XpertKerbalKSP

Ideas for a fully re-usable launch vehicle?

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26 minutes ago, sevenperforce said:

For LEO, the main advantage is that a big fluffy re-entry vehicle is much safer and endures lower peak heating and lower gees than a smaller vehicle. That's true whether the crew vehicle is a capsule or a lifting body; the version which retains the stage will have an easier entry than the version which doesn't.

For BLEO, you pretty much have to have your capsule and your stage connected for EDL, since you can't re-integrate for relaunch. So that's an absolute requirement. You can get around it for the moon, since there is no atmosphere to make entry sticky, but it's automatically necessary for Mars.

Agreed. Although...

26 minutes ago, sevenperforce said:

I mean, you can do a capsule on top of an MAV on top of a heat shield, but...egads.

This is still kind of possible. Barely, but can be a viable choice if payload mass must be conserved at all costs.

26 minutes ago, sevenperforce said:

If you're going to go the route of having the crew cabin detach from the upper stage, then you have to ask yourself whether the cabin is going to detach with or without ECLSS, the aeroshell, and so forth. If it detaches with ECLSS and aeroshell, then it is essentially a separate capsule that can serve as a lifeboat, and so you have to ask whether it makes sense to give it an independent emergency re-entry heat shield. And so forth.

I'm going under the assumption that the crew cabin ejects only during launch and ascent, so I'd leave most of the ECLSS on the upper stage, leaving just enough oxygen in the cabin for post-abort EDL, and waiting for the rescue crew. The heatshield would then be scaled for, at most, LEO reentry. All that is to shave mass in order to lighten the crew cabin's post-abort landing system (I'm assuming a Soyuz-style parachute-and-landing-solid-rockets), so that the landing system's mass can be minimized. Basically, in an aborted launch before reaching orbit, only the crew cabin returns, the rest of the rocket is written off.

If anything bad happens to the upper stage after the vehicle reaches orbit that warrants aborting the mission, a better course of action would be to send an empty, unmanned vehicle, dock the new vehicle with the damaged one, transfer the crew to the new vehicle, use the new vehicle's engine to deorbit both vehicles, then land the new vehicle while dumping the damaged one towards the ocean.

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4 hours ago, shynung said:

I don't see much advantage in making them reenter together if the upper stage and crew vehicle can reenter independently.

The crew cabin can be designed to be detached from the upper stage for emergencies, then have a launch abort tower stuck on top.

Or rather using an new shepard solid rocket or an dragon2 style system even if that is more complex it give more abort options during landing, you don't need the soft landing ability and have an lighter pod so you need less fuel 
However one major issue with an combined system is loiter time because of boil off , an second stage don't need long loiter time, an dragon style pod who dock with an space station you want to stay there for months, you will need some days anyway for docking.  

Edited by magnemoe

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2 hours ago, shynung said:
Quote

I mean, you can do a capsule on top of an MAV on top of a heat shield, but...egads.

This is still kind of possible. Barely, but can be a viable choice if payload mass must be conserved at all costs.

Barely, yes. There's not much mass saved, though, really. A lifting body only needs ~600 m/s of dV to land on Mars, whereas a ballistic capsule needs 1000 m/s or more. You can add chutes to drive this down a little, but that increases your dry mass. 600 m/s of dV is nothing compared to the 4.1 km/s your MAV will need to get back to Martian orbit, so there's no sense doing an Apollo-style EDL stage separate from the ascent stage.

Plus, your ballistic heat shield needs to be much beefier than the TPS on a lifting body, so that's extra mass to deal with.

2 hours ago, shynung said:

I'm going under the assumption that the crew cabin ejects only during launch and ascent, so I'd leave most of the ECLSS on the upper stage, leaving just enough oxygen in the cabin for post-abort EDL, and waiting for the rescue crew. The heatshield would then be scaled for, at most, LEO reentry. All that is to shave mass in order to lighten the crew cabin's post-abort landing system (I'm assuming a Soyuz-style parachute-and-landing-solid-rockets), so that the landing system's mass can be minimized. Basically, in an aborted launch before reaching orbit, only the crew cabin returns, the rest of the rocket is written off.

If anything bad happens to the upper stage after the vehicle reaches orbit that warrants aborting the mission, a better course of action would be to send an empty, unmanned vehicle, dock the new vehicle with the damaged one, transfer the crew to the new vehicle, use the new vehicle's engine to deorbit both vehicles, then land the new vehicle while dumping the damaged one towards the ocean.

The problem is something like Columbia; even if they had identified the foam strike while the orbiter was still on the mission, staging a rescue would have been almost impossible. The inclination couldn't be reached by the Soyuz, and even if they could have pushed Atlantis ahead to do a rescue, it would have required a dizzying set of EVAs. They didn't have nearly enough dV to abort to the ISS, either. 

