What It Would Take To Have Heavy Lift SSTO's (like Star Wars) IRL

[Bamax]

This is in no way better than the stuff Outsider uses, but it would be a start in the direction of making reality like scifi.

Sadly I doubt we have tech to pull it off, but nothing about the scheme is overall breaking what we know of science... so if our tech WAS good enough we COULD do the following:




Picture this.... a large belly lander SSTO, using reusable chemical rockets for VTOL to get in the air, and then it starts to nearly flip backward before firing it's main rear engine which has a single, thick bodied nozzle.

The main engine shoots out a long straight plume of bluish white fire in a single pulse, and despite the spaceship being large and heavy it literally shoots off with acceleration that is rapid.. like a tiny bottle rocket.



No slow rising here! This rocket engine has oomph to spare!



What is it?



Pure Fusion Pulse rocket: I basically considered what matterbeam wanted for a pure fusion orion and thought why not use that tech for a rocket?



What it would probably take to make:



Some sort of vacuum chamber lined with powerful super magnetic coils or devices. A pure fusion bomb would be inserted into a chamber and detonated, and the resulting fusion plasma would be shunted via magnetic fields into a reaction chamber where it would mix with the propellant as it leaves the nozzle.

Realistically I am not sure we have magnetic coils powerful enough and small enough that they do not need to be gigantic to pull off a feat of directing the plasma on par with a nuke for energy.

But we would need smaller more uber magnet tech to ever havs scifi SSTO's that take off like Star Wars on their bellies.



Unlike Star Wars I do not see constant flow pure fusion rocket SSTO's being a thing.



Why not?

Powerful high g pulsed acceleration is more fuel efficient than constant flow lower g acceleration.



High g pulsed acceleration does generate waste heat, but with sufficient ingenuity I don't see why that cannot be averted by dumping the heat into the propellant as it leaves the nozzle.



So... I think, if heavy SSTO's ever are made, they will be pure fusion pulsed rockets.

Using chemical rocketry to land.



Unlike project orion you do not have to lug around a heavy pusher plate and pistons, but I think the main advantage is that critical mass for a fission reaction no longer matters.

If I read correctly, pure fusion reactions can be scaled up or down as needed, which means if you want a smaller acceleration you can have it... not all your pulses need to be fusion death beams that leave a mini-mushroom dirt cloud where you launched from lol.

[Keklas Rekobah]

↑ You might want to check out the Atomic Rockets website.  It takes a more mathematical approach to the subject.

[Demarquis]

"Powerful high g pulsed acceleration is more fuel efficient than constant flow lower g acceleration."

Actually, that's wrong. It's the other way around.

[gaerzi]

Picture this.... a large belly lander SSTO, using reusable chemical rockets for VTOL to get in the air, and then it starts to nearly flip backward before firing it's main rear engine which has a single, thick bodied nozzle.

Is it truly an SSTO if it uses rockets for take off ?

If you mean it has internal rocket engines, that's one thing; but you said "reusable rockets" so that brings to mind a two-stage setup where at some point the rockets detach.

I'm also not sure about the interest of VTOL for a belly lander. The historical precedent here is the Space Shuttle, and you can compare its size to the size of the rockets used to lift it. No surprise that concepts for SSTO vehicles tend to be space planes.

This is especially true for landing, because you need as much energy to land vertically as you do for taking off. Whereas a conventional airplane-style landing can be done without power, just by gliding.

But, sure. It doesn't look as cool as Star Wars repulsorlift technology.

[Demarquis]

That's one reason why the SpaceX Starship design seems so counter-intuitive, at least to me. It's multi-stage to orbit, yet comes in gliding before going nose up and landing vertically. That's so backwards, yet it works.

To get SSTO, you need a lot of power density. There are drive designs that could deliver that level of power (Orion stye Nuclear Pulse rockets for example) but they aren't very clean (as in, "they kill everything downwind of the launching site and the flight path" not clean), so that's a problem.

[Bamax]

That's one reason why the SpaceX Starship design seems so counter-intuitive, at least to me. It's multi-stage to orbit, yet comes in gliding before going nose up and landing vertically. That's so backwards, yet it works.

To get SSTO, you need a lot of power density. There are drive designs that could deliver that level of power (Orion stye Nuclear Pulse rockets for example) but they aren't very clean (as in, "they kill everything downwind of the launching site and the flight path" not clean), so that's a problem.

The folks over at KSP know their space stuff, calculations included.

I recently learned that if one did detonate a fusion bomb and force it through the nozzle.... it would blow up the nozzle!

Basically.. the only heavy lift Star Wars belly lander that would be really viable would be a pure fusion bomb belly lander irion with a rear pusher plate.

Standard orion with common nukes require a critical mass, which means you really cannot scale down the blast by much.

