Forum designs new rocket to replace the SLS

[magnemoe]

22 minutes ago, shynung said:

Glide back, so the booster can use every last drop of propellant to push the main stack. The wings and landing gear would be sized for an empty booster, and it would have no parachutes or wheel brakes -  just a tail hook, to stop it Navy-style.

Glide back is more fuel efficient, but its also far more complex and expensive to develop. When do you fold out the wings, you are supersonic all the time until glide. 
However it will also depend on your release attitude, higher make it less efficient unless you add an atmospheric engine for fly back. 
You can also do barge landings with boost.  
 

[sevenperforce]

58 minutes ago, shynung said:

Glide back, so the booster can use every last drop of propellant to push the main stack. The wings and landing gear would be sized for an empty booster, and it would have no parachutes or wheel brakes -  just a tail hook, to stop it Navy-style.

One can assume that landing gear would be approximately equivalent in weight to landing legs, but unless the wings are wet, the wings themselves are almost definitely going to outmass propellant landing reserves...at least for ASDS recovery. And that's not even accounting for the additional body reinforcement you need for dual-axis operation.

On the flip side, I've had a reasonable amount of success with this design: feathered tail canards and very small wings work wonders. Aux engines mostly because the low-atmospheric L/D ratio isn't enough for a horizontal landing. Of course, it's more an upper stage design than a booster design.

The original SLS proposal, pioneered by the guys (and gals) from the NSF forums, was all about reusing Shuttle hardware and staff. That is no longer really part of SLS; thus, SLS is useless.

[wumpus]

16 minutes ago, magnemoe said:

Glide back is more fuel efficient, but its also far more complex and expensive to develop. When do you fold out the wings, you are supersonic all the time until glide. 
However it will also depend on your release attitude, higher make it less efficient unless you add an atmospheric engine for fly back. 
You can also do barge landings with boost.  

The Shuttle had a glide ratio of 4:1 [i.e. a brick] on those redonkulously massive wings.  Presumably there were reasons you couldn't use X-15 style wings (they worked fine at mach 4.  For mach 14 you might need shuttle wings).  I'd have to wonder if a few fins or maybe a more elliptical booster could allow a glide ratio of at least 1:1 (although I wouldn't be surprised if falcon can do that on its own).  At that point you have cut your terminal velocity (and thus your final suicide delta-v) in half.

[magnemoe]

16 minutes ago, wumpus said:

The Shuttle had a glide ratio of 4:1 [i.e. a brick] on those redonkulously massive wings.  Presumably there were reasons you couldn't use X-15 style wings (they worked fine at mach 4.  For mach 14 you might need shuttle wings).  I'd have to wonder if a few fins or maybe a more elliptical booster could allow a glide ratio of at least 1:1 (although I wouldn't be surprised if falcon can do that on its own).  At that point you have cut your terminal velocity (and thus your final suicide delta-v) in half.

Boosters will be slower than F9 first stage but still high supersonic. Extending the wings will be challenging unless you are so high you can ignore the atmosphere.

And for an SLS super heavy lift replacement it will be used so rarely adding re-usability would be pointless. The falcon super heavy would be an exception as it use existing hardware for boosters and here it would just be reusable for testing and for replacing falcon heavy disposable. 

[DDE]

OK, why hasn't anyone mentioned the Rombus?

To jump back on my Russian high horse, I do wonder what such a vehicle would come out looking like if it used tripropellant motors, with the drop tanks carrying kerolox while the center stage is hydrolox.

Edited May 21, 2017 by DDE

[shynung]

1 hour ago, magnemoe said:

Glide back is more fuel efficient, but its also far more complex and expensive to develop. When do you fold out the wings, you are supersonic all the time until glide. 
However it will also depend on your release attitude, higher make it less efficient unless you add an atmospheric engine for fly back. 

Which is why I intended this kind of thing to be a strap-on booster rather than the core - they're meant to be jettisoned pretty early on. They'd be using gas-generator cycle engines, sacrificing some specific impulse for pure TWR.

