Author Topic: Abort options for Starship and Starship/SuperHeavy  (Read 252237 times)

Offline InterestedEngineer

  • Senior Member
  • *****
  • Posts: 2314
  • Seattle
  • Liked: 1803
  • Likes Given: 2930
Re: Abort options for Starship and Starship/SuperHeavy
« Reply #20 on: 06/28/2022 04:39 am »
Here's an extremely crude drawing (I'm sorry) of a capsule inside the starship that could fire some sideway pointing solid rocket motors (or hypergolics) for a brief period to clear the starship, then fire the downward pointing abort motors once clear. Similar to how some missiles are jettisoned then fired once clear of the vehicle they were in.

Obviously the shape of the capsule could probably be quite simple - the astros would only need to be in it for a few minutes during takeoff and landing.

I would suggest a payload module - in this case a "crew module" roughly shaped like this:

I think it is plausible how this shape could contain a crew compartment that
1. Shares the outer moldline with Starship  (its roof)
2. Is aerodynamically stable and controllable
3. Can rocket away from Starship and land - for example  via parachute.
4. Can jetison itself during any flight phase of Starship, including on the ground

I respectfully suggest that hypergolic fuel onboard will be far more dangerous than a Starship w/o any abort will be in 5-7 years.

There have already been one explosion and one scare related to hypergolics in... half a dozen flights or so.  Yikes.  If your failure rate is 1:100 on the basic platform then hypergolics might make sense.  If it's 1:1000 hypergolics make things less safe.

The separable & aerodynamic & parachute are probably good, they won't subtract from safety by themselves. 

How does the separation happen without explosives or hypergolic fuel?  Aerodynamic?

TL;DR - active abort system w/ explosives or hypergolics makes the entire system less safe, not more safe.

Offline CorvusCorax

  • Full Member
  • ****
  • Posts: 1860
  • Germany
  • Liked: 4010
  • Likes Given: 2738
Re: Abort options for Starship and Starship/SuperHeavy
« Reply #21 on: 06/28/2022 09:37 am »


I respectfully suggest that hypergolic fuel onboard will be far more dangerous than a Starship w/o any abort will be in 5-7 years.

There have already been one explosion and one scare related to hypergolics in... half a dozen flights or so.  Yikes.  If your failure rate is 1:100 on the basic platform then hypergolics might make sense.  If it's 1:1000 hypergolics make things less safe.

The separable & aerodynamic & parachute are probably good, they won't subtract from safety by themselves. 

How does the separation happen without explosives or hypergolic fuel?  Aerodynamic?

The main thrusters could be solids. They have typically a longer shelf-life than hypergolics, You have that on ejection seats on military airplanes, but also parachute recovery systems in general aviation (https://en.wikipedia.org/wiki/Cirrus_Airframe_Parachute_System) which is getting more and more standard for modern single engine planes. - The parachute is typically actuated with a solid rocket motor to make it engage faster. That pyrotechnics do not decrease the safety of the system.

It's basically a crew escape pod where the whole aircraft is the crew escape pod. Rocket powered.

Hypergolics can be scary - mostly because of their toxicity and reactivity, but they are not systematically more dangerous than the liquid methane and liquid oxygen Starship carries anyway. And - especially for ejection at high altitudes - you might want some reaction control thrusters. Yes, you could go for a few good old nitrogen filled COPVs and solids for the main escape thruster if you want to avoid them, but hypergolic systems aren't "inhandelable" or always unsafe.

Quote
TL;DR - active abort system w/ explosives or hypergolics makes the entire system less safe, not more safe.

This is just not true. If so you'd never add a hypergolic system as a safety/fallback system to anything that doesn't have hypergolics on its own. Lots of counter-examples. Famous one, the EPU on the F16 jet fighter. A pure emergency system to keep the fly-by-wire system powered in case of a midair engine failure. Powered by Hydrazine.

Yes, Dragon2 had a design flaw that led to a hypergolic related explosion during a ground test. But that does not justify irrational fear of hypergolics. They are being used for many decades, well understood, and the risks involved can be managed very well.

