Space Shuttle V2 Thought Experiment

[shynung]

7 hours ago, fredinno said:

I was responding to your statement that Energia could carry 100T to LEO. I responded that it could only do that when expendable, and with a upper stage, so it was cheating. It was not supposed to be reusable.

And what you propose would basically be a reusable SLS with a hypergol upper stage. BTW, Hypergols are not cheap anymore due to enivronmental and handling costs. And any design that needs NTRs is a unrealistic dream. I know KSPers love NTR, but still...

Today, you'd just use a SLS w/o upper stage (IUS would be used for MEO, GEO, and planetary robotic missions, while Exploration Upper Stage is used for manned lunar and asteroid missions.) with 2x F-1C Dynetics-esque boosters. These would land vertically via smaller landing engines (which can also serve as booster verniers). The SSMEs would be reused Vulcan-style, with helicopter recovery, while the core would be expendable. Even then, since Dynetics + SLS Block I could launch 120T to LEO, you would have a lot of payload capacity left over. So much, you might be able to just put a massive inflatable heat shield on the core, then return both the tanks and the engines via parafoil and horizontal landing on a runway. The deorbit burn would be done by disposable small solid motors. The boosters can't be reused like this since you would need jet engines to do so, and those would increase the complexity enormously.

 

Actually, fuel tanks are about 45% of cost (excluding avionics). They are cheap in terms of mass-to cost ratio, but not in actual cost. However, disposing tanks are a good way of getting the most payload out of a RLV, while keeping costs down as much as possible.

Hmm. A single SLS first stage with propulsive-landing-flyback boosters, that returns to Earth by a massive inflatable heat shield, and glides to the runway via parafoils. That sounds like it would carry well past 60 tons.

Also, the Russian Baikal flyback booster has a jet engine in the nosecone for returning the booster to a runway.

Were we talking about LH2 tanks? If so, yes, I should've noted them being costly

[fredinno]

59 minutes ago, shynung said:

Hmm. A single SLS first stage with propulsive-landing-flyback boosters, that returns to Earth by a massive inflatable heat shield, and glides to the runway via parafoils. That sounds like it would carry well past 60 tons.

Also, the Russian Baikal flyback booster has a jet engine in the nosecone for returning the booster to a runway.

Were we talking about LH2 tanks? If so, yes, I should've noted them being costly

No, I got those numbers from Atlas V, numbers which ULA made themselves. So, no, I'm talking about Rp-1 tanks, but H2 O2 tanks are likely even worse.

[sevenperforce]

On 2/7/2016 at 11:26 AM, Nibb31 said:

I don't understand the fascination that some people have for winged space ships.

I do. It bridges the gap; allows the public to draw the connection between flight and spaceflight. Seeing someone plunge into the ocean in a tiny cramped capsule vs seeing someone soar out of the skies on the wings of a gigantic spaceplane...it's a very different appeal.

But of course something like the Shuttle is utterly preposterous from an engineering standpoint.

That rule of cool appeal is one of the reasons why SpaceX has gathered such a following. Vertically landed boosters and a vertically landed crew ship are...pretty badass. And unlike the Shuttle program, I think they can actually make it cost-effective.

On 2/7/2016 at 11:36 AM, SpaceplaneAddict said:

We should just strap a newer, larger shuttle to the back of another, larger fuel tank, and the SRB's be replaced with Falcon Heavy boosters. The fuel tank is discarded, the shuttle oes on to perform orbital stuff, and the Falcon Heavy rockets fly back to base.

[Spaceplanes] are a billion billion billion percent cooler. And are easy to recover.

Spaceplanes are cool. Know what's cooler than a spaceplane? A spaceship. Spaceplanes land on a runway; spaceships land on a launch pad.

As long as you have enough heat shielding to survive reentry, the weight of fuel to kill terminal velocity will almost always be less than the weight of wings to glide in. IIRC, the suicide burn on the Falcon 9 boosters consumes only a very small amount of fuel; more fuel is burned in the boostback and velocity-kill phase.

I would really, really like to see an air-augmented SSTO that takes off and lands vertically in a horizontal configuration. Don't know if it's realizable, but damn does it make everything so much easier.