The rescue mission approach is only possible if you had a large enough fleet of RLVs and androgynous docking ports, so a rescue mission could launch almost immediately, rendezvous, and dock for the crew transfer. Of course, that assumes the rescue vehicle has enough seats for all the crew onboard the crippled vehicle.

I agree that in an abort before reaching orbit, the crew cabin is the only thing you need to save. The only reason I was thinking of having the stage be able to independently re-enter is so that you could swap out the same upper stage for payload launches and crewed launches, since the upper stage will be re-entering by itself after payload launches. Of course, if you want downmass capability, then you don't build a swappable upper stage at all; you build two different vehicles with the same-size tanks: a crew version and a cargo bay version.

17 minutes ago, magnemoe said:

However one major issue with an combined system is loiter time because of boil off , an second stage don't need long loiter time, an dragon style pod who dock with an space station you want to stay there for months, you will need some days anyway for docking.

You'd want to use something like methalox and intertanks, like the ITS has.

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Build a secondstage/spacecraft with a bi-conic profile. give it cargo bay doors similar to shuttle. Send crew up as cargo in a pod in the bay. Launch abort sideways after blowing the doors. Or go a step further for crew mission and remove the doors and have the crew pod fit in flush (this would also allow for much easier access to a docking port for in space transfers_.  Separate everything needed by the crew from the vehicle to the pod.

 

If the vehicle gets compromised for use on re-entry you're pretty much stuck where every other vehicle would be if it's heatshield has been compromised: having to do a crew transfer on orbit to another vehicle. Unless of course this monstrosity of a system has enough payload mass to allow for the crew pod to have it's own secondary heatshield.  But that's really starting to cut into the mass of the vehicle for scenario that has only occurred once in the history of manned space flight.

Edited by sojourner

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1 hour ago, sojourner said:

Build a secondstage/spacecraft with a bi-conic profile. give it cargo bay doors similar to shuttle. Send crew up as cargo in a pod in the bay. Launch abort sideways after blowing the doors. Or go a step further for crew mission and remove the doors and have the crew pod fit in flush (this would also allow for much easier access to a docking port for in space transfers_.  Separate everything needed by the crew from the vehicle to the pod.

 

If the vehicle gets compromised for use on re-entry you're pretty much stuck where every other vehicle would be if it's heatshield has been compromised: having to do a crew transfer on orbit to another vehicle. Unless of course this monstrosity of a system has enough payload mass to allow for the crew pod to have it's own seondary heatshield.  But that's really starting to cut into the mass of the vehicle for scenario that has only occurred once in the history of manned space flight.

That is the skylon plan, crew module in cargo bay and it has benefits with one design only. Removing the doors also makes sense, abort is easier and you would save weight. 
Removing doors should be fairly simple but crew module would have to do the cooling if the doors hold radiators. 
Main issue is pad or low attitude abort. You would need an more complex system for this. 

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At high altitude they also need a heatshield and aerodynamic shape, not just a nice cylinder.

And this results into:
1) Klingon-style: no rescue system
2) 2-3 persons craft with ejection seats (at low altitude) and separating cabin (to survive till the low altitude).
3) hull-sized cabin, what means no ejectable cabin at all.
 

Edited by kerbiloid

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13 hours ago, sevenperforce said:

Barely, yes. There's not much mass saved, though, really. A lifting body only needs ~600 m/s of dV to land on Mars, whereas a ballistic capsule needs 1000 m/s or more. You can add chutes to drive this down a little, but that increases your dry mass. 600 m/s of dV is nothing compared to the 4.1 km/s your MAV will need to get back to Martian orbit, so there's no sense doing an Apollo-style EDL stage separate from the ascent stage.

Plus, your ballistic heat shield needs to be much beefier than the TPS on a lifting body, so that's extra mass to deal with

Yep. It'll be handy if the mission is stuck with low-performance engines like hypergolics, but that's about it. It's basically an extreme form of staging.

13 hours ago, sevenperforce said:

The problem is something like Columbia; even if they had identified the foam strike while the orbiter was still on the mission, staging a rescue would have been almost impossible. The inclination couldn't be reached by the Soyuz, and even if they could have pushed Atlantis ahead to do a rescue, it would have required a dizzying set of EVAs. They didn't have nearly enough dV to abort to the ISS, either. 

The rescue mission approach is only possible if you had a large enough fleet of RLVs and androgynous docking ports, so a rescue mission could launch almost immediately, rendezvous, and dock for the crew transfer. Of course, that assumes the rescue vehicle has enough seats for all the crew onboard the crippled vehicle.

I'm taking the scenario depicted in your second paragraph, with the added tidbit that the vehicle can be controlled remotely. Hence, the rescue vehicle can launch with empty seats, so we can safely assume there will be enough seats for the rescued crew.