If without this emergency system, Starship has large "black zones" during its flight envelope where no abort is possible, and with it, there are none, then the overall loss of life risk will be lower. Getting the risk of the whole rocket lower than the extra risk of a well understood and designed recovery system would take many thousands of flights to surface and mitigate all the yet unknown unknowns. Even with Starlink launches SpaceX won't have that many launches. You don't want to wait until the 2040's or later until you fly the first manned Starship. But this all borders on "Option 1" discussion anyway which we should try to avoid, agreed?
« Last Edit: 06/28/2022 12:49 pm by CorvusCorax »

Online spacenut

  • Senior Member
  • *****
  • Posts: 5183
  • East Alabama
  • Liked: 2588
  • Likes Given: 2896
Re: Abort options for Starship and Starship/SuperHeavy
« Reply #22 on: 06/28/2022 12:48 pm »
I still say on early Starships, just use a F9 with Dragon crew to dock with an orbiting Starship.  No worries about Aborts with Starship Until enough have launched and landed safely by deploying Starlinks and using tanker Starships. 

However, how many successful launches and landings of Starships will be needed to satisfy putting crew on Starships at launch.  A Dragon capsule in the Starship is not a good idea.  It takes up valuable space for a cargo or crew.  As mentioned, it has hypergolics that would have to be stored inside the Starship which is extremely dangerous. 

If people insist on some type of Abort options, why not just use ejection seats for crew during launches.  It would take up less space inside and could be installed near the nose with ejection ports on the opposite side of the heat shield.  This would be like the Gemini capsule.  Ejection direction could be angled up and away to allow for ejection on the pad and still allow the parachutes for the crew to open before they hit the ground. 

The size of crew would be limited with ejection seats and the large window would probably have to be done away with on the crew Starship.   

Offline CorvusCorax

  • Full Member
  • ****
  • Posts: 1860
  • Germany
  • Liked: 4010
  • Likes Given: 2738
Re: Abort options for Starship and Starship/SuperHeavy
« Reply #23 on: 06/28/2022 01:12 pm »
I still say on early Starships, just use a F9 with Dragon crew to dock with an orbiting Starship.  No worries about Aborts with Starship Until enough have launched and landed safely by deploying Starlinks and using tanker Starships. 

However, how many successful launches and landings of Starships will be needed to satisfy putting crew on Starships at launch.  A Dragon capsule in the Starship is not a good idea.  It takes up valuable space for a cargo or crew.  As mentioned, it has hypergolics that would have to be stored inside the Starship which is extremely dangerous. 

If people insist on some type of Abort options, why not just use ejection seats for crew during launches.  It would take up less space inside and could be installed near the nose with ejection ports on the opposite side of the heat shield.  This would be like the Gemini capsule.  Ejection direction could be angled up and away to allow for ejection on the pad and still allow the parachutes for the crew to open before they hit the ground. 

The size of crew would be limited with ejection seats and the large window would probably have to be done away with on the crew Starship.   

Standard Ejection seats are not feasible for Starship from a technical point of view.
- On the pad they offer insufficient separation for a pad abort. You would not get to minimum safe distance if something were to happen to the Superheavy.
- Past Max Q  ejecting into a supersonic and then hypersonic airstream and rapidly thinning atmopshere with no protection but an IVA suit is most likely not survivable. Even if, it would require a significant redesign of the suits, to turn them basically into wearable survival-pods. You'd rather design proper, larger escape pods that include the seat of the astronaut, and can get far enough away from the vehicle in all flight stages.
- Between launch and MaxQ you get roasted by the Superheavy's exhaust.

----

Launching and recovering people with crew dragon and a separate Falcon9 launch might be an early option for NASA launches. It'd be a really nice early alternative for Artemis for example. Getting rid of SLS/Orion to rendezvous with Starship in earth orbit.  But it doesn't scale, and it adds up to 100 million $ to each manned Starship launch while simultaneously restricting it to a max of 7 crew. For most missions (anything that is not Artemis) this would be more expensive than just sending a Dragon in the first place to do the job.

This is a ok option for manned moon lander missions, but even for "Dear Moon", this is not feasible, since Dragon doesn't have the crew capacity. You'd need multiple Dragon missions and multiple rendezvous to get the crew contingent to the Starship and back.