Staging your orbital insertion engines is really, really tricky if you want to reuse them. You can't side-mount your orbiter or you run into the Columbia problem. Putting them at the top won't let you fire them at launch, which means your other engines have to be heavier, which is acceptable, but still not ideal.

For putting people into orbit, I'm wondering if the second stage could be replaced with an extended payload fairing housing a drop tank full of fuel for the SuperDraco engines onboard the Dragon V2. The Dragon's engines are angled just enough that it might save the payload fairing without costing much thrust. Workable?

For heavy cargo it's hard to figure out a way to get that final stage back to Earth. Really hard. NTRs are extremely risky to restart, for one thing, so their utility as enduring space tugs is limited at best and probably nil.

[StrandedonEarth]

When I first read the title I wondered if a German V2 would fit in the Space Shuttle's payload bay. So I looked up the stats on the V2 (development name was the A4):

Weight	12,500 kg (27,600 lb)
Length	14 m (45 ft 11 in)
Diameter	1.65 m (5 ft 5 in)

Hmm, I guess it would. As for why? Good Question!

[fredinno]

4 hours ago, sevenperforce said:

I do. It bridges the gap; allows the public to draw the connection between flight and spaceflight. Seeing someone plunge into the ocean in a tiny cramped capsule vs seeing someone soar out of the skies on the wings of a gigantic spaceplane...it's a very different appeal.

But of course something like the Shuttle is utterly preposterous from an engineering standpoint.

That rule of cool appeal is one of the reasons why SpaceX has gathered such a following. Vertically landed boosters and a vertically landed crew ship are...pretty badass. And unlike the Shuttle program, I think they can actually make it cost-effective.

Spaceplanes are cool. Know what's cooler than a spaceplane? A spaceship. Spaceplanes land on a runway; spaceships land on a launch pad.

As long as you have enough heat shielding to survive reentry, the weight of fuel to kill terminal velocity will almost always be less than the weight of wings to glide in. IIRC, the suicide burn on the Falcon 9 boosters consumes only a very small amount of fuel; more fuel is burned in the boostback and velocity-kill phase.

I would really, really like to see an air-augmented SSTO that takes off and lands vertically in a horizontal configuration. Don't know if it's realizable, but damn does it make everything so much easier.

Staging your orbital insertion engines is really, really tricky if you want to reuse them. You can't side-mount your orbiter or you run into the Columbia problem. Putting them at the top won't let you fire them at launch, which means your other engines have to be heavier, which is acceptable, but still not ideal.

For putting people into orbit, I'm wondering if the second stage could be replaced with an extended payload fairing housing a drop tank full of fuel for the SuperDraco engines onboard the Dragon V2. The Dragon's engines are angled just enough that it might save the payload fairing without costing much thrust. Workable?

For heavy cargo it's hard to figure out a way to get that final stage back to Earth. Really hard. NTRs are extremely risky to restart, for one thing, so their utility as enduring space tugs is limited at best and probably nil.

You can drop your engines on the 2nd stage Vulcan-Style, and keep the engines in a special pod for recovery.

And I though spaceships are just spacecraft, but bigger, manned, and cooler looking. VTVL are not manned. 

[sevenperforce]

35 minutes ago, fredinno said:

You can drop your engines on the 2nd stage Vulcan-Style, and keep the engines in a special pod for recovery.

And I though spaceships are just spacecraft, but bigger, manned, and cooler looking. VTVL are not manned. 

I don't much like the idea of ejecting engines and tossing them and hoping they land someplace that's not too dangerous. Is it feasible to equip them with an expandable heat shield large enough to double as parachute/impact cushion? I suppose if you're already in orbit it costs only very negligible dv to aim for a particular region, but that's not exactly a recipe for pinpoint accuracy, and landing is going to be a major shock. 

I'm a little curious about the feasibility of using a non-cylindrical reusable single stage with two or maybe four strap-on boosters and propellant crossfeed. Something fairly alien in appearance, like an isoceles-triangular hyperboloid lifting body with an elliptic cross-section. The boosters would all strap on to one side, perhaps with a gap in between them for a raised payload bay. Double linear aerospike on the orbiter, but running the same fuel as the boosters, obviously.

