly woman), number of passengers on a plane(hundreds) and the fact that the passengers would need training. Nobody would think of designing an experimental craft , bomber or a fighter jet without some consideration of escape.

In this time period and age BFR is closer to an experimental aircraft than anything else and If the shuttle had lived up to it's safety claims Columbia and Challenger would not have occurred.


The first BFR flights will not  have such a number of people that it is impossible to put in an LES. In fact I don't think you could find as many people as Elon hopes to travel to the moon, mars or LEO at the price he is offering on any regular bias. The most likely paying passenger at the moment for better or worse is going to be NASA and not private citizens.

Mitigated by the thought that the BFS/R will spend a considerable proportion of its experimental period being flown by computers with no-one on board.
Title: Re: Should the ITS have a launch escape system?
Post by: yg1968 on 10/13/2017 02:33 PM
Its LES is pretty much the engines on the bottom of the ship, you can't have an escape system that large.

It's similar to the crewed Dream Chaser's abort system.

...Which they were having problems with, even at Dreamchasers much smaller scale. When DC was dropped from commercial crew, they were in the middle of evaluating new propulsion ideas to replace it. (It was a hybrid system) The cargo DC has no such system.

I was under the impression that it was the hybrid motor which was problematic, not the LAS. The acquisition of Orbitec gave them better options for propulsion.
Title: Re: Should the BFR have a launch escape system?
Post by: envy887 on 10/13/2017 04:00 PM
...
The first BFR flights will not  have such a number of people that it is impossible to put in an LES. In fact I don't think you could find as many people as Elon hopes to travel to the moon, mars or LEO at the price he is offering on any regular bias. The most likely paying passenger at the moment for better or worse is going to be NASA and not private citizens.

If there are so few passengers, then they can launch and return on F9R/Dragon 2 until BFR completes hundreds of successful flights.
Title: Re: Should the BFR have a launch escape system?
Post by: Robotbeat on 10/13/2017 11:07 PM
...
The first BFR flights will not  have such a number of people that it is impossible to put in an LES. In fact I don't think you could find as many people as Elon hopes to travel to the moon, mars or LEO at the price he is offering on any regular bias. The most likely paying passenger at the moment for better or worse is going to be NASA and not private citizens.

If there are so few passengers, then they can launch and return on F9R/Dragon 2 until BFR completes hundreds of successful flights.
Bingo. And how much does, say, 300 flights cost of SpaceX gets costs as low as they want? Just $600m, less than developing a LAS.
Title: Re: Should the BFR have a launch escape system?
Post by: intrepidpursuit on 10/13/2017 11:15 PM
...
The first BFR flights will not  have such a number of people that it is impossible to put in an LES. In fact I don't think you could find as many people as Elon hopes to travel to the moon, mars or LEO at the price he is offering on any regular bias. The most likely paying passenger at the moment for better or worse is going to be NASA and not private citizens.

If there are so few passengers, then they can launch and return on F9R/Dragon 2 until BFR completes hundreds of successful flights.
Bingo. And how much does, say, 300 flights cost of SpaceX gets costs as low as they want? Just $600m, less than developing a LAS.

The Dragon flights will still be very expensive. They will get lots of experience with the ship before they are ready to put people on it anyway, no need to kludge dragon in there.
Title: Re: Should the BFR have a launch escape system?
Post by: Robotbeat on 10/13/2017 11:20 PM
...
The first BFR flights will not  have such a number of people that it is impossible to put in an LES. In fact I don't think you could find as many people as Elon hopes to travel to the moon, mars or LEO at the price he is offering on any regular bias. The most likely paying passenger at the moment for better or worse is going to be NASA and not private citizens.

If there are so few passengers, then they can launch and return on F9R/Dragon 2 until BFR completes hundreds of successful flights.
Bingo. And how much does, say, 300 flights cost of SpaceX gets costs as low as they want? Just $600m, less than developing a LAS.

The Dragon flights will still be very expensive. They will get lots of experience with the ship before they are ready to put people on it anyway, no need to kludge dragon in there.
We weren't saying kludge a Dragon on there, we were saying launch the Dragon on F9 and transfer crew to the BFR, just like NASA was/is planning for Altair or the Mars transfer vehicle, then return to the Dragon for entry.
Title: Re: Should the BFR have a launch escape system?
Post by: yg1968 on 10/13/2017 11:26 PM
...
The first BFR flights will not  have such a number of people that it is impossible to put in an LES. In fact I don't think you could find as many people as Elon hopes to travel to the moon, mars or LEO at the price he is offering on any regular bias. The most likely paying passenger at the moment for better or worse is going to be NASA and not private citizens.

If there are so few passengers, then they can launch and return on F9R/Dragon 2 until BFR completes hundreds of successful flights.
Bingo. And how much does, say, 300 flights cost of SpaceX gets costs as low as they want? Just $600m, less than developing a LAS.

The Dragon flights will still be very expensive. They will get lots of experience with the ship before they are ready to put people on it anyway, no need to kludge dragon in there.
We weren't saying kludge a Dragon on there, we were saying launch the Dragon on F9 and transfer crew to the BFR, just like NASA was/is planning for Altair or the Mars transfer vehicle, then return to the Dragon for entry.

The objective of BFR is to replace Dragon, Falcon 9 and FH. So it would be strange to have to rely on them.
Title: Re: Should the BFR have a launch escape system?
Post by: intrepidpursuit on 10/13/2017 11:28 PM
...
The first BFR flights will not  have such a number of people that it is impossible to put in an LES. In fact I don't think you could find as many people as Elon hopes to travel to the moon, mars or LEO at the price he is offering on any regular bias. The most likely paying passenger at the moment for better or worse is going to be NASA and not private citizens.

If there are so few passengers, then they can launch and return on F9R/Dragon 2 until BFR completes hundreds of successful flights.
Bingo. And how much does, say, 300 flights cost of SpaceX gets costs as low as they want? Just $600m, less than developing a LAS.

The Dragon flights will still be very expensive. They will get lots of experience with the ship before they are ready to put people on it anyway, no need to kludge dragon in there.
We weren't saying kludge a Dragon on there, we were saying launch the Dragon on F9 and transfer crew to the BFR, just like NASA was/is planning for Altair or the Mars transfer vehicle, then return to the Dragon for entry.

The kludge is making it a part of the system, whether it is built into the rocket or not. It is impossible for BFR to be cheaper than Falcon 9 if you still have to launch a Falcon 9 (or several). They won't put people on BFR until they are comfortable launching them along with it.
Title: Re: Should the BFR have a launch escape system?
Post by: Robotbeat on 10/13/2017 11:29 PM
...
The first BFR flights will not  have such a number of people that it is impossible to put in an LES. In fact I don't think you could find as many people as Elon hopes to travel to the moon, mars or LEO at the price he is offering on any regular bias. The most likely paying passenger at the moment for better or worse is going to be NASA and not private citizens.

If there are so few passengers, then they can launch and return on F9R/Dragon 2 until BFR completes hundreds of successful flights.
Bingo. And how much does, say, 300 flights cost of SpaceX gets costs as low as they want? Just $600m, less than developing a LAS.

The Dragon flights will still be very expensive. They will get lots of experience with the ship before they are ready to put people on it anyway, no need to kludge dragon in there.
We weren't saying kludge a Dragon on there, we were saying launch the Dragon on F9 and transfer crew to the BFR, just like NASA was/is planning for Altair or the Mars transfer vehicle, then return to the Dragon for entry.

The objective of BFR is to replace Dragon, Falcon 9 and FH. So it would be strange to have to rely on them.
That's not at all the only objective of BFR. And if NASA insists on a LAS, then using the already-proven F9/Dragon combo would be much cheaper than adding one to BFR.
Title: Re: Should the BFR have a launch escape system?
Post by: Robotbeat on 10/13/2017 11:37 PM
...
The first BFR flights will not  have such a number of people that it is impossible to put in an LES. In fact I don't think you could find as many people as Elon hopes to travel to the moon, mars or LEO at the price he is offering on any regular bias. The most likely paying passenger at the moment for better or worse is going to be NASA and not private citizens.

If there are so few passengers, then they can launch and return on F9R/Dragon 2 until BFR completes hundreds of successful flights.
Bingo. And how much does, say, 300 flights cost of SpaceX gets costs as low as they want? Just $600m, less than developing a LAS.

The Dragon flights will still be very expensive. They will get lots of experience with the ship before they are ready to put people on it anyway, no need to kludge dragon in there.
We weren't saying kludge a Dragon on there, we were saying launch the Dragon on F9 and transfer crew to the BFR, just like NASA was/is planning for Altair or the Mars transfer vehicle, then return to the Dragon for entry.

The kludge is making it a part of the system, whether it is built into the rocket or not. It is impossible for BFR to be cheaper than Falcon 9 if you still have to launch a Falcon 9 (or several). They won't put people on BFR until they are comfortable launching them along with it.
The point of BFR isn't just to be cheaper than F9.

NASA has no way to get to Mars orbit, Mars surface, or Moon surface. BFR solves that. If for the first Mars trip, NASA insists on a LAS, then SpaceX will be happy to launch the crew on the reusable Falcon 9 and Dragon.

This really isn't that hard to understand.
Title: Re: Should the BFR have a launch escape system?
Post by: intrepidpursuit on 10/13/2017 11:40 PM
If you are going to take BFR to the moon or mars then you are relying on it not to fail anyway. Adding in a Dragon, a Falcon 9, and two crew transfers isn't going to make the system appreciably safer.

NASA will either accept the BFR for human use or not. I don't see any helpful middle ground other than just using it for cargo only.

(keeps telling me the body is empty if I try reply with the quoted thread)
Title: Re: Should the BFR have a launch escape system?
Post by: Robotbeat on 10/13/2017 11:43 PM
If you are going to take BFR to the moon or mars then you are relying on it not to fail anyway. Adding in a Dragon, a Falcon 9, and two crew transfers isn't going to make the system appreciably safer.

NASA will either accept the BFR for human use or not. I don't see any helpful middle ground other than just using it for cargo only.

(keeps telling me the body is empty if I try reply with the quoted thread)
Nope. NASA didn't put a LAS on Altair, but they insist on one for Orion. That contradicts your logic.
Title: Re: Should the BFR have a launch escape system?
Post by: pathfinder_01 on 10/14/2017 06:06 AM
If you are going to take BFR to the moon or mars then you are relying on it not to fail anyway. Adding in a Dragon, a Falcon 9, and two crew transfers isn't going to make the system appreciably safer.

NASA will either accept the BFR for human use or not. I don't see any helpful middle ground other than just using it for cargo only.

(keeps telling me the body is empty if I try reply with the quoted thread)

In practice refueling on orbit with cryogens could be viewed as risky. It could be a good idea to use a dragon or specially adapted BFR(i.e. one with a LES) for a crew transfer after the BFR is fully fueled and checked out. ESP. if going to Mars(five refueling flights sounds like it could take a lot of time).

Also a Cargo BFR could be adapted to be crewed in space if it has a habitation or other module in the cargo bay with a docking port. This could be cheaper(and faster) than having to develop the crewed version and much more suitable to smaller crew sizes. It also plays well with other companies and organizations(i.e. Space X does not need to develop the payload).

That being said at the moment there is little value of a LES on the Moon or Mars(i.e. no one to rescue you should it go off) and a lot of dead weight to drag there.
Title: Re: Should the BFR have a launch escape system?
Post by: su27k on 10/11/2018 04:56 PM
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.
Title: Re: Should the BFR have a launch escape system?
Post by: ethan829 on 10/11/2018 06:19 PM
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.

It did not:
https://twitter.com/jeff_foust/status/1050396464483115008 (https://twitter.com/jeff_foust/status/1050396464483115008)

That said, Soyuz can use its own engines to abort if needed (and did so in 1975 (https://en.wikipedia.org/wiki/Soyuz_7K-T_No.39)).
Title: Re: Should the BFR have a launch escape system?
Post by: TrevorMonty on 10/11/2018 06:34 PM
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.
Title: Re: Should the BFR have a launch escape system?
Post by: Patchouli on 10/11/2018 06:35 PM

The point of BFR isn't just to be cheaper than F9.

NASA has no way to get to Mars orbit, Mars surface, or Moon surface. BFR solves that. If for the first Mars trip, NASA insists on a LAS, then SpaceX will be happy to launch the crew on the reusable Falcon 9 and Dragon.

This really isn't that hard to understand.

A stripped down BFS with a small upper stage could be used to put a Dragon into orbit.
Title: Re: Should the BFR have a launch escape system?
Post by: envy887 on 10/11/2018 07:26 PM
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.

[citation needed]
Title: Re: Should the BFR have a launch escape system?
Post by: hkultala on 10/11/2018 07:34 PM
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.

Title: Re: Should the BFR have a launch escape system?
Post by: Torbjorn Larsson, OM on 10/11/2018 07:47 PM
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.
Title: Re: Should the BFR have a launch escape system?
Post by: GalacticIntruder on 10/11/2018 07:47 PM
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.
Title: Re: Should the BFR have a launch escape system?
Post by: Rocket Science on 10/11/2018 08:02 PM
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...
Title: Re: Should the BFR have a launch escape system?
Post by: Tulse on 10/11/2018 08:10 PM
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.
Title: Re: Should the BFR have a launch escape system?
Post by: Rocket Science on 10/11/2018 08:16 PM
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...
Title: Re: Should the BFR have a launch escape system?
Post by: Lars-J on 10/11/2018 11:55 PM
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.
Title: Re: Should the BFR have a launch escape system?
Post by: Rocket Science on 10/12/2018 12:32 AM
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?
Title: Re: Should the BFR have a launch escape system?
Post by: lamontagne on 10/12/2018 02:43 AM
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 :-)

Title: Re: Should the BFR have a launch escape system?
Post by: lamontagne on 10/12/2018 03:05 AM
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.

Title: Re: Should the BFR have a launch escape system?
Post by: Robotbeat on 10/12/2018 04:12 AM
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.
Title: Re: Should the BFR have a launch escape system?
Post by: Robotbeat on 10/12/2018 04:15 AM
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, thatís 4 tons of parachute. Might be worth it.
Title: Re: Should the BFR have a launch escape system?
Post by: RonM on 10/12/2018 04:44 AM
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.
Title: Re: Should the BFR have a launch escape system?
Post by: KelvinZero on 10/12/2018 05:02 AM
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.
Title: Re: Should the BFR have a launch escape system?
Post by: RonM on 10/12/2018 05:35 AM
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.
Title: Re: Should the BFR have a launch escape system?
Post by: JonathanD on 10/12/2018 06:34 AM
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 :)
Title: Re: Should the BFR have a launch escape system?
Post by: speedevil on 10/12/2018 10:09 AM
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.
Title: Re: Should the BFR have a launch escape system?
Post by: Zed_Noir on 10/12/2018 09:21 PM
<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.
Title: Re: Should the BFR have a launch escape system?
Post by: Rocket Science on 10/12/2018 10:00 PM
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
Title: Re: Should the BFR have a launch escape system?
Post by: envy887 on 10/12/2018 11:57 PM
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, thatís 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.
Title: Re: Should the BFR have a launch escape system?
Post by: Zed_Noir on 10/13/2018 01:45 AM
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

You do realized that an explosive line charge is required to cut the crew compartment from the rest of the vehicle along with some sort of abort motors in the crew compartment. This proposal appears to be similar to the initial crew escape pod for the Rockwell B-1 with more oomph.
Title: Re: Should the BFR have a launch escape system?
Post by: Rocket Science on 10/13/2018 08:23 AM
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

You do realized that an explosive line charge is required to cut the crew compartment from the rest of the vehicle along with some sort of abort motors in the crew compartment. This proposal appears to be similar to the initial crew escape pod for the Rockwell B-1 with more oomph.
No, the launch/entry cabin I envision is in essence is a capsule like Dragon (BFD) with the forward fins attached to them. So its more like separating from the trunk currently, in the BFS the crew quarters/common area and the remainder of the ship left behind. It's already in their area of expertise only on a lager scale (what isn't in BFS?). I already mentioned the abort motors similar to the SD. The crew/passengers only need to be seated in the cabin area for launch/entry after closing a hatch like Gemini B MOL... This could be a fail safe "lifeboat" solution for return where some were concerned with fin damage from ice to give one example from another thread or during pre-entry checks a stuck/frozen rear control fin or another failures... I believe you could add the F-111 Aardvark to your list of aircraft, there were others like the Bell X-2 for which the pilot would need to bail out after separation though...
https://falsesteps.wordpress.com/2012/07/15/the-manned-orbiting-laboratory-a-usaf-space-station/
Title: Re: Should the BFR have a launch escape system?
Post by: speedevil on 10/13/2018 10:06 AM
This could be a fail safe "lifeboat" solution for return where some were concerned with fin damage from ice to give one example from another thread or during pre-entry checks a stuck/frozen rear control fin or another failures...
If pre-entry checks fail, you do not deploy the capsule, you apologise to the passengers, announce there will be a slight delay while they change vehicles.
Title: Re: Should the BFR have a launch escape system?
Post by: Rocket Science on 10/13/2018 01:30 PM
This could be a fail safe "lifeboat" solution for return where some were concerned with fin damage from ice to give one example from another thread or during pre-entry checks a stuck/frozen rear control fin or another failures...
If pre-entry checks fail, you do not deploy the capsule, you apologise to the passengers, announce there will be a slight delay while they change vehicles.
I mentioned that as contingency after the announcement in that thread and had to listen to flack from that as well. What do you do after entry and a failure occurs?
https://forum.nasaspaceflight.com/index.php?topic=46387.440
Flack starts after I mention it in post #441
Title: Re: Should the BFR have a launch escape system?
Post by: Darkseraph on 10/13/2018 02:22 PM
By the way, a LAS would add its own risk factors. For instance, if the LAS on Orion fails to separate, the crew dies.
And commercial airlines are so safe that if you added a LAS or ejection seats to them, the extra risks would greatly outweigh the abort advantages, and you'd REDUCE overall safety.

Again, for those in the back:
If BFR is as reliable as Musk wants it to be, adding a LAS would REDUCE safety.

Here's the problem, assuming BFR will have anything like airline levels of safety in the near future. Musk may want it to be that reliable as any normal person would but wanting it to be so doesn't make it so. Those are huge assumptions to make. The proven safety of launch vehicles today is roughly 2 failures out of 100 launches. We're being asked to believe the safety of launch vehicles in just a couple of years will increase by several orders of magnitude when there's been barely any increase in reliability in decades.

SpaceX have very smart engineers undoubtedly. There's the chance reuse does greatly improve reliability after many thousands of flights and many failures that lead to improvements in rocket design, but given there are less than 100 flights per year in the entire world, that is at best decades away. Even the real reliability of Falcon 9 is an open question at it has flown far less than 100 times and had two failures. The BFR itself incorporates many novel technologies in launch vehicle design and will likely be less safe initially compared to tried and tested designs.

I'd agree escape system would be counterproductive if the reliability of BFR-like rockets approached that of airliners. But there's zero evidence that is the case or will be in the near future.



Title: Re: Should the BFR have a launch escape system?
Post by: Robotbeat on 10/13/2018 05:45 PM
It wonít get there in just a couple years. It also wonít be carrying a hundred people in a couple years. With fewer crew, they could afford something like ejection seats.
Title: Re: Should the BFR have a launch escape system?
Post by: RonM on 10/13/2018 05:54 PM
It wonít get there in just a couple years. It also wonít be carrying a hundred people in a couple years. With fewer crew, they could afford something like ejection seats.

If the crew is small enough on early missions, send them to orbit in a Dragon 2 and transfer to BFS. Sure it will cost more, but it allows crewed flights while BFR is building up a flight history.
Title: Re: Should the BFR have a launch escape system?
Post by: Rocket Science on 10/13/2018 06:10 PM
It wonít get there in just a couple years. It also wonít be carrying a hundred people in a couple years. With fewer crew, they could afford something like ejection seats.
What was that about ejection seats on launch vehicles is like "attempting suicide to avoid certain deathĒ... or something along those lines...
Title: Re: Should the BFR have a launch escape system?
Post by: Robotbeat on 10/13/2018 06:28 PM
It wonít get there in just a couple years. It also wonít be carrying a hundred people in a couple years. With fewer crew, they could afford something like ejection seats.
What was that about ejection seats on launch vehicles is like "attempting suicide to avoid certain deathĒ... or something along those lines...
Thatís true for regular abort, too.
Title: Re: Should the BFR have a launch escape system?
Post by: lamontagne on 10/13/2018 06:30 PM
I think we really need to ask a launch escape system for when?  For what event?
To answer, we need to imagine the test program for BFR, the probable missions and to figure out if a launch escape system is the best solution to whatever hazard might happen.
So we need a list of hazards as well.

Would we all agree that the BFB BFS does not need a pilot, will not have a pilot at any time and can be operated entirely without human presence?  The Mars program of SpaceX, as presented up till now, requires a ship that can land itself; the Falcon 9 rocket and the Dragon capsule are vehicles that can land themselves.  This does not seem likely to change, and would be kind of stupid to change.
So where in the test program is  the requirement for a crew escape system?
In fact where is the requirement for a crew? 

The BFR can make money as a satellite launcher without ever having to carry a human.  Almost from the first flight, certainly from the first orbital flight.
SpaceX can run literally billions of simulations with large scale simulators that it should already have in hand. Once it has data from a few initial test flights, it will be able to run the virtual ship through every conceivable operational scenario.  With million of variations. (Ok, I may be underestimating the computing power requirements here)
This is already how Tesla, and any number or other artificial intelligence users are doing their testing.  This is how car autopilot software is created (as far as I know  ;-).

So the fist time humans will be at risk will be on a vehicle that has already been flown many times, has virtually flown millions of times and willl probably have a very high degree of survivability to all the likely and unlikely accidents that could happen. 
Ruptured fuel lines?   Tested
Engine explosion? Tested
Actuator failure? Tested
Loading error? unbalanced center of gravity? Rain, sleet, snow?  Ice?
Tower explosion?  Terrorism? Internal tanks coming off because of ruptured attachments?  Tested.  Oh, yeah, not tested because been there and done that.  No internal tanks  :-)

If there is a mode of failure that makes an escape system required, it seems very unlikely the ship will not be re- designed until that mode of failure diseapears. 
We might even posit that a launch escape system is not a proof of good design, it is a proof of bad design.

So my question would be, is there an event that could never be survived without a launch escape system, that could not be designed out, and if such an event exists, how could the BFR ever be reliable enough to do its final and defining mission: be a mass transportation system for Mars?

Title: Re: Should the BFR have a launch escape system?
Post by: Rocket Science on 10/13/2018 06:46 PM
It wonít get there in just a couple years. It also wonít be carrying a hundred people in a couple years. With fewer crew, they could afford something like ejection seats.
What was that about ejection seats on launch vehicles is like "attempting suicide to avoid certain deathĒ... or something along those lines...
Thatís true for regular abort, too.
Nah, two fellas probably say otherwise this past week I bet... ;)
Title: Re: Should the BFR have a launch escape system?
Post by: Robotbeat on 10/13/2018 06:48 PM
It won’t get there in just a couple years. It also won’t be carrying a hundred people in a couple years. With fewer crew, they could afford something like ejection seats.
What was that about ejection seats on launch vehicles is like "attempting suicide to avoid certain death”... or something along those lines...
That’s true for regular abort, too.
Nah, two fellas probably say otherwise this past week I bet... ;)
The attempted suicide was unsuccessful. Most are, same with most rounds of Russian roullette.
Title: Re: Should the BFR have a launch escape system?
Post by: RonM on 10/13/2018 07:02 PM
So my question would be, is there an event that could never be survived without a launch escape system, that could not be designed out, and if such an event exists, how could the BFR ever be reliable enough to do its final and defining mission: be a mass transportation system for Mars?

BFB explosion on the pad or during max q. BFS engines won't have enough time to spool up to escape. Of course, if those risks are determined to be very low then a LAS won't be necessary.

Mass transportation to Mars is far down the road. Later generations of BFR will include design improvements. Maybe one of those improvements will be a LAS. Who knows?
Title: Re: Should the BFR have a launch escape system?
Post by: lamontagne on 10/13/2018 07:14 PM
So my question would be, is there an event that could never be survived without a launch escape system, that could not be designed out, and if such an event exists, how could the BFR ever be reliable enough to do its final and defining mission: be a mass transportation system for Mars?

BFB explosion on the pad or during max q. BFS engines won't have enough time to spool up to escape. Of course, if those risks are determined to be very low then a LAS won't be necessary.

Mass transportation to Mars is far down the road. Later generations of BFR will include design improvements. Maybe one of those improvements will be a LAS. Who knows?
The explosion is the consequence, what if you eliminate all the causes?
There should be a limited number of causes, that you can deal with by design?
Title: Re: Should the BFR have a launch escape system?
Post by: Rocket Science on 10/13/2018 07:29 PM
Failures of imagination and unknown, unkowns....
Title: Re: Should the BFR have a launch escape system?
Post by: Rocket Science on 10/13/2018 07:31 PM
It wonít get there in just a couple years. It also wonít be carrying a hundred people in a couple years. With fewer crew, they could afford something like ejection seats.
What was that about ejection seats on launch vehicles is like "attempting suicide to avoid certain deathĒ... or something along those lines...
Thatís true for regular abort, too.
Nah, two fellas probably say otherwise this past week I bet... ;)
The attempted suicide was unsuccessful. Most are, same with most rounds of Russian roullette.
Shooting blanks I guess... ;D
Title: Re: Should the BFR have a launch escape system?
Post by: RonM on 10/13/2018 07:31 PM
So my question would be, is there an event that could never be survived without a launch escape system, that could not be designed out, and if such an event exists, how could the BFR ever be reliable enough to do its final and defining mission: be a mass transportation system for Mars?

BFB explosion on the pad or during max q. BFS engines won't have enough time to spool up to escape. Of course, if those risks are determined to be very low then a LAS won't be necessary.