As such, this is viable OK "plan b" if for whatever reason Starship cannot be man rated for launches from earth in time. You could use Falcon9 launched Dragons for manned missions where you **need** Starship (moon and mars) and the extra Dragon launch costs are a minor factor. This will likely be the case for Artemis and possibly for the earliest manned mars missions which have small pathfinder crew contingents. It's also a viable option for early manned Starship test flights (Polaris)  But all in all it's a form of "Option 1" and as such should probably not be discussed further unless you have game-changing ideas. After all, this thread is about Starship abort options, not how to work around not having one using other launch vehicles.


« Last Edit: 06/28/2022 01:13 pm by CorvusCorax »

Offline JayWee

  • Full Member
  • ****
  • Posts: 997
  • Liked: 993
  • Likes Given: 1838
Re: Abort options for Starship and Starship/SuperHeavy
« Reply #24 on: 06/28/2022 01:50 pm »
I would suggest a payload module - in this case a "crew module" roughly shaped like this:
... picture of the said module ...
I like it! Looks very natural.
And actually - something I've wondered too - where are they going to build the crew cabin stuff anyway?
This kind of kills two birds with one stone. Build and OUTFIT the Crew compartment in a factory somewhere else, ship it to launch site and plug it in.

Online spacenut

  • Senior Member
  • *****
  • Posts: 5183
  • East Alabama
  • Liked: 2588
  • Likes Given: 2896
Re: Abort options for Starship and Starship/SuperHeavy
« Reply #25 on: 06/28/2022 01:51 pm »
Ok, so what everyone is saying is there is not an Abort option short of Starship aborting itself. 

If ejection seats won't work, and putting a Dragon capsule inside a Starship won't work, then the only thing is a drastic redesign of the way Starship would eject and parachute down a crew.  This would severely limit crew quarters, long term supplies, cargo, etc.  So launching a separate Dragon capsule or capsules for the crew is the only option.  Then dock and transfer to Starship. 

At what point do any of you think Starship will be able to carry the crew?  At what point would they be able to carry passengers point to point?  10 years into the future?

Offline JayWee

  • Full Member
  • ****
  • Posts: 997
  • Liked: 993
  • Likes Given: 1838
Re: Abort options for Starship and Starship/SuperHeavy
« Reply #26 on: 06/28/2022 02:00 pm »
Ok, so what everyone is saying is there is not an Abort option short of Starship aborting itself. 

If ejection seats won't work, and putting a Dragon capsule inside a Starship won't work, then the only thing is a drastic redesign of the way Starship would eject and parachute down a crew.  This would severely limit crew quarters, long term supplies, cargo, etc.  So launching a separate Dragon capsule or capsules for the crew is the only option.  Then dock and transfer to Starship. 

...
Have you not seen CorvusCorax pod idea?
 I don't believe it'd limit crew quarters that much. Of course one should do a study whether such a pod is able to separate from the Starship under any liftoff circumstance. It's gonna be much lighter than the whole SS, so more likely parachutes will work, than parachuting the whole SS.

Online spacenut

  • Senior Member
  • *****
  • Posts: 5183
  • East Alabama
  • Liked: 2588
  • Likes Given: 2896
Re: Abort options for Starship and Starship/SuperHeavy
« Reply #27 on: 06/28/2022 02:17 pm »
Ok, so what everyone is saying is there is not an Abort option short of Starship aborting itself. 

If ejection seats won't work, and putting a Dragon capsule inside a Starship won't work, then the only thing is a drastic redesign of the way Starship would eject and parachute down a crew.  This would severely limit crew quarters, long term supplies, cargo, etc.  So launching a separate Dragon capsule or capsules for the crew is the only option.  Then dock and transfer to Starship. 

...
Have you not seen CorvusCorax pod idea?
 I don't believe it'd limit crew quarters that much. Of course one should do a study whether such a pod is able to separate from the Starship under any liftoff circumstance. It's gonna be much lighter than the whole SS, so more likely parachutes will work, than parachuting the whole SS.