If you really wanted to get creative, it could even glide in to kill velocity and then descend vertically on overengineered SuperDraco OMS engines. That way you don't have to directly factor in extra weight for landing gear or wings, but you still get the advantage of gliding return, lowered terminal velocity, and propulsive landing. Even better, you land in a horizontal attitude.

I'll see about doing a mockup tomorrow.

And the bit about spacecraft vs spaceships was a bit of hyperbole on my part.

[Rakaydos]

2 minutes ago, sevenperforce said:

I don't much like the idea of ejecting engines and tossing them and hoping they land someplace that's not too dangerous. Is it feasible to equip them with an expandable heat shield large enough to double as parachute/impact cushion? I suppose if you're already in orbit it costs only very negligible dv to aim for a particular region, but that's not exactly a recipe for pinpoint accuracy, and landing is going to be a major shock.

"Vulcan style" implies you have aircraft in the "recovery zone" to snatch the falling engines out of the air and return them to the factory for re-integration.

[sevenperforce]

7 minutes ago, Rakaydos said:

"Vulcan style" implies you have aircraft in the "recovery zone" to snatch the falling engines out of the air and return them to the factory for re-integration.

Dang. Even with autonomous "catch", atmospheric rendezvous seems like a logistics nightmare.

[Nothalogh]

So, with some "highly scientific" testing, I found I could Dyna-Soar a loaded full size orbiter.

Is there any reason not to?

[Rakaydos]

1 hour ago, sevenperforce said:

Dang. Even with autonomous "catch", atmospheric rendezvous seems like a logistics nightmare.

Not really. Engine unit deploys parachutes, plane sees parachutes, snags the cable between engine and chute, flies off into the sunset.

[sevenperforce]

30 minutes ago, Rakaydos said:

Not really. Engine unit deploys parachutes, plane sees parachutes, snags the cable between engine and chute, flies off into the sunset.

Ah, parachutes. Makes much more sense now.

[Nibb31]

1 hour ago, sevenperforce said:

Ah, parachutes. Makes much more sense now.

Yeah, and it was done in the 60's with Corona capsules. The difference here is the size of the pod. It's going to need a seriously heavy lift helicopter, like a CH-53. I'm not sure it's going to be cost-effective.

[magnemoe]

4 hours ago, Nibb31 said:

Yeah, and it was done in the 60's with Corona capsules. The difference here is the size of the pod. It's going to need a seriously heavy lift helicopter, like a CH-53. I'm not sure it's going to be cost-effective.

Capturing an upper stage engine should be plausible. the Merlin second stage engine only weight 470 kg.
Yes you would also want to return the avionic, need an heat shield and parachute who increasing the weight but is should not get so much past one ton making it doable for medium helicopters if not the capture mechanism or pressure on capture is to heavy. 

[sevenperforce]

If you really want a replacement for the Shuttle, something that can put payloads into space regularly and be completely reusable...well, here you go.

41 meters high, 20 meters wide, 10 meters deep. Payload bay is the same size as the Shuttle Orbiter's, but the lack of control surfaces allows surrounding space to be used for additional fuel.

The engine is a truncated aerospike:

The high-thrust aerospike engines provide optimal thrust and Isp respective to altitude.

Optional/detachable cabin:

The crew cabin module has about half as much space as the Shuttle Orbiter but three times the space of the Dragon V2. It fits into the main body and is equipped with multiple high-thrust hypergolic engines which also act as the OMS and RCS system. These allow the crew cabin to eject during launch abort.

For crew transfer only, the payload bay is fitted with an additional internal tank and a disposable strap-on tank, allowing SSTO with the loss of the external tank alone. For unmanned flights, the crew cabin module is replaced with an autonomous control module with an auxiliary fuel tank but the same hypergolic engines. For manned flights including payload, or for higher-dV unmanned missions, 2-4 strap-on FH-style boosters are attached with propellant crossfeed; these detach at fairly low speed to return autonomously.

