My idea for a nuclear pusher plate launch

[Spacescifi]

Step one: Build a VERY long magnetic rail tunnel on the ground that can flip upward to vertical, thus standing hundreds of kilometers in the air. When not in use it will flip back onto the ground. It must be tall enough to escape much of the denser atmopsheric layers.

 

Step two: Build a fleet of orions that can fit in the magnetic rail tunnel that can ride the rails.

Step three: Have one ship at a time ride the magnetic rail as it it is vertical and launch it into the air clear of the rail tower so that when it does to the pulse detonation, the launch tower won't be obliterated.

Step four: Have the orion tilt in flight for orbital trajectory. Done! Go where you wanna go.

 

 

Like I have said before in a prior post. I actually favor horizontal belly lander orions, with dual axis landing thrusters for VTOL. While the ship uses it's pusher plate to actually get to orbit and would have to flip upward. Fortunately the ship should not have to do that on Earth. since that is what the magnetic rail tower would be for for launching.

 

It should be able to land anywhere safely though with a combination of chemical fuels, with maybe a nuclear reactor with heat exchangers to get more thrust per pound of fuel spent.

 

 

[DDE]

1 hour ago, Spacescifi said:

Step one: Build a VERY long magnetic rail tunnel on the ground that can flip upward to vertical, thus standing hundreds of kilometers in the air.

Maybe just a space elevator?

Orion is interesting precisely because it's easily built with 1960s tech.

[Guest]

An assisted launch with Orion is a good idea, though. Not for people, mind you (I'm not convinced this kind of pulse propulsion is very good for crewed launches, anyway), but for getting huge payloads into orbit. The mass driver (no curved track needed, just a big coilgun) would launch the Orion high enough to prevent the nuke from causing problems on the ground. Landing would be by giant parachutes and lithobraking with the pusher plate. Full reuseability, no miracle tech, dead simple in concept. 

[DDE]

13 minutes ago, Dragon01 said:

The mass driver (no curved track needed, just a big coilgun) would launch the Orion high enough to prevent the nuke from causing problems on the ground.

Ground launch isn't less safe than air launch, so long as you use a big graphite plate to avert undesirable types of fallout.

[sturmhauke]

2 hours ago, Spacescifi said:

Step one: Build a VERY long magnetic rail tunnel on the ground that can flip upward to vertical, thus standing hundreds of kilometers in the air. When not in use it will flip back onto the ground.

That would need to withstand immense shear and torque forces and be incredibly lightweight. You're basically talking about magic at that point.

[Guest]

21 minutes ago, DDE said:

Ground launch isn't less safe than air launch, so long as you use a big graphite plate to avert undesirable types of fallout.

Yes, but a mass driver would also reduce pulse unit consumption and size (if you launch it high enough, you don't need TWR>1, meaning more payload for the same pulse unit size). Also, a graphite plate would necessitate some very mobile launch equipment for payload handling and the like, which you'd have to get out of way before launch. Assisted launch would allow just loading the Orion onto the launch rail, integrating the payload and launching when ready, without fussing about with mobile servicing systems. With a mass driver you could It would also be a safety benefit if the first pulse unit was fired over water, as opposed to close to the ground (so in case of a failure the whole shebang ends up in the ocean, instead of crashing to the ground). You wouldn't even have to loft it very high.

[wumpus]

One thing you seem to ignore is the shear size of an Orion.  You could make an unmanned one small, but in general both the pusher plate and the rest of the vessel require a lot of inertial mass.  Think roughly the size of a WWII battleship (or small modern carrier) and you might grasp the size of these things.  Putting it on magnetic rails and zipping it off to space is clearly off the table.

Who knows, maybe someone may try a fuel-air pusher plate done at a small-scale.  According to the last thread that eventually became a pusher-plate thread, that may be possible (at least for the first stage, you'll need a more conventional vacuum stage after that).

[razark]

Good thinking.  Giant, mobile towers, hundreds of kilometers high¹, with enough power to magnetically throw an aircraft carrier.  Once we manage that engineering, we've got quite a few problems knocked out.

What does that level of magnetic field mean to any electronics in the projectile vehicle?

And what could go wrong with high-altitude nuclear detonations?

 

"hundreds of kilometers in the air"
"tall enough to escape much of the denser atmopsheric layer"

If you don't see what's wrong with that, you really need to start over at square one.

 

 

¹And flexible ones, no less, else they wouldn't exactly lay flat and out of the way when not in use, would they?

Edited August 29, 2019 by razark

[DDE]

7 hours ago, Dragon01 said:

(so in case of a failure the whole shebang ends up in the ocean, instead of crashing to the ground)

Not sure the need to recover unspent nukes from under water is an improvement.

8 hours ago, sturmhauke said:

That would need to withstand immense shear and torque forces and be incredibly lightweight. You're basically talking about magic at that point.