Mass transportation to Mars is far down the road. Later generations of BFR will include design improvements. Maybe one of those improvements will be a LAS. Who knows?
The explosion is the consequence, what if you eliminate all the causes?
There should be a limited number of causes, that you can deal with by design?

I think SpaceX is off to a good start. Both F9 losses were due to second stage explosions and those were due to the helium pressurization system. BFR won't have a system like that. F9 boosters haven't failed, although early on one engine failed during flight, but the mission made it to orbit.

With testing and many cargo and refueling flights, SpaceX will have a pretty good idea about the risk.
Title: Re: Should the BFR have a launch escape system?
Post by: Hominans Kosmos on 10/13/2018 08:09 PM
So my question would be, is there an event that could never be survived without a launch escape system, that could not be designed out, and if such an event exists, how could the BFR ever be reliable enough to do its final and defining mission: be a mass transportation system for Mars?

BFB explosion on the pad or during max q. BFS engines won't have enough time to spool up to escape. Of course, if those risks are determined to be very low then a LAS won't be necessary.

Mass transportation to Mars is far down the road. Later generations of BFR will include design improvements. Maybe one of those improvements will be a LAS. Who knows?
The explosion is the consequence, what if you eliminate all the causes?
There should be a limited number of causes, that you can deal with by design?
 

Or you design the Ship to be robust enough to be likely to survive a booster anomaly and the engines with a short enough thrust ramp for the zero velocity low altitude scenario.
Title: Re: Should the BFR have a launch escape system?
Post by: ChrisWilson68 on 10/13/2018 08:31 PM
By the way, a LAS would add its own risk factors. For instance, if the LAS on Orion fails to separate, the crew dies.
And commercial airlines are so safe that if you added a LAS or ejection seats to them, the extra risks would greatly outweigh the abort advantages, and you'd REDUCE overall safety.

Again, for those in the back:
If BFR is as reliable as Musk wants it to be, adding a LAS would REDUCE safety.

Here's the problem, assuming BFR will have anything like airline levels of safety in the near future. Musk may want it to be that reliable as any normal person would but wanting it to be so doesn't make it so. Those are huge assumptions to make. The proven safety of launch vehicles today is roughly 2 failures out of 100 launches. We're being asked to believe the safety of launch vehicles in just a couple of years will increase by several orders of magnitude when there's been barely any increase in reliability in decades.

No.  The safety of the launch vehicle doesn't need to get to airliner level.  It just needs to get to the level where it's safer than having a launch abort system.

I'd say if reliability increases even one or two orders of magnitude, it's likely safer without the LAS.

SpaceX have very smart engineers undoubtedly. There's the chance reuse does greatly improve reliability after many thousands of flights

There are several reasons to believe that BFR/BFS will be an order of magnitude safer after far fewer than "thousands" of flights than that 2% failure rate you quote:

1. Some of the same factors that make BFR/BFS cheaper make it simpler and less prone to failures.  There are no side boosters coming off, no side-mounting, etc.

2. Reusable vehicles can be examined after every flight.  That tends to make them safer than expendables with the same number of flights.  That's because you can closely examine everything after it lands and notice things that were close to failing or outside of expected tolerances during flight.  Then you can fix those problems.

3. The 2% number includes many failures while launch vehicles had a small number of flights.  What's the failure rate for launches after the first 100 flights of a given model?

4. The 2% number includes recent Russian failures due to poor quality, due to factors unlikely to be present at SpaceX.

and many failures that lead to improvements in rocket design, but given there are less than 100 flights per year in the entire world,

That's in the past.  If BFR works, SpaceX will be flying it often and cheaply to launch Skylink.  That will give it a long flight history quickly.

that is at best decades away. Even the real reliability of Falcon 9 is an open question at it has flown far less than 100 times and had two failures.

Yes, two design flaws that have been fixed.  It's expected future reliability should be far greater.

The BFR itself incorporates many novel technologies in launch vehicle design and will likely be less safe initially compared to tried and tested designs.

People won't be put on it until those issues have been worked out and BFR/BFS is itself a tried and tested design.
Title: Re: Should the BFR have a launch escape system?
Post by: lamontagne on 10/13/2018 09:53 PM
Failures of imagination and unknown, unkowns....
But are there enough of those to require a launch escape system?  And would the launch escape system be enough?  Aren't there always unknown unknowns?
Title: Re: Should the BFR have a launch escape system?
Post by: lamontagne on 10/13/2018 10:04 PM
Regarding the maximum q, might BFR be designed to use more fuel and be less mass ooptimised in order to have a wider margin of safety?
And how long does it take to turn on the engines?  Or, alternatively, can the ship survive a booster explosion and turn on the engines some time before it crashes?  I expect there is a minimum height/time for this?
Title: Re: Should the BFR have a launch escape system?
Post by: speedevil on 10/13/2018 10:48 PM
Regarding the maximum q, might BFR be designed to use more fuel and be less mass ooptimised in order to have a wider margin of safety?
And how long does it take to turn on the engines?  Or, alternatively, can the ship survive a booster explosion and turn on the engines some time before it crashes?  I expect there is a minimum height/time for this?

Extra margin helps.
If you load the BFS halfway, it will have around 2G to get away from a failed stage (it will have notably less payload).

'Explosion' is a word that needs broken down.

Some things are going to cause prompt explosions by any meaning - for example massive structural failure of the intertank meaning the propellants mix, followed by an igniting spark.
Anything other than this, or truly massive spontaneous structural failures in the booster are likely to result in not 'survive a booster explosion' - but 'can BFS survive a 1s period after thrust termination'.
If you design the BFR somewhat like russian rockets, where lighting the next stage is possible even without seperating first, this helps lots with positive sep.

You don't care about what happens to the first stage, after you have detached from it in an emergency.
The lack of large helium tanks of pressurant basically mean that it is impossible to quickly overpressurise the tanks like the failures of F9.
Any pressurisation system malfunction will result in an engine system shutdown with warning, and the pressurisation system is an active system which can be turned off.
The booster needs to cope with worst case engine explosions while retaining RCS capabiity and being able to safely terminate thrust.

Booster failure anywhere in the first seconds of flight, when the debris from the exploding on impact booster may impact BFS is a hard to eliminate risk. Once you're half a minute or so in, you're probably safe from that. This can be mitigated with lower fuel load on BFS, but probably not meaningfully.

Past that, the only real risk from the booster is uncontrolled large attitude changes before Q drops, as absent these, even if thrust terminates, BFS can keep the stack pointed into the wind with RCS, and abort once Q drops to a safe level.


Title: Re: Should the BFR have a launch escape system?
Post by: Rocket Science on 10/13/2018 11:42 PM
Failures of imagination and unknown, unkowns....
But are there enough of those to require a launch escape system?  And would the launch escape system be enough?  Aren't there always unknown unknowns?
On a clean sheet design and with due diligence one should strive to learn from past failures and to minimize or ideally eliminate Black Zones. With the explosive potential of a small nuclear weapon, one should not seek to emulate the hubris of the designers of the Titanic...
Title: Re: Should the BFR have a launch escape system?
Post by: Robotbeat on 10/14/2018 12:00 AM
Failures of imagination and unknown, unkowns....
But are there enough of those to require a launch escape system?  And would the launch escape system be enough?  Aren't there always unknown unknowns?
On a clean sheet design and with due diligence one should strive to learn from past failures and to minimize or ideally eliminate Black Zones. With the explosive potential of a small nuclear weapon, one should not seek to emulate the hubris of the designers of the Titanic...
What if it doubles the development cost and halves the payload? Then it wouldn't fly as often and it may never happen at all.

Existing rockets are 90-99% reliable. Add a LAS tower, and you maybe increased survivability by a factor of 3 (because it doesn't cover all possible ways to die and even when it is relevant, it only saves you 9 out of 10 times). Launch 50 times in a row successfully and you're on par. 300 times successfully in a row, and you've already equalled the best existing systems WITH a LAS.
Title: Re: Should the BFR have a launch escape system?
Post by: Rocket Science on 10/14/2018 01:47 AM
Failures of imagination and unknown, unkowns....
But are there enough of those to require a launch escape system?  And would the launch escape system be enough?  Aren't there always unknown unknowns?
On a clean sheet design and with due diligence one should strive to learn from past failures and to minimize or ideally eliminate Black Zones. With the explosive potential of a small nuclear weapon, one should not seek to emulate the hubris of the designers of the Titanic...
What if it doubles the development cost and halves the payload? Then it wouldn't fly as often and it may never happen at all.

Existing rockets are 90-99% reliable. Add a LAS tower, and you maybe increased survivability by a factor of 3 (because it doesn't cover all possible ways to die and even when it is relevant, it only saves you 9 out of 10 times). Launch 50 times in a row successfully and you're on par. 300 times successfully in a row, and you've already equalled the best existing systems WITH a LAS.
I wouldn't use a tower, I already said Dragon's SD abort methodology would be the way to go. Hindsight is great except when you have to look in the eyes and explain to the survivors of the victims why you didn't design a LES in... We have had passenger liners for over 100 plus years yet with all the knowledge base and safe passages we still have not eliminated lifeboats on them no matter the monetary cost or mass penalty...
Lastly my concern would be the impact of a LOC on the birth of a new industry resulting in a total stillbirth...
I leave you with our friend Wayne Hale's 4 part blog on Black Zones...
http://www.spaceref.com/news/viewsr.html?pid=29847
Title: Re: Should the BFR have a launch escape system?
Post by: Robotbeat on 10/14/2018 02:19 AM
You don't get it. If you make the vehicle too expensive, it's less safe. Even with a LAS.
Title: Re: Should the BFR have a launch escape system?
Post by: su27k on 10/14/2018 02:43 AM
Failures of imagination and unknown, unkowns....

Unknown unkowns would show up during the first dozens of flights, which will be unmanned. Both fatal flaws of STS showed up in the first 26 flights.

We have had passenger liners for over 100 plus years yet with all the knowledge base and safe passages we still have not eliminated lifeboats on them no matter the monetary cost or mass penalty...

Lifeboats are unpowered and with limited supplies, plenty of people died on lifeboats because they're not rescued in time. What you're asking in LAS is analogous to a lifeboat with engines and supplies that can take people to land, no passenger liner has such lifeboats since they would be too expensive.
Title: Re: Should the BFR have a launch escape system?
Post by: su27k on 10/14/2018 02:46 AM
Regarding the maximum q, might BFR be designed to use more fuel and be less mass ooptimised in order to have a wider margin of safety?
And how long does it take to turn on the engines?  Or, alternatively, can the ship survive a booster explosion and turn on the engines some time before it crashes?  I expect there is a minimum height/time for this?

I do hope SpaceX look seriously into SSTO for LEO passenger transport. If the Soyuz accident showed us anything, it's that staging is still very dangerous. Besides, they don't need the full performance of the booster for LEO passenger transport, it's way too overpowered.
Title: Re: Should the BFR have a launch escape system?
Post by: Robotbeat on 10/14/2018 03:22 AM
What is needed is the same sort of thing we have for passenger planes: ways of increasing survival without significantly increasing dry mass. A full LAS is probably out of the question. Ejection seats might be fine for small crews. Maybe a whole-vehicle parachute for larger passenger numbers, combined with toughening of the structure.
Title: Re: Should the BFR have a launch escape system?
Post by: Robotbeat on 10/14/2018 03:24 AM
Maybe ejection seats combined with some MOOSE-like inflatable aero shielding. Before the 2016 IAC announcement, I had imagined that sort of scenario. In principle, you could get the per-person additional dry mass down to as low as 100kg. That's only 10 additional tons.
Title: Re: Should the BFR have a launch escape system?
Post by: ppb on 10/14/2018 03:52 AM

There are several reasons to believe that BFR/BFS will be an order of magnitude safer after far fewer than "thousands" of flights than that 2% failure rate you quote:
   -------------------------
2. Reusable vehicles can be examined after every flight.  That tends to make them safer than expendables with the same number of flights.  That's because you can closely examine everything after it lands and notice things that were close to failing or outside of expected tolerances during flight.  Then you can fix those problems.
----------------------------
People won't be put on it until those issues have been worked out and BFR/BFS is itself a tried and tested design.

I especially agree with this assessment.  The only sentence I would change is "Then you MUST fix those problems." We had a reusable system where everything was inspected after flights and things were found to be lacking (e.g. O-ring erosion and tile damage).  Unfortunately, the "normalization of deviation" mindset took hold and those unfixed tolerance excursions killed 14 people.  Hopefully SpaceX well remembers those painful lessons.
Title: Re: Should the BFR have a launch escape system?
Post by: Robotbeat on 10/14/2018 04:02 AM
Is what SpaceX doing with BFR and Mars and all that worth it if some people die?

Because that's going to happen. Eventually. No matter what.
Title: Re: Should the BFR have a launch escape system?
Post by: lamontagne on 10/14/2018 04:15 AM
Is what SpaceX doing with BFR and Mars and all that worth it if some people die?

Because that's going to happen. Eventually. No matter what.
Everybody dies.  Life is worth living even if you die at the end.😀
Title: Re: Should the BFR have a launch escape system?
Post by: ncb1397 on 10/14/2018 04:35 AM
Is what SpaceX doing with BFR and Mars and all that worth it if some people die?

Because that's going to happen. Eventually. No matter what.

Safety or even the appearance of safety will affect the economics. There are about 3,000 billionaires in the world, while 1 has signed up 2 years after the announcement. How many of those billionaires have problems flying? Not many. If the issue is price and not safety, then that is a problem in and of itself if it is too "rich" for their taste. And then you have a problem with NASA having learned their lesson with Shuttle - now being replaced with 3 crew vehicles all with abort features as requirements and safety (not cost) being the primary factor. From where I am sitting, Elon Musk/SpaceX isn't judging the actual market for this vehicle - and is instead concocting some sci fi fantasy that exists only between their ears. That "sci fi fantasy" might be step Z, while they are on A and haven't fully thought out steps B-Y and the engineering choices needed to complete those steps.

Your analysis of "people will die, so it doesn't matter" doesn't properly distinguish between 3 people dying and 300. It weighs both of those equally. And it doesn't properly distinguish between ideal human behavior because something is objectively "worth it" for the species as the whole and actual human behavior (equivalent to marxism being too idealistic and not properly accounting for underlying biology). You can see that with the current crop of ~3000 people that can absolutely afford this. Only 1 is willing to "take one for the team" or they simply have other causes they are passionate about and may be objectively more worthwhile for the human condition. And then you have the fact that a subset of the 3000 that happen to be passionate about space, are effectively arch rivals against SpaceX.
Title: Re: Should the BFR have a launch escape system?
Post by: pathfinder_01 on 10/14/2018 06:20 AM
What is needed is the same sort of thing we have for passenger planes: ways of increasing survival without significantly increasing dry mass. A full LAS is probably out of the question. Ejection seats might be fine for small crews. Maybe a whole-vehicle parachute for larger passenger numbers, combined with toughening of the structure.

For Airliners and even the Shuttle there are additional safety systems. A LES only handles a specific type of problem the rocket exploding or going off course(and needing to be destroyed). There are a wide range of other problems that the designers of BFR are going to have to deal with like fire on the pad  and depressurization as well various abort options.

I don't think the first generation of BFR will be able to support 100 people and docking\refueling in space presents it own risks and can take time. I think using a NASA crew and a commercial crew craft (CST-100 or Dragon) to transfer crew to a fueled BFR in Orbit would be the most reasonable way to do it.

For the #DearMoon project, I think they are just going to have to bite the bullet and launch with a crew and no escape system. I suspect for the number of people he wants to bring that Ejector seats might not be practical and it would take at least two Dragon flights to bring up the crew(time/expense) and the time factor(boil off) could mean another propellant flight(expense).

For a NASA mission of say a crew of 4, Ejection seats might be a good option because they might be able to handle a landing problem and some(but not all launch problems).

As for other abort options that is going to get complicated as to if the BFR has enough propellant to make it back to somewhere safe to land and I think ditching in the ocean is going to a bad idea(hot rocket engines and extremely cold propellant tanks) but if it is survivable(doubtful) then some sort of floatation device or raft maybe needed.

For depressurization I think Space suites will work even for the Dear Moon Project but if you have 100 travelers something else maybe needed(separate launch cabins able to hold pressure and oxygen masks perhaps)?

I also think there could be an additional version of the BFR one adapted to handle launching the crew and the others more suited for deep space travel\return. That version might have launch escape systems and safety systems in place of all the other stuff that a deep space craft would need.
Title: Re: Should the BFR have a launch escape system?
Post by: meekGee on 10/14/2018 12:12 PM
The problem is that unless you find a way to break-away the cabin, having BFS escape from BFB doesn't help if BFS malfunctions, and BFS accounts for most of the flight events - multiple restarts, reentry, etc.

And BFS can already escape from BFB, in later flight stages.

So this leaves very few scenarios where an escape system has any value...   Basically the fail-to-liftoff scenario.

I think SpaceX will do what they can to reduce that window (e.g. fast start for raptors) and that will be that.

-----
ABCD: Always Be Counting Down

Title: Re: Should the BFR have a launch escape system?
Post by: Rocket Science on 10/14/2018 12:20 PM
Failures of imagination and unknown, unkowns....

Unknown unkowns would show up during the first dozens of flights, which will be unmanned. Both fatal flaws of STS showed up in the first 26 flights.

We have had passenger liners for over 100 plus years yet with all the knowledge base and safe passages we still have not eliminated lifeboats on them no matter the monetary cost or mass penalty...

Lifeboats are unpowered and with limited supplies, plenty of people died on lifeboats because they're not rescued in time. What you're asking in LAS is analogous to a lifeboat with engines and supplies that can take people to land, no passenger liner has such lifeboats since they would be too expensive.
So then call to remove all the lifeboats, davits and all associated gear off ships, while you at it get rid of life jackets as well...
I have spoken my conscience, I'll leave the rest to those that hold an apposing view...
Title: Re: Should the BFR have a launch escape system?
Post by: Yaotzin on 10/14/2018 01:11 PM
So then call to remove all the lifeboats, davits and all associated gear off ships, while you at it get rid of life jackets as well...
I have spoken my conscience, I'll leave the rest to those that hold an apposing view...
Life jackets etc on ships are an easy tradeoff - increased safety, trivial effect on performance and cost. A LAS for a fully reusable orbital rocket would be more like trying to add ejector seats for everyone on planes.

Safety is not worth it at any price. Space spending on safety is already highly questionable. The high cost to improve astronauts' odds and the low cost of alternative ways to save lives, means that most spending on spaceflight safety is probably unethical.

There's also the very real risk of strangling the baby in the crib. High risk commercial spaceflight is better than no commercial spaceflight. No reason people shouldn't get to choose.
Title: Re: Should the BFR have a launch escape system?
Post by: philw1776 on 10/14/2018 01:32 PM
Lots of agonizing today to make Commercial Crew reach safety goal of better than 1 in 270 fatal accidents with a LES.
IF BFR flies as much as expected with Skynet, etc. launches, it rationally can be expected to eventually greatly exceed this safety factor if that's a corporate priority, which it is.  Flights with 100 passengers in my view (others disagree) are way off.  Time for lots of reliability enhancements pioneered by myriad cargo flights, tanker flights and flights with small #s of passengers, not that anyone cares that they were just one of 12 passengers killed vs one of 100.
It is not clear that adding each tonne of LES results in a better chance of avoiding mass death that each tonne of robust reliability enhancements.
Title: Re: Should the BFR have a launch escape system?
Post by: Rocket Science on 10/14/2018 02:41 PM
Those of you that enjoy the "numbers game" for statistical predictions for LOV/LOC would do well to research the "voodoo numbers" being thrown around to sell the STS program pre-first flight and compare it to post Columbia...
Perspective sometimes only comes as a result of age and experience... Reality bites...
Title: Re: Should the BFR have a launch escape system?
Post by: speedevil on 10/14/2018 04:57 PM
Those of you that enjoy the "numbers game" for statistical predictions for LOV/LOC would do well to research the "voodoo numbers" being thrown around to sell the STS program pre-first flight and compare it to post Columbia...
Perspective sometimes only comes as a result of age and experience... Reality bites...
Or reality is awesome.
"I think there is a world market for maybe five computers," - as a chairman of IBM probably did not say.

It is often unclear when an invention will become practical.

LOC/LOM numbers initially can be rather simply resolved by flying a single vehicle 150 times.
Title: Re: Should the BFR have a launch escape system?
Post by: Rocket Science on 10/14/2018 05:24 PM
Those of you that enjoy the "numbers game" for statistical predictions for LOV/LOC would do well to research the "voodoo numbers" being thrown around to sell the STS program pre-first flight and compare it to post Columbia...
Perspective sometimes only comes as a result of age and experience... Reality bites...
Or reality is awesome.
"I think there is a world market for maybe five computers," - as a chairman of IBM probably did not say.

It is often unclear when an invention will become practical.

LOC/LOM numbers initially can be rather simply resolved by flying a single vehicle 150 times.
Watch-out on 151... ;)
Title: Re: Should the BFR have a launch escape system?
Post by: envy887 on 10/14/2018 05:37 PM
Those of you that enjoy the "numbers game" for statistical predictions for LOV/LOC would do well to research the "voodoo numbers" being thrown around to sell the STS program pre-first flight and compare it to post Columbia...
Perspective sometimes only comes as a result of age and experience... Reality bites...

The statistical predictions before STS-1 were in alignment with those calculated after Columbia. NASA just ignored them and relied on "engineering judgement" instead.

Probabilistic risk analysis is not voodoo. "Engineering judgement" is voodoo.
Title: Re: Should the BFR have a launch escape system?
Post by: Rocket Science on 10/14/2018 05:53 PM
Those of you that enjoy the "numbers game" for statistical predictions for LOV/LOC would do well to research the "voodoo numbers" being thrown around to sell the STS program pre-first flight and compare it to post Columbia...
Perspective sometimes only comes as a result of age and experience... Reality bites...

The statistical predictions before STS-1 were in alignment with those calculated after Columbia. NASA just ignored them and relied on "engineering judgement" instead.

Probabilistic risk analysis is not voodoo. "Engineering judgement" is voodoo.
Go find them and let me know...
Title: Re: Should the BFR have a launch escape system?
Post by: envy887 on 10/14/2018 06:21 PM
Those of you that enjoy the "numbers game" for statistical predictions for LOV/LOC would do well to research the "voodoo numbers" being thrown around to sell the STS program pre-first flight and compare it to post Columbia...
Perspective sometimes only comes as a result of age and experience... Reality bites...

The statistical predictions before STS-1 were in alignment with those calculated after Columbia. NASA just ignored them and relied on "engineering judgement" instead.

Probabilistic risk analysis is not voodoo. "Engineering judgement" is voodoo.
Go find them and let me know...

https://spectrum.ieee.org/tech-history/heroic-failures/the-space-shuttle-a-case-of-subjective-engineering
Title: Re: Should the BFR have a launch escape system?
Post by: Rocket Science on 10/14/2018 07:47 PM
Those of you that enjoy the "numbers game" for statistical predictions for LOV/LOC would do well to research the "voodoo numbers" being thrown around to sell the STS program pre-first flight and compare it to post Columbia...
Perspective sometimes only comes as a result of age and experience... Reality bites...

The statistical predictions before STS-1 were in alignment with those calculated after Columbia. NASA just ignored them and relied on "engineering judgement" instead.

Probabilistic risk analysis is not voodoo. "Engineering judgement" is voodoo.
Go find them and let me know...

https://spectrum.ieee.org/tech-history/heroic-failures/the-space-shuttle-a-case-of-subjective-engineering
Thanks for the link, I actually posted that one on here a while back, not a bad article. The first time actually looked at some STS numbers was in something called a "book" in the early 90's (people still use those?). Is was a statistical analysis on LOV/LOC pre and post Challenger... Going from memory it's an "eye-popping" (10X or more?) difference. I have been looking for those numbers for a while again online and then the factoring of Columbia. If I ever find them I'll let you know and would appreciate if you could do the same...
Title: Re: Should the BFR have a launch escape system?
Post by: Arb on 10/14/2018 09:45 PM
All the best spaceships have lifeboats; in SF at least...
Title: Re: Should the BFR have a launch escape system?
Post by: meekGee on 10/14/2018 09:52 PM
All the best spaceships have lifeboats; in SF at least...
Yup - interstellar-capable ones, no less.

Not on the first version of BFS, methinks.
Title: Re: Should the BFR have a launch escape system?
Post by: Rocket Science on 10/14/2018 10:49 PM
@envy
I found a historical review of STS LOCV
Have a look at page 15 and how it was underestimated, something in line what I looked at back in the early 90's...
Title: Re: Should the BFR have a launch escape system?
Post by: Lee Jay on 10/14/2018 11:31 PM
Lots of crazy talk in this thread.

The reason airliners are so incredibly safe (on the order of 1 in 10 million), is not that they are ultra-reliable.  They are not ultra-reliable.  Breakdowns occur every day, many of them in the air.  You don't hear about them much because everyone gets down safe despite the failures.

Airliners are so safe because they have intact abort modes throughout the entire flight and because they can still abort with most types of failures present, often several simultaneous failures.

If this vehicle doesn't have that, it will not come close to matching airliner safety.

I don't see how this vehicle can have intact abort modes in all phases of flight, for most types of failures and for simultaneous failures.  Maybe I'm just not up-to-date on this.
Title: Re: Should the BFR have a launch escape system?
Post by: rakaydos on 10/14/2018 11:55 PM
Lots of crazy talk in this thread.

The reason airliners are so incredibly safe (on the order of 1 in 10 million), is not that they are ultra-reliable.  They are not ultra-reliable.  Breakdowns occur every day, many of them in the air.  You don't hear about them much because everyone gets down safe despite the failures.

Airliners are so safe because they have intact abort modes throughout the entire flight and because they can still abort with most types of failures present, often several simultaneous failures.

If this vehicle doesn't have that, it will not come close to matching airliner safety.

