Project Orion Vs Medusa

[EpicRootHairCell]

What are the relative advantages of a Orion style space craft and a Medusa style space craft? I understand the advantage of nuclear pulse propulsion over more conventional methods, namely both high thrust and specific impulse but I cannot find the comparative advantages and disadvantages between them.

[Ralathon]

Medusa is tensile based and has a much larger collection area. This means a Medusa spacecraft can be much lighter meaning more dV. However, it is much harder to make a sheet that can survive repeated nuclear blasts.

So Medusa is higher efficiency and lighter, but more taxing on your materials while Orion is very heavy but relatively simple. Orion also has the added advantage where the pusher plate simultaneously acts as radiation shield for the payload.

[Idobox]

Orion use a heavy pusher plate and dampener. Heavy is bad.

Medusa uses a light parachute thing, and a length of rope, which is better.

That being said, you need to make a parachute and ropes able to survive many blasts, and the pusher plate of Orion also serves as shielding for the craft, so Medusa needs additional shielding

edit : ninja'd

[Aghanim]

Orion could be use as single stage to Mars orbit vehicle (and all environmentalists are screaming in pain) while Medusa cannot.

[NERVAfan]

Orion could be use as single stage to Mars orbit vehicle (and all environmentalists are screaming in pain) while Medusa cannot.

I think it can do even better than that -- Earth to Enceladus, IIRC.

[KASASpace]

One fact not being considered is stability.

A trailer type craft, where the engines "pull" the vehicle along, is more stable than a tractor, where it gets "pushed"

So, Medusa is more stable.

[rdfox]

Orion use a heavy pusher plate and dampener. Heavy is bad.

Actually, Freeman Dyson and the rest of his team were very shocked to find out that, due to the need to keep the acceleration down to levels that were survivable, nuclear pulse propulsion actually *gains* efficiency with increased mass (to a point--I believe they found that the break-even point was a 500 ton SSTO design using 1 kiloton devices, but don't quote me on those numbers). This is because the vehicle's increased mass reduces the acceleration from each force pulse, and thus reduces the amount of shock absorption required to keep the G loadings in the tolerable range. Once you reach the break-even point, where your maximum acceptable G loading won't be exceeded even with a fully rigid system (no shock absorption), THEN heavy becomes bad, but up until then, counterintuitively, a heavier Orion-type ship is MORE efficient, because it spends less of the mass budget on the shock damping, freeing that up for payload.

(As a side note... I will always tear my hair out at how ST:TNG convinced everyone that it's "dampener." It's not. A damper is something that reduces the effects of something else--indeed, the car parts known as "shock absorbers" in North America are generally referred to as "dampers" elsewhere. A dampENer is something that gets other things wet.)

[Jolbucley]

Actually, Freeman Dyson and the rest of his team were very shocked to find out that, due to the need to keep the acceleration down to levels that were survivable, nuclear pulse propulsion actually *gains* efficiency with increased mass (to a point--I believe they found that the break-even point was a 500 ton SSTO design using 1 kiloton devices, but don't quote me on those numbers). This is because the vehicle's increased mass reduces the acceleration from each force pulse, and thus reduces the amount of shock absorption required to keep the G loadings in the tolerable range. Once you reach the break-even point, where your maximum acceptable G loading won't be exceeded even with a fully rigid system (no shock absorption), THEN heavy becomes bad, but up until then, counterintuitively, a heavier Orion-type ship is MORE efficient, because it spends less of the mass budget on the shock damping, freeing that up for payload.

(As a side note... I will always tear my hair out at how ST:TNG convinced everyone that it's "dampener." It's not. A damper is something that reduces the effects of something else--indeed, the car parts known as "shock absorbers" in North America are generally referred to as "dampers" elsewhere. A dampENer is something that gets other things wet.)

First of all, thank you for clearing that damper business up. Second, even if heavier is good, you still don’t want to have a heavier propulsion system, which I think is what Idobox meant. Medusa’s winch-style damping makes the drive system much lighter that Orion’s push plate plus piston dampers, which means even more of your ship can be payload than in Orion’s case.

We should note that a Medusa-style propulsion system is not a feasible SSTO option, as the sail would have to be in the air before launch in order to avoid being obliterated. The system is supposed to deploy in space; if we want to use a nuclear pulse propulsion system for launch, Orion is a much better idea.

[Nothalogh]

What are the relative advantages of a Orion style space craft and a Medusa style space craft? I understand the advantage of nuclear pulse propulsion over more conventional methods, namely both high thrust and specific impulse but I cannot find the comparative advantages and disadvantages between them.

