Any plausible non chemical rocket based space launch system on Earth?

[GTOM]

I write an sf story, and an important part is an attack on a big, expensive space launch system on Earth.
But what system could be built without pretty much magic? Looks like space elevator couldnt be made even from carbon nanotubes.
Maybe a space cannon, that could launch cargo to space with suborbital speed, then lifted further with nanotube cables and a space station below GEO orbit?

 

[.Scott]

Perhaps "SpinLaunch", which is cargo-only.
Also, if you are looking to avoid "big, expensive", then a space elevator wouldn't fit the bill.
There is also "Air-launch-to-Orbit".

This paper describes a proposed 120-foot super-sonic jet carrying a SpaceX Falcon 1 for launch to orbit. For comparison, the Concorde SST was about 200 feet long.

 

[phyzguy]

It's a story. Just say there was a breakthrough in high strength materials that made the space elevator possible.

 

[Filip Larsen]

Depending on how "feasible" the launch system must be, it may be quite tricky to come up with a system that doesn't use chemical rockets.
One option could of course be a nuclear SSTO, if such will fly with your story universe.
Or perhaps some kind of air breather (meaning chemical jet propulsion rather than chemical rocket) to bring the cargo high into the atmosphere and then something like a skyhook to lift it into orbit, but even then both the skyhook and the orbital cargo would require additional momentum change and there are only so many ways you can that while in orbit. For instance, circularizing cargo orbit from a sub-orbital injection trajectory is not super feasible to do with electric rockets.

 

[DaveC426913]

Sorry, what's wrong with the Beanstalk (space elevator)? It's not happening now, but do you really think it's a dead-end?

OK, what about a skyhook then?

 

[GTOM]

Perhaps "SpinLaunch", which is cargo-only.
Also, if you are looking to avoid "big, expensive", then a space elevator wouldn't fit the bill.
There is also "Air-launch-to-Orbit".

This paper describes a proposed 120-foot super-sonic jet carrying a SpaceX Falcon 1 for launch to orbit. For comparison, the Concorde SST was about 200 feet long.

It describes a rocket in the stratosphere phase. Could it really withstand such big acceleration?

 

[GTOM]

Sorry, what's wrong with the Beanstalk (space elevator)? It's not happening now, but do you really think it's a dead-end?

OK, what about a skyhook then?

i dont want to bring some sort of unobtanium to explain how it can hold the weight. the structure should be still ruinable without nukes.

 

[.Scott]

By "It", I am guessing you mean the SpinLaunch system ... And by "it", I am guessing you mean the SpinLaunch second stage.
Yes, a second stage rocket can be designed to withstand the 10,000Gs inflicted by a SpinLaunch launch.

 

[DaveC426913]

i dont want to bring some sort of unobtanium to explain how it can hold the weight. the structure should be still ruinable without nukes.

An incremental advance in carbon nano-fibre tech?

Last I heard, the rate-limiting step wasn't the strength of the fibre, it was the ability to produce 35,000 miles of it (and do so in space).

 

[Hornbein]

Rail gun? It would big and expensive, I think.

 

[GTOM]

An incremental advance in carbon nano-fibre tech?

Last I heard, the rate-limiting step wasn't the strength of the fibre, it was the ability to produce 35,000 miles of it (and do so in space).

Well, for story purposes, it should be destructible from the ground.

 

[oz93666]

Imagine a long tube about a meter in diameter , 100km long . The start of the tube is horizontal but gently curves upwards using a tall mountain , like Everest , for support , perhaps tunneled through the mountain at places , end of the tube is about 30deg to horizontal ...
So the tube has air evacuated , the capsual is electromagnetically accellerated , low g force due to long length and gentle curve , when capsule reaches end of tube closure (door) is opened at end of tube to let capsule out.

 

[GTOM]

Imagine a long tube about a meter in diameter , 100km long . The start of the tube is horizontal but gently curves upwards using a tall mountain , like Everest , for support , perhaps tunneled through the mountain at places , end of the tube is about 30deg to horizontal ...
So the tube has air evacuated , the capsual is electromagnetically accellerated , low g force due to long length and gentle curve , when capsule reaches end of tube closure (door) is opened at end of tube to let capsule out.

the nasty part is when air hit it. At another place, they said no present day material withstand that if cargo reach orbital speed in thick air.

 

[oz93666]

Well , there won't be much air to hit way above the height of Mt Everest .. Search shows it's a third of sea level atmospheric pressure .... at Mach 20 a nicely pointed nose on the capsule should cut through the remaining air without too much drag or heating , and then a very small booster rocket ignites.

 

[oz93666]

The above is a bit like Bransons 'Virgin Orbit' idea which failed from lack of finance ... only he took the payload (in a small rocket ) up to Mt Everest height in a 747 , then fired it into orbit ... If you can get above those first 10km of dense atmospher you save a lot of fuel/energy.... The big difference is , his rocket didn't even have Mach 1 at launch.

 

[.Scott]

How about using a balloon to carry the second stage to 30Km altitude.
If you use this in your story, I wouldn't call it "Acme Space". Not only would that be a hokey name, but it's also the name of the company that plans on doing it (and the source of the rendition above).

 

[Drakkith]

If you can get above those first 10km of dense atmospher you save a lot of fuel/energy....

Not really. You need about 7800 m/s of delta V to get to orbital speed, and an additional 1,500 to 2,000 m/s to account for gravity losses, drag, etc. Of that additional delta V, the majority of it, between 1,000 and 1,500 m/s will be lost to gravity losses. So you're looking at maybe 500 m/s of delta V lost to drag. This accounts for only around 5% of total delta V. Raising a multi-thousand-ton rocket up to any altitude would be far more expensive, complicated, and dangerous than simply launching it from the ground.

I do like the idea of a long launch tube that accelerates the rocket up to several km/s. It would be a massive project, but maybe you could get the end of the tube above 50,000 ft. Additionally, since you aren't accelerating the rocket using chemical engines during this whole process (which means mass isn't nearly as much of an issue), you have much more leeway as to how you build it. You could build some sort of cheap protective cover around the fragile rocket that better withstands the large aerodynamic forces and heating, which could then be jettisoned to fall back to Earth once the rocket is above 300,000 ft to save weight. Then you ignite the rocket engines and accelerate up the rest of the way conventionally.

Even if you could get just 2.5 km/s, this is an ENORMOUS weight savings. The Saturn V first stage had a mass of 2,200 tons out of a total of 2,800-2,900 tons for the total mass of the launch vehicle, but only accelerated the vehicle up to about 2.4 km/s. You could potentially reduce the size/mass of the rocket by 2/3 using this method.