Re-entry will be...exciting. The aerospike already has to be able to handle very high heat fluxes and will probably already be actively cooled, so the orbiter enters tail-first and upside down to burn off most of its speed, with active use of the RCS system for stabilization. As soon as enough speed has dropped off, the orbiter begins to rotate forward, exposing more and more of its underside. The lower speed at this point means that the heat shield on its underside can be constructed of a lightweight, non-ablative, lower-performing, highly reusable material rather than requiring the tiles that the Shuttle used. Active RCS stabilization continues as speed decreases, ultimately entering a low-L/D gliding flight:

The orbiter does not make a very good glider and cannot manage a level approach, which is all the better because it doesn't have heavy landing gear. Instead, the RCS system returns the craft to a high angle of attack, and the aerospike engines are ignited, killing terminal velocity in a near-suicide burn. Then, the RCS system reduces power, allowing the angle of attack to drop until the orbiter is horizontal, and both the RCS system and the aerospike engines in combination fire to lower the orbiter to the ground:

If the aerospike cannot be directed downward enough to execute such a landing, then additional RCS thrusters can be incorporated in the aft portion of the orbiter.

Ambitious? Perhaps...but it seems like the best possible combination of geometry to allow for the capabilities of the shuttle with next-generation technology.

The amount of hypergolic fuel, internal fuel, and the number of strap-on boosters can be adapted to each mission. By using in-orbit staging and/or refueling, the orbiter could easily manage a lunar transfer. Depending on the fuel capacity of the crew cabin, it could manage a landing on its own on hypergolics, or lunar-orbit refueling could allow the entire orbiter to make the descent to the lunar surface and return to refuel and make the transfer to LEO again. The ability to take off and land vertically in a horizontal attitude reduces the instabilities and risks of vertical landings and allows far simpler crew egress.

Edited February 9, 2016 by sevenperforce

[Emperor of the Titan Squid]

I say that we make the first stage tanks built in and reusable, winged or Saturn shuttle style.Baikal boosters, falcon style upper stage. Interchangeable boosters, example: RBCC catapult launched air craft.That or giant SERV.Anyone considered that yet?

[Beowolf]

I don't like combining cargo-carrying with crew. Yes, the shuttle did that, but with today's hindsight it was clearly a bad idea that forced them into an inherently unsafe design. What about all those times you just want to swap a few ISS astronauts? You're wasting the costly launch of a heavy-lifter, unless you just happen to also have a new space station module or 50 tons of satellites ready to lift as well. 

My support would go to dual programs. The smaller crewed craft would be >99% reusable, and nothing lost but fairings and SRBs on the cargo craft. Both should have simple enough support requirements that they could theoretically reposition to, and operate from, any simple spaceport worldwide with a single custom-built support building. The idea being to sell or lease them, rather than the manufacturer operating them.

The crew version, if winged, could perhaps be something like Faget's DC-3 shuttle. Yes, wings are wasteful but my goal isn't to be the most efficient, but to have the highest safety and lowest operating costs. Half a dozen astronauts and their gear don't mass very much, and being able to land either under power or with a shuttle-style glide is one heck of a safety feature.

For vertical launch systems, the 2016 version of Falcon 9 gets impressively close to qualifying. They're already assembled horizontally in a hangar, and have pretty simple support requirements, so no trouble there. But it isn't reusable enough yet. I'd want to see 2nd stages recovered and reused, and we'd have to do something about that trunk. Musk's said their internal analysis concluded recovering the 2nd stage was possible but not economically practical right now, so maybe the next generation. He clearly wants a fully-reusable system and is moving in that direction as fast as possible.

As for the cargo carrier, didn't you pretty much just describe what a Falcon Heavy's supposed to do? It's rated at 53 tons instead of 60, and we don't yet know about the maintenance costs or longevity, but otherwise your specs seem dead on target.

Or, for a traditionally-Kerbal solution, we could tie four Skylons together with struts and lift 60 tons.  

On 2/8/2016 at 4:07 PM, sevenperforce said:

For putting people into orbit, I'm wondering if the second stage could be replaced with an extended payload fairing housing a drop tank full of fuel for the SuperDraco engines onboard the Dragon V2. The Dragon's engines are angled just enough that it might save the payload fairing without costing much thrust. Workable?

Certainly it can! I've done that in KSP using Laztek's Falcon 9, so obviously it works IRL, right?  