The advantage is that Orion can be built tomorrow all with the existing technology of the 1960s

- - - Updated - - -

500 ton SSTO design using 1 kiloton devices

500 ton SSTO

The very concept makes me smile like a maniac

[ChrisSpace]

They are both really dumb ideas. Your welcome.

[steve_v]

Personally, I'd beg to differ. But as you provide no reasoning whatsoever, I guess you're entitled to your opinion.

[CalculusWarrior]

They are both really dumb ideas. Your welcome.

I agree. Suggesting to provide a spacecraft with propulsion by nuking the hell out of it is a phenomenally stupid idea. But hey, if it's stupid and it works, it's not stupid.

[steve_v]

If the physics works, it works. Implementation might be a little problematic though, and the politics downright unpleasant

I too like the concept of the '500ton SSTO', but the idea of detonating hundreds of nuclear weapons inside the atmosphere might meet a little resistance.

- - - Updated - - -

I guess my vote goes to medusa, if only because space is a somewhat safer environment for playing with nukes, as far as long term consequences go.

[Rune]

Hum. I guess it would depend on what you are going for.

If it is a ship meant to do "short" jaunts about a star system, with a mass on the order of thousands of mT, the old Orion pusher system is probably best, since it allows tail landings and takeoffs, and a more "manoeuvrable" ship to orient for "burns". Hell, it could have a secondary chemical system of titanic proportions for RCS and/or soft terminal touchdowns. In this design, you really don't care about efficiency since your effective exhaust speed is a few orders of magnitude higher than your mission dV.

Now if you are building a starship, to push out the maximum dV (guesstimated at around 5-12% of c depending on a bunch of assumptions), then you want to go really big, so you can use very efficient thermonuclear pulse units of high yield (>1 megatons). And then probably the Medusa configurations will save you a few million tons in structural mass. I'm talking about a humongous generation starship with a habitat the size of a O'Neil colony at least, of course.

Both things, are, shall we say, some time away. But it's comforting to know right now that both are very buildable, and the science has been proven for literally, generations.

Rune. OTOH, these things would be a child's play to build for a solar-system-wide civilization, with a taxpayer base numbering in the trillions.

Edited September 1, 2015 by Rune

[jfull]

Orion also has the added advantage where the pusher plate simultaneously acts as radiation shield for the payload.

I've also heard that it could be used as a heat shield if you plan on landing the whole craft as a one-way colony shot to mars

[Rakaydos]

Hum. I guess it would depend on what you are going for.

If it is a ship meant to do "short" jaunts about a star system, with a mass on the order of thousands of mT, the old Orion pusher system is probably best, since it allows tail landings and takeoffs, and a more "manoeuvrable" ship to orient for "burns". Hell, it could have a secondary chemical system of titanic proportions for RCS and/or soft terminal touchdowns. In this design, you really don't care about efficiency since your effective exhaust speed is a few orders of magnitude higher than your mission dV.

Now if you are building a starship, to push out the maximum dV (guesstimated at around 5-12% of c depending on a bunch of assumptions), then you want to go really big, so you can use very efficient thermonuclear pulse units of high yield (>1 megatons). And then probably the Medusa configurations will save you a few million tons in structural mass. I'm talking about a humongous generation starship with a habitat the size of a O'Neil colony at least, of course.

Both things, are, shall we say, some time away. But it's comforting to know right now that both are very buildable, and the science has been proven for literally, generations.

Rune. OTOH, these things would be a child's play to build for a solar-system-wide civilization, with a taxpayer base numbering in the trillions.

An interesting concept, and even with your conservitave numbers for maxumun DV (.05C) you're looking at 80 years to Alpha Centauri. One of the benifits of a medusa format also, is you can use it as a Solar Sail for stopping at your target system, too, though you should probably reserve some DV for slowing down to managable speeds first...

[SciMan]

To be honest, I like the slightly "tamer" idea of inertially confined laser initiated fusion of D/He3 pellets in a magnetic nozzle.

Of course, it's a firecracker under a tin can in comparison.

On the other hand, it can get better performance because the magnetic nozzle directs the reaction products mostly in the direction opposite of thrust, which is much more efficient than the "surfing the blastwave" that Orion relies on.

Now, if you wanted to go totally "feasible in the 1960's, but absolutely crazy", you want a Nuclear Salt-Water Rocket.

Take an orion drive, and remove the "pulsing" from separate bombs going off in succession.

Instead, you have a mixture of water and enriched uranium that will reach a critical mass if enough of it collects in one place, and a way to contain and direct the resulting continuously detonating nuclear fireball. That last part is the difficult bit, but the reward is something that has both extremely high thrust and high specific impulse.

[Nothalogh]

Nuclear Salt-Water Rocket

Oh hell, the one design that actually gives me the heebie jeebies