Blue Origin Thread (merged)

[sevenperforce]

29 minutes ago, CatastrophicFailure said:

Pure speculation here, but I'm guessing the coming upgrades for the F9-B5 might save enough mass to make it possible. That, and IIRC they might put one of the new methane Raptors on it, maybe all together that's enough to make up the difference. 

Okay, so let's say they have an extra mass budget to play with.

How can it be done?

An inflatable heat shield under the payload adapter? Superdracos and fold-down legs on the sides? TPS paint on one side?

29 minutes ago, CatastrophicFailure said:

30 minutes ago, sevenperforce said:

And landing on one's tail isn't the best way to land crew, either, for multiple reasons.

This is exactly how the planned crew Dragon will land... eventually... 

Well, the planned Crew Dragon isn't landing on its tail so much. It's a capsule, so it's more like it's landing on its large, well-padded rump.

6 minutes ago, Camacha said:

31 minutes ago, sevenperforce said:

And landing on one's tail isn't the best way to land crew, either, for multiple reasons.

What reasons are those?

Two primary reasons: tip-over and egress.

[TheEpicSquared]

2 minutes ago, tater said:

All pre-shuttle US craft landed that way (on their backs, really). As do the Soviet/Russian capsules. Oh, and the Chinese. And BO's capsule will as well. So far, we have 1 example of people landing seated with their posteriors down, everyone else lands on the astronaut's back (reduced spinal compression in the case of a hard landing).

And the Dragon V2.. and the Orion.. and the Starliner.. and the Russian Federation capsule..

[sevenperforce]

8 minutes ago, TheEpicSquared said:

And the Dragon V2.. and the Orion.. and the Starliner.. and the Russian Federation capsule..

To be fair, the Dragon V2 and the New Shepard capsule both land in a reclined position halfway between "back" and "butt".

In any case, I'm not so terribly concerned about the seat orientation; I'm more concerned about landing stability and what comes after. If you're landing anything larger than a capsule, going tail-first means your crew is stuck at the top of a smoldering, potentially unstable tower. There's a lot that can go wrong.

[CatastrophicFailure]

12 minutes ago, sevenperforce said:

An inflatable heat shield under the payload adapter? Superdracos and fold-down legs on the sides? TPS paint on one side?

*shrugs* All I know is what I've seen in their videos, a Dragon heat shield under the payload adapter, legs, and IIRC superdracos in addition to the Merlin/Raptor. 

An empty second stage is pretty light, I imagine I would slow down very quickly, maybe avoiding some thermal stress. 

[Camacha]

16 minutes ago, sevenperforce said:

Two primary reasons: tip-over and egress.

If you solve the latter, you solve the former. It seems to me that being at the back or top end of a craft is the most ideal position for egress. It is the same as it is with a launch, except that the direction of travel would be in your favour.

[sevenperforce]

9 minutes ago, Camacha said:

If you solve the latter, you solve the former. It seems to me that being at the back or top end of a craft is the most ideal position for egress. It is the same as it is with a launch, except that the direction of travel would be in your favour.

I'm not sure how solving egress solves tip-over. If you're perched at the top of a top-heavy, unstable, smoking tower, things can get very messy very fast.

If a landing leg fails, you're dead no matter what egress plans you may have had.

14 minutes ago, CatastrophicFailure said:

*shrugs* All I know is what I've seen in their videos, a Dragon heat shield under the payload adapter, legs, and IIRC superdracos in addition to the Merlin/Raptor. 

An empty second stage is pretty light, I imagine I would slow down very quickly, maybe avoiding some thermal stress. 

Slowing down quickly means higher peak heating which means more thermal stress. Unless you're approaching the problem from a different angle than I'm imagining.

I'm not sure putting a Dragon heat shield under the payload adapter will work all that well. Keeping center of pressure behind the center of mass would be virtually impossible. 

The key to successfully re-entering a whole stage from orbital velocities is to use as much of the cross-section as possible. Stages are fluffy. Strengthen it biaxially and make it enter normal to prograde.

[Rakaydos]

1 hour ago, sevenperforce said:

Slight change of topic: Musk is yet again making noises about second-stage reuse. Any idea how they'd want to try and manage this, or what modifications S2 would need in order to permit reuse? What kind of payload penalty would be involved?