I don't see how this vehicle can have intact abort modes in all phases of flight, for most types of failures and for simultaneous failures.  Maybe I'm just not up-to-date on this.
mainly, BFS relies on Multi-Engine Out capability.. the chance of LOC due to multiple engine failures is all but nonexisttant. So vertical landing can be counted on in the case of any other failure.
The brakerons and the multi-ton RCS system provide a level of redundancy for each other during decent. Off-pad landing capability provides for navigation failure. Navigation and the pre-programmed flight path back up a landing radar failure.

And so on.
Title: Re: Should the BFR have a launch escape system?
Post by: KelvinZero on 10/15/2018 12:13 AM
@envy
I found a historical review of STS LOCV
Have a look at page 15 and how it was underestimated, something in line what I looked at back in the early 90's...
I just really hope the BFR can close the business case with unmanned projects such as the satellite constellation, and let passenger-confidence take as long as it takes.

The major issue with the shuttle IMO was the price and the politics that stuck us with (roughly) one non-evolving design that always carried crew.

That is one concern with the "Dear Moon" project.. it does imply the passenger design gets locked down a lot earlier. I would prefer the passenger design gets finalised only after the cargo version has an excellent flight history.
Title: Re: Should the BFR have a launch escape system?
Post by: lamontagne on 10/15/2018 12:28 AM
@envy
I found a historical review of STS LOCV
Have a look at page 15 and how it was underestimated, something in line what I looked at back in the early 90's...
I just really hope the BFR can close the business case with unmanned projects such as the satellite constellation, and let passenger-confidence take as long as it takes.

The major issue with the shuttle IMO was the price and the politics that stuck us with (roughly) one non-evolving design that always carried crew.

That is one concern with the "Dear Moon" project.. it does imply the passenger design gets locked down a lot earlier. I would prefer the passenger design gets finalised only after the cargo version has an excellent flight history.
I think there is a reason Elon Musk said about a dozen times that Yusaku Maezawa was a brave man in the Dear Moon presentation.  I have the feeling the moon shot will happen before all the safety numbers are in.
Title: Re: Should the BFR have a launch escape system?
Post by: speedevil on 10/15/2018 12:33 AM
I think there is a reason Elon Musk said about a dozen times that Yusaku Maezawa was a brave man in the Dear Moon presentation.  I have the feeling the moon shot will happen before all the safety numbers are in.

You pump up the buyer, to get more buyers.
More seriously, by the time Dear Moon rolls around, you are likely to have over a hundred launches, due to Starlink et al, as well as normal launches switched from F9.
Title: Re: Should the BFR have a launch escape system?
Post by: lamontagne on 10/15/2018 12:58 AM
Aircraft would not survive the explosion of a fuel tank.  However, that is not a problem since the fuel tank never explodes.  So there is no launch abort system for fuel tank explosion.

Can the same thing be done for a rocket, or is the inherent risk always higher because the vehicle carries both the oxydizer and the fuel?.

Some interesting statistics about aircraft, from https://www.flightdeckfriend.com/ask-a-captain/why-do-planes-crash.

''It is however widely accepted that the following statistics are a reasonable representation:

55% Pilot Error  -  shouldn't apply to BFR
17% Aircraft Mechanical Error   -  possible
13% Weather  -  possible, in particular if flights are frequent
8% Sabotage  -  possible
7% Other (ATC, Ground Handling, Unknown)   - possible
Examples of Pilot Error include ďLoss of Control in FlightĒ and ďCFITĒ (Controlled Flight Into Terrain).   - unlikely unless the controls are pirated.

''Percentages of fatal accidents based on phase of flight:

13% Take-off  -
8% Climb  -this is where the LAS system would be useful
27% Cruise  -   
17% Decent Initial Approach  - 
38% Final Approach / Landing  -

Therefore, statistically, the most dangerous phase of flight is landing.''


There are a huge number of problems for which a LAS would be useless.  After all, it might be sabotaged itself and cause the crash! 
However, perhaps the simulations will show that in a certain number of cases, a LAS system would save lives.  And that these are more common than the situations when the LAS goes wrong and destroys the vehicle.
That might make the development of a LAS system an obligation, in particular for passengers that are not taking the risks for appropriate reasons (ignorance, for one).



Title: Re: Should the BFR have a launch escape system?
Post by: speedevil on 10/15/2018 01:06 AM
Aircraft would not survive the explosion of a fuel tank.  However, that is not a problem since the fuel tank never explodes.  So there is no launch abort system for fuel tank explosion.
Except when it does.
https://en.wikipedia.org/wiki/TWA_Flight_800
Title: Re: Should the BFR have a launch escape system?
Post by: Lee Jay on 10/15/2018 01:21 AM
Can the same thing be done for a rocket, or is the inherent risk always higher because the vehicle carries both the oxydizer and the fuel?.

That, and the fact that the energy levels are as much as 3 orders of magnitude higher, the outside air pressure is zero, it takes longer to de-orbit than it does to descend to a safe breathing altitude, entry is hot, rockets don't glide (well, not well anyway - even Shuttle), and in this case, landing requires propulsion to be operating.

Chemical rocketry will always be many orders of magnitude more dangerous than flying on an airliner.
Title: Re: Should the BFR have a launch escape system?
Post by: lamontagne on 10/15/2018 01:28 AM
Aircraft would not survive the explosion of a fuel tank.  However, that is not a problem since the fuel tank never explodes.  So there is no launch abort system for fuel tank explosion.
Except when it does.
https://en.wikipedia.org/wiki/TWA_Flight_800
''On July 18, 2008, the Secretary of Transportation visited the facility and announced a final rule designed to prevent accidents caused by fuel-tank explosions. The rule would require airlines to pump inert gas into the tanks, and will cover the centre-wing tank on all new passenger and cargo airliners, and passenger planes built in most of the 1990s, but not old cargo planes.[55] The NTSB had first recommended such a rule just five months after the incident and 33 years after a similar recommendation issued by the Civil Aeronautics Board Bureau of Safety on December 17, 1963, nine days after the crash of Pan Am Flight 214.[56]''

So solving the problem at the source.  I.E. preventing sparks.
I think it would be interesting to see how well the BFS could survive a BFR explosion.  Isn't the main reason a LAS system seems attractive is that it might have saved the Challenger crew?
Title: Re: Should the BFR have a launch escape system?
Post by: lamontagne on 10/15/2018 01:32 AM
Can the same thing be done for a rocket, or is the inherent risk always higher because the vehicle carries both the oxydizer and the fuel?.

That, and the fact that the energy levels are as much as 3 orders of magnitude higher, the outside air pressure is zero, it takes longer to de-orbit than it does to descend to a safe breathing altitude, entry is hot, rockets don't glide (well, not well anyway - even Shuttle), and in this case, landing requires propulsion to be operating.

Chemical rocketry will always be many orders of magnitude more dangerous than flying on an airliner.
But most of these problems do not address the initial question, does the BFR require a launch escape system.
They are interesting in the light of  'can the BFR ever be as safe as an airliner'.
By adding extra mass, is it possible the LES might make other phases of the overall operation more dangerous?
Title: Re: Should the BFR have a launch escape system?
Post by: Rocket Science on 10/15/2018 01:53 AM
Can the same thing be done for a rocket, or is the inherent risk always higher because the vehicle carries both the oxydizer and the fuel?.

That, and the fact that the energy levels are as much as 3 orders of magnitude higher, the outside air pressure is zero, it takes longer to de-orbit than it does to descend to a safe breathing altitude, entry is hot, rockets don't glide (well, not well anyway - even Shuttle), and in this case, landing requires propulsion to be operating.

Chemical rocketry will always be many orders of magnitude more dangerous than flying on an airliner.
But most of these problems do not address the initial question, does the BFR require a launch escape system.
They are interesting in the light of  'can the BFR ever be as safe as an airliner'.
By adding extra mass, is it possible the LES might make other phases of the overall operation more dangerous?
Use the Saturn V as a reference from our friend Dwayne...
http://www.thespacereview.com/article/591/1
Title: Re: Should the BFR have a launch escape system?
Post by: Robotbeat on 10/15/2018 02:46 AM
Can the same thing be done for a rocket, or is the inherent risk always higher because the vehicle carries both the oxydizer and the fuel?.

That, and the fact that the energy levels are as much as 3 orders of magnitude higher, the outside air pressure is zero, it takes longer to de-orbit than it does to descend to a safe breathing altitude, entry is hot, rockets don't glide (well, not well anyway - even Shuttle), and in this case, landing requires propulsion to be operating.

Chemical rocketry will always be many orders of magnitude more dangerous than flying on an airliner.
Energy levels aren't that different. Energy required on very long distance flights (in the form of fuel) is about the same as orbit, or nearly so.

Chemical or non-chemical rocketry could indeed be just as safe as flying in an airliner. It just depends on flight count.
Title: Re: Should the BFR have a launch escape system?
Post by: KelvinZero on 10/15/2018 03:11 AM
I think there is a reason Elon Musk said about a dozen times that Yusaku Maezawa was a brave man in the Dear Moon presentation.  I have the feeling the moon shot will happen before all the safety numbers are in.
Sure. That really wasn't at all what I was referring to. My concern was that it would force the crew design to be solidified early before lessons from many BFR launches of the cargo design could be incorporated. Apart from this one project, the manned side does not seem to be a vital part of the business model. Plenty of time to get it right.. apart from this project.
Title: Re: Should the BFR have a launch escape system?
Post by: ncb1397 on 10/15/2018 03:49 AM
Energy levels aren't that different. Energy required on very long distance flights (in the form of fuel) is about the same as orbit, or nearly so.

Chemical or non-chemical rocketry could indeed be just as safe as flying in an airliner. It just depends on flight count.

The fuel load isn't published for the 2017 BFR booster, but I think between the upper and lower stage, you are looking at well over 800,000 kg of fuel. The 2018 version is even bigger. For comparison, a 787 carries a maximum of 102,000 kg of fuel. A380 is ~250,000 kg. So, you are probably looking at a fuel load for the 2018 version of ~4x the largest commercial airliner. Jet fuel energy density is about 45 MJ/kg. Methane is 56 MJ/kg. Factoring in energy density bumps it up to 5x.
Title: Re: Should the BFR have a launch escape system?
Post by: Robotbeat on 10/15/2018 04:07 AM
Energy levels aren't that different. Energy required on very long distance flights (in the form of fuel) is about the same as orbit, or nearly so.

Chemical or non-chemical rocketry could indeed be just as safe as flying in an airliner. It just depends on flight count.

The fuel load isn't published for the 2017 BFR booster, but I think between the upper and lower stage, you are looking at well over 800,000 kg of fuel. The 2018 version is even bigger. For comparison, a 787 carries a maximum of 102,000 kg of fuel. A380 is ~250,000 kg. So, you are probably looking at a fuel load for the 2018 version of ~4x the largest commercial airliner. Jet fuel energy density is about 45 MJ/kg. Methane is 56 MJ/kg. Factoring in energy density bumps it up to 5x.
BFR is not the limit of chemical rocket efficiency. You can probably improve on it by a factor of 2 at least by using careful adjustment of mixture ratios, running stoichiometric hydrolox for the upper stage, and operating deeply oxygen-rich for the first stage.

It's pretty close, same order of magnitude. Not "as much as 3 orders of magnitude higher."
Title: Re: Should the BFR have a launch escape system?
Post by: ncb1397 on 10/15/2018 05:32 AM
Energy levels aren't that different. Energy required on very long distance flights (in the form of fuel) is about the same as orbit, or nearly so.

Chemical or non-chemical rocketry could indeed be just as safe as flying in an airliner. It just depends on flight count.

The fuel load isn't published for the 2017 BFR booster, but I think between the upper and lower stage, you are looking at well over 800,000 kg of fuel. The 2018 version is even bigger. For comparison, a 787 carries a maximum of 102,000 kg of fuel. A380 is ~250,000 kg. So, you are probably looking at a fuel load for the 2018 version of ~4x the largest commercial airliner. Jet fuel energy density is about 45 MJ/kg. Methane is 56 MJ/kg. Factoring in energy density bumps it up to 5x.
BFR is not the limit of chemical rocket efficiency. You can probably improve on it by a factor of 2 at least by using careful adjustment of mixture ratios, running stoichiometric hydrolox for the upper stage, and operating deeply oxygen-rich for the first stage.

It's pretty close, same order of magnitude. Not "as much as 3 orders of magnitude higher."

I believe he is talking about the kinectic energy of a fixed mass which is proportional to the square of the velocity. So, comparing an Apollo capsule at 40,000 kilometers per hour and sub sonic jet liner at 1050 kph yields a kinectic energy of 1 kg of 1450x or 3 orders of magnitude. Burning off the energy of an airliner is not very stressful and very easy. Burning off the energy of an Apollo capsule? Not so much.

He is essentially describing the danger of increased speed. A train moving at 5 miles per hour isn't really a danger to its passengers no matter what happens. It can derail and it wouldn't be suprising if everyone lives. Now compare that to a train moving at 300 miles per hour derailing. The forces on the human body and the train itself then go way way up.
Title: Re: Should the BFR have a launch escape system?
Post by: Robotbeat on 10/15/2018 06:07 AM
But a passenger airplane moving at nearly the speed of sound is safer per mile than trains and cars moving an order of magnitude slower. And those, in turn, are safer per mile than walking/running which is an order of magnitude slower again.
Title: Re: Should the BFR have a launch escape system?
Post by: meekGee on 10/15/2018 06:27 AM
It will be hard to make BFS fly 10,000,000 times straight without having a fatal accident.  (Airplanes do that).

Airplanes do that because even though they malfunction all the time, it takes a lot of malfunctions to bring down an airplane.

However, even if BFS flies 10 times a day for a year, that's only 3000 flights.  BFS doesn't have to be as safe as airplanes.  It has to be safe enough for its intended use.

Adding a LAS (LAS, remember LAS? This is a thread about LAS) will not improve the safety aspect of BFS by much, since it's only effective during initial lift-off.  During late ascent, BFS can already escape, and during landing, a LAS can't do much.

The good news is that once re-entry is figured out, there's none of the "order of magnitude higher" energy anymore.  At that point, it's not much more demanding than airplanes landing in cross winds, as is performed 1000 of times a day around the globe.






Title: Re: Should the BFR have a launch escape system?
Post by: Lee Jay on 10/15/2018 07:28 AM
Can the same thing be done for a rocket, or is the inherent risk always higher because the vehicle carries both the oxydizer and the fuel?.

That, and the fact that the energy levels are as much as 3 orders of magnitude higher, the outside air pressure is zero, it takes longer to de-orbit than it does to descend to a safe breathing altitude, entry is hot, rockets don't glide (well, not well anyway - even Shuttle), and in this case, landing requires propulsion to be operating.

Chemical rocketry will always be many orders of magnitude more dangerous than flying on an airliner.
Energy levels aren't that different.

I was talking about kinetic energy + potential energy of flight, which has to be dissipated, not stored chemical energy which can remain stored or be jettisoned.
Title: Re: Should the BFR have a launch escape system?
Post by: alang on 10/15/2018 07:41 AM
I suspect that if this is not going to be used by NASA then most people will only be concerned to limit the risk to uninvolved third parties. Horse riding, rock climbing, sport flying and cave diving are still legal, as is private gun ownership in some jurisdictions.
The cynic in me thinks that part of the reason for public dismay about previous astronaut deaths was their relative celebrity. Was it Tom Wolfe who pointed out that few cared about test pilots prior to the Gemini programme?
Things have changed again though: how extensively reported was the recent ejection from an F-35? - maybe it was in the U.S. but little in a country that's buying them. The recent Soyuz escape was instructive: 30 years ago it would have been much bigger news.
Of course, any failure Elon Musk is involved in will be bigger news than it might otherwise be. Also, an explosion on the pad or a slow lonely death in radio contact will be bigger news than a sudden death hidden from cameras.
I suggest that the substantive issue here is not the safety but whether in order to be financially viable BFS needs NASA people carrying business and what U.S. regulators are willing to put up with. I feel confident that other countries won't be so squeamish and some people will be sufficiently ideologically motivated to make other arrangements. I'm reminded of the words of Tom Lehrer:
""In German, oder Englisch, I know how to count down
Und I'm learning Chinese!" says Wernher von Braun".
 (prediction: this thread is about to be trimmed.)
Title: Re: Should the BFR have a launch escape system?
Post by: speedevil on 10/15/2018 10:32 AM
Sure. That really wasn't at all what I was referring to. My concern was that it would force the crew design to be solidified early before lessons from many BFR launches of the cargo design could be incorporated. Apart from this one project, the manned side does not seem to be a vital part of the business model. Plenty of time to get it right.. apart from this project.
What parts of passenger safety are not optimised by ensuring a low vehicle failure rate?
(Assuming for the moment, deliberate trades to make BFS less reliable are not taken).
Title: Re: Should the BFR have a launch escape system?
Post by: ncb1397 on 10/15/2018 12:06 PM
But a passenger airplane moving at nearly the speed of sound is safer per mile than trains and cars moving an order of magnitude slower. And those, in turn, are safer per mile than walking/running which is an order of magnitude slower again.

We are comparing aircraft vs aircraft. My previous train comparison was trains vs trains. The record for airplanes vs trains likely comes down to other factors like commercial airline requirements of a co-pilot.

Anyways, the record for planes clearly shows a negative correlation between safety and speed. The rank for safety with 1 being the highest is

1.)747..and all other subsonic commercial air liners.
2.)Concorde
3.)Shuttle

And besides, walking is only more dangerous because of faster modes of travel - cars and such. It doesn't disprove the speed/safety correlation, it just is an externality of car transport and the speeds involved. Walking is dangerous because cars are dangerous, not pedestrian - pedestrian collisions.
Quote
Between 2000 and 2009, the number of deaths per billion passenger-miles caused by trains was 0.43.
Ö.
According to that same study, the number of deaths per billion passenger-miles caused by airplanes is a measly 0.07. And this statistic is just one of many that illustrate just how safe air travel is.
Ö
According to the National Transportation Safety Board's stats, of the 891 train deaths in the U.S. in 2013, only six of them were passengers. The vast majority were pedestrians or drivers who were struck by a train.
https://www.bustle.com/articles/83287-are-trains-safer-than-planes-statistics-are-clear-about-which-mode-of-transportation-is-safest

32.3 billion passenger miles in 2013: https://www.bts.gov/content/us-passenger-miles
Of those 6 deaths, 4 of them were due to having no co-pilot and the engineer falling asleep: https://en.wikipedia.org/wiki/List_of_rail_accidents_(2010Ėpresent)
Without that which is due to no co-pilot, 2/32.3 billion passenger miles is .06 passenger fatalities in 2013 which is better than the 2000-2009 air number.

As such, BFS will not likely beat commercial passenger air travel, unless it meets more stringent safety requirements. And considering that regulatory environment is way less stringent for commercial space travel and it strips away safety features that are standard with current space transportation systems, I wouldn't hold my breath.

And you are ignoring the per-trip or deaths per hour of use statistics which are arguably more important. This would comparatively disadvantage faster modes of transport vs passenger-mile based statistics (or passenger-miles based statistics disadvantage slower forms of transport). The starship enterprise would beat everything in deaths per billion passenger miles even if it exploded half the time you engaged the propulsion system. Would such a vehicle be considered safe? Would riding in one be safer than riding in a 737?

A more realistic example would be BFS traveling to Mars and back. Mars Orbit is about 50 million miles farther from the sun and so let's say that each round trip is 100 million miles of passenger miles per passenger (this just assumes that it hops very fast from earth orbit to mars orbit at closest approach). According to passenger mile statistics, it would be safer than airlines if 1 in every 140 trips ended with the death of all on board.
Title: Re: Should the BFR have a launch escape system?
Post by: Rocket Science on 10/15/2018 01:40 PM
It will be hard to make BFS fly 10,000,000 times straight without having a fatal accident.  (Airplanes do that).

Airplanes do that because even though they malfunction all the time, it takes a lot of malfunctions to bring down an airplane.

However, even if BFS flies 10 times a day for a year, that's only 3000 flights.  BFS doesn't have to be as safe as airplanes.  It has to be safe enough for its intended use.

Adding a LAS (LAS, remember LAS? This is a thread about LAS) will not improve the safety aspect of BFS by much, since it's only effective during initial lift-off.  During late ascent, BFS can already escape, and during landing, a LAS can't do much.

The good news is that once re-entry is figured out, there's none of the "order of magnitude higher" energy anymore.  At that point, it's not much more demanding than airplanes landing in cross winds, as is performed 1000 of times a day around the globe.
Perhaps you missed it but what I proposed could be used during multiple phases of the flight including EDL so that we're all on the same page...

Edit to add: Some (not you) either forget it or ignore it...
Title: Re: Should the BFR have a launch escape system?
Post by: meekGee on 10/15/2018 02:07 PM
But a passenger airplane moving at nearly the speed of sound is safer per mile than trains and cars moving an order of magnitude slower. And those, in turn, are safer per mile than walking/running which is an order of magnitude slower again.

We are comparing aircraft vs aircraft. My previous train comparison was trains vs trains. The record for airplanes vs trains likely comes down to other factors like commercial airline requirements of a co-pilot.

Anyways, the record for planes clearly shows a negative correlation between safety and speed. The rank for safety with 1 being the highest is

1.)747..and all other subsonic commercial air liners.
2.)Concorde
3.)Shuttle

And besides, walking is only more dangerous because of faster modes of travel - cars and such. It doesn't disprove the speed/safety correlation, it just is an externality of car transport and the speeds involved. Walking is dangerous because cars are dangerous, not pedestrian - pedestrian collisions.
Quote
Between 2000 and 2009, the number of deaths per billion passenger-miles caused by trains was 0.43.
Ö.
According to that same study, the number of deaths per billion passenger-miles caused by airplanes is a measly 0.07. And this statistic is just one of many that illustrate just how safe air travel is.
Ö
According to the National Transportation Safety Board's stats, of the 891 train deaths in the U.S. in 2013, only six of them were passengers. The vast majority were pedestrians or drivers who were struck by a train.
https://www.bustle.com/articles/83287-are-trains-safer-than-planes-statistics-are-clear-about-which-mode-of-transportation-is-safest

32.3 billion passenger miles in 2013: https://www.bts.gov/content/us-passenger-miles
Of those 6 deaths, 4 of them were due to having no co-pilot and the engineer falling asleep: https://en.wikipedia.org/wiki/List_of_rail_accidents_(2010Ėpresent)
Without that which is due to no co-pilot, 2/32.3 billion passenger miles is .06 passenger fatalities in 2013 which is better than the 2000-2009 air number.

As such, BFS will not likely beat commercial passenger air travel, unless it meets more stringent safety requirements. And considering that regulatory environment is way less stringent for commercial space travel and it strips away safety features that are standard with current space transportation systems, I wouldn't hold my breath.

And you are ignoring the per-trip or deaths per hour of use statistics which are arguably more important. This would comparatively disadvantage faster modes of transport vs passenger-mile based statistics (or passenger-miles based statistics disadvantage slower forms of transport). The starship enterprise would beat everything in deaths per billion passenger miles even if it exploded half the time you engaged the propulsion system. Would such a vehicle be considered safe? Would riding in one be safer than riding in a 737?

A more realistic example would be BFS traveling to Mars and back. Mars Orbit is about 50 million miles farther from the sun and so let's say that each round trip is 100 million miles of passenger miles per passenger (this just assumes that it hops very fast from earth orbit to mars orbit at closest approach). According to passenger mile statistics, it would be safer than airlines if 1 in every 140 trips ended with the death of all on board.
Actually, GA airplanes are the worst, by far, when compared to jetliners.  Probably including Concorde too.

And if you're going to include Shuttle, you may as well include cars.  Shuttle failed as a rocket, not as an airplane.






-----
ABCD: Always Be Counting Down

Title: Re: Should the BFR have a launch escape system?
Post by: envy887 on 10/15/2018 02:29 PM
@envy
I found a historical review of STS LOCV
Have a look at page 15 and how it was underestimated, something in line what I looked at back in the early 90's...

Yes, that's also an interesting paper.

While early data-driven risk analyses did underestimate the risk (compared to the PRAs done later with larger datasets), they were not that far off. Weatherwax's ~1:35 is only off by a factor of 3.5, vs. studies based on engineering judgement that were off by factors of 100 to 10,000. If you can find a copy of the Weatherwax paper, I'd like to read it.

If this graph were plotted on a log scale the accuracy of early probabilistic studies would be a lot more evident. As shown, the reasonably accurate 1:35 and the wildly inaccurate 1:10,000 derived with very different methods, look far too similar.
Title: Re: Should the BFR have a launch escape system?
Post by: ncb1397 on 10/15/2018 03:00 PM
Actually, GA airplanes are the worst, by far, when compared to jetliners.  Probably including Concorde too.

And if you're going to include Shuttle, you may as well include cars.  Shuttle failed as a rocket, not as an airplane.

My 3 examples all had similar maintanence practices. Bringing up Uncle Tom's beater aircraft that he works on himself is just being argumentative.

The wing damage on Columbia was likely survivable if it wasn't going at the speed it was when it hit the atmosphere. Aircraft have lost entire wings and landed.

http://www.military.com/video/military-aircraft-operations/aviation-accidents/f-15-lands-on-one-wing/644325471001
Title: Re: Should the BFR have a launch escape system?
Post by: Rocket Science on 10/15/2018 03:15 PM
Actually, GA airplanes are the worst, by far, when compared to jetliners.  Probably including Concorde too.

And if you're going to include Shuttle, you may as well include cars.  Shuttle failed as a rocket, not as an airplane.

My 3 examples all had similar maintanence practices. Bringing up Uncle Tom's beater aircraft that he works on himself is just being argumentative.

The wing damage on Columbia was likely survivable if it wasn't going at the speed it was when it hit the atmosphere. Aircraft have lost entire wings and landed.

http://www.military.com/video/military-aircraft-operations/aviation-accidents/f-15-lands-on-one-wing/644325471001
I personally avoided flying on the weekend do to two close mid-airs... One guy almost hit me as I turned left into the downwind after I took off doing circuits. Another guy was trying to land on top of me while I was on final as I looked up at his landing gear near my head... This was at an uncontrolled airfield...
Title: Re: Should the BFR have a launch escape system?
Post by: Rocket Science on 10/15/2018 03:17 PM
@envy
I found a historical review of STS LOCV
Have a look at page 15 and how it was underestimated, something in line what I looked at back in the early 90's...

