Quote from: chopsticks on 06/27/2022 03:00 pmHere'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 that1. Shares the outer moldline with Starship (its roof)2. Is aerodynamically stable and controllable3. 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
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 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.
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.
I would suggest a payload module - in this case a "crew module" roughly shaped like this:... picture of the said module ...
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. ...
Quote from: spacenut on 06/28/2022 01:51 pmOk, 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.
Quote from: JayWee on 06/28/2022 02:00 pmQuote from: spacenut on 06/28/2022 01:51 pmOk, 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.
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....
Quote from: TheRadicalModerate on 06/28/2022 03:00 pmMaybe 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.
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"
I don't think there's a prayer of blowing an abort module off to the side at high mach numbers.
Quote from: CorvusCorax on 06/28/2022 02:46 pmThe 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.
Quote from: TheRadicalModerate on 06/28/2022 03:00 pmI 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'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.
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
Quote from: CorvusCorax on 06/28/2022 05:09 pmDesigning 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 axisSo 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.