Pure fusion (using high explosives and magnetic fields to compress fusion fuel to fusion) could scale down the blast since no critical mass like with fission is needed.

All you need to do is to compress some fusion fuel to fusion and you have a bomb.


Additionally, pure fusion bombs could in theory be made as strong as nukes.... but they have much less in the way of cancerous radiation afterward.

Pure fusion is so low with radiation that some fear it would open up their use to the battlefid with impunity.

[Demarquis]

I know that drive design by the term "Nuclear Pulse Propulsion" You can read about it here: https://en.wikipedia.org/wiki/Nuclear_pulse_propulsion

Or here: http://www.projectrho.com/public_html/r ... p#boomboom (that ISP should take you straight to "Orion" under "Pulse" If not, then do a "search on page" until you find it. There are many varieties and derivatives of this design, most of which you can read about there.

However, I have no idea how clean a magnetic confinement fusion pulse drive might be. Do you have a link for that?

[Bamax]

I know that drive design by the term "Nuclear Pulse Propulsion" You can read about it here: https://en.wikipedia.org/wiki/Nuclear_pulse_propulsion

Or here: http://www.projectrho.com/public_html/r ... p#boomboom (that ISP should take you straight to "Orion" under "Pulse" If not, then do a "search on page" until you find it. There are many varieties and derivatives of this design, most of which you can read about there.

However, I have no idea how clean a magnetic confinement fusion pulse drive might be. Do you have a link for that?

https://toughsf.blogspot.com/2022/03/fu ... d.html?m=1


It's a long article but worth it if you wanna know.

[Demarquis]

A new Tough SF article! Awesome.

[Bamax]

Actually there may be yet a case for a nozzle that can survive a plume so powerful it has the equivalent power of a nuke pushing it.
Accirding to nuke testing articles I have read, metal balls were suspened in the air above ground zero where a nuke would detonate.

The balls were covered with a thin layer of oil, and afterward the balls were found far away but otherwise intact and NOT melted.

Interestingly project Orion was supposed to employ the same trick of coating the plate with oil so that each blast would not slowly ablate it.

So why not employ the same trick between pulses on a rocket nozzle?

I actually think in this respect a rocket nozzle may be better, because not only will the exhaust be directed only where you need it, but with a bomb comes shrapnel, unless the casing was designed to be vaporized upon detonation.

At any rate I would fear bomb shrapnel may escape the bomb blasts and cause uneven wear on the pusher plate over time.

[avatar576]

Actually there may be yet a case for a nozzle that can survive a plume so powerful it has the equivalent power of a nuke pushing it.
Accirding to nuke testing articles I have read, metal balls were suspened in the air above ground zero where a nuke would detonate.

The balls were covered with a thin layer of oil, and afterward the balls were found far away but otherwise intact and NOT melted.

Interestingly project Orion was supposed to employ the same trick of coating the plate with oil so that each blast would not slowly ablate it.

So why not employ the same trick between pulses on a rocket nozzle?

I actually think in this respect a rocket nozzle may be better, because not only will the exhaust be directed only where you need it, but with a bomb comes shrapnel, unless the casing was designed to be vaporized upon detonation.

At any rate I would fear bomb shrapnel may escape the bomb blasts and cause uneven wear on the pusher plate over time.

I think the problem with using a nozzle to direct exhaust from a nuclear explosion is that the explosion itself must be contained within a combustion chamber. The shrapnel you'd need to worry about would likely come from the vehicle itself as you blow the whole thing to smithereens. Unless it was a very, very large nozzle. (Kinda wish I still had all my notes from my propulsion classes in college now)
But it's like the old saying about firecrackers. Hold a lit one in the palm of your hand and you'll be wearing bandages for a week. Hold one in a closed fist and your mother will be tying your shoes for you for the rest of your life.

[Bamax]

Right.... elsewhere I learned the pressure would blow up the reaction chamber.

In fact the only way to avoid that is with uber diamagnetic fields we do not have the tech to even make.

And yes the nozzle would be huge.

So the irony is pusher plate orion remains the only way we know of getting massive payloads to orbit all at once.

Getting stuff back down again (a fully loaded Orion) is not happening.

It would take multiple shuttle orange giant boosters to land a huge orion.

So at best one could load an orion Spacex witj starships as shuttlecraft.

[Demarquis]

Which is why people speculate about things like space elevators.

[QuakeIV]

An orbital ring is a lot more practical and realistic.

[Demarquis]

Another solution is the so-called "Sky Hook", or, as I prefer to call them, "Space Tethers": technology that transfers passenger craft from atmosphere to interplanetary orbit using technology we could manufacture today. https://www.youtube.com/watch?v=dqwpQarrDwk

Note that this idea is especially compatible with the spaceplane design.