If the Starship itself fires away from the booster, it will not use all of it's fuel.  It would still have enough fuel to land, either on water, or back at the launch site.  No parachutes needed.  Remember it will be full of fuel in case of booster failure.  At least until the point of stage separation, but at that point it can get to orbit. 
« Last Edit: 06/28/2022 02:18 pm by spacenut »

Offline CorvusCorax

  • Full Member
  • ****
  • Posts: 1860
  • Germany
  • Liked: 4010
  • Likes Given: 2738
Re: Abort options for Starship and Starship/SuperHeavy
« Reply #28 on: 06/28/2022 02:46 pm »
Ok, so what everyone is saying is there is not an Abort option short of Starship aborting itself. 

If ejection seats won't work, and putting a Dragon capsule inside a Starship won't work, then the only thing is a drastic redesign of the way Starship would eject and parachute down a crew.  This would severely limit crew quarters, long term supplies, cargo, etc.  So launching a separate Dragon capsule or capsules for the crew is the only option.  Then dock and transfer to Starship. 

...
Have you not seen CorvusCorax pod idea?
 I don't believe it'd limit crew quarters that much. Of course one should do a study whether such a pod is able to separate from the Starship under any liftoff circumstance. It's gonna be much lighter than the whole SS, so more likely parachutes will work, than parachuting the whole SS.

If the Starship itself fires away from the booster, it will not use all of it's fuel.  It would still have enough fuel to land, either on water, or back at the launch site.  No parachutes needed.  Remember it will be full of fuel in case of booster failure.  At least until the point of stage separation, but at that point it can get to orbit.

The problem isn't even so much the booster but starship itself. If Starship loses thrust anywhere on the way up, it becomes aerodynamically unstable as has been shown in that paper linked in the other thread (see 1st post).  The whole reentry - belly flop - landing  sequence is only possible when the Starship propellant tanks are basically empty, and the header tanks are full. If they are not, the center of mass will be too far back, Starship will be tail heavy, and it will not be able to keep its angle of attack in the required range to steer towards a landing facility and land.

Similarly, if Superheavy has a loss of thrust on the way up while still in the atmosphere. Starship will immediately find itself under negative G's - since it is affected by aerodynamic forces. Starting the Rapors under these conditions is anything but a sure thing, but would have to happen within a very short timeframe, otherwise Starship will start tumbling and break up. So the issue of "hot staging" is made a lot worse by immense time pressure. This would be an incredibly risky maneuver. Starship can NOT glide on its own - nose first - to apogee and then reenter and belly flop with full tanks.

With full tanks, Starship has a DeltaV of thousands of meters per second, and it will have to burn through more or less all of this to even be able to land. Unless someone designs a method to dump fuel (but realistically raptors at full throttle ARE the quickest way to pump fuel out of starship - short of zipping the tanks open with explosives)

So long story short. If anything goes wrong with superheavy or starships propulsion on the way up, you are between a fire and a hot plate. This whole "using Starship as a LAS to get away from superheavy" is a lot less practical than we (here in the forum) previously thought.

This kinda necessitates the need for a crew rescue system for launch aborts.


Offline TheRadicalModerate

  • Senior Member
  • *****
  • Posts: 4397
  • Tampa, FL
  • Liked: 3315
  • Likes Given: 639
Re: Abort options for Starship and Starship/SuperHeavy
« Reply #29 on: 06/28/2022 03:00 pm »
Maybe you never launch crews on a Starship with elonerons; use a non-EDL variant, similar to lunar Starship.

The biggest problem is the canards on the front.  I don't think there's a prayer of blowing an abort module off to the side at high mach numbers.  But if you have a "crew nose" for the system with no canards, then you can load up with as many abort motors, quick releases, or even pryros as you want, and the problem is reduced to something that's already been more-or-less solved.

The down side is that the crew has no abort-once-around capability, and there must be a successful RPOD to take them off, either to their next destination or back to Earth.  Whether trading an immediate return from orbit on the same vehicle for a clean aerodynamic abort actually reduces your pLOC is a good question.

Not to start a food fight, but this subject is peripherally related to the old payload integration question:  Are Starship noses removable, so that their payloads can be integrated in a low- or mid-bay, and then attached to the propulsion section, or are all payloads integrated in a high-bay?  If you're going with the detachable nose, then a lot of the engineering for that detachment can do double duty as an abort detachment mechanism.