A spacescraper, specifically.

 

8 hours ago, Dragon01 said:

(if you launch it high enough, you don't need TWR>1, meaning more payload for the same pulse unit size)

Orion is not thrust-limited, and larger pulse units are desirable.

[Nothalogh]

12 hours ago, Spacescifi said:

escape much of the denser atmopsheric layers.

Orions gain efficiency with atmospheric density.

They are the anti-rocket.

 

[kerbiloid]

7 hours ago, wumpus said:

Who knows, maybe someone may try a fuel-air pusher plate done at a small-scale. 

A fuel-air makes a shockwave and a local pressure in a static medium.
While Orion doesn't need a shockwave, in needs a moving medium (gas flow), accelerated by its shaped charge.

1 hour ago, Nothalogh said:

Orions gain efficiency with atmospheric density.

It may gain or may not, depending on certain circumstances.
It needs a gas flow.

In vacuum the gas jet flows until it dissipates. It pushes Orion.
In atmosphere any gas flow gets stopped by atmospheric pressure visible as a shining sphere.
Next to that, a spherical shockwave (originally expanding as fast as the hot sphere) breaks from it and keeps moving in stattic medium.
The free shockwave doesn't move air, it causes a raise-and-fall of local pressure. It can throw light weight objects or push objects with great cross-section area, but Orion doesn't need a shockwave hit, it needs the gas flow.

So, in atmosphere Orion show keep moving with its plate right next to the surface of the fireball, at 8000 K temperature and on the shocwave.
It's bad itself. But more of that, as the atmosphere conditions would be changing every several hundred meters, i.e. every blast, its trajectory should be perfectly adjusted with the nukes.

So, unlikely launching Orion in atmosphere more than once after building is a good idea.

***

As originally the Orion project have grown up from a shaped warhead nuke , and the combat version of Orion should be armed with Casaba nuke howitzers *.
So, let's build an Orion Shooting Tug.

One Orion (a barge), with plate but without nukes flies forward.
Another Orion (a tug), a full-featured one, and armed with a nose cannon, flies behind and shoots after him.
So, the self-propelled Orion tug pushes the nukeless Orion barge.

We can use one nuked Orion with several Orion barges on demand.

 

* Still can't get, why "howitzer" when it's a projectile gun, rather than a ballistic one. Probably they like how this word is written.

[Guest]

9 hours ago, DDE said:

Orion is not thrust-limited, and larger pulse units are desirable.

From raw performance standpoint, yes. From economic standpoint? A larger nuke contains more highly enriched uranium, which is expensive. As always in those cases, it's a matter of what grows faster: money you can get from payload, or the cost of the nuke. Not only that, a large vehicle is, itself, a bigger engineering problem, subject to greater stresses and so on. If you plan on making a habit of launching those things (and if you're even considering a mass driver, you are), those are important considerations. Electricity from a power plant will always be cheaper than a nuke, because enriching uranium to weapons grade is expensive, while enriching to powerplant grade is less so. 

10 hours ago, DDE said:

Not sure the need to recover unspent nukes from under water is an improvement.

It's better than them impacting the ground, likely setting off the conventional explosives and scattering uranium all over the place. Water is pretty good at containing radioactive materials. Quite a few Orion concepts used conventional rockets for initial acceleration, and for good reason. For low rate non-reusable launch operations, a graphite plate is a simpler solution, but again, any scenario involving mass drivers assumes routine usage. The graphite pad would wear out faster than a coilgun, especially seeing as the former would be repeatedly nuked at contact range and the latter would not.

[Bill Phil]

31 minutes ago, Dragon01 said:

From raw performance standpoint, yes. From economic standpoint? A larger nuke contains more highly enriched uranium, which is expensive. As always in those cases, it's a matter of what grows faster: money you can get from payload, or the cost of the nuke. Not only that, a large vehicle is, itself, a bigger engineering problem, subject to greater stresses and so on. If you plan on making a habit of launching those things (and if you're even considering a mass driver, you are), those are important considerations. Electricity from a power plant will always be cheaper than a nuke, because enriching uranium to weapons grade is expensive, while enriching to powerplant grade is less so. 

Actually costs for nuclear explosives generally don’t increase as fast as yield. Fission boosted weapons can have much higher yields than normal atomic bombs with the same mass of fissile material (higher burnup fraction) and thermonuclear explosives also use less expensive materials for secondaries.

Basically bigger Orion pulse units will cost more, but not extremely so, and the cost per unit impulse will likely not increase substantially.

Bigger Orions will of course cost more in absolute terms, but their performance will be much higher - it’s entirely possible that bigger Orions will be cheaper per kg than smaller ones. 

