Author Topic: Should the BFR have a launch escape system?  (Read 11792 times)

Online meekGee

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Re: Should the ITS have a launch escape system?
« Reply #40 on: 09/24/2017 01:48 AM »
I really like the idea of five 20-person escapable capsules, one on each tanker flight.
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Offline su27k

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Re: Should the ITS have a launch escape system?
« Reply #41 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.

Online docmordrid

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Re: Should the ITS have a launch escape system?
« Reply #42 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.
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Offline John Alan

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Re: Should the ITS have a launch escape system?
« Reply #43 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...
« Last Edit: 09/25/2017 12:30 AM by John Alan »

Online spacenut

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Re: Should the ITS have a launch escape system?
« Reply #44 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. 

Offline drzerg

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Re: Should the ITS have a launch escape system?
« Reply #45 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




Offline DreamyPickle

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Re: Should the ITS have a launch escape system?
« Reply #46 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.

Offline Athrithalix

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Re: Should the ITS have a launch escape system?
« Reply #47 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.

Offline DreamyPickle

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Re: Should the ITS have a launch escape system?
« Reply #48 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:


Offline su27k

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Re: Should the ITS have a launch escape system?
« Reply #49 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.
« Last Edit: 09/26/2017 12:33 PM by su27k »

Online RonM

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Re: Should the ITS have a launch escape system?
« Reply #50 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.

Online envy887

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Re: Should the ITS have a launch escape system?
« Reply #51 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.

Offline su27k

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Re: Should the ITS have a launch escape system?
« Reply #52 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.

Offline Norm38

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Re: Should the ITS have a launch escape system?
« Reply #53 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.

Offline woods170

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Re: Should the ITS have a launch escape system?
« Reply #54 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.

Online Lee Jay

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Re: Should the ITS have a launch escape system?
« Reply #55 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.
« Last Edit: 10/07/2017 01:08 AM by Lar »

Online cppetrie

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Re: Should the ITS have a launch escape system?
« Reply #56 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.

Online cppetrie

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Re: Should the ITS have a launch escape system?
« Reply #57 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.

Offline DJPledger

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Re: Should the ITS have a launch escape system?
« Reply #58 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.

Offline DJPledger

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Re: Should the ITS have a launch escape system?
« Reply #59 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.

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