Yes, that's also an interesting paper.

While early data-driven risk analyses did underestimate the risk (compared to the PRAs done later with larger datasets), they were not that far off. Weatherwax's ~1:35 is only off by a factor of 3.5, vs. studies based on engineering judgement that were off by factors of 100 to 10,000. If you can find a copy of the Weatherwax paper, I'd like to read it.

If this graph were plotted on a log scale the accuracy of early probabilistic studies would be a lot more evident. As shown, the reasonably accurate 1:35 and the wildly inaccurate 1:10,000 derived with very different methods, look far too similar.
Will do if I find a copy...
Title: Re: Should the BFR have a launch escape system?
Post by: meekGee on 10/15/2018 03:25 PM
Actually, GA airplanes are the worst, by far, when compared to jetliners.  Probably including Concorde too.

And if you're going to include Shuttle, you may as well include cars.  Shuttle failed as a rocket, not as an airplane.

My 3 examples all had similar maintanence practices. Bringing up Uncle Tom's beater aircraft that he works on himself is just being argumentative.

The wing damage on Columbia was likely survivable if it wasn't going at the speed it was when it hit the atmosphere. Aircraft have lost entire wings and landed.

http://www.military.com/video/military-aircraft-operations/aviation-accidents/f-15-lands-on-one-wing/644325471001
All your airplane examples have pilots. BFS doesn't. So they are not equivalent.

You're cherry-picking the examples, and this just makes your argument weaker.

Faster does not mean less safe. RBs point was well made.

Jetliners currently hold the safety record, even though they are faster than most other modes of transportation, involve high amounts of energy, operate in a very inhospitable environment, and are less forgiving to mishaps than cars for example.

Maybe it's because they represent some sweet spot in the whole engineering space...  But for sure the argument that "it's unsafe because it's high energy" is proven wrong.

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ABCD: Always Be Counting Down

Title: Re: Should the BFR have a launch escape system?
Post by: ncb1397 on 10/15/2018 03:33 PM
Actually, GA airplanes are the worst, by far, when compared to jetliners.  Probably including Concorde too.

And if you're going to include Shuttle, you may as well include cars.  Shuttle failed as a rocket, not as an airplane.

My 3 examples all had similar maintanence practices. Bringing up Uncle Tom's beater aircraft that he works on himself is just being argumentative.

The wing damage on Columbia was likely survivable if it wasn't going at the speed it was when it hit the atmosphere. Aircraft have lost entire wings and landed.

http://www.military.com/video/military-aircraft-operations/aviation-accidents/f-15-lands-on-one-wing/644325471001
All your airplane examples have pilots. BFS doesn't. So they are not equivalent.


Quote
Yes a plane can land by itself using a system that is often referred to as ďautolandĒ. The pilots can program the auto pilot to carry out the landing automatically whilst the pilots monitor the aircraft. However there are limitations as to when the autoland system can be used.
Automatic landings probably account for less then 1% of all landings on commercial flights. Many pilots actually think itís much easier to land the aircraft manually, as monitoring the auto pilot in the autoland stage of flight is itself very demanding with a very high level of vigilance required at all stages.
https://www.flightdeckfriend.com/can-a-plane-land-automatically

BFS possibly doesn't have a pilot because there is no BFS vehicle (currently). The differentiation between an airliner with autopilot/autoland and a BFS is splitting hairs. Okay, BFS doesn't have a pilot monitoring anything and that somehow makes it safer? But they have to have a pilot. They just may be on the ground.
Title: Re: Should the BFR have a launch escape system?
Post by: meekGee on 10/15/2018 03:47 PM
Actually, GA airplanes are the worst, by far, when compared to jetliners.  Probably including Concorde too.

And if you're going to include Shuttle, you may as well include cars.  Shuttle failed as a rocket, not as an airplane.

My 3 examples all had similar maintanence practices. Bringing up Uncle Tom's beater aircraft that he works on himself is just being argumentative.

The wing damage on Columbia was likely survivable if it wasn't going at the speed it was when it hit the atmosphere. Aircraft have lost entire wings and landed.

http://www.military.com/video/military-aircraft-operations/aviation-accidents/f-15-lands-on-one-wing/644325471001
All your airplane examples have pilots. BFS doesn't. So they are not equivalent.


Quote
Yes a plane can land by itself using a system that is often referred to as ďautolandĒ. The pilots can program the auto pilot to carry out the landing automatically whilst the pilots monitor the aircraft. However there are limitations as to when the autoland system can be used.
Automatic landings probably account for less then 1% of all landings on commercial flights. Many pilots actually think itís much easier to land the aircraft manually, as monitoring the auto pilot in the autoland stage of flight is itself very demanding with a very high level of vigilance required at all stages.
https://www.flightdeckfriend.com/can-a-plane-land-automatically

BFS possibly doesn't have a pilot because there is no BFS vehicle (currently). The differentiation between an airliner with autopilot/autoland and a BFS is splitting hairs. Okay, BFS doesn't have a pilot monitoring anything and that somehow makes it safer?
Auto-pilots (or FMSs, in modern jet liners) are very limited in what they do.

Given how many airplanes crash due to pilot error, I don't think you can credibly claim it's "hair splitting".



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ABCD: Always Be Counting Down

Title: Re: Should the BFR have a launch escape system?
Post by: ncb1397 on 10/15/2018 03:52 PM
Actually, GA airplanes are the worst, by far, when compared to jetliners.  Probably including Concorde too.

And if you're going to include Shuttle, you may as well include cars.  Shuttle failed as a rocket, not as an airplane.

My 3 examples all had similar maintanence practices. Bringing up Uncle Tom's beater aircraft that he works on himself is just being argumentative.

The wing damage on Columbia was likely survivable if it wasn't going at the speed it was when it hit the atmosphere. Aircraft have lost entire wings and landed.

http://www.military.com/video/military-aircraft-operations/aviation-accidents/f-15-lands-on-one-wing/644325471001
All your airplane examples have pilots. BFS doesn't. So they are not equivalent.


Quote
Yes a plane can land by itself using a system that is often referred to as ďautolandĒ. The pilots can program the auto pilot to carry out the landing automatically whilst the pilots monitor the aircraft. However there are limitations as to when the autoland system can be used.
Automatic landings probably account for less then 1% of all landings on commercial flights. Many pilots actually think itís much easier to land the aircraft manually, as monitoring the auto pilot in the autoland stage of flight is itself very demanding with a very high level of vigilance required at all stages.
https://www.flightdeckfriend.com/can-a-plane-land-automatically

BFS possibly doesn't have a pilot because there is no BFS vehicle (currently). The differentiation between an airliner with autopilot/autoland and a BFS is splitting hairs. Okay, BFS doesn't have a pilot monitoring anything and that somehow makes it safer?
Auto-pilots (or FMSs, in modern jet liners) are very limited in what they do.

Given how many airplanes crash due to pilot error, I don't think you can credibly claim it's "hair splitting".

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ABCD: Always Be Counting Down

Is this considered pilot error?

Quote
Continental / Colgan Air Flight 3407 is a really troubling one. Flying into Buffalo/Niagara airport one cold night, a Bombardier regional jet carrying 49 passengers collected a fair bit of ice on the wing. As the plane descended on landing approach, the pilots failed to notice that the airspeed had fallen below the approach speed that was appropriate for ice buildup conditions. The plane stalled.
https://www.quora.com/What-were-the-worst-pilot-errors-in-airplanes-crashes

How realible is your computer going to be at measuring and understanding all conditions of flight? And if it was that good, it would be just as effective as an assistant warning the pilot that their air speed is too low due to ice build up (as an example).

I wouldn't expect the software to be that great to begin with. Cargo dragon didn't even deploy the parachutes after CRS-7 in flight break up. In an automated system, the programmer is the pilot. I wouldn't expect him to be immune to mistakes as seen by the recent failure of Ariane V. The wrong parameters were put into the autopilot system and BFS won't have a human level AI. Sorry...
Title: Re: Should the BFR have a launch escape system?
Post by: Rocket Science on 10/15/2018 04:22 PM
Let's not disregard potential hacking...
https://motherboard.vice.com/en_us/article/3km4eb/pentagon-weapons-easily-hacked-gao-report
Title: Re: Should the BFR have a launch escape system?
Post by: meekGee on 10/15/2018 04:31 PM
Actually, GA airplanes are the worst, by far, when compared to jetliners.  Probably including Concorde too.

And if you're going to include Shuttle, you may as well include cars.  Shuttle failed as a rocket, not as an airplane.

My 3 examples all had similar maintanence practices. Bringing up Uncle Tom's beater aircraft that he works on himself is just being argumentative.

The wing damage on Columbia was likely survivable if it wasn't going at the speed it was when it hit the atmosphere. Aircraft have lost entire wings and landed.

http://www.military.com/video/military-aircraft-operations/aviation-accidents/f-15-lands-on-one-wing/644325471001
All your airplane examples have pilots. BFS doesn't. So they are not equivalent.


Quote
Yes a plane can land by itself using a system that is often referred to as ďautolandĒ. The pilots can program the auto pilot to carry out the landing automatically whilst the pilots monitor the aircraft. However there are limitations as to when the autoland system can be used.
Automatic landings probably account for less then 1% of all landings on commercial flights. Many pilots actually think itís much easier to land the aircraft manually, as monitoring the auto pilot in the autoland stage of flight is itself very demanding with a very high level of vigilance required at all stages.
https://www.flightdeckfriend.com/can-a-plane-land-automatically

BFS possibly doesn't have a pilot because there is no BFS vehicle (currently). The differentiation between an airliner with autopilot/autoland and a BFS is splitting hairs. Okay, BFS doesn't have a pilot monitoring anything and that somehow makes it safer?
Auto-pilots (or FMSs, in modern jet liners) are very limited in what they do.

Given how many airplanes crash due to pilot error, I don't think you can credibly claim it's "hair splitting".

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ABCD: Always Be Counting Down

Is this considered pilot error?

Quote
Continental / Colgan Air Flight 3407 is a really troubling one. Flying into Buffalo/Niagara airport one cold night, a Bombardier regional jet carrying 49 passengers collected a fair bit of ice on the wing. As the plane descended on landing approach, the pilots failed to notice that the airspeed had fallen below the approach speed that was appropriate for ice buildup conditions. The plane stalled.
https://www.quora.com/What-were-the-worst-pilot-errors-in-airplanes-crashes

How realible is your computer going to be at measuring and understanding all conditions of flight? And if it was that good, it would be just as effective as an assistant warning the pilot that their air speed is too low due to ice build up (as an example).

I wouldn't expect the software to be that great to begin with. Cargo dragon didn't even deploy the parachutes after CRS-7 in flight break up. In an automated system, the programmer is the pilot. I wouldn't expect him to be immune to mistakes as seen by the recent failure of Ariane V. The wrong parameters were put into the autopilot system and BFS won't have a human level AI. Sorry...
If you've ever followed how airspace is managed around a modern airport, you'd know how unstructured and human-dependent it is.

Very very far from the notion of a bunch of auto-controlled airplanes merging and lining up for approach.

More like a bunch of kids with bad accents, bad walkie talkies, and on a shared frequency...

Very different from BFS "one shot" flight profiles

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ABCD: Always Be Counting Down

Title: Re: Should the BFR have a launch escape system?
Post by: JamesH65 on 10/15/2018 04:50 PM
Actually, GA airplanes are the worst, by far, when compared to jetliners.  Probably including Concorde too.

And if you're going to include Shuttle, you may as well include cars.  Shuttle failed as a rocket, not as an airplane.

My 3 examples all had similar maintanence practices. Bringing up Uncle Tom's beater aircraft that he works on himself is just being argumentative.

The wing damage on Columbia was likely survivable if it wasn't going at the speed it was when it hit the atmosphere. Aircraft have lost entire wings and landed.

http://www.military.com/video/military-aircraft-operations/aviation-accidents/f-15-lands-on-one-wing/644325471001
All your airplane examples have pilots. BFS doesn't. So they are not equivalent.


Quote
Yes a plane can land by itself using a system that is often referred to as ďautolandĒ. The pilots can program the auto pilot to carry out the landing automatically whilst the pilots monitor the aircraft. However there are limitations as to when the autoland system can be used.
Automatic landings probably account for less then 1% of all landings on commercial flights. Many pilots actually think itís much easier to land the aircraft manually, as monitoring the auto pilot in the autoland stage of flight is itself very demanding with a very high level of vigilance required at all stages.
https://www.flightdeckfriend.com/can-a-plane-land-automatically

BFS possibly doesn't have a pilot because there is no BFS vehicle (currently). The differentiation between an airliner with autopilot/autoland and a BFS is splitting hairs. Okay, BFS doesn't have a pilot monitoring anything and that somehow makes it safer?
Auto-pilots (or FMSs, in modern jet liners) are very limited in what they do.

Given how many airplanes crash due to pilot error, I don't think you can credibly claim it's "hair splitting".

-----
ABCD: Always Be Counting Down

Is this considered pilot error?

Quote
Continental / Colgan Air Flight 3407 is a really troubling one. Flying into Buffalo/Niagara airport one cold night, a Bombardier regional jet carrying 49 passengers collected a fair bit of ice on the wing. As the plane descended on landing approach, the pilots failed to notice that the airspeed had fallen below the approach speed that was appropriate for ice buildup conditions. The plane stalled.
https://www.quora.com/What-were-the-worst-pilot-errors-in-airplanes-crashes

How realible is your computer going to be at measuring and understanding all conditions of flight? And if it was that good, it would be just as effective as an assistant warning the pilot that their air speed is too low due to ice build up (as an example).

I wouldn't expect the software to be that great to begin with. Cargo dragon didn't even deploy the parachutes after CRS-7 in flight break up. In an automated system, the programmer is the pilot. I wouldn't expect him to be immune to mistakes as seen by the recent failure of Ariane V. The wrong parameters were put into the autopilot system and BFS won't have a human level AI. Sorry...

Software to fly the BFS will be less complex that that currently in Tesla cars. Those systems need to deal with a huge number of circumstances just to drive round the block. And whilst they do improve that every generation, even the first system was impressive, because they were able to test it offline. The same applies to the BFS. Simulation will mean the software is sophisticated from the first flown version.
Title: Re: Should the BFR have a launch escape system?
Post by: ncb1397 on 10/15/2018 04:57 PM
If you've ever followed how airspace is managed around a modern airport, you'd know how unstructured and human-dependent it is.

Very very far from the notion of a bunch of auto-controlled airplanes merging and lining up for approach.

More like a bunch of kids with bad accents, bad walkie talkies, and on a shared frequency...

Very different from BFS "one shot" flight profiles

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ABCD: Always Be Counting Down

Yeah, sure, that is why the last U.S. major civilian mid-air collision was in 1986. Out of how many flights? That was half a century ago. Mid-air collision isn't a major contributor to airline safety stats, so the elimination of that mode is not going to significantly help BFS. It didn't help Shuttle much. And really, all it takes is for LEO collision warnings to be off by a little bit and you have exactly the same problem.

The ISS has screwed this up before due to human error. You have zero evidence that BFS won't have the same problems.
Title: Re: Should the BFR have a launch escape system?
Post by: meekGee on 10/15/2018 05:20 PM
If you've ever followed how airspace is managed around a modern airport, you'd know how unstructured and human-dependent it is.

Very very far from the notion of a bunch of auto-controlled airplanes merging and lining up for approach.

More like a bunch of kids with bad accents, bad walkie talkies, and on a shared frequency...

Very different from BFS "one shot" flight profiles

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ABCD: Always Be Counting Down

Yeah, sure, that is why the last U.S. major civilian mid-air collision was in 1986. Out of how many flights? That was half a century ago. Mid-air collision isn't a major contributor to airline safety stats, so the elimination of that mode is not going to significantly help BFS. It didn't help Shuttle much. And really, all it takes is for LEO collision warnings to be off by a little bit and you have exactly the same problem.

The ISS has screwed this up before due to human error. You have zero evidence that BFS won't have the same problems.

Sorry?  The statistics are upthread.

Taking off from wrong runways (with fatalities), mishandling stall conditions (with fatalities), almost landing into 3 taxiing planes, the list is long.

BFS won't have a pilot since the whole operational paradigm is different.  That's a big safety plus.

It remains to be seen whether technical reliability can be as high.  I'm skeptical, but OTOH I don't think it needs to be as high, since the expected number of flights is much lower.

If BFS flies 5000 times a year, for 20 years, that's 100,000 flights.  Most people will accept a 1:100,000 accident rate under those conditions.
Title: Re: Should the BFR have a launch escape system?
Post by: envy887 on 10/15/2018 05:28 PM
Actually, GA airplanes are the worst, by far, when compared to jetliners.  Probably including Concorde too.

And if you're going to include Shuttle, you may as well include cars.  Shuttle failed as a rocket, not as an airplane.

My 3 examples all had similar maintanence practices. Bringing up Uncle Tom's beater aircraft that he works on himself is just being argumentative.

The wing damage on Columbia was likely survivable if it wasn't going at the speed it was when it hit the atmosphere. Aircraft have lost entire wings and landed.

http://www.military.com/video/military-aircraft-operations/aviation-accidents/f-15-lands-on-one-wing/644325471001
All your airplane examples have pilots. BFS doesn't. So they are not equivalent.

You're cherry-picking the examples, and this just makes your argument weaker.

Faster does not mean less safe. RBs point was well made.

Jetliners currently hold the safety record, even though they are faster than most other modes of transportation, involve high amounts of energy, operate in a very inhospitable environment, and are less forgiving to mishaps than cars for example.

Maybe it's because they represent some sweet spot in the whole engineering space...  But for sure the argument that "it's unsafe because it's high energy" is proven wrong.

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ABCD: Always Be Counting Down

Jetliners are safe because thousands of people died figuring out how to make them safe, and because manufacturers and operators are regulated so they heed the lessons that were learned.

From a "total number of people killed" perspective, spaceflight is WAY safer than commercial aviation, so far. Hopefully fewer people have to die while we make spaceflight as safe by other, more comforting, metrics.
Title: Re: Should the BFR have a launch escape system?
Post by: ncb1397 on 10/15/2018 05:42 PM
Software to fly the BFS will be less complex that that currently in Tesla cars. Those systems need to deal with a huge number of circumstances just to drive round the block. And whilst they do improve that every generation, even the first system was impressive, because they were able to test it offline. The same applies to the BFS. Simulation will mean the software is sophisticated from the first flown version.

It really isn't that great. It isn't meant for driving around the block. It is for highway driving.

https://www.youtube.com/watch?v=6QCF8tVqM3I

It has been known to make stupid mistakes a well selected and trained driver(no, I don't mean alcoholics/teenagers) wouldn't make.

The current software is basically don't cross lines until commanded to and don't hit objects in front of you. It is equivalent to BFS landing at certain designated spot on a marked landing pad and not hitting the ground hard.

Title: Re: Should the BFR have a launch escape system?
Post by: butters on 10/15/2018 06:00 PM
Seems like there would be a higher risk of LOV on the way down than on the way up and probably highest during the orbital phase of the mission. Engine failure seems unlikely to result in LOV because of engine-out redundancy. The propellant system or life support could have bad failure modes throughout the mission. The moveable aero surfaces could have bad failure modes during entry/landing. If adding a LAS creates any additional challenges for entry or landing, then it could make the system less safe overall. How do you design a LAS that can separate from the vehicle during hypersonic reentry? How do you rescue crew that has separated from their spaceship in an escape capsule somewhere in Mars Transfer Orbit? You don't.
Title: Re: Should the BFR have a launch escape system?
Post by: Rocket Science on 10/15/2018 07:52 PM
Seems like there would be a higher risk of LOV on the way down than on the way up and probably highest during the orbital phase of the mission. Engine failure seems unlikely to result in LOV because of engine-out redundancy. The propellant system or life support could have bad failure modes throughout the mission. The moveable aero surfaces could have bad failure modes during entry/landing. If adding a LAS creates any additional challenges for entry or landing, then it could make the system less safe overall. How do you design a LAS that can separate from the vehicle during hypersonic reentry? How do you rescue crew that has separated from their spaceship in an escape capsule somewhere in Mars Transfer Orbit? You don't.
Off the top of my head I would think along the lines of a Soyuz off-nominal non-separation of compartments entry as an example:
https://www.nasaspaceflight.com/2018/02/soyuz-ms-06-three-iss-crew-members-earth/
Title: Re: Should the BFR have a launch escape system?
Post by: Lemurion on 10/15/2018 08:49 PM
The problem I have with the whole BFS LAS issue is that I think it's the wrong question.

The real concern is making sure the system is as safe as possible throughout its entire flight regime, and that question may or may not involve any specific safety system. I personally don't think a traditional LAS is appropriate for BFS because the protection it provides is offset by the trade-offs you have to make in order to add one.

Emergency staging of the BFS away from the booster is not only probably the closest we're going to get to one but also most likely the best trade-off available.
Title: Re: Should the BFR have a launch escape system?
Post by: Rocket Science on 10/15/2018 09:47 PM
The problem I have with the whole BFS LAS issue is that I think it's the wrong question.

The real concern is making sure the system is as safe as possible throughout its entire flight regime, and that question may or may not involve any specific safety system. I personally don't think a traditional LAS is appropriate for BFS because the protection it provides is offset by the trade-offs you have to make in order to add one.

Emergency staging of the BFS away from the booster is not only probably the closest we're going to get to one but also most likely the best trade-off available.
All I can say is when Elon was invited to come fly on Dear Moon he didn't say yes...
Title: Re: Should the BFR have a launch escape system?
Post by: JamesH65 on 10/15/2018 10:22 PM
Software to fly the BFS will be less complex that that currently in Tesla cars. Those systems need to deal with a huge number of circumstances just to drive round the block. And whilst they do improve that every generation, even the first system was impressive, because they were able to test it offline. The same applies to the BFS. Simulation will mean the software is sophisticated from the first flown version.

It really isn't that great. It isn't meant for driving around the block. It is for highway driving.

https://www.youtube.com/watch?v=6QCF8tVqM3I

It has been known to make stupid mistakes a well selected and trained driver(no, I don't mean alcoholics/teenagers) wouldn't make.

The current software is basically don't cross lines until commanded to and don't hit objects in front of you. It is equivalent to BFS landing at certain designated spot on a marked landing pad and not hitting the ground hard.

Disagree. Completely. Have you seen the footages of it driving around the block, stopping for pedestrians, stopping and waiting at junctions etc? Autonomous driving is away more complex task than flying a bfr, and the prototype Tesla's are way better than you give them credit for.
Title: Re: Should the BFR have a launch escape system?
Post by: Torbjorn Larsson, OM on 10/15/2018 10:46 PM

<snip>

It has been known to make stupid mistakes a well selected and trained driver(no, I don't mean alcoholics/teenagers) wouldn't make.

The current software is basically don't cross lines until commanded to and don't hit objects in front of you. It is equivalent to BFS landing at certain designated spot on a marked landing pad and not hitting the ground hard.

Disagree. Completely. Have you seen the footages of it driving around the block, stopping for pedestrians, stopping and waiting at junctions etc? Autonomous driving is away more complex task than flying a bfr, and the prototype Tesla's are way better than you give them credit for.

Besides, "stupid mistakes and selected drivers" are anecdotes, not statistics. An automatic car average accident rate has to be lower than a driver average accident rate. Seeing how humans are accidents waiting to happen, software will assuredly eventually exceed them.*

An airplane/spaceplane will transport two orders of magnitude more people many orders of magnitude more km. Seen over transport work it should not be different, though you hear people kvetch when the rare airplane accident occurs.

*So there were an early rationale that maybe they cannot. But deep AI networks can now predict chaotic systems better than our statistical methods can, somehow allowing us to see an order of magnitude longer time series after predictivity 'should' be lost. I no longer see any problem here.
Title: Re: Should the BFR have a launch escape system?
Post by: lamontagne on 10/16/2018 01:02 AM
So where should it be separated?
Title: Re: Should the BFR have a launch escape system?
Post by: Rocket Science on 10/16/2018 01:55 AM
So where should it be separated?
Just aft of the fins where the white part of the nose ends as an estimate...
Title: Re: Should the BFR have a launch escape system?
Post by: KelvinZero on 10/16/2018 02:33 AM
So where should it be separated?
Three cases I can think of:

(1) Adaptions that let the BFS escape the BRB in more cases.. Perhaps solid rockets between the stages that typically remain with the BRB.. or some adaption to allow raptors to respond faster. Or some sort of high thrust ridiculously low ISP thrusters, just dumping fuel from the tanks as fast as possible, like cold gas thrusters?

It might just be reinforcement to allow the raptors to start without putting distance from the BRB, or the ability to tilt the rockets so far out that they do not damage the BRB. Im not sure it could currently handle BFS liftoff on the launch pad without the BRB exploding.

(2) Some detachable upper portion, perhaps the crew section without the cargo section or even smaller, has its own thrusters sort of like a dragon 2. However it probably enters sideways using the existing heat shield both to save mass and to avoid a door through the heat-shield.

One bonus of this is that perhaps it could additionally solve the problem of landing on unprepared ground anywhere: Mars, Moon, Callisto... These Dragon-like rockets could fire in the last moments and still be high above the ground.

(3) Some sort of general purpose lifeboat(s) held internally that also could serve as shuttles to visit the ISS or an asteroid and various other purposes. This is the coolest, but not really relevant to any initially intended purpose...but I really like the idea of having lifeboats when I am pirate plowing the spacelanes between the moons of Saturn :)
Title: Re: Should the BFR have a launch escape system?
Post by: meekGee on 10/16/2018 02:39 AM
So where should it be separated?
Just aft of the fins where the white part of the nose ends as an estimate...