As a related off-shoot from the now-closed ITS-bashing thread:

While SpaceX is probably not going to do this any time soon, I'd love to see a cogent design for a fully-reusable combined second stage+Crew Dragon which lands propulsively but doesn't compromise safety. It's a tricky problem. You can't just do a scaled-down ITS because the MVac cannot be used in the atmosphere...in fact, it would be ripped to shreds if it is exposed to the atmosphere at all. And landing on one's tail isn't the best way to land crew, either, for multiple reasons.

Actually, i think a scaled down ITS might work, but not with Raptors or Merlins. The ITS also has planned a set of methane-gas thrusters it uses for RCS- we have no specs for this, it may not even be designed yet, but as a smaller thruster using meth/ox, it could run the same combination of sealevel/orbital nozzles that the larger ITS would run.

[Camacha]

6 minutes ago, sevenperforce said:

I'm not sure how solving egress solves tip-over. If you're perched at the top of a top-heavy, unstable, smoking tower, things can get very messy very fast.

If a landing leg fails, you're dead no matter what egress plans you may have had.

Ehm. No? Landing in such a fashion is no different from a take-off, except, again, the direction of travel is in your favour. Slowing down to get out of the way is much easier than speeding up to outrun your rocket.

See for yourself:

 

[sevenperforce]

10 minutes ago, Rakaydos said:

Actually, i think a scaled down ITS might work, but not with Raptors or Merlins. The ITS also has planned a set of methane-gas thrusters it uses for RCS- we have no specs for this, it may not even be designed yet, but as a smaller thruster using meth/ox, it could run the same combination of sealevel/orbital nozzles that the larger ITS would run.

The methalox thrusters for the ITS will be hot-gas pressure-fed from the autogenous pressurization tanks configured with the Raptors.

The Raptor engine cools itself by cycling subcooled CH₄ and LOX through heat exchangers. The fluid is boiled by the heat exchanger and used to pressurize dedicated pressure vessels inside the tanks (with the hot oxygen gas being stored inside the LOX tank and the hot methane being stored inside the subcooled CH₄ tank). These pressure vessels are each then vented to their enclosing tank to maintain ullage pressure to the turbopumps.

The same pressure vessels are tapped to run the methalox thrusters for the RCS system on the ITS spaceship (and, for that matter, the reaction thrusters on the ITS booster).

Without the Raptor and its heat exchanger, then, there's no way to pressurize the tanks for the methalox thrusters.

[Rakaydos]

1 minute ago, sevenperforce said:

The methalox thrusters for the ITS will be hot-gas pressure-fed from the autogenous pressurization tanks configured with the Raptors.

The Raptor engine cools itself by cycling subcooled CH₄ and LOX through heat exchangers. The fluid is boiled by the heat exchanger and used to pressurize dedicated pressure vessels inside the tanks (with the hot oxygen gas being stored inside the LOX tank and the hot methane being stored inside the subcooled CH₄ tank). These pressure vessels are each then vented to their enclosing tank to maintain ullage pressure to the turbopumps.

The same pressure vessels are tapped to run the methalox thrusters for the RCS system on the ITS spaceship (and, for that matter, the reaction thrusters on the ITS booster).

Without the Raptor and its heat exchanger, then, there's no way to pressurize the tanks for the methalox thrusters.

I wouldnt say there's no way to solve that problem, but you are right in that an alternate heat source is something that needs to be engineered around.

[sevenperforce]

14 minutes ago, Camacha said:

Ehm. No? Landing in such a fashion is no different from a take-off, except, again, the direction of travel is in your favour. Slowing down to get out of the way is much easier than speeding up to outrun your rocket.

I think it's generally agreed that suicide burns/hoverslams are more precise and exacting than aborts, even if the g-forces of the latter are more severe. In an abort, you don't really care how much thrust you have, as long as it is enough to get you out of harm's way. In a hoverslam, you've got to have precisely the right amount of thrust at precisely the right amount of time so that your legs touch down exactly when your engines shut down. Any residual lateral velocity and you break a leg or tip over entirely.