[Beowolf]

2 hours ago, sevenperforce said:

If you really want a replacement for the Shuttle, something that can put payloads into space regularly and be completely reusable...well, here you go.

That's a gorgeous design, but I don't believe in your landing. I don't think you can angle a linear aerospike's thrust like that without pivoting the whole engine assembly, and RCS thrust is orders of magnitude too tiny to hold the nose up.

But add some SuperDraco-style engines on the underside for final deceleration and landing, and you have a sweet ship. You will still need landing gear, IMO. It can be pretty simple and lightweight but without it ground handling seems like it'd be a nightmare.

[tater]

It's odd seeing that design, and "Beowolf" in the same place, because that design looks rather a lot like like a Traveller scout ship variant. It's even about the same size (within 2m)

[shynung]

8 hours ago, Beowolf said:

As for the cargo carrier, didn't you pretty much just describe what a Falcon Heavy's supposed to do? It's rated at 53 tons instead of 60, and we don't yet know about the maintenance costs or longevity, but otherwise your specs seem dead on target.

Wasn't FH-Reusable's payload closer to 20 tons rather than 53? It would need 3 FH-Rs clustered together, if that's even possible.

[sevenperforce]

6 hours ago, shynung said:

Wasn't FH-Reusable's payload closer to 20 tons rather than 53? It would need 3 FH-Rs clustered together, if that's even possible.

53 tonnes to LEO, 20 tonnes to GTO, 16 tonnes to LLO, and 8 tonnes to LMO. If I remember correctly. Although those numbers are based on a Falcon Heavy comprising three Falcon 9v1.1 boosters rather then the larger, enhanced Full Thrust version. And whether the boosters are reused or not also factors in.

11 hours ago, tater said:

It's odd seeing that design, and "Beowolf" in the same place, because that design looks rather a lot like like a Traveller scout ship variant. It's even about the same size (within 2m)

Odd, it does, although I had never seen those before.

I chose that shape because I wanted to maximize internal volume and re-entry cross-section but also maintain a small ascent cross-section to avoid excessive drag and aerodynamic loading. I also wanted the option of a crew module with the same basic shape for launch abort reasons. I need to run the numbers to see how close to SSTO this would get in its various configurations.

14 hours ago, Beowolf said:

That's a gorgeous design, but I don't believe in your landing. I don't think you can angle a linear aerospike's thrust like that without pivoting the whole engine assembly, and RCS thrust is orders of magnitude too tiny to hold the nose up.

But add some SuperDraco-style engines on the underside for final deceleration and landing, and you have a sweet ship. You will still need landing gear, IMO. It can be pretty simple and lightweight but without it ground handling seems like it'd be a nightmare.

Yeah, I mentioned above that the RCS/OMS system is based on a hypergolic SuperDraco-style engine. You're right, though; linear aerospike engines can be used quite easily for pitch control during ascent but a horizontally-oriented vertical landing would probably be asking too much. And gimballing conventional engines by 90 degrees is out of the question. I am just wary of the weight cost of adding more thrusters for landing alone. I have a design knocking around in my head that would allow the ascent engines to be used for horizontally-oriented takeoff and landing, which is pretty much the ultimate spaceship fantasy, but it is air-augmented.

14 hours ago, Beowolf said:

I don't like combining cargo-carrying with crew. Yes, the shuttle did that, but with today's hindsight it was clearly a bad idea that forced them into an inherently unsafe design. What about all those times you just want to swap a few ISS astronauts? You're wasting the costly launch of a heavy-lifter, unless you just happen to also have a new space station module or 50 tons of satellites ready to lift as well. 

Certainly [using a drop tank with the Dragon V2 as the Falcon 9 upper stage] can [work]! I've done that in KSP using Laztek's Falcon 9, so obviously it works IRL, right?  

Heh. I'll run the numbers on that too, just for kicks.

Using a HLV for crew transport is a pretty big waste, I agree, but using completely separate systems instead of recombining components to fit each individual mission is a big waste as well. That's why I rather like the idea of a cargo shuttle with a removable crew module, so it can take crew up SSTO by putting an internal tank in its payload bay OR be configured for heavy lift by swapping out the crew module for additional tankage and slapping on some reusable boosters.