Update:  Actually, I take it back.  If you can blow a capsule off the nose, then the capsule can have a rear heat shield, and it can do a capsule-style EDL.
« Last Edit: 06/28/2022 03:05 pm by TheRadicalModerate »

Online DanClemmensen

  • Senior Member
  • *****
  • Posts: 5489
  • Earth (currently)
  • Liked: 4323
  • Likes Given: 1759
Re: Abort options for Starship and Starship/SuperHeavy
« Reply #30 on: 06/28/2022 03:10 pm »
The problem isn't even so much the booster but starship itself. If Starship loses thrust anywhere on the way up, it becomes aerodynamically unstable as has been shown in that paper linked in the other thread (see 1st post).  The whole reentry - belly flop - landing  sequence is only possible when the Starship propellant tanks are basically empty, and the header tanks are full. If they are not, the center of mass will be too far back, Starship will be tail heavy, and it will not be able to keep its angle of attack in the required range to steer towards a landing facility and land.
Unfortunately the original poster asked us to restrict this discussion to a certain set of scenarios, which in my opinion are only useful for a small subset of failure modes. Specifically: failures causing loss of all thrust but the crew survives the initial failure. In my opinion, the probability of loss of all thrust is very low because Starship has six engines. If SpaceX feels the need to further reduce pLOC, then they should further reduce the probability of loss of all thrust. Adding subsystems, even safety subsystems, increases the complexity of a system in the worst case can increase pLOC.

Offline CorvusCorax

  • Full Member
  • ****
  • Posts: 1860
  • Germany
  • Liked: 4010
  • Likes Given: 2738
Re: Abort options for Starship and Starship/SuperHeavy
« Reply #31 on: 06/28/2022 03:13 pm »
Maybe you never launch crews on a Starship with elonerons; use a non-EDL variant, similar to lunar Starship.

The biggest problem is the canards on the front.  I don't think there's a prayer of blowing an abort module off to the side at high mach numbers.  But if you have a "crew nose" for the system with no canards, then you can load up with as many abort motors, quick releases, or even pryros as you want, and the problem is reduced to something that's already been more-or-less solved.

...

I would assume, the whole point is to keep Starship a fully reusable launch vehicle. That necessitates the flaps and heat shield.

An escape capsule in the front of the nose would still be possible (although then the header tank has to go elsewhere. But that's not a real issue, Elon Musk already mentioned that Starships that bring their payload (crew) back from orbit can have the tank further back. It's only needed in the tip if the Payload (starlink cargo) goes away to still have center of mass in the right spot.

The main issue with the nose mounted escape capsule is its size. You'd end up with a relatively small crew contingent.

An escape pod on the Starships back has more freedom to scale up. But I see its main advantage in the commonality between starship variants. You could have 1 common Starship design into which a payload module is fitted in this place. This could be either a Starlink dispenser, or large sats, or a crew module (including its own rescue system) and integration of these modules would be relatively easy thanks to standardisation. Since they would be self contained, you might not even need the "high bay" - putting that in and out could maybe be done by the chopsticks (or a se of smaller chopsticks) on the pad.

Payloads would be integrated into the payload dispenser module inside a clean room, then it would be sealed, and driven to the pad for integration and launch.

Making the entire nose section of Starship modular would offer similar flexibility, but it would be more complicated since now control surfaces and fuel lines as well as the heat shield run across the "seam"

« Last Edit: 06/28/2022 03:15 pm by CorvusCorax »

Offline TheRadicalModerate

  • Senior Member
  • *****
  • Posts: 4397
  • Tampa, FL
  • Liked: 3315
  • Likes Given: 639
Re: Abort options for Starship and Starship/SuperHeavy
« Reply #32 on: 06/28/2022 03:49 pm »
Maybe you never launch crews on a Starship with elonerons; use a non-EDL variant, similar to lunar Starship.

The biggest problem is the canards on the front.  I don't think there's a prayer of blowing an abort module off to the side at high mach numbers.  But if you have a "crew nose" for the system with no canards, then you can load up with as many abort motors, quick releases, or even pryros as you want, and the problem is reduced to something that's already been more-or-less solved.

...

I would assume, the whole point is to keep Starship a fully reusable launch vehicle. That necessitates the flaps and heat shield.

Yeah, fair point.

I guess you could come up with a version where you could blow the front canards off as part of the separation process.