If the side thrusters are as powerful as we've figured, who knows - this may hold water.  We're talking about a mass of about - 20 tons?   30?
Title: Re: Should the BFR have a launch escape system?
Post by: CJ on 10/16/2018 06:58 AM
Do we know, for certain, that BFR/BFS does not have a LAS?
What I mean is, do we know for sure that the BFS's raptor engines can't separate it in time from a failing BFR? Because if they can, and would in an emergency, isn't that a LAS? I'm also reminded of Dreamchaser. If I remember right, its LAS required the LV to cease thrusting.
I'm aware of the usual prechilling of Merlins, but is it the same for Raptor, and could they be used without it?


I've looked for an answer to this question in the thread, but haven't found it. Apologies if I missed it.
Title: Re: Should the BFR have a launch escape system?
Post by: speedevil on 10/16/2018 10:22 AM
Do we know, for certain, that BFR/BFS does not have a LAS?
What I mean is, do we know for sure that the BFS's raptor engines can't separate it in time from a failing BFR?
We know that in some realms of flight, for a nominally filled BFS, the acceleration is very slow - 1.2G or so at max.
It is also plausible that the top of BFR is designed to cope (once) with staging like soyuz - panels blow out and you light the engines while connected to reduce launch time, and assure separation is robust.
The engines can in principle be pre-chilled and spun up very fast with the large gas reserves available for the RCS.

Or, even as an unlikely possibility, to cope with the thrust from solid escape rockets mounted as aft cargo.

Absent solid escape rockets, having escaped from BFR doesn't mean you're safe.
BFS probably can make a safe recovery from any speed BFS can push it to, even with some damage, but withstanding a near-pad explosion at zero speeds is questionable.

BFR has no systems amenable to making large explosions.
Unless you manage to get cross-tank leakage, merely losing engines doesn't do it.
Getting sideways to the airstream doesn't do it - as you would turn off the first stage and stage on malfunction of INS. (something impossible to recover from, so not bothered with with current non passenger vehicles).
Pressurisation tanks failing doesn't do it as there are none inside the main tanks, and it uses a (slow) gas generator system to produce pressurisation gas from the propellants.
Falling back on the pad remains - and that one is hard to avoid being an issue, because 1.2G isn't very fast.
Unless you have a large trapdoor for the stage to fall in, then explode with the door closed, but that raises other issues.

Title: Re: Should the BFR have a launch escape system?
Post by: KelvinZero on 10/16/2018 10:40 AM
BFS probably can make a safe recovery from any speed BFS can push it to, even with some damage, but withstanding a near-pad explosion at zero speeds is questionable.
In the recent F9 pad upper stage explosion, the payload looked remarkably intact (until it hit the ground of course) and I think a slightly tougher launch tower would have survived unscathed as well. The crew might be able to survive a launch pad explosion if the launch tower does not drop them.

(edit: to clarify, my original point was that a slow LAS acceleration might be sufficient, then I meandered into the case of not leaving the launch pad at all.)
Title: Re: Should the BFR have a launch escape system?
Post by: speedevil on 10/16/2018 10:43 AM
BFS probably can make a safe recovery from any speed BFS can push it to, even with some damage, but withstanding a near-pad explosion at zero speeds is questionable.
In the recent F9 pad upper stage explosion, the payload looked remarkably intact (until it hit the ground of course) and I think a slightly tougher launch tower would have survived unscathed as well. The crew might be able to survive a launch pad explosion if the launch tower does not drop them.
For F9 - sure, if you could keep them secure from fire, they would likely have been OK.
For BFR - there is no launch tower, and BFS weighs 1100 tons, and that does not eliminate the concern of if the engines fail 20m above the pad.
Title: Re: Should the BFR have a launch escape system?
Post by: envy887 on 10/16/2018 11:13 AM
BFS probably can make a safe recovery from any speed BFS can push it to, even with some damage, but withstanding a near-pad explosion at zero speeds is questionable.
In the recent F9 pad upper stage explosion, the payload looked remarkably intact (until it hit the ground of course) and I think a slightly tougher launch tower would have survived unscathed as well. The crew might be able to survive a launch pad explosion if the launch tower does not drop them.
For F9 - sure, if you could keep them secure from fire, they would likely have been OK.
For BFR - there is no launch tower, and BFS weighs 1100 tons, and that does not eliminate the concern of if the engines fail 20m above the pad.
How long did OA-3 have between the turbopumps blowing up (all loss of thrust) and the big fireball on the pad?
Title: Re: Should the BFR have a launch escape system?
Post by: lamontagne on 10/16/2018 12:11 PM
Here is my attempt at a LAS placement.
The best place I found was integrated just behind the fins, probably under a fairing.
These are 1/3 scale Raptors, so 0,43m wide, power divided by 9 =22 tonnes of thrust if run on MethaLox with turbopumps, less if pressure fed or some other chemical combination. They are set at 15 degrees. There are 4.  0,6 tonnes per second of propellant would be required.

The ship has a 15%angle in the hull at that point, so engines integrated into the hull would need to be over 30 degrees angles. I think this would give them too much angle losses.
Interior volume of the escape capsule is about 180 m3.

I still think of this as a failure of design; but if reality is such that the failure rate is high for some inherent reason, then this suggests a solution.
500   kg engines
3000 kg   fins
1000   kg tanks
4000   kg hull
10000 kg   crew ( a bit of wiggle room here)
18500 kg dry with crew   
7500   kg propellant
26000 kg wet
21.3 T per engine, 84 tonnes thrust total
12   seconds of operation


Title: Re: Should the BFR have a launch escape system?
Post by: lamontagne on 10/16/2018 12:20 PM
It's not a very good fit, would take a lot of work to integrate.  But perhaps with 500mm more.  Too lazy to model it :-)
Title: Re: Should the BFR have a launch escape system?
Post by: speedevil on 10/16/2018 12:22 PM
How long did OA-3 have between the turbopumps blowing up (all loss of thrust) and the big fireball on the pad?
Some 12s into flight the engines shutoff, and some 7s after that, it hit the ground, perhaps 100m up and 20m/s when the incident happened.
7s after the incident, continuing to accelerate at 1.2g, and neglecting staging time, it would have been at around 30m/s, and 300m or so. By the time any debris moving at the speed of sound could reach the BFS, it would be another 30m higher.


This is in the range where it is quite plausible it would be unscathed.
Much under 10s is more questionable.
Title: Re: Should the BFR have a launch escape system?
Post by: hopalong on 10/16/2018 01:02 PM
How long did OA-3 have between the turbopumps blowing up (all loss of thrust) and the big fireball on the pad?
Some 12s into flight the engines shutoff, and some 7s after that, it hit the ground, perhaps 100m up and 20m/s when the incident happened.
7s after the incident, continuing to accelerate at 1.2g, and neglecting staging time, it would have been at around 30m/s, and 300m or so. By the time any debris moving at the speed of sound could reach the BFS, it would be another 30m higher.


This is in the range where it is quite plausible it would be unscathed.
Much under 10s is more questionable.

Given that we a talking about a high power, short duration burn with a very short reaction time, would solids or a version of the Drago be better? Reusability will not be a factor here.
Title: Re: Should the BFR have a launch escape system?
Post by: Rocket Science on 10/16/2018 01:42 PM
It's not a very good fit, would take a lot of work to integrate.  But perhaps with 500mm more.  Too lazy to model it :-)
Thank you for your efforts so far, It's a great starting point! Fantastic to see a graphic of what
I had in my head! 8) That's not exactly where I would have thought about the position the engines, but you showed me an other option...
Title: Re: Should the BFR have a launch escape system?
Post by: Rocket Science on 10/16/2018 01:44 PM
So where should it be separated?
Just aft of the fins where the white part of the nose ends as an estimate...

If the side thrusters are as powerful as we've figured, who knows - this may hold water.  We're talking about a mass of about - 20 tons?   30?
Are you talking about the suggestion of nose landing engines I mentioned in the other thread?
Title: Re: Should the BFR have a launch escape system?
Post by: meekGee on 10/16/2018 02:14 PM
So where should it be separated?
Just aft of the fins where the white part of the nose ends as an estimate...

If the side thrusters are as powerful as we've figured, who knows - this may hold water.  We're talking about a mass of about - 20 tons?   30?
Are you talking about the suggestion of nose landing engines I mentioned in the other thread?
Preamble - I don't think an LAS is in the works, and not convinced such a system will improve safety.

However.  The idea of a sealed nose section (extra mass there) containing the launch seats (redesign, extra mass) that can separate from the main body and propulsively pull away, to land with a parachute (mass, mass..) is not completely laughable.  It will provide escape ability during some portions of flight that are currently not covered.

Yes, it should reuse the large thrusters, which in turn can also be used for landing.

It can cover preflight through early ascent  and it can cover the post reentry segment.  That's not small change.

---

One clear problem in the design is the conflict between BFS being a Mars ship that has a mission cycle of at least 2 years, and BFS being an earth-to-LEO ship, or a p2p ship, with a mission length of an hour, and strapped to a BFR.

It's like you'd want the Mars ship with a large nose area dedicated to livabale space, to launch empty (and full of payload), and the people to launch on a p2p ship, with seating at the nose section, and an LAS.

-----
ABCD: Always Be Counting Down

Title: Re: Should the BFR have a launch escape system?
Post by: ncb1397 on 10/16/2018 02:21 PM

However.  The idea of a sealed nose section (extra mass there) containing the launch seats (redesign, extra mass)

How are launch seats extra mass?
Title: Re: Should the BFR have a launch escape system?
Post by: meekGee on 10/16/2018 02:25 PM

However.  The idea of a sealed nose section (extra mass there) containing the launch seats (redesign, extra mass)

How are launch seats extra mass?
Because for a long-duration ship you still need cabins with seats/beds, which otherwise would double as launch seats.

Converting the nose to an escape pod means more mass there, less living space, and little mass savings in the cabins area.

That's why I'm saying maybe put seats in nose for a p2p ship, use it also for LEO ascent, and keep the Mars-bound ship as a long duration ship, no LAS, and launch it with payload only.

-----
ABCD: Always Be Counting Down

Title: Re: Should the BFR have a launch escape system?
Post by: Rocket Science on 10/16/2018 02:30 PM
So where should it be separated?
Just aft of the fins where the white part of the nose ends as an estimate...

If the side thrusters are as powerful as we've figured, who knows - this may hold water.  We're talking about a mass of about - 20 tons?   30?
Are you talking about the suggestion of nose landing engines I mentioned in the other thread?
Preamble - I don't think an LAS is in the works, and not convinced such a system will improve safety.

However.  The idea of a sealed nose section (extra mass there) containing the launch seats (redesign, extra mass) that can separate from the main body and propulsively pull away, to land with a parachute (mass, mass..) is not completely laughable.  It will provide escape ability during some portions of flight that are currently not covered.

Yes, it should reuse the large thrusters, which in turn can also be used for landing.

It can cover preflight through early ascent  and it can cover the post reentry segment.  That's not small change.

---

One clear problem in the design is the conflict between BFS being a Mars ship that has a mission cycle of at least 2 years, and BFS being an earth-to-LEO ship, or a p2p ship, with a mission length of an hour, and strapped to a BFR.

It's like you'd want the Mars ship with a large nose area dedicated to livabale space, to launch empty (and full of payload), and the people to launch on a p2p ship, with seating at the nose section, and an LAS.

-----
ABCD: Always Be Counting Down
I like the idea of Dragons multiple use engines and not dedicated abort engines is why I asked for efficiency. Same prop and the mass penalty comes from extra engines and plumbing if one uses the combination of both nose mounted tractor and lower pusher engines along with RCS for which little is known...
Title: Re: Should the BFR have a launch escape system?
Post by: Nightstalker89 on 10/16/2018 02:32 PM
What about four conical pods on the top with a crane in the center with the pods interconnected by hatches.  One launch Escape system for each of the four pods. And with a crane in the center you could offload the entire living area on Mars one cone at a time and reconnect them. This way you would have living quarters that could be arranged on the ground on Mars. The launch Escape system becomes four separate smaller launch Escape systems and and is much more manageable to design and build as well as giving you the ability to change each pod out for different types of cargo or fuel loads.  Much the way military planes have cargo pods.  In this case the pod is on the outside of the craft or part of it.
Title: Re: Should the BFR have a launch escape system?
Post by: Rocket Science on 10/16/2018 02:35 PM
The launch/entry cabin seats could be stowed or repurposed for Mars trips the the section can be used as the common area... Seats on Apollo CM and Shuttle were reconfigurable or stowed...
Title: Re: Should the BFR have a launch escape system?
Post by: ncb1397 on 10/16/2018 03:07 PM

However.  The idea of a sealed nose section (extra mass there) containing the launch seats (redesign, extra mass)

How are launch seats extra mass?
Because for a long-duration ship you still need cabins with seats/beds, which otherwise would double as launch seats.

Converting the nose to an escape pod means more mass there, less living space, and little mass savings in the cabins area.


Seats and beds? Where are you going to put the pool table? This is about the luxury you can expect : http://artpictures.club/vago.html

Except the floor area in that picture is about 4x too large.

https://www.youtube.com/watch?v=UyFYgeE32f0

Maybe you could outfit one like a yacht, but then it would be for a small amount of people (like 5) and the launch seats aren't a big factor.

Title: Re: Should the BFR have a launch escape system?
Post by: Rocket Science on 10/16/2018 03:27 PM

However.  The idea of a sealed nose section (extra mass there) containing the launch seats (redesign, extra mass)

How are launch seats extra mass?
Because for a long-duration ship you still need cabins with seats/beds, which otherwise would double as launch seats.

Converting the nose to an escape pod means more mass there, less living space, and little mass savings in the cabins area.


Seats and beds? Where are you going to put the pool table? This is about the luxury you can expect : http://artpictures.club/vago.html

Except the floor area in that picture is about 4x too large.


Maybe you could outfit one like a yacht, but then it would be for a small amount of people (like 5) and the launch seats aren't a big factor.
Pool in zero-g, now that's a "bank-shot"! ;D
Title: Re: Should the BFR have a launch escape system?
Post by: ncb1397 on 10/16/2018 03:31 PM

However.  The idea of a sealed nose section (extra mass there) containing the launch seats (redesign, extra mass)

How are launch seats extra mass?
Because for a long-duration ship you still need cabins with seats/beds, which otherwise would double as launch seats.

Converting the nose to an escape pod means more mass there, less living space, and little mass savings in the cabins area.


Seats and beds? Where are you going to put the pool table? This is about the luxury you can expect : http://artpictures.club/vago.html

Except the floor area in that picture is about 4x too large.

https://www.youtube.com/watch?v=UyFYgeE32f0

Maybe you could outfit one like a yacht, but then it would be for a small amount of people (like 5) and the launch seats aren't a big factor.
Pool in zero-g, now that's a "bank-shot"! ;D

Well, presumably the beds and seats that were "needed" in the cabins that MeekGee was referring to were for martian-g/lunar-g. They are pretty useless in zero-g. A prison like bunk-bed  layout might be included, but then the bed could act as a seat. That being said, this feature wouldn't make a good launch seat (and a launch seat wouldn't make a good bed). So, moving those out of the cabin to the upper deck doesn't cost you anything.

This is probably the best you can expect luxury wise if you aren't Yusaku Maezawa wealthy:
https://www.youtube.com/watch?v=OsDZKCvpYL4

There is a seat, but it is a negligible amount of the mass of the rest of the outfitting and the seat makes up a small portion of the mass required for a launch/entry seat.
Title: Re: Should the BFR have a launch escape system?
Post by: Rocket Science on 10/16/2018 03:36 PM
Wall padding to bounce off of... :)
Title: Re: Should the BFR have a launch escape system?
Post by: DistantTemple on 10/17/2018 02:30 AM
If the launch seats are like the ones in the D2, then they look fairly low mass.
Title: Re: Should the BFR have a launch escape system?
Post by: CJ on 10/17/2018 08:48 AM
Do we know, for certain, that BFR/BFS does not have a LAS?
What I mean is, do we know for sure that the BFS's raptor engines can't separate it in time from a failing BFR?
We know that in some realms of flight, for a nominally filled BFS, the acceleration is very slow - 1.2G or so at max.
It is also plausible that the top of BFR is designed to cope (once) with staging like soyuz - panels blow out and you light the engines while connected to reduce launch time, and assure separation is robust.
The engines can in principle be pre-chilled and spun up very fast with the large gas reserves available for the RCS.

Or, even as an unlikely possibility, to cope with the thrust from solid escape rockets mounted as aft cargo.

Absent solid escape rockets, having escaped from BFR doesn't mean you're safe.
BFS probably can make a safe recovery from any speed BFS can push it to, even with some damage, but withstanding a near-pad explosion at zero speeds is questionable.

BFR has no systems amenable to making large explosions.
Unless you manage to get cross-tank leakage, merely losing engines doesn't do it.
Getting sideways to the airstream doesn't do it - as you would turn off the first stage and stage on malfunction of INS. (something impossible to recover from, so not bothered with with current non passenger vehicles).
Pressurisation tanks failing doesn't do it as there are none inside the main tanks, and it uses a (slow) gas generator system to produce pressurisation gas from the propellants.
Falling back on the pad remains - and that one is hard to avoid being an issue, because 1.2G isn't very fast.
Unless you have a large trapdoor for the stage to fall in, then explode with the door closed, but that raises other issues.

Thank you, Speedevil, for this VERY informative reply.

IMHO, after considering your response, I think that if BFS does have the capability of separating and boosting away (via its raptors) from a malfunctioning BFR, it's a fairly good LAS. I agree with your concerns about a fall back to the pad, but even that might be survivable, depending on BFS engine response time. The exhaust plume from the BFS raptors should be helpful in deflecting low velocity debris from a deflagrating BFR on the pad.

A LAS relying on BFS raptors isn't perfect, but IMHO it's a design compromise; making it "perfect" would add too much mass, plus likely introduce other failure modes.

On the other hand, if the BFS is not given the ability to boost away from a malfunctioning BFR, and thus have no LAS at all, then I'd tend to agree with those here who say it's a conceptual flaw in the system. 

Thanks again!


Title: Re: Should the BFR have a launch escape system?
Post by: tyrred on 10/17/2018 08:52 AM
Do we know, for certain, that BFR/BFS does not have a LAS?
What I mean is, do we know for sure that the BFS's raptor engines can't separate it in time from a failing BFR?
We know that in some realms of flight, for a nominally filled BFS, the acceleration is very slow - 1.2G or so at max.
It is also plausible that the top of BFR is designed to cope (once) with staging like soyuz - panels blow out and you light the engines while connected to reduce launch time, and assure separation is robust.
The engines can in principle be pre-chilled and spun up very fast with the large gas reserves available for the RCS.

Or, even as an unlikely possibility, to cope with the thrust from solid escape rockets mounted as aft cargo.

[/b]Absent solid escape rockets, having escaped from BFR doesn't mean you're safe.[/b]
BFS probably can make a safe recovery from any speed BFS can push it to, even with some damage, but withstanding a near-pad explosion at zero speeds is questionable.

BFR has no systems amenable to making large explosions.
Unless you manage to get cross-tank leakage, merely losing engines doesn't do it.
Getting sideways to the airstream doesn't do it - as you would turn off the first stage and stage on malfunction of INS. (something impossible to recover from, so not bothered with with current non passenger vehicles).
Pressurisation tanks failing doesn't do it as there are none inside the main tanks, and it uses a (slow) gas generator system to produce pressurisation gas from the propellants.
Falling back on the pad remains - and that one is hard to avoid being an issue, because 1.2G isn't very fast.
Unless you have a large trapdoor for the stage to fall in, then explode with the door closed, but that raises other issues.

Thank you, Speedevil, for this VERY informative reply.

IMHO, after considering your response, I think that if BFS does have the capability of separating and boosting away (via its raptors) from a malfunctioning BFR, it's a fairly good LAS. I agree with your concerns about a fall back to the pad, but even that might be survivable, depending on BFS engine response time. The exhaust plume from the BFS raptors should be helpful in deflecting low velocity debris from a deflagrating BFR on the pad.

A LAS relying on BFS raptors isn't perfect, but IMHO it's a design compromise; making it "perfect" would add too much mass, plus likely introduce other failure modes.

On the other hand, if the BFS is not given the ability to boost away from a malfunctioning BFR, and thus have no LAS at all, then I'd tend to agree with those here who say it's a conceptual flaw in the system. 

Thanks again!

Bold mine.  This led me to ponder what type of solid escape motors could *possibly be implemented in the cargo pod "petals" for early testing of BFS?  Is ther anything "off-the-shelf" that SpaceX could procure, or would it be necessary to engineer their own?
Title: Re: Should the BFR have a launch escape system?
Post by: Zed_Noir on 10/17/2018 09:35 AM
<snip>
This led me to ponder what type of solid escape motors could *possibly be implemented in the cargo pod "petals" for early testing of BFS?  Is ther anything "off-the-shelf" that SpaceX could procure, or would it be necessary to engineer their own?

With gross vehicle mass of 1335 tonnes at launch (according to wikipedia) for the BFS. Really doubt any type of motors that can be fitted in the "petals" can provide adequate thrust required by themselves.

Maybe to augmented the Raptors in abort situations if fitted with supplement rocket pods. Which is likely to be equipped Super-Dracos, since SX have no expertise with solid motors.
Title: Re: Should the BFR have a launch escape system?
Post by: speedevil on 10/17/2018 09:47 AM
Bold mine.  This led me to ponder what type of solid escape motors could *possibly be implemented in the cargo pod "petals" for early testing of BFS?  Is ther anything "off-the-shelf" that SpaceX could procure, or would it be necessary to engineer their own?
There is no particular reason the abort motors couldn't be hypergolic.
Doubling the accelleration to 2G would need around a hundred superdracos.

This would somewhat mitigate the weight by allowing use of this propellant some seconds into flight nominally, leaving only the masses of the tanks and motors remaining, and not costing as much as doing the same with solids per flight.
Of course, such a system has its own risks.
You now have a system guaranteed to kill you if it goes off asymetrically, or on the pad.
As well as requiring a couple of toxic fluids.

Very abbreviated nozzle raptors could fit in the ring of 'cargo' containers also. If they can be spun up rapidly, they may suit for improving escape thrust.

Or, it may be reasonable to think you may be able to reduce the risk for this portion of the flight to nearly zero.
Robust engine wells and shielding that can contain worst-case failure for BFS.
Overbuilt structure that can similarly easily contain multiple engine failure.
Autogenous pressurisation system off for the moments of launch. (if that is a concern).
BFS capable of safely lighting the engines without separating.
Per-engine 30s header tank?

All of these apart for the last couple are things you would likely want anyway for reuse reasons.
The remaining risk is from the rocket suddenly falling apart under internal or external loads - which can be mitigated by range safety, and proper design.

Title: Re: Should the BFR have a launch escape system?
Post by: JamesH65 on 10/17/2018 12:06 PM
Bold mine.  This led me to ponder what type of solid escape motors could *possibly be implemented in the cargo pod "petals" for early testing of BFS?  Is ther anything "off-the-shelf" that SpaceX could procure, or would it be necessary to engineer their own?

Why would early testing needs a LES, when there won't be anyone on board anyway?
Title: Re: Should the BFR have a launch escape system?
Post by: wilbobaggins on 10/17/2018 01:39 PM
[snip snip]

Bold mine.  This led me to ponder what type of solid escape motors could *possibly be implemented in the cargo pod "petals" for early testing of BFS?  Is ther anything "off-the-shelf" that SpaceX could procure, or would it be necessary to engineer their own?

The Atlas 5 441 is $6m more expensive than the 401 and the only difference I think is 1 extra SRB. The Gem 63 is what is going to be used as the SRB. I guess it would be cheaper than the current one they use but I will keep it.

So these are 1.6m wide and so fit in aft cargo containers. They can lift 166 tons each. 12 of them can lift just under 2000 tons. i.e the entire fueled BFS at about 1.66g. Add raptors and you get a nice acceleration.

Using just 6 or so seconds of the 84-second burn time would drop it to maybe 3 meters long including nozzle. I would put these at 4-5 tons each. This would put the total mass at around 48-60. Cost probably $10m-$30m

However, this would not drop the payload to orbit by that much if you drop them just after stage separation. Its only like a 4% increase on mass first stage has to lift. You might still get a few m3 of space behind the boosters for cargo. Especially if you extend them down from where current cargo containers are. (firing them sequentially after stage separation could also actually improve payload mass maybe? though risky)

All in all maybe:

Extra cost of $20m a launch with maybe 10 tons off mass to orbit.
or if you recover them then around 50 tons off mass to orbit. Oh, and it reduces your landing payload to less than half.

So I could see it being used on early, high passenger flights. This is when reliability is not that proven and $20m extra a flight is still not that big a mission cost %.
Title: Re: Should the BFR have a launch escape system?
Post by: Rocket Science on 10/17/2018 02:12 PM
When I brought up the concept of a launch/entry escape cabin it was with zero interest in solid motors. Hypergolics based on SDs are the way to go and the expertise is already in-house at SpaceX...
Title: Re: Should the BFR have a launch escape system?
Post by: docmordrid on 10/17/2018 04:31 PM
ISTM the low-hanging fruit be is  to drop the aft cargo pods at abort separation in order to maximize T/W.

Is there a practical way to dump some props to do the same, reserving just enough for fly-back and landing?
Title: Re: Should the BFR have a launch escape system?
Post by: rakaydos on 10/17/2018 04:58 PM
ISTM the low-hanging fruit be is  to drop the aft cargo pods at abort separation in order to maximize T/W.

Is there a practical way to dump some props to do the same, reserving just enough for fly-back and landing?
The refueling lines need pumps to manage fuel transfer in a reasonable amount of time. The question is whether there would be any additional problems from literally dumping fuel (and oxidiser) on the fire the BFS is escaping from.
Title: Re: Should the BFR have a launch escape system?
Post by: AncientU on 10/17/2018 05:16 PM
When I brought up the concept of a launch/entry escape cabin it was with zero interest in solid motors. Hypergolics based on SDs are the way to go and the expertise is already in-house at SpaceX...

Either solids or hypergolics would need to be massive and dead weight for essentially all flights. Would you jettison them after launch?  Carry them to the Moon or Mars?