Edited February 10, 2016 by sevenperforce

[fredinno]

20 hours ago, sevenperforce said:

If you really want a replacement for the Shuttle, something that can put payloads into space regularly and be completely reusable...well, here you go.

41 meters high, 20 meters wide, 10 meters deep. Payload bay is the same size as the Shuttle Orbiter's, but the lack of control surfaces allows surrounding space to be used for additional fuel.

The engine is a truncated aerospike:

The high-thrust aerospike engines provide optimal thrust and Isp respective to altitude.

Optional/detachable cabin:

The crew cabin module has about half as much space as the Shuttle Orbiter but three times the space of the Dragon V2. It fits into the main body and is equipped with multiple high-thrust hypergolic engines which also act as the OMS and RCS system. These allow the crew cabin to eject during launch abort.

For crew transfer only, the payload bay is fitted with an additional internal tank and a disposable strap-on tank, allowing SSTO with the loss of the external tank alone. For unmanned flights, the crew cabin module is replaced with an autonomous control module with an auxiliary fuel tank but the same hypergolic engines. For manned flights including payload, or for higher-dV unmanned missions, 2-4 strap-on FH-style boosters are attached with propellant crossfeed; these detach at fairly low speed to return autonomously.

Re-entry will be...exciting. The aerospike already has to be able to handle very high heat fluxes and will probably already be actively cooled, so the orbiter enters tail-first and upside down to burn off most of its speed, with active use of the RCS system for stabilization. As soon as enough speed has dropped off, the orbiter begins to rotate forward, exposing more and more of its underside. The lower speed at this point means that the heat shield on its underside can be constructed of a lightweight, non-ablative, lower-performing, highly reusable material rather than requiring the tiles that the Shuttle used. Active RCS stabilization continues as speed decreases, ultimately entering a low-L/D gliding flight:

The orbiter does not make a very good glider and cannot manage a level approach, which is all the better because it doesn't have heavy landing gear. Instead, the RCS system returns the craft to a high angle of attack, and the aerospike engines are ignited, killing terminal velocity in a near-suicide burn. Then, the RCS system reduces power, allowing the angle of attack to drop until the orbiter is horizontal, and both the RCS system and the aerospike engines in combination fire to lower the orbiter to the ground:

If the aerospike cannot be directed downward enough to execute such a landing, then additional RCS thrusters can be incorporated in the aft portion of the orbiter.

Ambitious? Perhaps...but it seems like the best possible combination of geometry to allow for the capabilities of the shuttle with next-generation technology.

The amount of hypergolic fuel, internal fuel, and the number of strap-on boosters can be adapted to each mission. By using in-orbit staging and/or refueling, the orbiter could easily manage a lunar transfer. Depending on the fuel capacity of the crew cabin, it could manage a landing on its own on hypergolics, or lunar-orbit refueling could allow the entire orbiter to make the descent to the lunar surface and return to refuel and make the transfer to LEO again. The ability to take off and land vertically in a horizontal attitude reduces the instabilities and risks of vertical landings and allows far simpler crew egress.

Wouldn't making the rocket a little larger and packing fuel for supersonic retro prop be easier and a lot less risky?

Also, what are you using for Hypergolic/OMS/RCS?

Where's the docking port?

Also, the external tank thing in the cargo bay bothers me. That's a recipe for disaster- ie Shuttle-Centaur. Also, it's performance increase wouldn't be as big due to the fact it can't be dropped. Also, good luck fitting an auxiliary tank to the top and cargo bay- that's basically like cross-feeding, and that is DIFFICULT.

Why not just get rid of the cargo bay, and put all cargo in a "payload fairing" at the top?

[fredinno]

 

18 hours ago, Beowolf said:

I don't like combining cargo-carrying with crew. Yes, the shuttle did that, but with today's hindsight it was clearly a bad idea that forced them into an inherently unsafe design. What about all those times you just want to swap a few ISS astronauts? You're wasting the costly launch of a heavy-lifter, unless you just happen to also have a new space station module or 50 tons of satellites ready to lift as well. 

My support would go to dual programs. The smaller crewed craft would be >99% reusable, and nothing lost but fairings and SRBs on the cargo craft. Both should have simple enough support requirements that they could theoretically reposition to, and operate from, any simple spaceport worldwide with a single custom-built support building. The idea being to sell or lease them, rather than the manufacturer operating them.