Tipping over in a capsule isn't a big problem, because even if you did happen to lose a leg partially (Thiacom-8) or completely (Jason-3), you'll still be mostly upright. In the unlikely event that you come in at an angle like CRS-5 or tip over completely like CRS-6 (which almost certainly won't happen since the height-to-width ratio is so low), you end up rolling, which won't be much fun for the occupants but at least the capsule itself will probably remain intact.

But when you're thinking about landing a mini-ITS on its tail, with the crew perched on top, it's a lot more risky. A Thiacom-8 problem, and you're teetering on the top of a tower that's rocking back and forth while you hang on for dear life. Jason-3? You're dead. CRS-6? You're dead. CRS-5? You're so very very dead. 

And even in an ideal case, you're still perched on top of a tower with no way to get out on your own.

29 minutes ago, Rakaydos said:

32 minutes ago, sevenperforce said:

The methalox thrusters for the ITS will be hot-gas pressure-fed from the autogenous pressurization tanks configured with the Raptors.

Without the Raptor and its heat exchanger, then, there's no way to pressurize the tanks for the methalox thrusters.

I wouldnt say there's no way to solve that problem, but you are right in that an alternate heat source is something that needs to be engineered around.

Raptor and Merlin both have high specific impulse for their propellant type and high TWR because their chamber pressures are very high.

The ITS methalox thrusters are technically an autogenous pressure-fed cycle, which works fine in the ITS because it is using the Raptor as its heat exchanger, but wouldn't work otherwise. You could go to helium pressure-fed cycle, like the Kestrel, but that really hurts engine efficiency and TWR while driving up the dry mass of the stage. A hot-gas expander cycle could be used, but that's also inefficient and doesn't scale up very well.

[Camacha]

25 minutes ago, sevenperforce said:

I think it's generally agreed that suicide burns/hoverslams are more precise and exacting than aborts, even if the g-forces of the latter are more severe. In an abort, you don't really care how much thrust you have, as long as it is enough to get you out of harm's way. In a hoverslam, you've got to have precisely the right amount of thrust at precisely the right amount of time so that your legs touch down exactly when your engines shut down. Any residual lateral velocity and you break a leg or tip over entirely.

Tipping over in a capsule isn't a big problem, because even if you did happen to lose a leg partially (Thiacom-8) or completely (Jason-3), you'll still be mostly upright. In the unlikely event that you come in at an angle like CRS-5 or tip over completely like CRS-6 (which almost certainly won't happen since the height-to-width ratio is so low), you end up rolling, which won't be much fun for the occupants but at least the capsule itself will probably remain intact.

But when you're thinking about landing a mini-ITS on its tail, with the crew perched on top, it's a lot more risky. A Thiacom-8 problem, and you're teetering on the top of a tower that's rocking back and forth while you hang on for dear life. Jason-3? You're dead. CRS-6? You're dead. CRS-5? You're so very very dead.

And even in an ideal case, you're still perched on top of a tower with no way to get out on your own.

It seems you are creating problems where there are none, or where well tested solutions exist. Egress systems exist, have existed for quite a while and have been built and tested.

Jason-3? Very slow topple and therefore an easy escape. Fire your escape system and you are well clear of any explosion. CRS-6? Same story. CRS-5 is probably the most dramatic failure and even that provided ample time to egress. As long as the craft is not inverted or anywhere near that, you have the option of using the escape tower like system. That is exactly what they are designed for. Ejection seats save pilots from aircraft that were heading towards the ground uncontrollably, ejecting at about a 90 angle and close to the ground. Being on top of a rocket at near standstill is, by comparison, a much better starting position.

Being on top of a tower has been solved by humanity a while back and was successfully used in space and other bodies. All Apollo craft that reached the moon employed a ladder system to allow the crew to exit their craft.

 

 

 

Edited March 31, 2017 by Camacha

[sevenperforce]

10 minutes ago, Camacha said:

It seems you are creating problems where there are none, or where well tested solutions exist. Egress systems exist, have existed for quite a while and have been built and tested.

Jason-3? Very slow topple and therefore an easy escape. Fire your escape system and you are well clear of any explosion. CRS-6? Same story. CRS-5 is probably the most dramatic failure and even that provided ample time to egress. As long as the craft is not inverted or anywhere near that, you have the option of using the escape tower like system. That is exactly what they are designed for. Ejection seats save pilots from aircraft that were heading towards the ground uncontrollably, ejecting at about a 90 angle and close to the ground. Being on top of a rocket at near standstill is, by comparison, a much better starting position.