The BFR will be flight proven for large number of flights, and the spaceship will always have T/W >1.2 or so.  If you run the numbers, this will likely be safer than anything currently carrying crew to space.  They won't revert to 1960s LAS technology.
Title: Re: Should the BFR have a launch escape system?
Post by: Rocket Science on 10/17/2018 05:27 PM
When I brought up the concept of a launch/entry escape cabin it was with zero interest in solid motors. Hypergolics based on SDs are the way to go and the expertise is already in-house at SpaceX...

Either solids or hypergolics would need to be massive and dead weight for essentially all flights. Would you jettison them after launch?  Carry them to the Moon or Mars?

The BFR will be flight proven for large number of flights, and the spaceship will always have T/W >1.2 or so.  If you run the numbers, this will likely be safer than anything currently carrying crew to space.  They won't revert to 1960s LAS technology.

No, they would be plumbed/integrated into the RCS system using the same fuel as I have mentioned...
Title: Re: Should the BFR have a launch escape system?
Post by: Lars-J on 10/17/2018 05:32 PM
ISTM the low-hanging fruit be is  to drop the aft cargo pods at abort separation in order to maximize T/W.

Is there a practical way to dump some props to do the same, reserving just enough for fly-back and landing?

The fastest way to empty propellant tanks is to use the engines.  :)
Title: Re: Should the BFR have a launch escape system?
Post by: speedevil on 10/17/2018 05:44 PM
ISTM the low-hanging fruit be is  to drop the aft cargo pods at abort separation in order to maximize T/W.

Is there a practical way to dump some props to do the same, reserving just enough for fly-back and landing?
The refueling lines need pumps to manage fuel transfer in a reasonable amount of time. The question is whether there would be any additional problems from literally dumping fuel (and oxidiser) on the fire the BFS is escaping from.

This is probably not true.
The tanks are pressurised to ~3 bar.
Looking at the observed pipe diameter, and computing the pressure drop, the fuel transfer 'pump' can be achieved by simply lowering the pressure setpoint on one autogenous pressurisation system to 2 bar.

This results in a flow fast enough to transfer over 150t of fuel in only a couple of minutes.

However, as Lars mentioned later, the engines burn all the fuel in ~4 minutes or so at full thrust.

There are semi-reasonable arguments for _massive_ dump valves - for example if BFR dies 10s in, you cut enough holes in it that it dumps all of the liquid oxygen out in three seconds at altitude, so some of it does not make it down to react promptly with the methane on impact.
But, these pretty much have to be explosively cut as they are so large, or the additional weight would be prohibitive, meaning they are a massive risk all on their own.
Title: Re: Should the BFR have a launch escape system?
Post by: Lars-J on 10/17/2018 11:38 PM
There are semi-reasonable arguments for _massive_ dump valves - for example if BFR dies 10s in, you cut enough holes in it that it dumps all of the liquid oxygen out in three seconds at altitude, so some of it does not make it down to react promptly with the methane on impact.
But, these pretty much have to be explosively cut as they are so large, or the additional weight would be prohibitive, meaning they are a massive risk all on their own.

That's not a good idea while the Raptors are running. That would be like dumping gasoline right next to a fire.  (and with re-circulation it WILL ignite)

Where do you plan on dumping it?
Title: Re: Should the BFR have a launch escape system?
Post by: speedevil on 10/17/2018 11:39 PM
There are semi-reasonable arguments for _massive_ dump valves - for example if BFR dies 10s in, you cut enough holes in it that it dumps all of the liquid oxygen out in three seconds at altitude, so some of it does not make it down to react promptly with the methane on impact.
But, these pretty much have to be explosively cut as they are so large, or the additional weight would be prohibitive, meaning they are a massive risk all on their own.

That's not a good idea while the Raptors are running. That would be like dumping gasoline right next to a fire.  (and with re-circulation it WILL ignite)

Where do you plan on dumping it?
I was assuming a case of a BFR failure, with no engines working.

I don't think it is useful.
Title: Re: Should the BFR have a launch escape system?
Post by: Robotbeat on 10/17/2018 11:44 PM
Nice thing about liquid rockets is they're easy to shut off. Doesn't mean it's safe to dump a bunch of fuel on them while they're still hot (and probably still partly on fire), but at least the thrust will be gone.
Title: Re: Should the BFR have a launch escape system?
Post by: KelvinZero on 10/18/2018 12:05 AM
There are semi-reasonable arguments for _massive_ dump valves - for example if BFR dies 10s in, you cut enough holes in it that it dumps all of the liquid oxygen out in three seconds at altitude, so some of it does not make it down to react promptly with the methane on impact.
But, these pretty much have to be explosively cut as they are so large, or the additional weight would be prohibitive, meaning they are a massive risk all on their own.

That's not a good idea while the Raptors are running. That would be like dumping gasoline right next to a fire.  (and with re-circulation it WILL ignite)

Where do you plan on dumping it?
The recent launch pad explosion looked fairly gentle and survivable, with the payload remaining intact after the upper stage disintegrated. I think it would have been even more so if the dispersion of fuel was designed to keep it gentle. My guess is that the main thing you have to avoid is detonation, eg a fuel air explosive where you mix a large volume and THEN ignite it.

Maybe you could actually keep the engines cooler  during a mishap if you dumped a large amount of one tank BEFORE dumping a large amount of the other tank, or even just dumping them out opposite sides and making sure any burning happens immediately at the interface instead of after significant mixing.

Im guessing oxygen would be the best to dump first? It is heavier, so you get rid of weight faster, and it cannot even react with the 20% oxygen in the air. Without proportional amounts of combustion and energy being sucked up by the transition from liquid to gas it would probably be super cold so not particularly reactive (Im guessing)
Title: Re: Should the BFR have a launch escape system?
Post by: Lemurion on 10/18/2018 12:16 AM
Do we know, for certain, that BFR/BFS does not have a LAS?
What I mean is, do we know for sure that the BFS's raptor engines can't separate it in time from a failing BFR?
We know that in some realms of flight, for a nominally filled BFS, the acceleration is very slow - 1.2G or so at max.
It is also plausible that the top of BFR is designed to cope (once) with staging like soyuz - panels blow out and you light the engines while connected to reduce launch time, and assure separation is robust.
The engines can in principle be pre-chilled and spun up very fast with the large gas reserves available for the RCS.

Or, even as an unlikely possibility, to cope with the thrust from solid escape rockets mounted as aft cargo.

Absent solid escape rockets, having escaped from BFR doesn't mean you're safe.
BFS probably can make a safe recovery from any speed BFS can push it to, even with some damage, but withstanding a near-pad explosion at zero speeds is questionable.

BFR has no systems amenable to making large explosions.
Unless you manage to get cross-tank leakage, merely losing engines doesn't do it.
Getting sideways to the airstream doesn't do it - as you would turn off the first stage and stage on malfunction of INS. (something impossible to recover from, so not bothered with with current non passenger vehicles).
Pressurisation tanks failing doesn't do it as there are none inside the main tanks, and it uses a (slow) gas generator system to produce pressurisation gas from the propellants.
Falling back on the pad remains - and that one is hard to avoid being an issue, because 1.2G isn't very fast.
Unless you have a large trapdoor for the stage to fall in, then explode with the door closed, but that raises other issues.

Thank you, Speedevil, for this VERY informative reply.

IMHO, after considering your response, I think that if BFS does have the capability of separating and boosting away (via its raptors) from a malfunctioning BFR, it's a fairly good LAS. I agree with your concerns about a fall back to the pad, but even that might be survivable, depending on BFS engine response time. The exhaust plume from the BFS raptors should be helpful in deflecting low velocity debris from a deflagrating BFR on the pad.

A LAS relying on BFS raptors isn't perfect, but IMHO it's a design compromise; making it "perfect" would add too much mass, plus likely introduce other failure modes.

On the other hand, if the BFS is not given the ability to boost away from a malfunctioning BFR, and thus have no LAS at all, then I'd tend to agree with those here who say it's a conceptual flaw in the system. 

Thanks again!

(emphasis mine, L)


Given that BFS is designed to boost away from BFR as part of its normal operation procedure I personally think it would probably be harder to remove the ability to boost away from a malfunctioning booster than to implement it.
Title: Re: Should the BFR have a launch escape system?
Post by: lamontagne on 10/18/2018 01:34 AM
Given that BFS is designed to boost away from BFR as part of its normal operation procedure I personally think it would probably be harder to remove the ability to boost away from a malfunctioning booster than to implement it.

Actually, the 2017 BFS (and I believe it is a common occurence for second stages) did not have the thrust for an accelerated separation.  Separation depends on the deceleration of the first stage after engine cut off.  Another example, Falcon 9 block 5 second stage mass is 116 tonnes but the thrust of the engine is 95 tonnes.

So the Falcon 9 second stage, for example, would be incapable of separating from the first stage while on the pad.
I find it quite interesting that the added 7th engine does give the 2018 BFS the capacity to separate from the BFB even from the launch pad.
Title: Re: Should the BFR have a launch escape system?
Post by: lamontagne on 10/18/2018 01:40 AM
I also thing the great physical separation between the tower and the BFR assembly is a 'lessons learned'.  This from a great reply up thread about Saturn 5.  Reply 219. by Rocket Science.

Use the Saturn V as a reference from our friend Dwayne...
http://www.thespacereview.com/article/591/1
Title: Re: Should the BFR have a launch escape system?
Post by: Lars-J on 10/18/2018 04:30 PM
I also thing the great physical separation between the tower and the BFR assembly is a 'lessons learned'.  This from a great reply up thread about Saturn 5.  Reply 219. by Rocket Science.

Use the Saturn V as a reference from our friend Dwayne...
http://www.thespacereview.com/article/591/1

It would be interesting to see that article updated in light of Amos-6... Now that there is actual data for the effects of an exploding booster to either validate or invalidate the assumptions in that paper that the article references.
Title: Re: Should the BFR have a launch escape system?
Post by: Rocket Science on 10/18/2018 04:52 PM
I also thing the great physical separation between the tower and the BFR assembly is a 'lessons learned'.  This from a great reply up thread about Saturn 5.  Reply 219. by Rocket Science.

Use the Saturn V as a reference from our friend Dwayne...
http://www.thespacereview.com/article/591/1
Yes that and all that shrapnel you are "trying to out-run" from that exploding stage below... No problem, I'll just fire my engines and fly away... Now did that shrapnel penetrate the BFS I'm in as I'm about to ignite the engines? Oh, wait...
Title: Re: Should the BFR have a launch escape system?
Post by: Lars-J on 10/18/2018 05:00 PM
I also thing the great physical separation between the tower and the BFR assembly is a 'lessons learned'.  This from a great reply up thread about Saturn 5.  Reply 219. by Rocket Science.

Use the Saturn V as a reference from our friend Dwayne...
http://www.thespacereview.com/article/591/1
Yes that and all that shrapnel you are "trying to out-run" from that exploding stage below... No problem, I'll just fire my engines and fly away... Now did that shrapnel penetrate the BFS I'm in as I'm about to ignite the engines? Oh, wait...

Much of that risk (to the engines) can be reduced by building a shielding structure into the base of the interstage.
Title: Re: Should the BFR have a launch escape system?
Post by: Rocket Science on 10/18/2018 05:01 PM
I also thing the great physical separation between the tower and the BFR assembly is a 'lessons learned'.  This from a great reply up thread about Saturn 5.  Reply 219. by Rocket Science.

Use the Saturn V as a reference from our friend Dwayne...
http://www.thespacereview.com/article/591/1
Yes that and all that shrapnel you are "trying to out-run" from that exploding stage below... No problem, I'll just fire my engines and fly away... Now did that shrapnel penetrate the BFS I'm in as I'm about to ignite the engines? Oh, wait...

Much of that risk (to the engines) can be reduced by building a shielding structure into the base of the interstage.
Like?
Title: Re: Should the BFR have a launch escape system?
Post by: Lars-J on 10/18/2018 05:04 PM
I also thing the great physical separation between the tower and the BFR assembly is a 'lessons learned'.  This from a great reply up thread about Saturn 5.  Reply 219. by Rocket Science.

Use the Saturn V as a reference from our friend Dwayne...
http://www.thespacereview.com/article/591/1
Yes that and all that shrapnel you are "trying to out-run" from that exploding stage below... No problem, I'll just fire my engines and fly away... Now did that shrapnel penetrate the BFS I'm in as I'm about to ignite the engines? Oh, wait...

Much of that risk (to the engines) can be reduced by building a shielding structure into the base of the interstage.
Like?

Do I need to elaborate? Something similar to what is done to protected F9 engines from each other. Using some sort of shielding material as the base of the interstage would significantly reduce shrapnel risk from the BFB.
Title: Re: Should the BFR have a launch escape system?
Post by: Rocket Science on 10/18/2018 05:08 PM
I also thing the great physical separation between the tower and the BFR assembly is a 'lessons learned'.  This from a great reply up thread about Saturn 5.  Reply 219. by Rocket Science.

Use the Saturn V as a reference from our friend Dwayne...
http://www.thespacereview.com/article/591/1
Yes that and all that shrapnel you are "trying to out-run" from that exploding stage below... No problem, I'll just fire my engines and fly away... Now did that shrapnel penetrate the BFS I'm in as I'm about to ignite the engines? Oh, wait...

Much of that risk (to the engines) can be reduced by building a shielding structure into the base of the interstage.
Like?

Do I need to elaborate? Something similar to what is done to protected F9 engines from each other. Using some sort of shielding material as the base of the interstage would significantly reduce shrapnel risk from the BFB.
Yes...
Title: Re: Should the BFR have a launch escape system?
Post by: lamontagne on 10/18/2018 05:16 PM
I also thing the great physical separation between the tower and the BFR assembly is a 'lessons learned'.  This from a great reply up thread about Saturn 5.  Reply 219. by Rocket Science.

Use the Saturn V as a reference from our friend Dwayne...
http://www.thespacereview.com/article/591/1
Yes that and all that shrapnel you are "trying to out-run" from that exploding stage below... No problem, I'll just fire my engines and fly away... Now did that shrapnel penetrate the BFS I'm in as I'm about to ignite the engines? Oh, wait...
1- Interestingly, the article has an answer to that.  An explosion would not produce debris going straight up, as this direction would be shielded by the propellant and vehicle mass that was in the way of the explosion.  They seemed to feel the explosion would be likely to happen close to the base, rather than close to the top.
What they did worry about was the shockwave from the explosion, that was going to damage the command module.  So the main risk would be the high pressure shock.  Since the BFR separating will be moving quite slowly, it will suffer the full blast.  Can't quantify this, however.  But likely to be  severe?  Like all such things it should go down to the inverse square of distance, but see point 3 bellow:

2- I wonder how much mixing there would be between the fuel and the oxygen?  There has to be some delay between the beginning of the explosion and the time the two mix; I guess there must be some data from liquid natural gas ships?  Or LNG explosions over the years?

3- Another point, the acceleration of the BFR will not be 1.2g.  It will be 1.2g-1g = 0,2g, or about 1 to 2 m per second per second, so not enough to get very far, very fast. 1400 T / 1200 T = 1.16.  If the thrust was equal to the mass, it would just hover.


Title: Re: Should the BFR have a launch escape system?
Post by: speedevil on 10/18/2018 05:32 PM
Do I need to elaborate? Something similar to what is done to protected F9 engines from each other. Using some sort of shielding material as the base of the interstage would significantly reduce shrapnel risk from the BFB.
It seems also likely that whatever is done at the top of the soyuz to permit staging while not separated would also help quite a lot, both in rapid escape, and reducing any potential schrapnel.
Title: Re: Should the BFR have a launch escape system?
Post by: Rocket Science on 10/18/2018 07:05 PM
Do I need to elaborate? Something similar to what is done to protected F9 engines from each other. Using some sort of shielding material as the base of the interstage would significantly reduce shrapnel risk from the BFB.
It seems also likely that whatever is done at the top of the soyuz to permit staging while not separated would also help quite a lot, both in rapid escape, and reducing any potential schrapnel.
The Soyuz event was not at zero-zero...
Title: Re: Should the BFR have a launch escape system?
Post by: speedevil on 10/18/2018 10:16 PM
Do I need to elaborate? Something similar to what is done to protected F9 engines from each other. Using some sort of shielding material as the base of the interstage would significantly reduce shrapnel risk from the BFB.
It seems also likely that whatever is done at the top of the soyuz to permit staging while not separated would also help quite a lot, both in rapid escape, and reducing any potential schrapnel.
The Soyuz event was not at zero-zero...

I never said it was.
And the one in the 80s was (https://en.wikipedia.org/wiki/Soyuz_7K-ST_No._16L).
Title: Re: Should the BFR have a launch escape system?
Post by: Rocket Science on 10/18/2018 11:01 PM
Do I need to elaborate? Something similar to what is done to protected F9 engines from each other. Using some sort of shielding material as the base of the interstage would significantly reduce shrapnel risk from the BFB.
It seems also likely that whatever is done at the top of the soyuz to permit staging while not separated would also help quite a lot, both in rapid escape, and reducing any potential schrapnel.
The Soyuz event was not at zero-zero...

I never said it was.
And the one in the 80s was (https://en.wikipedia.org/wiki/Soyuz_7K-ST_No._16L).
Way to move the goal post... Good thing it had a LES that saved the crew... ;)
Title: Re: Should the BFR have a launch escape system?
Post by: meekGee on 10/18/2018 11:28 PM
Do I need to elaborate? Something similar to what is done to protected F9 engines from each other. Using some sort of shielding material as the base of the interstage would significantly reduce shrapnel risk from the BFB.
It seems also likely that whatever is done at the top of the soyuz to permit staging while not separated would also help quite a lot, both in rapid escape, and reducing any potential schrapnel.
The Soyuz event was not at zero-zero...

I never said it was.
And the one in the 80s was (https://en.wikipedia.org/wiki/Soyuz_7K-ST_No._16L).
Way to move the goal post... Good thing it had a LES that saved the crew... ;)
That LES fired very late and the capsule didn't "outrun" anything.

That whole outrunning concept IMOnis a red herring.

You need to have a controlled departure, ability to  survive even in thick airflow, and ability to land.

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ABCD: Always Be Counting Down

Title: Re: Should the BFR have a launch escape system?
Post by: Rocket Science on 10/19/2018 06:46 AM
Do I need to elaborate? Something similar to what is done to protected F9 engines from each other. Using some sort of shielding material as the base of the interstage would significantly reduce shrapnel risk from the BFB.
It seems also likely that whatever is done at the top of the soyuz to permit staging while not separated would also help quite a lot, both in rapid escape, and reducing any potential schrapnel.
The Soyuz event was not at zero-zero...

I never said it was.
And the one in the 80s was (https://en.wikipedia.org/wiki/Soyuz_7K-ST_No._16L).
Way to move the goal post... Good thing it had a LES that saved the crew... ;)
That LES fired very late and the capsule didn't "outrun" anything.

That whole outrunning concept IMOnis a red herring.

You need to have a controlled departure, ability to  survive even in thick airflow, and ability to land.

-----
ABCD: Always Be Counting Down
Now you're moving the goal post back to back to the recent Soyuz event... You both tag-teaming me? ???
See the N-1 rocket at 2:40 (mute the music), no upward shrapnel there either I guess...  For you hand wavers..."You're entitled to you own opinions, but not your own physics"...
https://www.youtube.com/watch?v=U9fkYIrRwbo
Title: Re: Should the BFR have a launch escape system?
Post by: woods170 on 10/19/2018 07:08 AM
Sixteen pages of completely pointless discussion on whether BFR/BFS should have a launch escape system.

Here's the thing: If SpaceX figured it should have one, than it would have one. The fact that there is (apparently) no launch escape system on BFR/BFS is telling.
Remember: having a LES is something that is required by NASA (and possibly DoD). All other involved government agencies (such as the FAA) only require passengers to sign a piece of paper acknowledging that they might die in a launch incident.

Remember: airline-like operations. Which means: don't get NASA and/or DoD involved on manned versions of BFR/BFS. And apparently that is exactly what SpaceX is doing.
Title: Re: Should the BFR have a launch escape system?
Post by: Rocket Science on 10/19/2018 07:15 AM
Sixteen pages of completely pointless discussion on whether BFR/BFS should have a launch escape system.

Here's the thing: If SpaceX figured it should have one, than it would have one. The fact that there is (apparently) no launch escape system on BFR/BFS is telling.
Remember: having a LES is something that is required by NASA (and possibly DoD). All other involved government agencies (such as the FAA) only require passengers to sign a piece of paper acknowledging that they might die in a launch incident.

Remember: airline-like operations. Which means: don't get NASA and/or DoD involved on manned versions of BFR/BFS. And apparently that is exactly what SpaceX is doing.
Elon refused to accept a ride on Dear Moon... Doing so would result what's called "building confidence in the machine" That speaks volumes itself from the "chief designer"...
Title: Re: Should the BFR have a launch escape system?
Post by: Lars-J on 10/19/2018 07:36 AM
I didnít realize that we had lowered the bar enough in this discussion to the point where a design isnít safe until the chief designer insists on riding it first.
Title: Re: Should the BFR have a launch escape system?
Post by: woods170 on 10/19/2018 11:44 AM
I didnít realize that we had lowered the bar enough in this discussion to the point where a design isnít safe until the chief designer insists on riding it first.

Yeah, I didn't hear Rocket Science make the same statement when Jeff Bezos announced he would not be on the first manned mission of New Shepard.
Title: Re: Should the BFR have a launch escape system?
Post by: JamesH65 on 10/19/2018 12:49 PM
I didnít realize that we had lowered the bar enough in this discussion to the point where a design isnít safe until the chief designer insists on riding it first.

Igor Sikorski once said "At that time [1909] the chief engineer was almost always the chief test pilot as well. That had the fortunate result of eliminating poor engineering early in aviation.Ē

Although I also think that is Musk doesn't want to go, that's fine with me. He's the chief designer, but doesn't actually design anything, so the point is utterly moot.
Title: Re: Should the BFR have a launch escape system?
Post by: Robotbeat on 10/19/2018 12:58 PM
ďDoesnít design anythingĒ is actually a lie spread by people who hate Musk. Thereís no truth to it.
Title: Re: Should the BFR have a launch escape system?
Post by: lamontagne on 10/19/2018 12:59 PM
I didnít realize that we had lowered the bar enough in this discussion to the point where a design isnít safe until the chief designer insists on riding it first.

Yeah, I didn't hear Rocket Science make the same statement when Jeff Bezos announced he would not be on the first manned mission of New Shepard.
I thought this was a discussion about Launch Escape Systems on BFS?  The argument should be about the LES, not personal attacks by citing out of topic items.  Please.

Do the Blue origin rockets have LES in their designs would be more to the point.

Arguing a LES is not required because there isn't one in the design is not useful.  Everyone on this thread knows there is no LES on the BFR.  Might as well argue that wings on a re entry vehicle are not required because the 2017 design did not have them.  Oups, but they are there now.

Personally, I do not think a LES system is required, but exploring the concept through discussion is not useless, the fun is in the exchange about the ideas.
Up till now, I got to read an interesting article about saturn 5, got the motivation to upgrade my BFR model, got reminded of the N-1 rocket explosions and added some info about what a LES system is really for to my general info store.  Seems usefull to me.

And can we please stay away from Musk telepathy? 

Title: Re: Should the BFR have a launch escape system?
Post by: lamontagne on 10/19/2018 01:27 PM
For the N-1 video, it appears the upper stages did survive for a few seconds before going off themselves.  Wonder if there is a detailed review of the explosion somewhere?
Title: Re: Should the BFR have a launch escape system?
Post by: Rocket Science on 10/19/2018 02:00 PM
I didnít realize that we had lowered the bar enough in this discussion to the point where a design isnít safe until the chief designer insists on riding it first.

Yeah, I didn't hear Rocket Science make the same statement when Jeff Bezos announced he would not be on the first manned mission of New Shepard.
Is there a video announcement of the first operational BEO passenger mission of New Shepard where he refused an invite, perhaps I missed it...
Title: Re: Should the BFR have a launch escape system?
Post by: Rocket Science on 10/19/2018 02:05 PM
I didnít realize that we had lowered the bar enough in this discussion to the point where a design isnít safe until the chief designer insists on riding it first.
Valuing human life is lowering the bar? ???
Title: Re: Should the BFR have a launch escape system?
Post by: Semmel on 10/19/2018 02:18 PM
I didnít realize that we had lowered the bar enough in this discussion to the point where a design isnít safe until the chief designer insists on riding it first.
Valuing human life is lowering the bar? ???

No the illusion is to think that space travel is safe. It is not. And every person has to make the own decision whether or not to accept the risk. If Musk sais he is not fine with the risks involved, thats his decision and should not be held against the rocket. He wants to see certain things done before he puts his life in danger I imagine. If there are more risk prone people to ride a rocket, thats fine too.

The discussion is: can BFS outrun an exploding BFB? Is it possible to design BFR so that BFS can outrun an exploding BFB, either by it self or with a LAS? And if it needs a LAS, is the technical solution safer than not having a LAS, considering the entire mission profile? Maybe a LAS reduces the reliability for LEO departure, mars descent, Mars ascent and Earth return more than it improves the BFB ascent reliability?

But that is all pointless discussion because to answer these without full knowledge of the system is not possible. So in essence, only SpaceX can answer it. And I bet they have looked at it, its such an obvious thing to do. And they (as far as we know) have decided NOT to implement a LAS. No armchair engineering will come up with better data than this. If our knowledge is wrong, so be it and we need to change our view when we learn more. But we will not be learn more by discussion.
Title: Re: Should the BFR have a launch escape system?
Post by: Rocket Science on 10/19/2018 02:23 PM
ďDoesnít design anythingĒ is actually a lie spread by people who hate Musk. Thereís no truth to it.
So when he ordered the risky-er design changes to BFS to resemble Tin-Tin for esthetic reasons what does that make him?
Title: Re: Should the BFR have a launch escape system?
Post by: Rocket Science on 10/19/2018 02:31 PM
I didnít realize that we had lowered the bar enough in this discussion to the point where a design isnít safe until the chief designer insists on riding it first.
Valuing human life is lowering the bar? ???