Also, I vouch for the practice of keeping a second, unmanned vehicle ready on the pad whenever a crewed launch is underway, especially if abort-to-ISS is unfeasible. If the crewed vehicle cannot return to earth after reaching orbit, the second unmanned vehicle would launch a rescue mission.

13 hours ago, sevenperforce said:

I agree that in an abort before reaching orbit, the crew cabin is the only thing you need to save. The only reason I was thinking of having the stage be able to independently re-enter is so that you could swap out the same upper stage for payload launches and crewed launches, since the upper stage will be re-entering by itself after payload launches. Of course, if you want downmass capability, then you don't build a swappable upper stage at all; you build two different vehicles with the same-size tanks: a crew version and a cargo bay version.

I'm thinking of a two-type vehicle with a cargo and crew variant, but sharing most of the propulsion hardware. Downmass capability is not something that we have a lot of currently, and it can be useful for dropping massive cargo in Lunar or Mars missions.

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11 hours ago, kerbiloid said:

At high altitude they also need a heatshield and aerodynamic shape, not just a nice cylinder.


 

Not true. Falcon 9 first stage does just fine without a heat shield.  A heat shield is only really necessary if you need to shed orbital velocity.

 

pad abort would be the tricky part with a side ejecting pod. Low altitude shouldn't be a problem. Depending on what you mean by "low". The abort motor system would have to be designed to take the pod laterally at first to clear the rocket and then curve into a vertical climb to give it enough altitude to deploy chutes.

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10 minutes ago, sojourner said:

Falcon 9 first stage does just fine without a heat shield.

When its velocty is just hypersonic.

The rescue capsule must survive total reentry with orbital speed.

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5 hours ago, kerbiloid said:

When its velocty is just hypersonic.

The rescue capsule must survive total reentry with orbital speed.

From my original post:

If the vehicle gets compromised for use on re-entry you're pretty much stuck where every other vehicle would be if it's heatshield has been compromised: having to do a crew transfer on orbit to another vehicle. Unless of course this monstrosity of a system has enough payload mass to allow for the crew pod to have it's own secondary heatshield.  But that's really starting to cut into the mass of the vehicle for scenario that has only occurred once in the history of manned space flight.

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3 hours ago, sojourner said:

to do a crew transfer on orbit to another vehicle.

On orbit.

Most likely the crew cabin would be ejected during the ascent phase. So, no possible transfer.
When the ship is already on orbit and awaits Chip & Dale rescue rangers, why separate the cabin?

Edited by kerbiloid

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5 hours ago, sojourner said:

From my original post:

If the vehicle gets compromised for use on re-entry you're pretty much stuck where every other vehicle would be if it's heatshield has been compromised: having to do a crew transfer on orbit to another vehicle. Unless of course this monstrosity of a system has enough payload mass to allow for the crew pod to have it's own secondary heatshield.  But that's really starting to cut into the mass of the vehicle for scenario that has only occurred once in the history of manned space flight.

This, the escape system here is designed for first stage burn or landing. 
During second stage burn or reentry you are stuck with upper stage until you get below hypersonic speed. 

The second weakness is time in orbit as O2 and CH4 is cryogenic. Either you limit time in orbit, have, have an system who limit loss a lot or a second fuel system like the space shuttle had. 
 

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3 hours ago, magnemoe said:

This, the escape system here is designed for first stage burn or landing. 
During second stage burn or reentry you are stuck with upper stage until you get below hypersonic speed. 

The second weakness is time in orbit as O2 and CH4 is cryogenic. Either you limit time in orbit, have, have an system who limit loss a lot or a second fuel system like the space shuttle had. 
 

Do what the ITS has and have the smaller tanks inside the main tanks for the boiloff, which is then used in the RCS system.

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40 minutes ago, Frozen_Heart said:

Do what the ITS has and have the smaller tanks inside the main tanks for the boiloff, which is then used in the RCS system.

You could probably do as ULA plan for the centaur follow up with re-pressurization. Losses will also be lower with CH4 than H2, still its limit loiter time. 
Should be enough for dock with an space station and return or doing stuff like recover an 3rd stage but you could not dock with an space station or carry out experiments for months. 

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14 hours ago, kerbiloid said:

Most likely the crew cabin would be ejected during the ascent phase. So, no possible transfer.

Which is not orbital velocity and would not need a heatshield. As demonstrated by Falcon first stage.

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On 5/4/2017 at 0:53 PM, OrbitalBuzzsaw said:

[cough] Skylon [cough]

Does that project have a real budget yet, or are they currently spending the kind of chump-change money that might buy them a single F9 launch?

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EM accelerated space plane?

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9 hours ago, sojourner said:

Which is not orbital velocity and would not need a heatshield.

Which can be orbital velocity minus 100 m/s and require a heatshield..

(Forget the Falcon, LES tower separates a minute later than the first stage)

Edited by kerbiloid

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