1 hour ago, sevenperforce said:

One can assume that landing gear would be approximately equivalent in weight to landing legs, but unless the wings are wet, the wings themselves are almost definitely going to outmass propellant landing reserves...at least for ASDS recovery. And that's not even accounting for the additional body reinforcement you need for dual-axis operation.

Well, yeah. We can make the wings wet, though that would make them thicker, creating additional drag.

OTOH, I'm also thinking of a blended wing-body rather than a winged-tube booster. Almost all of the internal volume could be used for propellant, plenty of space in the back for mounting several engines side-by-side, without sacrificing effective wing area. Of course, the additional drag is still there, plus the manufacturing costs would be much higher due to the complicated shape.

[53miner53]

My idea:

first stage: STS external fuel tank based with 3 RS-25E. Parachute recovery when possible

boosters: 2 updated F-1 engines per booster, 0, 2, and 4 booster configurations. Boosters would be recovered by parachute. 

second stage: single J-2X for small payloads, 2 for medium payloads, 3 for large payloads.

[sevenperforce]

23 minutes ago, shynung said:

OTOH, I'm also thinking of a blended wing-body rather than a winged-tube booster. Almost all of the internal volume could be used for propellant, plenty of space in the back for mounting several engines side-by-side, without sacrificing effective wing area. Of course, the additional drag is still there, plus the manufacturing costs would be much higher due to the complicated shape.

That would also be good for a second stage.

[Bill Phil]

Huh. Doing some math, an Atlas V and a skyhook about 2500 km long (yeah, that's long, but certainly more doable than a space elevator...) could put 76.5 tonnes into orbit. In just a single stage. Now the real problem is that we're running out of engine thrust... I guess we could use the Atlas V SRBs to help out a bit, and maybe boost payload slightly. Payload fraction is about 20%. Assuming fixed launch costs at 109 million, we get 1425 bucks a kilogram. Now, the Atlas V was never truly cost competitive, but eliminating the second stage may reduce cost by a good amount, and breaking the 1000 USD per kilogram barrier could* be done with a reusable rocket or with streamlined operations. Even this cost beats out the Falcon 9 in its current form, by more than a 1000 USD.

And this is an expendable kerolox booster. If reusability works out, then costs could go down quite a bit. Or if we used hydrolox, we could get higher payload mass fractions.

*this is about a tonne of salt

Also there's the cost of the skyhook itself, but that's likely to be government infrastructure like roads and canals, so the government would absorb most of the cost... and even if it didn't, the cost would likely amortize over time.

Edited May 21, 2017 by Bill Phil

[Jouni]

A few things to consider:

Payload size is more important than payload mass. If you can lift 50 tonnes in a single launch, you can lift 200 tonnes in four launches and assemble the payload in orbit. We already have decades of experience with that. On the other hand, if the payload is 10 m wide, assembling it will be complicated, if you can only lift 5 m wide payloads. This suggests that the core stage should be wide enough, perhaps 8 m or more.

Using additional first stages as boosters seems to be a cost-effective way to increase payload capacity. While the Russians have a 4-booster design, most others have concluded that using two boosters is the best trade-off between capabilities and complexity. Hence a conservative design should only use two boosters.

SpaceX has now reached the same point NASA reached a few decades ago. They have shown that partial reuse of launch vehicles is technically feasible. They do not know yet whether it is also reliable and cost-effective. While reusability should be a design goal, it should not be a critical element. The launch vehicle should still be viable, even if reusability turns out to be much harder than expected.

So: Aim for cost-effectiveness and avoid unnecessary complexity; design a wide rocket to launch big payloads; increase payload capacity with two optional boosters; and plan for reusability but do not rely on it.

[DDE]

6 minutes ago, Jouni said:

So: Aim for cost-effectiveness and avoid unnecessary complexity; design a wide rocket to launch big payloads; increase payload capacity with two optional boosters; and plan for reusability but do not rely on it.

Ahem...