Ooooh, I see. We were comparing apples and oranges. I was talking about a tailsitter landing being bad for crew with something like the ITS, where you don't have any separate escape system at all. If a mini-ITS pulled a CRS-5, CRS-6, or Jason-3, everyone dies. Even a Thiacom-8 is a very, very bad day.

It's safe enough to use LAS engines as landing engines for a capsule like the Dragon 2, because the capsule will not RUD even if a leg breaks or it tips over. A mini-ITS would not have any escape system, which is why I said I didn't like the idea of landing it on its tail.

[Rakaydos]

4 minutes ago, sevenperforce said:

Ooooh, I see. We were comparing apples and oranges. I was talking about a tailsitter landing being bad for crew with something like the ITS, where you don't have any separate escape system at all. If a mini-ITS pulled a CRS-5, CRS-6, or Jason-3, everyone dies. Even a Thiacom-8 is a very, very bad day.

It's safe enough to use LAS engines as landing engines for a capsule like the Dragon 2, because the capsule will not RUD even if a leg breaks or it tips over. A mini-ITS would not have any escape system, which is why I said I didn't like the idea of landing it on its tail.

What do you do if the LAS engines blow up?'

I seem to recall some famus person reportedly saying "you can put all your eggs in one basket, as long as you make DAMN sure you protect that basket." That is the ITS's escape strat- a reliable second stage that doesnt blow up.

[sevenperforce]

27 minutes ago, Camacha said:

Being on top of a tower has been solved by humanity a while back and was successfully used in space and other bodies. All Apollo craft that reached the moon employed a ladder system to allow the crew to exit their craft.

Hah! Yes, this is true. But things were a bit different for the LM. For one thing, the height-to-width of the LM was less than 1, so tip-over during egress was never a possibility. Plus, it wasn't the terminal stage; during landing, the ascent stage could have aborted to the command module at any time. When you're landing on Earth, you kind of want to be able to reliably get out of your vehicle if there was an emergency. Being at the top of a tower is one thing; being at the top of an unstable tower still partly filled with a bucket o' dV is another thing entirely.

12 minutes ago, Rakaydos said:

What do you do if the LAS engines blow up?'

I seem to recall some famus person reportedly saying "you can put all your eggs in one basket, as long as you make DAMN sure you protect that basket." That is the ITS's escape strat- a reliable second stage that doesnt blow up.

In the Dragon 2, if the LAS engines fail you can pop the chutes and let the legs crush...it'll be a bumpy landing but you'll be okay.

Anyway I'm not concerned so much about the engine integrity. Using one set of engines for launch, launch abort, and propulsive landing (e.g. ITS) is fine and dandy, but even 100% reliable engines can't save you from an RUD if you're landing on your tail and you start to tilt.

[Camacha]

2 minutes ago, sevenperforce said:

Ooooh, I see. We were comparing apples and oranges. I was talking about a tailsitter landing being bad for crew with something like the ITS, where you don't have any separate escape system at all. If a mini-ITS pulled a CRS-5, CRS-6, or Jason-3, everyone dies. Even a Thiacom-8 is a very, very bad day.

In space flight, humans have always been a little bit better protected than unmanned spacecraft. It seems obvious to me that some sort of backup would be present, especially considering they generally always have and that SpaceX has already tested an egress system. Of course, even a singular landing system could be designed in such a way that failure does not have to be the end. Using multiple engines, controlled by separate systems means you have a built in backup system. That is one of the reasons the Falcon 9 has so many engines.

2 minutes ago, sevenperforce said:

Hah! Yes, this is true. But things were a bit different for the LM. For one thing, the height-to-width of the LM was less than 1, so tip-over during egress was never a possibility. Plus, it wasn't the terminal stage; during landing, the ascent stage could have aborted to the command module at any time. When you're landing on Earth, you kind of want to be able to reliably get out of your vehicle if there was an emergency. Being at the top of a tower is one thing; being at the top of an unstable tower still partly filled with a bucket o' dV is another thing entirely.