Quote
The main issue with the nose mounted escape capsule is its size. You'd end up with a relatively small crew contingent.

This might be a case where time is on your side.  You only need a small crew contingent for a lot of years.  Maybe by the time you're trying to 50+ people in one go, you can rely on option #1 (the "make the vehicle insanely reliable" option).

Another possibility, though, would be to do the original propulsive landing that D2 was going to use.  Then there are no parachute loads.  You'll need a lot of thrust and delta-v, but if it's a dedicated crew ferry vehicle, you have all kinds of extra payload mass to play with.

Quote
An escape pod on the Starships back has more freedom to scale up. But I see its main advantage in the commonality between starship variants. You could have 1 common Starship design into which a payload module is fitted in this place. This could be either a Starlink dispenser, or large sats, or a crew module (including its own rescue system) and integration of these modules would be relatively easy thanks to standardisation. Since they would be self contained, you might not even need the "high bay" - putting that in and out could maybe be done by the chopsticks (or a se of smaller chopsticks) on the pad.

Payloads would be integrated into the payload dispenser module inside a clean room, then it would be sealed, and driven to the pad for integration and launch.

Making the entire nose section of Starship modular would offer similar flexibility, but it would be more complicated since now control surfaces and fuel lines as well as the heat shield run across the "seam"

That's an interesting idea for cargo payloads.  You'd essentially have a ventral shell of TPS, canards, LOX header, plumbing, and avionics, with a pod that could be loaded in on the pad.

The geometry is kinda weird.  It would have to strictly side-load, especially if the shell included the nose tip and header tank.  However, as long as the pod has hard points that can be handled by the chopsticks, it should be doable.

However, for crew, ejecting such a pod at high mach seems really improbable.  Just verifying the separation stability through the entire flight regime, under all failure conditions, would be a monumental task.

Even if you don't have an architecture that allows routine nose replacement on the pad, you might still be able to have a full crew nose that could be semi-permanently attached, either in the factory or in a high bay.  As long as you can blow the canard free, you've reduced the problem to just a big capsule.  It's still really complicated, though.

Online chopsticks

  • Full Member
  • ****
  • Posts: 1075
  • Québec, Canada
  • Liked: 1082
  • Likes Given: 165
Re: Abort options for Starship and Starship/SuperHeavy
« Reply #33 on: 06/28/2022 03:51 pm »
I don't think there's a prayer of blowing an abort module off to the side at high mach numbers.

At max-q would be the "worst" time for blowing an abort module off to the side, no? I imagine there would be some pretty complicated math in figuring out the most stressful time to do this, but I'm not that convinced that this would actually be so difficult. Fighter pilots have ejected at supersonic speeds and the human body seems like it would be a lot more fragile than a stainless steel capsule for example.

I would proposed a smaller capsule, designed to seat maybe 12 people. This is where the crew would be during the critical phases of flight, where an abort might be triggered during ascent and landing. EDL can probably be ruled out as a black zone for Starship because at that point it should be aerodynamically stable. An abort would likely only be triggered if the engines failed to light on the landing burn. The crew would board here and exit into the rest of the Starship while on orbit to do their other stuff.

The reason I think a smaller capsule might be better: It would be lighter, thereby making an abort quicker, smaller parachutes would be needed, smaller abort motors required, and in general easier to manage. Perhaps it wouldn't even need to be pressurized separately from the Starship, the crew could rely on their IVA suits during an abort. Regarding the idea of "just use Dragon", I say no way. Dragon way too overengineered for this. It has MMOD protection, has full TPS, etc., all stuff that would be unnecessary. My idea for a small abort capsule is way simpler. Maybe it could be made from stainless like the rest of the ship. When the abort motors are triggered, they could just fire into the cabin behind it - I mean the Starship at that point is already doomed anyway. I would suggest that it sits more or less directly below the header tank, thereby making the shape close to the traditional capsule shape. See the attached (terrible) drawing.