The crew version, if winged, could perhaps be something like Faget's DC-3 shuttle. Yes, wings are wasteful but my goal isn't to be the most efficient, but to have the highest safety and lowest operating costs. Half a dozen astronauts and their gear don't mass very much, and being able to land either under power or with a shuttle-style glide is one heck of a safety feature.

For vertical launch systems, the 2016 version of Falcon 9 gets impressively close to qualifying. They're already assembled horizontally in a hangar, and have pretty simple support requirements, so no trouble there. But it isn't reusable enough yet. I'd want to see 2nd stages recovered and reused, and we'd have to do something about that trunk. Musk's said their internal analysis concluded recovering the 2nd stage was possible but not economically practical right now, so maybe the next generation. He clearly wants a fully-reusable system and is moving in that direction as fast as possible.

As for the cargo carrier, didn't you pretty much just describe what a Falcon Heavy's supposed to do? It's rated at 53 tons instead of 60, and we don't yet know about the maintenance costs or longevity, but otherwise your specs seem dead on target.

Or, for a traditionally-Kerbal solution, we could tie four Skylons together with struts and lift 60 tons.  

Certainly it can! I've done that in KSP using Laztek's Falcon 9, so obviously it works IRL, right?  

I think crew should go in Expendable LVs until there is enough demand- or on something like F9R.

"Both should have simple enough support requirements that they could theoretically reposition to, and operate from, any simple spaceport worldwide with a single custom-built support building. The idea being to sell or lease them, rather than the manufacturer operating them."

Bad idea- that would be painful to engineer- also, you'd never sell it like that anyways.

DC-3 is likely too big tho- those things usually also carried 10T cargo, and still have pretty big crewed areas.

 

3 hours ago, sevenperforce said:

53 tonnes to LEO, 20 tonnes to GTO, 16 tonnes to LLO, and 8 tonnes to LMO. If I remember correctly. Although those numbers are based on a Falcon Heavy comprising three Falcon 9v1.1 boosters rather then the larger, enhanced Full Thrust version. And whether the boosters are reused or not also factors in.

Odd, it does, although I had never seen those before.

I chose that shape because I wanted to maximize internal volume and re-entry cross-section but also maintain a small ascent cross-section to avoid excessive drag and aerodynamic loading. I also wanted the option of a crew module with the same basic shape for launch abort reasons. I need to run the numbers to see how close to SSTO this would get in its various configurations.

Yeah, I mentioned above that the RCS/OMS system is based on a hypergolic SuperDraco-style engine. You're right, though; linear aerospike engines can be used quite easily for pitch control during ascent but a horizontally-oriented vertical landing would probably be asking too much. And gimballing conventional engines by 90 degrees is out of the question. I am just wary of the weight cost of adding more thrusters for landing alone. I have a design knocking around in my head that would allow the ascent engines to be used for horizontally-oriented takeoff and landing, which is pretty much the ultimate spaceship fantasy, but it is air-augmented.

Heh. I'll run the numbers on that too, just for kicks.

Using a HLV for crew transport is a pretty big waste, I agree, but using completely separate systems instead of recombining components to fit each individual mission is a big waste as well. That's why I rather like the idea of a cargo shuttle with a removable crew module, so it can take crew up SSTO by putting an internal tank in its payload bay OR be configured for heavy lift by swapping out the crew module for additional tankage and slapping on some reusable boosters.

The 53T numbers are for disposable FH, that's why it's so high. I'm 99% sure the 2nd stage doesn't even have enough thrust to carry 53T to LEO.

 

[sevenperforce]

4 minutes ago, fredinno said:

Wouldn't making the rocket a little larger and packing fuel for supersonic retro prop be easier and a lot less risky?

Also, what are you using for Hypergolic/OMS/RCS?

Where's the docking port?

Also, the external tank thing in the cargo bay bothers me. That's a recipe for disaster- ie Shuttle-Centaur. Also, it's performance increase wouldn't be as big due to the fact it can't be dropped. Also, good luck fitting an auxiliary tank to the top and cargo bay- that's basically like cross-feeding, and that is DIFFICULT.