No the illusion is to think that space travel is safe. It is not. And every person has to make the own decision whether or not to accept the risk. If Musk sais he is not fine with the risks involved, thats his decision and should not be held against the rocket. He wants to see certain things done before he puts his life in danger I imagine. If there are more risk prone people to ride a rocket, thats fine too.

The discussion is: can BFS outrun an exploding BFB? Is it possible to design BFR so that BFS can outrun an exploding BFB, either by it self or with a LAS? And if it needs a LAS, is the technical solution safer than not having a LAS, considering the entire mission profile? Maybe a LAS reduces the reliability for LEO departure, mars descent, Mars ascent and Earth return more than it improves the BFB ascent reliability?

But that is all pointless discussion because to answer these without full knowledge of the system is not possible. So in essence, only SpaceX can answer it. And I bet they have looked at it, its such an obvious thing to do. And they (as far as we know) have decided NOT to implement a LAS. No armchair engineering will come up with better data than this. If our knowledge is wrong, so be it and we need to change our view when we learn more. But we will not be learn more by discussion.
I think that would be a great question for Chris if he ever get the chance to interview Elon and to ask why or why not and the reasoning...
Title: Re: Should the BFR have a launch escape system?
Post by: rakaydos on 10/19/2018 02:39 PM
ďDoesnít design anythingĒ is actually a lie spread by people who hate Musk. Thereís no truth to it.
So when he ordered the risky-er design changes to BFS to resemble Tin-Tin for esthetic reasons what does that make him?
An engineer who values Esthetics.
Title: Re: Should the BFR have a launch escape system?
Post by: Rocket Science on 10/19/2018 02:48 PM
ďDoesnít design anythingĒ is actually a lie spread by people who hate Musk. Thereís no truth to it.
So when he ordered the risky-er design changes to BFS to resemble Tin-Tin for esthetic reasons what does that make him?
An engineer who values Esthetics.
I'm "a form follows function" guy...
Title: Re: Should the BFR have a launch escape system?
Post by: meekGee on 10/19/2018 02:54 PM
I didnít realize that we had lowered the bar enough in this discussion to the point where a design isnít safe until the chief designer insists on riding it first.
Valuing human life is lowering the bar? ???
No, but that's not what was said.  Aren't you the one crying about supposed moving of goal posts?


So first, the N1 explosion.  It is unclear from the video, which is tracking a fast moving vehicle in airflow, which bits are moving where. 

As for Musk flying first, that's ludicrous.  Initial flights are always more dangerous. Whatever the probability of accident is, you don't want to multiply it by the value of Musk.



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ABCD: Always Be Counting Down

Title: Re: Should the BFR have a launch escape system?
Post by: Rocket Science on 10/19/2018 02:59 PM
I didnít realize that we had lowered the bar enough in this discussion to the point where a design isnít safe until the chief designer insists on riding it first.
Valuing human life is lowering the bar? ???
No, but that's not what was said.  Aren't you the one crying about supposed moving of goal posts?


So first, the N1 explosion.  It is unclear from the video, which is tracking a fast moving vehicle in airflow, which bits are moving where. 

As for Musk flying first, that's ludicrous.  Initial flights are always more dangerous. Whatever the probability of accident is, you don't want to multiply it by the value of Musk.



-----
ABCD: Always Be Counting Down
You're moving it again... This will not be an initial flight, it's an operational paying passenger flight...
Title: Re: Should the BFR have a launch escape system?
Post by: programmerdan on 10/19/2018 03:02 PM
The spacecraft is likely to fly significant demonstrators before any passengers are allowed on board. This handwringing over who flies first seems rather pointless and off topic. Nobody will "fly first" -- the craft will fly first uncrewed, repeatedly, demonstrating key survival features and recovery features.

I'll only get concerned if for some reason, there is a push for passenger missions prior to those milestones.
Title: Re: Should the BFR have a launch escape system?
Post by: meekGee on 10/19/2018 03:07 PM
I didnít realize that we had lowered the bar enough in this discussion to the point where a design isnít safe until the chief designer insists on riding it first.
Valuing human life is lowering the bar? ???
No, but that's not what was said.  Aren't you the one crying about supposed moving of goal posts?


So first, the N1 explosion.  It is unclear from the video, which is tracking a fast moving vehicle in airflow, which bits are moving where. 

As for Musk flying first, that's ludicrous.  Initial flights are always more dangerous. Whatever the probability of accident is, you don't want to multiply it by the value of Musk.



-----
ABCD: Always Be Counting Down
You're moving it again... This will not be an initial flight, it's an operational paying passenger flight...

I didnít realize that we had lowered the bar enough in this discussion to the point where a design isnít safe until the chief designer insists on riding it first.
Valuing human life is lowering the bar? ???
No, but that's not what was said.  Aren't you the one crying about supposed moving of goal posts?


So first, the N1 explosion.  It is unclear from the video, which is tracking a fast moving vehicle in airflow, which bits are moving where. 

As for Musk flying first, that's ludicrous.  Initial flights are always more dangerous. Whatever the probability of accident is, you don't want to multiply it by the value of Musk.



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ABCD: Always Be Counting Down
Your moving it again... This will not be an initial flight, it's an operational paying passenger flight...

I said flights.

Yes, if it were my choice, I wouldn't let Musk fly for many years after BFS flies unmanned.

And other than your "valuing human life is lowering the bar" bit, nobody herr moved any goal posts.

The question was about survivability of the upper stage in the face of S1 having a failure.

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ABCD: Always Be Counting Down

Title: Re: Should the BFR have a launch escape system?
Post by: Rocket Science on 10/19/2018 03:11 PM
No, it's about safe return of crew from a catastrophic event...
Title: Re: Should the BFR have a launch escape system?
Post by: eriblo on 10/19/2018 03:46 PM
ďDoesnít design anythingĒ is actually a lie spread by people who hate Musk. Thereís no truth to it.
So when he ordered the risky-er design changes to BFS to resemble Tin-Tin for esthetic reasons what does that make him?
An engineer who values Esthetics.
I'm "a form follows function" guy...
Could you point me towards what made you come to this conclusion? I thought he ordered the lower risk changes to BFS that made it resemble Tin-Tin for performance reasons. I've only seen the "Intentionally so" tweet which I took as humorous reply acknowledging the similar design decisions resulting from solving very similar problems, given that Elon seems to be "a maximize form given function" guy...
Title: Re: Should the BFR have a launch escape system?
Post by: Rocket Science on 10/19/2018 03:52 PM
ďDoesnít design anythingĒ is actually a lie spread by people who hate Musk. Thereís no truth to it.
So when he ordered the risky-er design changes to BFS to resemble Tin-Tin for esthetic reasons what does that make him?
An engineer who values Esthetics.
I'm "a form follows function" guy...
Could you point me towards what made you come to this conclusion? I thought he ordered the lower risk changes to BFS that made it resemble Tin-Tin for performance reasons. I've only seen the "Intentionally so" tweet which I took as humorous reply acknowledging the similar design decisions resulting from solving very similar problems, given that Elon seems to be "a maximize form given function" guy...
See at 1:04 to 1:08
https://www.youtube.com/watch?v=zu7WJD8vpAQ&t=2481s
Title: Re: Should the BFR have a launch escape system?
Post by: eriblo on 10/19/2018 05:50 PM
ďDoesnít design anythingĒ is actually a lie spread by people who hate Musk. Thereís no truth to it.
So when he ordered the risky-er design changes to BFS to resemble Tin-Tin for esthetic reasons what does that make him?
An engineer who values Esthetics.
I'm "a form follows function" guy...
Could you point me towards what made you come to this conclusion? I thought he ordered the lower risk changes to BFS that made it resemble Tin-Tin for performance reasons. I've only seen the "Intentionally so" tweet which I took as humorous reply acknowledging the similar design decisions resulting from solving very similar problems, given that Elon seems to be "a maximize form given function" guy...
See at 1:04 to 1:08
[video]
Thank you for reminding me, I remembered another mention but was looking for a tweet. You are correct, he does say:

"I actually did not like the aesthetics of that design... [this design] is slightly riskier... I love the Tintin rocket design so I kind of want to bias it towards that."

He did put in a few extra important qualifiers between those words and also looks like he can't keep himself from smiling the whole time in appreciation of the Tintin punch-line, so my interpretation was and remains slightly less literal :)
Title: Re: Should the BFR have a launch escape system?
Post by: speedevil on 10/19/2018 06:20 PM
The spacecraft is likely to fly significant demonstrators before any passengers are allowed on board. This handwringing over who flies first seems rather pointless and off topic. Nobody will "fly first" -- the craft will fly first uncrewed, repeatedly, demonstrating key survival features and recovery features.

I'll only get concerned if for some reason, there is a push for passenger missions prior to those milestones.
Even if we assume the hard bare minimum of flights, it would have done somewhere around 12-26 operational launches for the first Synod to Mars. (depending on how much you believe it can get to orbit) by 2023.
If we add even a couple of years of operational launches at the usual F9 cadence, that's another 50-60.
Add Starlink, and test launches, and it could easily be over a hundred.

This is - assuming for the moment no loss of second-stage accidents - Soyuz-like demonstrated reliability.
If it keeps blowing up - well - at that point it's probably an idea to rethink this whole thing.
Title: Re: Should the BFR have a launch escape system?
Post by: Lar on 10/19/2018 07:46 PM
I think it's possible this design is not riskier and that the 3 fins add a lot. And don't interfere with adding a LES if one were needed. Which I think one is not.

Have we gotten anywhere new recently in this thread or has everyone had their say?
Title: Re: Should the BFR have a launch escape system?
Post by: Rocket Science on 10/19/2018 09:27 PM
I think it's possible this design is not riskier and that the 3 fins add a lot. And don't interfere with adding a LES if one were needed. Which I think one is not.

Have we gotten anywhere new recently in this thread or has everyone had their say?
As I did with my "grid-fin" suggestion years ago, I put forth another possible suggestion for a launch/entry escape cabin. My conscience is clear and I wish them continued success as always...
Title: Re: Should the BFR have a launch escape system?
Post by: RedLineTrain on 10/19/2018 10:31 PM
See at 1:04 to 1:08

I thought we had determined that Musk was referring to technical risk?
Title: Re: Should the BFR have a launch escape system?
Post by: meekGee on 10/19/2018 10:52 PM
I think it's possible this design is not riskier and that the 3 fins add a lot. And don't interfere with adding a LES if one were needed. Which I think one is not.

Have we gotten anywhere new recently in this thread or has everyone had their say?
I'll add this:

"Risky", in the context of the words that follow, refers to programmatic risk.  When subsystems are converged, it's easy for the schedule to be delayed, since there are more requirements on that subsystem.

This does not mean "operational risk".  Actually, when one subsystem performs two tasks, there's one less subsystem to fail...  So if your aerodynamic system is also a landing leg, you don't have a separate deploy subsystem, and so the design is safer, operationally.

Title: Re: Should the BFR have a launch escape system?
Post by: KelvinZero on 10/19/2018 11:18 PM
See at 1:04 to 1:08
I thought we had determined that Musk was referring to technical risk?
Yeah I came to that conclusion during the presentation, and later I saw other people had assumed that too.. To be more specific: the risk of combining legs and reentry control into the fin, which might clash later in the design phase, leaving you with a choice like dramatically increasing weight or going back to the drawing board.

My guess is that alternative designs are being advanced in parallel.. and the "sudden design changes" we see are really another idea edging ahead, and the reference to asethetics being partially jokey but also a reference to when there is no clear winner. What do you do? coin toss time or go with your feelings?
Title: Re: Should the BFR have a launch escape system?
Post by: pathfinder_01 on 10/20/2018 05:34 AM
I didnít realize that we had lowered the bar enough in this discussion to the point where a design isnít safe until the chief designer insists on riding it first.
Valuing human life is lowering the bar? ???

You can value human life, but there is a point where the risk, cost , and lack of practicality of a device makes it not worth it. For instance while Passenger and Cargo ships have enough lifeboat for all the crew, Navy ships do not. There is a only a certain amount needed. Likewise not all Air Force aircraft have ejector seats.

LES pose risks in themselves. If the LES tower on the Apollo capsule did not eject it would cause LOM and potentially loss of crew if the required spacewalk did not free it.

BFR can make a certain number of trips unmanned which is far more than the Shuttle or Apollo(to the moon for the first time) did. In fact the plan is 2-3 flights before the dearmoon project.

I think there are probably better ways of balancing risk than to require BFR to have a LES. Other craft could shuttle passengers or a LEO taxi adapted BFR could be designed. The trouble with a LES is that it would be dead weight  for most of the mission and only cover about one type of emergency.
Title: Re: Should the BFR have a launch escape system?
Post by: ncb1397 on 10/20/2018 05:44 AM

I think there are probably better ways of balancing risk than to require BFR to have a LES. Other craft could shuttle passengers or a LEO taxi adapted BFR could be designed. The trouble with a LES is that it would be dead weight  for most of the mission and only cover about one type of emergency.

Constructed the right way, it could cover multiple types of emergency - heatshield damage, launch escape, landing escape, etc. How many landing problems SpaceX has had vs how many launch problems suggest a LES(landing escape system) would be a higher priority, but 1 system can cover both.

SpaceX seems to be at the post Apollo phase of their experience. NASA in a similar phase of development came to the same conclusion - a launch escape system was not needed. The outcome has a good probability of being the same.
Title: Re: Should the BFR have a launch escape system?
Post by: pathfinder_01 on 10/20/2018 05:59 AM

I think there are probably better ways of balancing risk than to require BFR to have a LES. Other craft could shuttle passengers or a LEO taxi adapted BFR could be designed. The trouble with a LES is that it would be dead weight  for most of the mission and only cover about one type of emergency.

Constructed the right way, it could cover multiple types of emergency - heatshield damage, launch escape, landing escape, etc. How many landing problems SpaceX has had vs how many launch problems suggest a LES(landing escape system) would be a higher priority, but 1 system can cover both.

SpaceX seems to be at the post Apollo phase of their experience. NASA in a similar phase of development came to the same conclusion - a launch escape system was not needed. The outcome has a good probability of being the same.

Heatshield damage would be the one that would be nearly impossible to escape. It would require basically a separate space craft. Landing would be iffy given how fast this booster comes in. Post landing perhaps.

The problem with the shuttle is that it would have cut into the payload requirements for the shuttle and the side mount design of the shuttle makes escape difficult for aerodynamic reasons. A capsule is probably  the best method if a LES is desired.
Title: Re: Should the BFR have a launch escape system?
Post by: ncb1397 on 10/20/2018 06:03 AM
Landing would be iffy given how fast this booster comes in. Post landing perhaps.


You telling me that a launch escape system couldn't escape this?

https://www.youtube.com/watch?v=or5nVPL6E_Y

It is nearly identical to a launch pad abort.

You should review video of the landing failures.

https://www.youtube.com/watch?v=bvim4rsNHkQ

At time of catastrophic failure, the speed is not some insane number.

This isn't like NASA where they can afford to pay people to do some crazy stunt. People have to want to pay them. Passengers -> SpaceX not SpaceX -> passengers.
Title: Re: Should the BFR have a launch escape system?
Post by: RotoSequence on 10/20/2018 08:10 AM
I don't think I've seen any arguments in here for a while that don't reduce to how people feel about the inclusion (or lack thereof) of a launch abort system.
Title: Re: Should the BFR have a launch escape system?
Post by: JamesH65 on 10/20/2018 08:16 AM
ďDoesnít design anythingĒ is actually a lie spread by people who hate Musk. Thereís no truth to it.

it seems very unlikely to me that he sits behind a cad station and designs individual parts certainly he does overall design but nothing in detail. That was the point. he has an overall design view but it's individuals behind cad stations that actually design the parts and actually make the ship fly safely. if those guys don't want to go on a flight then the point may have some validity.
Title: Re: Should the BFR have a launch escape system?
Post by: meekGee on 10/20/2018 09:40 AM
ďDoesnít design anythingĒ is actually a lie spread by people who hate Musk. Thereís no truth to it.

it seems very unlikely to me that he sits behind a cad station and designs individual parts certainly he does overall design but nothing in detail. That was the point. he has an overall design view but it's individuals behind cad stations that actually design the parts and actually make the ship fly safely. if those guys don't want to go on a flight then the point may have some validity.
But the decision being belabored here is exactly a top level decision which is made at leqst partially by Musk.

As for Musk doing detailed design - srsly?  Tho I would not be surprised if he has a CAD station.

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ABCD: Always Be Counting Down

Title: Re: Should the BFR have a launch escape system?
Post by: docmordrid on 10/20/2018 09:50 AM
>
>
As for Musk doing detailed design - srsly?  Tho I would not be surprised if he has a CAD station.

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ABCD: Always Be Counting Down

The whole Y Combinator interview is interesting, but watch from 16:00 on. 80% of his time is spent on engineering and design.

Also, NASA embeds have reported in YouTube videos he is hands-on.

https://www.youtube.com/watch?v=ofGsaVvYmRc
Title: Re: Should the BFR have a launch escape system?
Post by: meekGee on 10/20/2018 09:54 AM
>
>
As for Musk doing detailed design - srsly?  Tho I would not be surprised if he has a CAD station.

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ABCD: Always Be Counting Down

The whole Y Combinator interview is interesting, but watch from 16:00 on. 80% of his time is spent on engineering and design.

Also, NASA embeds have reported in YouTube videos he is hands-on.

https://www.youtube.com/watch?v=ofGsaVvYmRc
That makes sense to me.   But detailed design - that's so time consuming  even on single components...  Musk is responsible for tens of thousands maybe even more... 

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ABCD: Always Be Counting Down

Title: Re: Should the BFR have a launch escape system?
Post by: docmordrid on 10/20/2018 10:05 AM
Reporting on an item from Ashlee  Vance's Musk biography...

CNBC... (https://www.cnbc.com/2018/10/18/saying-this-to-elon-musk-could-get-you-fired-off-your-projects-at-spacex.html)

Quote
Saying this to Elon Musk could get you fired off your projects at SpaceX

>
Employees who tell Musk there's no way to get the cost down on a project or say that Musk's deadlines don't give them enough time, could soon come to regret it. The CEO will simply respond, "Fine. You're off the project and I am now the CEO of the project. I will do your job and be CEO of two companies at the same time. I will deliver," Brogan BamBrogan, a former SpaceX engineer, tells Vance.

Even more surprising, says BamBrogan, is that Musk manages to fulfill that promise. "Every time he's fired someone and taken their job, he's delivered on whatever the project was."
>

Title: Re: Should the BFR have a launch escape system?
Post by: KelvinZero on 10/20/2018 12:16 PM
I don't think I've seen any arguments in here for a while that don't reduce to how people feel about the inclusion (or lack thereof) of a launch abort system.
I don't think there really is much you can say except wait and see.. aim for many unmanned flights and find out what the reliability actually is. I don't think anyone advocating a LAS can say it is so easy that it should be included before we even see how well the unmanned version performs, or that the other side can actually promise that this won't be (even fractionally) another shuttle debacle. SpaceX designed an entire propulsive landing Dragon 2.0 and now they are not going to use its propulsive landing.. because things do not always work out as planned.

SO.. that is why the technical side is more interesting. How would we design a BFS that could be its own LAS, even on the launch pad. How hard would a Dragon 2.0-like LAS for the nose of the BFS be? Could it be used during reenty too? Could it solve landings on unprepared ground? Whether we actually need it.. wait and see. The cargo version certainly does not need it.
Title: Re: Should the BFR have a launch escape system?
Post by: speedevil on 10/20/2018 12:41 PM
SO.. that is why the technical side is more interesting. How would we design a BFS that could be its own LAS, even on the launch pad. How hard would a Dragon 2.0-like LAS for the nose of the BFS be? Could it be used during reenty too? Could it solve landings on unprepared ground? Whether we actually need it.. wait and see. The cargo version certainly does not need it.
In principle, you can increase the thrust of BFS, and get it clear faster.
It would be nice if it was possible to get a twofer - BFS LAS could be used as third stage for cargo missions.

This is the only way I see this actually happening, and I don't believe it's a meaningfully high probability.
Title: Re: Should the BFR have a launch escape system?
Post by: envy887 on 10/20/2018 01:00 PM
See the N-1 rocket at 2:40 (mute the music), no upward shrapnel there either I guess...

NASA considered "the fragmentation hazards" to be "highly problematical", but did not estimate them and instead used shockwave overpressure as the determinant of the warning time required by the Apollo LES.

https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19700024995.pdf

The reason for not calculating the fragmentation hazards was not given, but is IMO because they could not get a analytical solution, and numerical solutions were not practical with the computers of the time.

However, extremely high resolution multi-discipline explosive effects simulation has been practical (although computationally expensive) for some time now, and SpaceX has some state-of-the-art techniques for those types of analyses:

https://www.youtube.com/watch?v=txk-VO1hzBY?t=2520

I expect SpaceX will model the effects of a booster fragmentation event on the upper stage and determine the actual contribution to the overall mission risk from this hazard. I expect it will be small, relative to other mission risks.

Title: Re: Should the BFR have a launch escape system?
Post by: Jcc on 10/20/2018 01:46 PM
SO.. that is why the technical side is more interesting. How would we design a BFS that could be its own LAS, even on the launch pad. How hard would a Dragon 2.0-like LAS for the nose of the BFS be? Could it be used during reenty too? Could it solve landings on unprepared ground? Whether we actually need it.. wait and see. The cargo version certainly does not need it.
In principle, you can increase the thrust of BFS, and get it clear faster.
It would be nice if it was possible to get a twofer - BFS LAS could be used as third stage for cargo missions.

This is the only way I see this actually happening, and I don't believe it's a meaningfully high probability.

No way a fully loaded BFS could escape at anything like 6 gees, but including a LAS-abort routine in the BFS flight software could increase the probability of survival above 0. That should include water landing contingencies.
Title: Re: Should the BFR have a launch escape system?
Post by: Rocket Science on 10/20/2018 01:46 PM
See the N-1 rocket at 2:40 (mute the music), no upward shrapnel there either I guess...

NASA considered "the fragmentation hazards" to be "highly problematical", but did not estimate them and instead used shockwave overpressure as the determinant of the warning time required by the Apollo LES.

https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19700024995.pdf

The reason for not calculating the fragmentation hazards was not given, but is IMO because they could not get a analytical solution, and numerical solutions were not practical with the computers of the time.

However, extremely high resolution multi-discipline explosive effects simulation has been practical (although computationally expensive) for some time now, and SpaceX has some state-of-the-art techniques for those types of analyses:

https://www.youtube.com/watch?v=txk-VO1hzBY?t=2520

I expect SpaceX will model the effects of a booster fragmentation event on the upper stage and determine the actual contribution to the overall mission risk from this hazard. I expect it will be small, relative to other mission risks.
Thank you for the paper...
Title: Re: Should the BFR have a launch escape system?
Post by: Lemurion on 10/20/2018 08:10 PM
At least for the short term a BFS boost away is probably the best that can be achieved with the current design. The one good thing is that with the current engine design it does have enough thrust to break away even if slower than a conventional LAS.

Beyond that the best temporary option is likely to be send crew up on Dragon to dock with an orbiting BFS. This approach also has the advantage that if BFS does suffer heat shield damage on takeoff the crew can use the same Dragon they came up on to get back down.

In fact that's a huge potential safety advantage for BFR as a system. If necessary, SpaceX could provide Dragon lifeboats for early missions and it would provide both an LAS for takeoff and a second heat shield for reentry if needed.
Title: Re: Should the BFR have a launch escape system?
Post by: meekGee on 10/20/2018 11:53 PM
Given that the skydiver design is relatively new, I expect to see a large step next year.  Same direction (this one feels "right") but now a focus on refinement.

I'm very curious as to the different configurations: Deployer, Tanker, P2P, Mars.

If P2P is real, then I can't see why not use P2P for earth ascent and crew load, and optimize the Mars ship for its mission, which is very different from short trips to LEO or Tokyo.

P2P can potentially have a detachable pax cabin section for escape, both on launch and landing. That's not too crazy, if it doesn't have to also be a long term ship.



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ABCD: Always Be Counting Down
Title: Re: Should the BFR have a launch escape system?
Post by: docmordrid on 10/21/2018 12:52 AM
Given that the skydiver design is relatively new...
>

https://forum.nasaspaceflight.com/index.php?topic=46395.msg1860063#msg1860063

Langley, 1959. Skip to 1:20

https://www.youtube.com/watch?v=mX2lRNjQyYY
Title: Re: Should the BFR have a launch escape system?
Post by: meekGee on 10/21/2018 12:58 AM
Given that the skydiver design is relatively new...
>

https://forum.nasaspaceflight.com/index.php?topic=46395.msg1860063#msg1860063

Langley, 1959. Skip to 1:20

https://www.youtube.com/watch?v=mX2lRNjQyYY

Edited:

I saw it back when originally posted. It was a tiny lightweight model in very subsonic, fully dense flow.  It was as relevant as Goddard's rockets to an F9...

Nobody claimed SpaceX invented vertical landings either - but I didn't see any geniuses here suggest the skydiver as an option for BFS, or even recognize it for what it was when shown it on a slide before the 2018 talk.

So the point stands, even in light of that video. (Which is awesome on its own merit)

And since it is new, I expect next years update to still be a large step, and am especially curious as to the breakdown into Mars/p2p/tanker/deployer variants.

 

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Title: Re: Should the BFR have a launch escape system?
Post by: ChrisWilson68 on 10/21/2018 01:21 AM
At least for the short term a BFS boost away is probably the best that can be achieved with the current design. The one good thing is that with the current engine design it does have enough thrust to break away even if slower than a conventional LAS.

Beyond that the best temporary option is likely to be send crew up on Dragon to dock with an orbiting BFS. This approach also has the advantage that if BFS does suffer heat shield damage on takeoff the crew can use the same Dragon they came up on to get back down.

In fact that's a huge potential safety advantage for BFR as a system. If necessary, SpaceX could provide Dragon lifeboats for early missions and it would provide both an LAS for takeoff and a second heat shield for reentry if needed.