Offline TheRadicalModerate

  • Senior Member
  • *****
  • Posts: 4397
  • Tampa, FL
  • Liked: 3315
  • Likes Given: 639
Re: Abort options for Starship and Starship/SuperHeavy
« Reply #34 on: 06/28/2022 04:07 pm »
The problem isn't even so much the booster but starship itself. If Starship loses thrust anywhere on the way up, it becomes aerodynamically unstable as has been shown in that paper linked in the other thread (see 1st post).  The whole reentry - belly flop - landing  sequence is only possible when the Starship propellant tanks are basically empty, and the header tanks are full. If they are not, the center of mass will be too far back, Starship will be tail heavy, and it will not be able to keep its angle of attack in the required range to steer towards a landing facility and land.
Unfortunately the original poster asked us to restrict this discussion to a certain set of scenarios, which in my opinion are only useful for a small subset of failure modes. Specifically: failures causing loss of all thrust but the crew survives the initial failure. In my opinion, the probability of loss of all thrust is very low because Starship has six engines. If SpaceX feels the need to further reduce pLOC, then they should further reduce the probability of loss of all thrust. Adding subsystems, even safety subsystems, increases the complexity of a system in the worst case can increase pLOC.

Just FYI:  Corvus is the OP.

Don't forget pad aborts, which are a high-runner failure mode.  You can reduce payload and prop loads for crew launches, but even with the minimum prop needed to get to LEO with a 20t crew module and crew, the T/W is only about 3.5.  It's better than nothing, but ground blasts have reflected shockwaves that make them very challenging to escape.  That's where the insane accelerations specified for Apollo and SLS come from.  Note that max-q is also quite challenging, simply because the thrust has to overcome the drag.

I also don't understand how you start six Raptors, three of which are RVacs, when the Starship hasn't separated from the SuperHeavy.  That's a lot of mass flow in a very confined space.

Offline stanerd

  • Member
  • Posts: 2
  • Earth
  • Liked: 3
  • Likes Given: 0
Re: Abort options for Starship and Starship/SuperHeavy
« Reply #35 on: 06/28/2022 04:52 pm »
I'm going to go out on a limb and question whether an abort system is really even necessary.  Correct me if I'm wrong, but I believe that none of the Mercury, Gemini, Apollo, or Shuttle missions actually aborted. 

An abort system to pull the astronauts away from the Shuttle stack may have been able to save the crew of Challenger, but Starship doesn't have SRBs.  I don't see how an abort system could have saved Columbia as it was already in orbit and was basically doomed once it started re-entry.  Starship doesn't have a foam-covered external tank like the Shuttle, so that shouldn't be a problem either.

Also, space is risky business.  As morbid as this sounds, accepting that you have a fair chance of something going wrong and dying is just part of the territory if you choose to become an astronaut.  Remember that aircraft fatalities were very common in the early days of flying.

Offline CorvusCorax

  • Full Member
  • ****
  • Posts: 1860
  • Germany
  • Liked: 4010
  • Likes Given: 2738
Re: Abort options for Starship and Starship/SuperHeavy
« Reply #36 on: 06/28/2022 05:09 pm »
I don't think there's a prayer of blowing an abort module off to the side at high mach numbers.

At max-q would be the "worst" time for blowing an abort module off to the side, no?

A tip mounted abort system has to overcome dynamic pressure and then some to get away from the vehicle, making that the flight phase with the highest thrust requirement to get away.

A side eject would only enter this stream perpendicular to its "get away" direction. If the crew module, or rather the part of the crew module that gets ejected, the "escape vehicle", enters this stream where it can utilise lift to get distance to the launch vehicle quicker!

 The crew module might also include parts that stay behind or break away, similar to some range extended artillery shells where an originally cylindrical round brakes up once leaving the barrel, exposing a dart shaped aerodynamic projectile - thus allowing for winglets and other control surfaces.

To hide a lifting body escape craft in a box module shape, you need a bit of foam filler. When the abort rockets fire, the foam just breaks into tiny bits.

Designing this is gonna be a really interesting challenge, especially so that it works both for pad abort as well as maxq and hypersonic and during bellyflop. But i see no fundamental roadblocks.

Since Starship is conical the actual trajectory doesnt have to be completely perpendicular but can be part forward, part sideways, aprox 45° to Starships X axis


« Last Edit: 06/28/2022 05:13 pm by CorvusCorax »

Offline Hog

  • Senior Member
  • *****
  • Posts: 2846
  • Woodstock
  • Liked: 1700
  • Likes Given: 6866
Re: Abort options for Starship and Starship/SuperHeavy
« Reply #37 on: 06/28/2022 05:13 pm »
I'm going to go out on a limb and question whether an abort system is really even necessary.  Correct me if I'm wrong, but I believe that none of the Mercury, Gemini, Apollo, or Shuttle missions actually aborted. 

