Two stage Sanger space plane.

[Cloakedwand72]

Could this two stage Sanger space plane work with todays tech? I know the carrier aircraft would probably have heating problems like how the SR71 did at high altitudes. But could these problems be solved nowadays and would this concept make for a good crew LEO taxi?

[SunlitZelkova]

It could indeed work. China is making their own version called Tengyun.

It is only intended for cargo transport though, although bigger versions with the same concept of operations (hypersonic carrier aircraft and piggy back spaceplane) are expected to be developed in the future.

[wumpus]

"Today's tech" would probably be pushing it.  If you used rocket engines, the mass of the wings would make a huge disadvantage over retro-propulsion landings of a first stage.  If you used some sort of air-breathing first stage (or at least included air-breathing engines for the carrier craft), it would certainly be a stretch even if you hired the design team of the X-43.  And of course, re-entry of the orbital stage has all kinds of issues.

[magnemoe]

Workable, you would want an as fast as possible jet engine, guess you could get mach 4 pushing it. Then I put an rocket engine on the plane and LOX, this let you get faster. 
Its an trade off here between liftoff mass and second stage size. For cargo one option is to put the payload internally, you release it in space so it does not need to be aerodynamic. 

Much more efficient than an rocket even Starship, but the plane would be much more expensive to develop and build. 
But its something you could build in the 70's.  

[steve9728]

Here we go

[wumpus]

On 3/15/2022 at 1:52 PM, magnemoe said:

Workable, you would want an as fast as possible jet engine, guess you could get mach 4 pushing it. Then I put an rocket engine on the plane and LOX, this let you get faster. 
Its an trade off here between liftoff mass and second stage size. For cargo one option is to put the payload internally, you release it in space so it does not need to be aerodynamic. 

Much more efficient than an rocket even Starship, but the plane would be much more expensive to develop and build. 
But its something you could build in the 70's.  

I have to suspect that renting out Stratolauncher would be a lot cheaper and roughly as effective than any 1970s tech airplane.  There isn't that much delta-v to grab (although the first bit matter the most).  Obviously too much of a "not invented here" for China, but in general you are reinventing stratolauncher unless you are using ramjets/scramjets/SABRE.

[KerikBalm]

On 3/17/2022 at 5:06 PM, wumpus said:

I have to suspect that renting out Stratolauncher would be a lot cheaper and roughly as effective than any 1970s tech airplane. 

No, just no.

https://en.wikipedia.org/wiki/Scaled_Composites_Stratolaunch#Specifications_(Model_351_Stratolaunch)

Performance

• Maximum speed: 460 kn (530 mph, 850 km/h)

That's a maximum speed of just 236 m/s

On 3/17/2022 at 5:06 PM, wumpus said:

There isn't that much delta-v to grab (although the first bit matter the most).  Obviously too much of a "not invented here" for China, but in general you are reinventing stratolauncher unless you are using ramjets/scramjets/SABRE.

Well, the Sanger design did propose using ramjets:

https://en.wikipedia.org/wiki/Saenger_(spacecraft)#Design

The 2nd variant: https://en.wikipedia.org/wiki/Saenger_(spacecraft)#Variants 

would release the 2nd stage at mach 7 (I suspect the hybrid turbboramjet/air turbo rocket https://en.wikipedia.org/wiki/Air_turborocket would have a closed cycle mode like the SABRE, but without any of that precooler business, or the 1st stage would have rocket engines itself to boost higher).... that works out to roughly 2,100 m/s.

That's a whole lot more dV than the stratolaunch gets you.

The stratolaunch gets you freedom to launch into different inclination orbits, and simplifies nozzle design allowing one to stick with a more vacuum optimized nozzle without compromizes for high air pressure of the first stage.

The 2 stage spaceplane designs like sanger (or even early STS concepts) have the carrier plane contributing large amounts of velocity to the 2nd stage.

[wumpus]

The point of stratolaunch isn't delta-v, but reduced air pressure on the nozzle of the spacecraft.  Launching with something optimized 90% or more closer to vacuum than sea level was presumably worth it for Pegasus and Virgin Orbital.  They don't care about the delta-v.

I'm only aware of 2 teams that managed to operate near mach 7.  Hyshot managed 7.6 (the first with net thrust, the second didn't achieve it), but needed to be started at mach 7.  X-43 managed 6.8 (starting below mach  3?) and net thrust (barely) at mach 9.6 (starting at mach 9.6).

https://en.wikipedia.org/wiki/NASA_X-43

Check the in-flight picture.  The shiny metal part is the X-43 "plane", the white part is "booster".  Current tech (let alone 1970s tech) is going to require a booster similar to a Saturn V to boost a 747-sized mach 7 carrier (maybe you can buy an SLS or Superheavy).

On the other hand, a Falcon 9 booster is perfectly capable of hitting mach 6-7, delivering an upper booster, and returning for  re-use.  The only realistic advantage for a scramjet is reduced fuel usage (which has to justify the airframe needed to guide enough air in the intakes to achieve the thrust).  The cost of launching a Falcon 9 is in the millions and the cost of the fuel is ~$30k.  Perhaps with Starship (or possibly a Rocketlabs competitor or even New Armstrong) rocket, the fuel costs will be  enough of a significant ratio to add scramjets (or maybe just air augmentation) to Superheavy.

For the 2020s anyway, you want to rent Stratolaunch for things like that.  Because you aren't getting the delta-v from an airbreather for remotely acceptable cost.