Stage 1 Reaching Escape Velocity And Returning

[Bhodi Li]

With modern spacecraft such as those produced by Space X and Blue Origin the first stage returns to the launch pad for reuse. I was thinking, what if we were to build a spacecraft where the first stage gets the spacecraft to escape velocity and once it does it can detach and return to the launch pad without the need of a second stage. The payload section would have small engines but those would mostly just be for guidance as there wouldn't really be any need to accelerate the craft any further once it reaches escape velocity.

 

[Hevach]

SSTO (single stage to orbit) has been a dream for decades. It's been a pipe dream, so far the tyranny of the rocket equation has killed every concept, and every technology that was hoped to make the difference, like aerospike engines, has fallen short.

 

[Classical Motion]

I am not a rocket engineer or a scientist but that aerospike engine concept is pure genius.

From what I have read, the size of our rocket engines is limited by that bell structure. Keeping the structure cool enough, long enough for the needed high powered high duration burns.

So we parallel smaller engines. Small bells.

If we invert the area of the bell concept, and put the combustion area outside the bell, we can mitigate the engine heat limitation.

With the bell, the combustion is corralled and directed with the interior surface of the bell. And it corrals the heat too.

With the inverted bell, the combustion is corralled on the outside of the inverted bell. The momentum is corralled, but not the heat.

And it can be arrayed, or a circular inverted bell. And the size can be large with present materials.

The output can be tuned into blurps. We can be seen. One could tune those blurp rates, with an adjustable length center spike. Or aperture.

Just supposition. I would suggest much more work on this engine. I love inverted thinking.

And then again, I might miss-understand the whole thing. Only I might be inverted.

 

[contrarian]

SSTO (single stage to orbit) has been a dream for decades.

Just for clarity, escape velocity is not the same as going into orbit. Orbital velocity requires about 17,500 mph for LEO.

Escape velocity is the speed required to get beyond the pull of earth's gravity, and is about 25,000 mph :

https://research.gatech.edu/why-does-rocket-have-go-25000-mph-escape-earth#:~:text=But even staging is not,into an orbit of Earth.

 

[Hevach]

I am not a rocket engineer or a scientist but that aerospike engine concept is pure genius.

They are quite brilliant. They have a much flatter performance curve with ambient pressure, so a single engine can perform viably at both sea level and in a vacuum. This isn't impossible with a bell nozzle, but where the RS-25 archives it with a deceptively complex novel geometry an aerospike does it mostly by virtue of being an aerospike.

When I say they fell short, I'm referring to early theoretical predictions from before robust computer modeling that ended up being very over promised. They didn't unlock SSTO ascents and mixed engine bell nozzles like nearly all rockets use today are still better in aggregate for staged ascents.

Upper stage recovery and reusability introduces some new options, though, as seen in Blue Origin's Jarvis. Rather than an SSTO where one engine has to work for an entire ascent the last stage needs to be able to function at sea level for recovery.

 

[Bhodi Li]

Just for clarity, escape velocity is not the same as going into orbit. Orbital velocity requires about 17,500 mph for LEO.

Escape velocity is the speed required to get beyond the pull of earth's gravity, and is about 25,000 mph :

https://research.gatech.edu/why-does-rocket-have-go-25000-mph-escape-earth#:~:text=But even staging is not,into an orbit of Earth.

The muzzle velocity of a slug from a .44 magnum can be 1000 mph. The muzzle velocity of a .220 Swift slug fired from a .220 Swift rifle, one of the fastest bullets in the world, is around 2800 mph.

That being said, escape velocity is quite fast, considering it's almost ten times the speed of a fast rifle round.