Why not just get rid of the cargo bay, and put all cargo in a "payload fairing" at the top?

Supersonic retrop prop at what point in the sequence?

I was thinking basically SuperDracos for hypergolic OMS/RCS. Docking port not illustrated; probably on top of the crew cabin or something.

The reason I was going to have a separate cargo bay was to allow for Shuttle-like operation in the specific cases where it would be needed -- for example, if you need to deliver a payload along with the crew members to install/operate it, or if you are doing a moon landing and need to bring along time-sensitive cargo. Of course, you'd need to have quite a few strap-on boosters in those cases, but that's part of the plan anyway.

You couldn't really put a payload fairing at the top per se. You'd need to replace the entire crew cabin with a payload module that would open to release the payload and then self-seal to protect the rest of the orbiter during re-entry. That puts tighter constraints on your payload dimensions than an internal centrally-located cargo bay.

Fitting an entire rocket upper stage with its payload into the cargo bay of the Shuttle was a bad idea, I agree, but a drop-in fuel tank could be specifically designed for the orbiter without much difficulty, I think. And why would adding an external back-mounted tank be a problem if the engines can handle lifting it? The Shuttle's external tank fed through the heat shields.

[fredinno]

1 hour ago, sevenperforce said:

Supersonic retrop prop at what point in the sequence?

I was thinking basically SuperDracos for hypergolic OMS/RCS. Docking port not illustrated; probably on top of the crew cabin or something.

The reason I was going to have a separate cargo bay was to allow for Shuttle-like operation in the specific cases where it would be needed -- for example, if you need to deliver a payload along with the crew members to install/operate it, or if you are doing a moon landing and need to bring along time-sensitive cargo. Of course, you'd need to have quite a few strap-on boosters in those cases, but that's part of the plan anyway.

You couldn't really put a payload fairing at the top per se. You'd need to replace the entire crew cabin with a payload module that would open to release the payload and then self-seal to protect the rest of the orbiter during re-entry. That puts tighter constraints on your payload dimensions than an internal centrally-located cargo bay.

Fitting an entire rocket upper stage with its payload into the cargo bay of the Shuttle was a bad idea, I agree, but a drop-in fuel tank could be specifically designed for the orbiter without much difficulty, I think. And why would adding an external back-mounted tank be a problem if the engines can handle lifting it? The Shuttle's external tank fed through the heat shields.

Retro prop likely in the final burn to land, and not use the flip-over thing. Another burn may be necessary to slow down its horizontal velocity tho.

Ah. It's just that toxic hypergol, like on the Superdraco, increases reuse costs a lot. RCS would likely be Rp-1/LOX + IVF, to minimise boil-off- though this would still limit lifetime.

A drop-in fuel tank would actually be pretty difficult- the tank in a enclosed space. Also, Shuttle-Centaur was designed for the Shuttle.

It's not really that external tanks aren't possible, but that doing so would pretty much be cross-feed, and add more enginneering difficulties to an already ambitious rocket.

[sevenperforce]

16 minutes ago, fredinno said:

Retro prop likely in the final burn to land, and not use the flip-over thing. Another burn may be necessary to slow down its horizontal velocity tho.

Ah. It's just that toxic hypergol, like on the Superdraco, increases reuse costs a lot. RCS would likely be Rp-1/LOX + IVF, to minimise boil-off- though this would still limit lifetime.

A drop-in fuel tank would actually be pretty difficult- the tank in a enclosed space. Also, Shuttle-Centaur was designed for the Shuttle.

It's not really that external tanks aren't possible, but that doing so would pretty much be cross-feed, and add more enginneering difficulties to an already ambitious rocket.

The reason I was going to suggest the tail-first retro burn was because the main propulsive engines are going to do a massively better job of slowing the ship down than hypergolic RCS engines, and with a lower propellant weight cost. I am trying to hammer out a design for an air-augmented engine that would be able to use the same engines to thrust vertically as horizontally without vectoring.

How is a drop-in fuel tank different from an internal fuel tank? And if I recall correctly, the Shuttle was retrofit to accommodate Shuttle-Centaur, not the other way around.

Edited February 10, 2016 by sevenperforce