An abort system to pull the astronauts away from the Shuttle stack may have been able to save the crew of Challenger, but Starship doesn't have SRBs.  I don't see how an abort system could have saved Columbia as it was already in orbit and was basically doomed once it started re-entry.  Starship doesn't have a foam-covered external tank like the Shuttle, so that shouldn't be a problem either.

Also, space is risky business.  As morbid as this sounds, accepting that you have a fair chance of something going wrong and dying is just part of the territory if you choose to become an astronaut.  Remember that aircraft fatalities were very common in the early days of flying.
Welcome to NSF.com

Apollo 13 aborted
STS-51-F aborted to orbit

Your first sentence "I'm going to go out on a limb and question whether an abort system is really even necessary." Is what Space X, at this juncture, is hoping for.

If STS-51L Challenger's crew had proper oxygen supply and parachutes, their chance of escape would have been better than zero.  As it was, crew was wearing cotton flight suits, and oxygen masks that had zero high altitude capability and no parachutes.
SS/SH having or not having Solid Rocket Boosters makes no difference, surviving the failure does, no matter the cause.

You last paragraph. Today's culture is much to averse to adverse results in spaceflight for that way of thinking.  Apollo days for sure, but these days lives aren't worth "flags and footprints" to most, the reward must be worth the risk..
Paul

Offline TheRadicalModerate

  • Senior Member
  • *****
  • Posts: 4397
  • Tampa, FL
  • Liked: 3315
  • Likes Given: 639
Re: Abort options for Starship and Starship/SuperHeavy
« Reply #38 on: 06/28/2022 05:27 pm »
Designing this is gonna be a really interesting challenge, especially so that it works both for pad abort as well as maxq and hypersonic and during bellyflop. But i see no fundamental roadblocks.

Since Starship is conical the actual trajectory doesnt have to be completely perpendicular but can be part forward, part sideways, aprox 45° to Starships X axis

So how do you see this working for a pad abort?  ISTM that you have two major conflicting design goals:

1) Clear the vehicle at max-q.  This would imply firing as perpendicularly as possible, to avoid crashing into the (possibly exploding) vehicle.

2) Clear the vehicle on the pad.  That implies the least perpendicular ejection, to avoid hitting the ground or going deep into the ground-reflection of the shock from an explosion.

Offline CorvusCorax

  • Full Member
  • ****
  • Posts: 1860
  • Germany
  • Liked: 4010
  • Likes Given: 2738
Re: Abort options for Starship and Starship/SuperHeavy
« Reply #39 on: 06/28/2022 05:40 pm »
Designing this is gonna be a really interesting challenge, especially so that it works both for pad abort as well as maxq and hypersonic and during bellyflop. But i see no fundamental roadblocks.

Since Starship is conical the actual trajectory doesnt have to be completely perpendicular but can be part forward, part sideways, aprox 45° to Starships X axis

So how do you see this working for a pad abort?  ISTM that you have two major conflicting design goals:

1) Clear the vehicle at max-q.  This would imply firing as perpendicularly as possible, to avoid crashing into the (possibly exploding) vehicle.

2) Clear the vehicle on the pad.  That implies the least perpendicular ejection, to avoid hitting the ground or going deep into the ground-reflection of the shock from an explosion.

The most problematic part would be the pad abort, since the abort vehicle must avoid the launch tower. Right now the vehicle afaik is oriented with the backside towards the tower, so any abort trajectory that is not straight up risks colission with the tower.

If the tower were not there, a 45° escape angle would work for both, but the tower blocks that. This suggests the escape vehicle needs to thrust forward only initially, but could - in an.inflight abort - use lift to get lateral distance, too.

Tags: LAS black zones 
 

Advertisement NovaTech
Advertisement Northrop Grumman
Advertisement
Advertisement Margaritaville Beach Resort South Padre Island
Advertisement Brady Kenniston
Advertisement NextSpaceflight
Advertisement Nathan Barker Photography
1