[sevenperforce]

If the Raptor engine really does end up being as amazing as expected (TWR > 200 and vacuum isp over 380 seconds), then honestly it really only makes sense to use it for everything. Especially because methane is so cheap.

Not being a SpaceX fanboy here; just saying. Hence Raptor-derived Falcon X.

[sevenperforce]

Alternately, I wonder if a partially-airbreathing first stage would ever be worth developing. VTOL style.

[tater]

Why replace SLS when it already has no payloads?

Unless you have some payloads, indeed X per year worth, the replacement is "nothing."

[ZooNamedGames]

8 minutes ago, tater said:

Why replace SLS when it already has no payloads?

Unless you have some payloads, indeed X per year worth, the replacement is "nothing."

We're replacing what the original purpose of the SLS was. The idea being to provide a super heavy lift vehicle above that of what other groups (such as SpaceX or Blue Origin) can provide. The payloads being whatever requires a launcher that big; possibly Martian hardware?

And I'm keeping silent as everyone else knows plenty more than what I can add. I just want to pop my head in and explain.

[sevenperforce]

3 minutes ago, ZooNamedGames said:

We're replacing what the original purpose of the SLS was. The idea being to provide a super heavy lift vehicle above that of what other groups (such as SpaceX or Blue Origin) can provide. The payloads being whatever requires a launcher that big; possibly Martian hardware?

And I'm keeping silent as everyone else knows plenty more than what I can add. I just want to pop my head in and explain.

The original purpose of the SLS was to repurpuse Shuttle-era hardware and personnel. That won't happen.

[tater]

The purpose was as a jobs program.

[ZooNamedGames]

6 minutes ago, sevenperforce said:

The original purpose of the SLS was to repurpuse Shuttle-era hardware and personnel. That won't happen.

And provide heavier lift than what was available in 2010.

This portion being what we're intending to aim for.

[_Augustus_]

23 minutes ago, tater said:

The purpose was as a jobs program.

I really wish that rather than being forced to fulfill political directives NASA would be allowed to come up with ideas of their own and then propose them for funding....

[tater]

Any HLV program that requires a certain launch cadence (assume, say 2 B$ a year in program costs) needs to have payloads first. Set mission goals, then build a vehicle.

[ZooNamedGames]

Just now, tater said:

Any HLV program that requires a certain launch cadence (assume, say 2 B$ a year in program costs) needs to have payloads first. Set mission goals, then build a vehicle.

If you need a payload that badly assume it's a 70,000lb lump of steel. Our payloads range from scientific payloads like the new James Webb Telescope to potential Martian space station modules. 

[tater]

If those payloads are not funded to exist when the vehicle does, then you don't need it.

[ZooNamedGames]

24 minutes ago, tater said:

If those payloads are not funded to exist when the vehicle does, then you don't need it.

Like the Saturn V which was designed to carry a "lunar lander" (S-5 designed with the LM still early development) and like it, we can take the liberty of assuming it will be ready when we are.

It is not our responsibility to make sure it is, but if again it prevents you from focusing on the rocket; just remember: the payload is a 70,000lb lump of steel.

[53miner53]

2 hours ago, _Augustus_ said:

I really wish that rather than being forced to fulfill political directives NASA would be allowed to come up with ideas of their own and then propose them for funding....

I agree.

1 hour ago, tater said:

If those payloads are not funded to exist when the vehicle does, then you don't need it.

We could design a 50 ton spaceplane to strap to the top of it and resupply the ISS or bring public made science experiments to orbit and back. Or we could build a moon base with it. 

1 hour ago, ZooNamedGames said:

Like the Saturn V which was designed to carry a "lunar lander" (S-5 designed with the LM still early development) and like it, we can take the liberty of assuming it will be ready when we are.

It is not our responsibility to make sure it is, but if again it prevents you from focusing on the rocket; just remember: the payload is a 70,000lb lump of steel.

I think the phrase you're looking for is "if you build it they will come." Or something like that.

[ZooNamedGames]

4 minutes ago, 53miner53 said:

I think the phrase you're looking for is "if you build it they will come." Or something like that.

Works for me.