[magnemoe]

Build it in orbit or combine something like 9 Saturn V first stages together to get it well above ground, air blasts is way less radioactive than ground blast as air is oxygen and nitrogen so the bombs themselves give most of the radiation while ground blasts will make other stuff radioactive. 
If you need to ground launch it you are so desperate the fallout can be ignored. 

[Guest]

37 minutes ago, Bill Phil said:

Bigger Orions will of course cost more in absolute terms, but their performance will be much higher - it’s entirely possible that bigger Orions will be cheaper per kg than smaller ones. 

Possibly, but we're not comparing big Orion to small Orion, with different payloads, but big Orion to small Orion+coilgun boost, with more or less identical payload. You can save a lot of pulse units (Orion is still subject to rocket equation), and make them much smaller (since they have lower thrust, having less Orion to push). 

In all cases, you'd optimize for as high burnup fraction as possible for both economic and safety reasons. This probably puts a minimum size on the design involved, but let's just say that's our baseline "small" Orion. I'd expect a fusion-heavy device, with an uranium burnup fraction near 100%. For regular launches, the tech needs to be safe and avoid fission products from the bomb itself, because while they're a much less significant risk than fallout, if you detonate enough bombs, they'll start adding up. 

28 minutes ago, magnemoe said:

Build it in orbit or combine something like 9 Saturn V first stages together to get it well above ground, air blasts is way less radioactive than ground blast as air is oxygen and nitrogen so the bombs themselves give most of the radiation while ground blasts will make other stuff radioactive. 

That's the idea behind the mass driver, but ground launch is feasible if the launchpad is a huge graphite plate. This will avoid fallout, though you'd have a bigger ship (and logistical concerns of keeping the plate in one piece over multiple launches) than in the mass driver scenario.

[kerbiloid]

If Orion without fragile equipment is as strong as a nuclear artillery shell, maybe they could try a well filled with some fluid, and a nuke on its bottom.
Say, put Orion on top, blast the nuke to evaporate the fluid and push Orion at an artillery shell speed up to, say, 10 kilometers.
Then start standard Orion nuking already in low-density medium which doesn't stop the gas jet flow. Also at such altitude nukes wouldn't make much fallout.

Btw, about the aerial blasting.
The tungsten plasma jet of Orion is normally ~150 km/s fast.
A shockwave in air is ~1 km/s fast, slowing down to 0.3 km/s.
Chemical explosive detonation wave ~7 km/s.
Incomparable.

Edited August 29, 2019 by kerbiloid

[Shpaget]

On 8/28/2019 at 9:28 PM, Spacescifi said:

Build a VERY long magnetic rail tunnel on the ground that can flip upward to vertical, thus standing hundreds of kilometers in the air. When not in use it will flip back onto the ground. It must be tall enough to escape much of the denser atmopsheric layers.

Why not just turn it into a trebuchet and fling the Orion directly into the orbit?

[sevenperforce]

10 hours ago, Shpaget said:

Why not just turn it into a trebuchet and fling the Orion directly into the orbit?

Trebuchets are too complicated. If we have metamaterials with this kind of strength, let's just go for a good old siege onager.

[KSK]

54 minutes ago, sevenperforce said:

Trebuchets are too complicated. If we have metamaterials with this kind of strength, let's just go for a good old siege onager.

Surely a ballista would work better? Place at bottom of angled track and fire the Orion up the track.

[kerbiloid]

XXI cent., a space game forum. They are discussing what's better to reach the sky: a siege tower or a siege machine.

Let's undermine a tunnel and get to there from inside.
Maybe even with a barrel of powder.

Edited August 31, 2019 by kerbiloid

[Shpaget]

1 minute ago, kerbiloid said:

XXI cent., a space game forum. They are discussing what's better to reach the sky: a siege tower or a siege machine.

Let's undermine a tunnel and get to there from inside.

How do you suggest we drill through the turtle shell?

Anyway, I still stand by my trebuchet idea, but with a twist.

In addition to the pile of rocks, the counterweight has an Orion drive facing up to help it swing down faster. One Orion up, one Orion down; ya know, to balance the things out.

[KSK]

32 minutes ago, Shpaget said:

How do you suggest we drill through the turtle shell?

Doesn't matter. It's turtles all the way down anyway, so why bother?

And yes, we're going slightly off-topic and silly here but, with all due respect, I don't think the original Orion + launch track proposal was terribly serious either.

Edited August 31, 2019 by KSK

[wumpus]

7 hours ago, kerbiloid said:

XXI cent., a space game forum. They are discussing what's better to reach the sky: a siege tower or a siege machine.

Let's undermine a tunnel and get to there from inside.
Maybe even with a barrel of powder.

Not a siege tower.  There's no reason to make a space elevator roll, and typically (anything not due East or West) will have poor consequences.  More like a defensive tower than an offensive one.