Putting Dragon on BFR/BFS in a way that it could function as an LAS is completely infeasible.  It would be an enormous design change, and it would increase risk more than it would decrease it.
Title: Re: Should the BFR have a launch escape system?
Post by: ChrisWilson68 on 10/21/2018 01:30 AM
Some people seem to think putting a LAS on BFR/BFS is comparable to putting it on a capsule design where the capsule is at the top of a rocket with two or more other stages.

It's not comparable.  The design of BFR/BFS is so much different that any sort of "LAS" on BFR/BFS would be so much different from an Apollo-style LAS that it's really not very useful to compare them.

There are a lot of ways to achieve safety.  A system like Saturn V/Apollo had certain risks that it made sense to mitigate with a tower on top of the capsule.  That only made sense because (1) the Saturn V had risks that couldn't be mitigated other ways; and (2) the fact that there was a very small, already separate, vehicle on the top of the stack made this kind of LAS reasonable in terms of additional cost and risk.

Neither of those is true of BFR/BFS.  Trying to apply the same solution to a very different situation isn't a good idea.

The primary question shouldn't be "should BFR have a launch escape system".  The primary question should be "what is the best way to mitigate risk on BFR/BFS"?
Title: Re: Should the BFR have a launch escape system?
Post by: moreno7798 on 10/21/2018 02:41 AM
"Should the BFR have a launch escape system?"

Short answer.... No.

BFS IS THE ESCAPE SYSTEM. An "additional" escape system would mean no boots on Mars until the 2040's.
Title: Re: Should the BFR have a launch escape system?
Post by: meekGee on 10/21/2018 02:48 AM
Some people seem to think putting a LAS on BFR/BFS is comparable to putting it on a capsule design where the capsule is at the top of a rocket with two or more other stages.

It's not comparable.  The design of BFR/BFS is so much different that any sort of "LAS" on BFR/BFS would be so much different from an Apollo-style LAS that it's really not very useful to compare them.

There are a lot of ways to achieve safety.  A system like Saturn V/Apollo had certain risks that it made sense to mitigate with a tower on top of the capsule.  That only made sense because (1) the Saturn V had risks that couldn't be mitigated other ways; and (2) the fact that there was a very small, already separate, vehicle on the top of the stack made this kind of LAS reasonable in terms of additional cost and risk.

Neither of those is true of BFR/BFS.  Trying to apply the same solution to a very different situation isn't a good idea.

The primary question shouldn't be "should BFR have a launch escape system".  The primary question should be "what is the best way to mitigate risk on BFR/BFS"?
Agreed you can't LAS the BFS, since it's an entire second stage...

But a p2p vehicle can be built so the cabin is separable, and then using the rather large guidance thrusters that are already required for landing the whole BFS in wind - the numbers don't prohibit it.

You'd end up escaping and parachuting a 30-ish ton cabin, but that's not impossible.

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ABCD: Always Be Counting Down

Title: Re: Should the BFR have a launch escape system?
Post by: Semmel on 10/21/2018 12:39 PM
Agreed you can't LAS the BFS, since it's an entire second stage...

But a p2p vehicle can be built so the cabin is separable, and then using the rather large guidance thrusters that are already required for landing the whole BFS in wind - the numbers don't prohibit it.

You'd end up escaping and parachuting a 30-ish ton cabin, but that's not impossible.

p2p is not a useful context for this thread.
The reason it came up at all is:
1. we need a cheep launch system that can transport ~100 people to Mars.
2. we need it to be vastly more reliable, otherwise people wouldnt go.

So IF we have a system that satisfies 1. and 2., what else can it do? Its practically an airliner to Mars. Well.. it it can go to Mars and it practically cant fail.. it can also BE an aircraft replacement on earth. So p2p was born. It is not a design goal for BFR, its a consequence of the _assumption_ that all design requirements can be satisfied. Thats a lot of assumptions. And an LAS/LES (can we please settle for ONE acronym?) is structurally not part of the discussion. In fact, if a LAS is not needed for Mars, and 1. and 2. are satisfied, LAS is not needed for p2p either. If a LAS is needed to satisfy 1. and 2., it will be needed for p2p and will be included.
Title: Re: Should the BFR have a launch escape system?
Post by: Rocket Science on 10/21/2018 02:55 PM
I know this thread is long and some may not have read all. What I proposed was a "launch/entry escape cabin" multiple abort modes from launch to entry, some try to twist that fact.... Please refrain from thinking of the Apollo methodology and replace it with the "saucer separation of the Enterprise" in philosophy; just as "Elon was inspired by Tintin" in his redesign... Sci-fi visionaries have moved many to push the limits of rigid-thinking...
Title: Re: Should the BFR have a launch escape system?
Post by: meekGee on 10/21/2018 03:30 PM
I know this thread is long and some may not have read all. What I proposed was a "launch/entry escape cabin" multiple abort modes from launch to entry, some try to twist that fact.... Please refrain from thinking of the Apollo methodology and replace it with the "saucer separation of the Enterprise" in philosophy; just as "Elon was inspired by Tintin" in his redesign... Sci-fi visionaries have moved many to push the limits of rigid-thinking...
Sadly you can't both ask the question and dictate the answer...


Semmel -

A mars ship is designed for months of travel, it has cabins, and a common area upfront.  It has an ECLSS. It has mars-surface provisions.

A P2P vehicle is designed for hour-long flights. It has seats packed up like in a jetliner, and a luggage/cargo area.

Once you have a p2p vehicle, you can't send people to Mars with it. Even 12 hours flights in a jetliner are hard to take.   But 3 months?

My observation is that the p2p requirements are much more amenable to a LAS, since the cabin area is compact.

A stage-wide LAS even if were possible would also have the issue of how to land a fueled stage in an unknown site.  If its just the cabin, there's a smaller issue with post landing fire and tip over.

And, you can call it star trekky, but it's just a variation on capsule separation which is a proven thing.  Based on a 737 mass breakdown, I called it ~20-30 tons.  That's not insane.

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ABCD: Always Be Counting Down
Title: Re: Should the BFR have a launch escape system?
Post by: Rocket Science on 10/21/2018 03:30 PM
Given that the skydiver design is relatively new...
>

https://forum.nasaspaceflight.com/index.php?topic=46395.msg1860063#msg1860063

Langley, 1959. Skip to 1:20

https://www.youtube.com/watch?v=mX2lRNjQyYY
Saw it back when originally posted. Tiny lightweight model in very subsonic fully dense flow.  As relevant as Goddard's rockets to an F9...

Nobody claimed SpaceX invented vertical landings either - but I didn't see any geniuses here suggest the skydiver as an option for BFS, or even recognize it for what it was when shown it on a slide before the 2018 talk.

So yeah, skydiver is completely new for BFS, and the rest of my post stands, even in light of that video. (Which is awesome on its own merit, before being unearthed to show nothing SpaceX does is original)

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ABCD: Always Be Counting Down
Please refrain from trying to imply a negative motivation and agenda to my posting of the video. It was posted to demonstrate the the control methodology was investigated looked sound and SpaceX's variation for BFS is a great concept... We all stand on the shoulders of giants... Leave pride out of it...
Title: Re: Should the BFR have a launch escape system?
Post by: meekGee on 10/21/2018 03:32 PM
Given that the skydiver design is relatively new...
>

https://forum.nasaspaceflight.com/index.php?topic=46395.msg1860063#msg1860063

Langley, 1959. Skip to 1:20

https://www.youtube.com/watch?v=mX2lRNjQyYY
Saw it back when originally posted. Tiny lightweight model in very subsonic fully dense flow.  As relevant as Goddard's rockets to an F9...

Nobody claimed SpaceX invented vertical landings either - but I didn't see any geniuses here suggest the skydiver as an option for BFS, or even recognize it for what it was when shown it on a slide before the 2018 talk.

So yeah, skydiver is completely new for BFS, and the rest of my post stands, even in light of that video. (Which is awesome on its own merit, before being unearthed to show nothing SpaceX does is original)

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ABCD: Always Be Counting Down
Please refrain from trying to imply a negative motivation and agenda to my posting of the video. It was posted to demonstrate the the control methodology was investigated looked sound and SpaceX's variation for BFS is a great concept... We all stand on the shoulders of giants... Leave pride out of it...
Fair enough. No argument on that part - I'll edit above... And done.

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ABCD: Always Be Counting Down
Title: Re: Should the BFR have a launch escape system?
Post by: Semmel on 10/21/2018 07:59 PM
Semmel -

A mars ship is designed for months of travel, it has cabins, and a common area upfront.  It has an ECLSS. It has mars-surface provisions.

A P2P vehicle is designed for hour-long flights. It has seats packed up like in a jetliner, and a luggage/cargo area.

Once you have a p2p vehicle, you can't send people to Mars with it. Even 12 hours flights in a jetliner are hard to take.   But 3 months?

My observation is that the p2p requirements are much more amenable to a LAS, since the cabin area is compact.

A stage-wide LAS even if were possible would also have the issue of how to land a fueled stage in an unknown site.  If its just the cabin, there's a smaller issue with post landing fire and tip over.

And, you can call it star trekky, but it's just a variation on capsule separation which is a proven thing.  Based on a 737 mass breakdown, I called it ~20-30 tons.  That's not insane.

I know, and your logic is sound, no argument from me. But I dont think p2p is a design driver for BFR. Therefore it cannot be used to decide whether a LAS is needed or not. If it was design driving, Musk might risk to compromise the Mars goal with BFR. I dont think he would do that. Obviously it is an assumption on my part that p2p is not a design driver, it was never explicitly stated. But then, making it a design driver is inconsistent with the presentations we have got. And I am happy to change my view, in light of better evidence when and if we get it. I hope the soon(tm) to be held AMA on reddit shines some light onto it.
Title: Re: Should the BFR have a launch escape system?
Post by: meekGee on 10/21/2018 08:10 PM
Semmel -

A mars ship is designed for months of travel, it has cabins, and a common area upfront.  It has an ECLSS. It has mars-surface provisions.

A P2P vehicle is designed for hour-long flights. It has seats packed up like in a jetliner, and a luggage/cargo area.

Once you have a p2p vehicle, you can't send people to Mars with it. Even 12 hours flights in a jetliner are hard to take.   But 3 months?

My observation is that the p2p requirements are much more amenable to a LAS, since the cabin area is compact.

A stage-wide LAS even if were possible would also have the issue of how to land a fueled stage in an unknown site.  If its just the cabin, there's a smaller issue with post landing fire and tip over.

And, you can call it star trekky, but it's just a variation on capsule separation which is a proven thing.  Based on a 737 mass breakdown, I called it ~20-30 tons.  That's not insane.

I know, and your logic is sound, no argument from me. But I dont think p2p is a design driver for BFR. Therefore it cannot be used to decide whether a LAS is needed or not. If it was design driving, Musk might risk to compromise the Mars goal with BFR. I dont think he would do that. Obviously it is an assumption on my part that p2p is not a design driver, it was never explicitly stated. But then, making it a design driver is inconsistent with the presentations we have got. And I am happy to change my view, in light of better evidence when and if we get it. I hope the soon(tm) to be held AMA on reddit shines some light onto it.
... unless the LAS is only implemented on p2p...  Not as an afterthought, but as one of the differentiators.

After all, p2p is supposed to launch people really often.

Tanker, cargo, and deployer never will.

BFS mars will carry people, but will operate on a two year (minimum) cycle, and will involve people undertaking the risks of Mars.

Since p2p will be transporting regular folk on a scheduled service, the whole concept of risk is different.  It really has to be as safe as a plane. 

I don't mind if BFS flies without a LAS, but once p2p exists, I can't see why not use it for earth ascent, with BFS launching just full of mars-bound cargo.



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ABCD: Always Be Counting Down

Title: Re: Should the BFR have a launch escape system?
Post by: Semmel on 10/21/2018 08:15 PM
Semmel -

A mars ship is designed for months of travel, it has cabins, and a common area upfront.  It has an ECLSS. It has mars-surface provisions.

A P2P vehicle is designed for hour-long flights. It has seats packed up like in a jetliner, and a luggage/cargo area.

Once you have a p2p vehicle, you can't send people to Mars with it. Even 12 hours flights in a jetliner are hard to take.   But 3 months?

My observation is that the p2p requirements are much more amenable to a LAS, since the cabin area is compact.

A stage-wide LAS even if were possible would also have the issue of how to land a fueled stage in an unknown site.  If its just the cabin, there's a smaller issue with post landing fire and tip over.

And, you can call it star trekky, but it's just a variation on capsule separation which is a proven thing.  Based on a 737 mass breakdown, I called it ~20-30 tons.  That's not insane.

I know, and your logic is sound, no argument from me. But I dont think p2p is a design driver for BFR. Therefore it cannot be used to decide whether a LAS is needed or not. If it was design driving, Musk might risk to compromise the Mars goal with BFR. I dont think he would do that. Obviously it is an assumption on my part that p2p is not a design driver, it was never explicitly stated. But then, making it a design driver is inconsistent with the presentations we have got. And I am happy to change my view, in light of better evidence when and if we get it. I hope the soon(tm) to be held AMA on reddit shines some light onto it.
... unless the LAS is only implemented on p2p...  Not as an afterthought, but as one of the differentiators.

After all, p2p is supposed to launch people really often.

Tanker, cargo, and deployer never will.

BFS mars will carry people, but will operate on a two year (minimum) cycle, and will involve people undertaking the risks of Mars.

Since p2p will be transporting regular folk on a scheduled service, the whole concept of risk is different.  It really has to be as safe as a plane. 

I don't mind if BFS flies without a LAS, but once p2p exists, I can't see why not use it for earth ascent, with BFS launching just full of mars-bound cargo.



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ABCD: Always Be Counting Down

Then you have a second problem: you need to design the LAS such that it is both non-interfeering with the Mars BFR design AND optional. So a capsule nose for instance is not possible, it would require a completely different structural design than one that does not have a capsule nose. But thats off topic for this thread, where technical solutions are beside the point of whether the LAS is needed or not.
Title: Re: Should the BFR have a launch escape system?
Post by: rakaydos on 10/21/2018 08:26 PM
Doesnt BFS only need 3 engines to safely land?

So the other 4 engines ARE the abort system.
Title: Re: Should the BFR have a launch escape system?
Post by: meekGee on 10/21/2018 08:27 PM
Semmel -

A mars ship is designed for months of travel, it has cabins, and a common area upfront.  It has an ECLSS. It has mars-surface provisions.

A P2P vehicle is designed for hour-long flights. It has seats packed up like in a jetliner, and a luggage/cargo area.

Once you have a p2p vehicle, you can't send people to Mars with it. Even 12 hours flights in a jetliner are hard to take.   But 3 months?

My observation is that the p2p requirements are much more amenable to a LAS, since the cabin area is compact.

A stage-wide LAS even if were possible would also have the issue of how to land a fueled stage in an unknown site.  If its just the cabin, there's a smaller issue with post landing fire and tip over.

And, you can call it star trekky, but it's just a variation on capsule separation which is a proven thing.  Based on a 737 mass breakdown, I called it ~20-30 tons.  That's not insane.

I know, and your logic is sound, no argument from me. But I dont think p2p is a design driver for BFR. Therefore it cannot be used to decide whether a LAS is needed or not. If it was design driving, Musk might risk to compromise the Mars goal with BFR. I dont think he would do that. Obviously it is an assumption on my part that p2p is not a design driver, it was never explicitly stated. But then, making it a design driver is inconsistent with the presentations we have got. And I am happy to change my view, in light of better evidence when and if we get it. I hope the soon(tm) to be held AMA on reddit shines some light onto it.
... unless the LAS is only implemented on p2p...  Not as an afterthought, but as one of the differentiators.

After all, p2p is supposed to launch people really often.

Tanker, cargo, and deployer never will.

BFS mars will carry people, but will operate on a two year (minimum) cycle, and will involve people undertaking the risks of Mars.

Since p2p will be transporting regular folk on a scheduled service, the whole concept of risk is different.  It really has to be as safe as a plane. 

I don't mind if BFS flies without a LAS, but once p2p exists, I can't see why not use it for earth ascent, with BFS launching just full of mars-bound cargo.



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ABCD: Always Be Counting Down

Then you have a second problem: you need to design the LAS such that it is both non-interfeering with the Mars BFR design AND optional. So a capsule nose for instance is not possible, it would require a completely different structural design than one that does not have a capsule nose. But thats off topic for this thread, where technical solutions are beside the point of whether the LAS is needed or not.

It's hard to discuss one without the other....

I think the structural difference would be similar to that between "the chomper" and a regular vanilla flavored cargo ship.

Everything up to the cabin area remains the same across all variants, and everything forward of the tanks is variant-specific, though some components (e.g. the forward fins) are still common.

Actually, whereas the chomper has to open and close in orbit, a detachable cabin means the cabin is sealed before lift-off and no in-space motion occurs.  It's actually probably simpler.

Title: Re: Should the BFR have a launch escape system?
Post by: Lemurion on 10/21/2018 08:59 PM
At least for the short term a BFS boost away is probably the best that can be achieved with the current design. The one good thing is that with the current engine design it does have enough thrust to break away even if slower than a conventional LAS.

Beyond that the best temporary option is likely to be send crew up on Dragon to dock with an orbiting BFS. This approach also has the advantage that if BFS does suffer heat shield damage on takeoff the crew can use the same Dragon they came up on to get back down.

In fact that's a huge potential safety advantage for BFR as a system. If necessary, SpaceX could provide Dragon lifeboats for early missions and it would provide both an LAS for takeoff and a second heat shield for reentry if needed.

Putting Dragon on BFR/BFS in a way that it could function as an LAS is completely infeasible.  It would be an enormous design change, and it would increase risk more than it would decrease it.


It's also not what I suggested.

My suggestion was to launch the crew separately on Dragon, which already has an LAS. Dragon would then dock with BFS in orbit and the crew would transfer. They could then either return on BFS or via Dragon--

It provides an LAS on the way up and a potential lifeboat for a second way back. At no time does it include strapping a Dragon to BFS as an LAS.
Title: Re: Should the BFR have a launch escape system?
Post by: hkultala on 10/26/2018 07:11 AM
My suggestion was to launch the crew separately on Dragon, which already has an LAS. Dragon would then dock with BFS in orbit and the crew would transfer. They could then either return on BFS or via Dragon--

It provides an LAS on the way up and a potential lifeboat for a second way back. At no time does it include strapping a Dragon to BFS as an LAS.

Way too expensive for mars colonization. Would require of tens of Falcon 9 / dragon launches (probably with expendable upper stage) to fill a BFS.

Title: Re: Should the BFR have a launch escape system?
Post by: Negan on 10/26/2018 04:03 PM
My suggestion was to launch the crew separately on Dragon, which already has an LAS. Dragon would then dock with BFS in orbit and the crew would transfer. They could then either return on BFS or via Dragon--

It provides an LAS on the way up and a potential lifeboat for a second way back. At no time does it include strapping a Dragon to BFS as an LAS.

Way too expensive for mars colonization. Would require of tens of Falcon 9 / dragon launches (probably with expendable upper stage) to fill a BFS.

Could another BFS retrieve both the Dragon and the second stage?
Title: Re: Should the BFR have a launch escape system?
Post by: wes_wilson on 10/27/2018 01:20 AM
My suggestion was to launch the crew separately on Dragon, which already has an LAS. Dragon would then dock with BFS in orbit and the crew would transfer. They could then either return on BFS or via Dragon--

It provides an LAS on the way up and a potential lifeboat for a second way back. At no time does it include strapping a Dragon to BFS as an LAS.

Way too expensive for mars colonization. Would require of tens of Falcon 9 / dragon launches (probably with expendable upper stage) to fill a BFS.

Certainly not too expensive for the earliest shakeout flights of BFS when there will likely only be minimal crew.  This might also be a good idea for very early test flights of BFS in NEO where BFS goes up unpiloted and does extended on-orbit stays to test out life support, refuelling, heating & cooling, and all the other things it's going to have to do in space for nearly a year. 

There's zero chance the first time an inhabited BFS spends 2 years in vacuum will be the first flight to mars.  They're going to park a couple of these in orbit and monitor and test systems near home for extended periods of time.  BFS space stations are going to be a thing if for no reason beyond testing before Mars.

Dragon is an absolutely excellent way to put people on & off BFS in the earliest test phases until a proven flight history exists.  Once the numbers show it's not needed, you stop doing it.


Title: Re: Should the BFR have a launch escape system?
Post by: JamesH65 on 10/27/2018 01:49 PM
My suggestion was to launch the crew separately on Dragon, which already has an LAS. Dragon would then dock with BFS in orbit and the crew would transfer. They could then either return on BFS or via Dragon--

It provides an LAS on the way up and a potential lifeboat for a second way back. At no time does it include strapping a Dragon to BFS as an LAS.

Way too expensive for mars colonization. Would require of tens of Falcon 9 / dragon launches (probably with expendable upper stage) to fill a BFS.

Certainly not too expensive for the earliest shakeout flights of BFS when there will likely only be minimal crew.  This might also be a good idea for very early test flights of BFS in NEO where BFS goes up unpiloted and does extended on-orbit stays to test out life support, refuelling, heating & cooling, and all the other things it's going to have to do in space for nearly a year. 

There's zero chance the first time an inhabited BFS spends 2 years in vacuum will be the first flight to mars.  They're going to park a couple of these in orbit and monitor and test systems near home for extended periods of time.  BFS space stations are going to be a thing if for no reason beyond testing before Mars.

Dragon is an absolutely excellent way to put people on & off BFS in the earliest test phases until a proven flight history exists.  Once the numbers show it's not needed, you stop doing it.

Why would you need people on board at all during the early (and not so early) test flights?
Title: Re: Should the BFR have a launch escape system?
Post by: yoram on 10/27/2018 02:33 PM
Right they will fly it unmanned as often as needed to be confident it is safe and only then put humans on it.
BFR is not like the shuttle which requires humans to fly.

Title: Re: Should the BFR have a launch escape system?
Post by: speedevil on 10/27/2018 02:46 PM
Right they will fly it unmanned as often as needed to be confident it is safe and only then put humans on it.
BFR is not like the shuttle which requires humans to fly.
The shuttle only required humans to fly for reasons of policy mainly.
Title: Re: Should the BFR have a launch escape system?
Post by: meekGee on 10/27/2018 05:55 PM
Right they will fly it unmanned as often as needed to be confident it is safe and only then put humans on it.
BFR is not like the shuttle which requires humans to fly.
The shuttle only required humans to fly for reasons of policy mainly.
Still tho....  :)

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ABCD: Always Be Counting Down

Title: Re: Should the BFR have a launch escape system?
Post by: wes_wilson on 11/01/2018 03:06 PM
My suggestion was to launch the crew separately on Dragon, which already has an LAS. Dragon would then dock with BFS in orbit and the crew would transfer. They could then either return on BFS or via Dragon--

It provides an LAS on the way up and a potential lifeboat for a second way back. At no time does it include strapping a Dragon to BFS as an LAS.

Way too expensive for mars colonization. Would require of tens of Falcon 9 / dragon launches (probably with expendable upper stage) to fill a BFS.

Certainly not too expensive for the earliest shakeout flights of BFS when there will likely only be minimal crew.  This might also be a good idea for very early test flights of BFS in NEO where BFS goes up unpiloted and does extended on-orbit stays to test out life support, refuelling, heating & cooling, and all the other things it's going to have to do in space for nearly a year. 

There's zero chance the first time an inhabited BFS spends 2 years in vacuum will be the first flight to mars.  They're going to park a couple of these in orbit and monitor and test systems near home for extended periods of time.  BFS space stations are going to be a thing if for no reason beyond testing before Mars.

Dragon is an absolutely excellent way to put people on & off BFS in the earliest test phases until a proven flight history exists.  Once the numbers show it's not needed, you stop doing it.

Why would you need people on board at all during the early (and not so early) test flights?

Testing in space repairs?
Doing inspections of a BFS that's been on orbit for several months? Or quarters...  Or years...
Because people would pay to visit an orbiting BFS that's doing an extended space test?  It is basically a ready made space hotel...

Lots of reasons people might want to go to/from a BFS while it's in orbit without actually flying up on one. 

Title: Re: Should the BFR have a launch escape system?
Post by: JamesH65 on 11/02/2018 01:59 PM
My suggestion was to launch the crew separately on Dragon, which already has an LAS. Dragon would then dock with BFS in orbit and the crew would transfer. They could then either return on BFS or via Dragon--

It provides an LAS on the way up and a potential lifeboat for a second way back. At no time does it include strapping a Dragon to BFS as an LAS.

Way too expensive for mars colonization. Would require of tens of Falcon 9 / dragon launches (probably with expendable upper stage) to fill a BFS.

Certainly not too expensive for the earliest shakeout flights of BFS when there will likely only be minimal crew.  This might also be a good idea for very early test flights of BFS in NEO where BFS goes up unpiloted and does extended on-orbit stays to test out life support, refuelling, heating & cooling, and all the other things it's going to have to do in space for nearly a year. 

There's zero chance the first time an inhabited BFS spends 2 years in vacuum will be the first flight to mars.  They're going to park a couple of these in orbit and monitor and test systems near home for extended periods of time.  BFS space stations are going to be a thing if for no reason beyond testing before Mars.

Dragon is an absolutely excellent way to put people on & off BFS in the earliest test phases until a proven flight history exists.  Once the numbers show it's not needed, you stop doing it.

Why would you need people on board at all during the early (and not so early) test flights?

Testing in space repairs?
Doing inspections of a BFS that's been on orbit for several months? Or quarters...  Or years...
Because people would pay to visit an orbiting BFS that's doing an extended space test?  It is basically a ready made space hotel...

Lots of reasons people might want to go to/from a BFS while it's in orbit without actually flying up on one.

None of those things will happen on a test flight though.
Title: Re: Should the BFR have a launch escape system?
Post by: Oli on 11/02/2018 02:54 PM

Has somebody posted this already?

https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20180004390.pdf

Might work for BFR.