Yes. For this reason, your exit strategy is important. I will point again to jet fighters, which are essentially slow rockets with wings. Very light, very powerful and, more often than not, very filled with combustible go juice. If you want to land on a tiny huge metal sliver in an even huger ocean, you make sure you have a plan B if the cable essential to plan A does not cooperate.

[sevenperforce]

11 minutes ago, Camacha said:

In space flight, humans have always been a little bit better protected than unmanned spacecraft. It seems obvious to me that some sort of backup would be present, especially considering they generally always have and that SpaceX has already tested an egress system. Of course, even a singular landing system could be designed in such a way that failure does not have to be the end. Using multiple engines, controlled by separate systems means you have a built in backup system. That is one of the reasons the Falcon 9 has so many engines.

Yes. For this reason, your exit strategy is important. I will point again to jet fighters, which are essentially slow rockets with wings. Very light, very powerful and, more often than not, very filled with combustible go juice. If you want to land on a tiny huge metal sliver in an even huger ocean, you make sure you have a plan B if the cable essential to plan A does not cooperate.

Spacex has already tested an egress system? By egress, I mean physically entering and exiting the vehicle.

Ejection seats work very well for aircraft. They would work well enough for landing a spacecraft on Earth, but less so during launch, and not at all on orbit.

[Camacha]

Just now, sevenperforce said:

Spacex has already tested an egress system? By egress, I mean physically entering and exiting the vehicle.

They have tested the egress system I posted earlier. I have no knowledge of EVA tests.

Just now, sevenperforce said:

Ejection seats work very well for aircraft. They would work well enough for landing a spacecraft on Earth, but less so during launch, and not at all on orbit.

Are you talking about just a literal  seat? It seems obvious you need to adjust your solution to the application. The comparable solution for space flight is an escape tower or pod.

[sevenperforce]

6 minutes ago, Camacha said:

Are you talking about just a literal  seat? It seems obvious you need to adjust your solution to the application. The comparable solution for space flight is an escape tower or pod.

There are numerous instances in which you may need an escape system, each with their own complications.

• 0/0 pad abort. You've got to go up very fast and get enough horizontal velocity that you come down, you don't land in fireball. You also need a way to come down without going splat.
• MaxQ abort. You've got to get clear of a fireball in air too thin to breathe, while you're already going supersonic, avoid tumbling uncontrollably beyond the aerodynamic limits of your vehicle, and then come down without going splat.
• On-orbit Lifeboat. For instances where your crew cabin is incorporated into your launch vehicle, you need a way to leave your launch vehicle behind on-orbit if its primary TPS or its structure is damaged during launch or on orbit (e.g., Columbia). Then you need to re-enter without burning up, and come down without going splat.
• Landing snafu. If your vehicle is coming down too hard/fast, then see 0/0 pad abort as above.

Ejection seats work for the 0/0 pad abort and the landing snafu, but not for the MaxQ abort or the On-orbit Lifeboat. An ejectable capsule/cabin with its own pusher engines will work for a MaxQ abort, but it needs to be chuted down, and it will only work as an on-orbit lifeboat if it has its own TPS. And it may not work for a 0/0 pad abort or a landing snafu, depending on its orientation to the rest of the vehicle.

[Kerbal01]

Absurd, coming from a man who has consistently overhyped and under produced, but it might work: https://mobile.twitter.com/elonmusk/status/847882289581359104

[TheEpicSquared]

2 minutes ago, DarthVader said:

Absurd, coming from a man who has consistently overhyped and under produced

Heh, everyone said that about reuse. But I hope it works out as well  

[CatastrophicFailure]

59 minutes ago, DarthVader said:

Absurd, coming from a man who has consistently overhyped and under produced, but it might work: https://mobile.twitter.com/elonmusk/status/847882289581359104

@sevenperforce Welp, whatever the (nonexistent) details, it would appear they're a lot closer to second stage recovery than anyone thought. 

[tater]

He mentioned that the fairing costs 6 M$. A new F9 launch sells for 62 M$.

Merlins are substantially cheaper than a fairing, apparently.

[sojourner]

Well, unless whatever test payload they put on the FH demo is very heavy or sent beyond LEO, the second stage on that flight is going to have a healthy margin of fuel left to play around with for a retro burn.  More so than on most operational flights.

[Spaceception]

Don't think this has been posted: