Could we make a flying saucer?

[Spacescifi]

 

I looked up the SLAM project, AKA project Pluto, a nuclear thermal jet which was designed to stay in the air indefinitely flying around mach 3 at sea level.

The shockwave air blast alone would kill designers thought, not to mention the radiation.

So if billionaire wanted to one-up Elon Musk and had both the funding and government support, could he/she build a large flying saucer with VTOL capabilty and orbital ability?

 

Using a modified SLAM engines that are not open cycle so that the exhaust is not radioactive?

Because I think the ability to stay in the air indefinitely is huge, but could SLAM engines be modified so the ship could hover if necessary?

 

Instead of using ramjets at mach 3, could it just hover and use it's nuclear thermal jet engines to hover?

Or would the air intake mechanics be too heavy? I do not think they would.

 

What is the heaviest payload you think it could lift?

1000 tons?

 

EDIT: Space capability should be optional and could be down with detachable boosters once the ship lifts to where the air thins out. Therefore saving on the propellant mass needed for orbital velocity.

Once in orbit you really are halfway to anywhere. Since that alone is a big enough challenge completed.

 

 

Edited August 10, 2019 by Spacescifi

[Wjolcz]

14 hours ago, Spacescifi said:

Using a modified SLAM engines that are not open cycle so that the exhaust is not radioactive?

So, basically NERVAs. They would still have radioactive exhaust.

[Guest]

No, they wouldn't. SLAM was not even radioactive because it was open cycle, it was radioactive because it was unshielded. That is, they ran air directly over the uranium fuel rods, without any kind of cladding. That caused pieces of uranium to fly out of the exhaust.  Of course, the thinking at the time was that it wasn't exactly a problem as long as it wasn't happening over the US... Atmospheric NTRs are quite doable, if complex to engineer. In fact, Russians have some sort of engine in that vein for their Burevestnik cruise missile, and I'm pretty sure it's cleaner than Pluto. It probably doesn't emit any radiation out of the exhaust whatsoever. 

As for saucer, we have already built them:

Several, in fact. This is not a movie prop, but an actual aircraft. They did not work very well and the project was eventually cancelled, but with a nuclear engine and modern computers, you could do it. The latter is actually more important, because you need to deal with stability issues that killed the previous saucer efforts.

BTW, NERVA exhaust wasn't radioactive, either. Hydrogen is not subject to neutron activation. Most things that are in the air aren't, either. Nuclear propulsion is quite benign when operating properly. 

[Spacescifi]

47 minutes ago, Dragon01 said:

No, they wouldn't. SLAM was not even radioactive because it was open cycle, it was radioactive because it was unshielded. That is, they ran air directly over the uranium fuel rods, without any kind of cladding. That caused pieces of uranium to fly out of the exhaust.  Of course, the thinking at the time was that it wasn't exactly a problem as long as it wasn't happening over the US... Atmospheric NTRs are quite doable, if complex to engineer. In fact, Russians have some sort of engine in that vein for their Burevestnik cruise missile, and I'm pretty sure it's cleaner than Pluto. It probably doesn't emit any radiation out of the exhaust whatsoever. 

As for saucer, we have already built them:

Several, in fact. This is not a movie prop, but an actual aircraft. They did not work very well and the project was eventually cancelled, but with a nuclear engine and modern computers, you could do it. The latter is actually more important, because you need to deal with stability issues that killed the previous saucer efforts.

BTW, NERVA exhaust wasn't radioactive, either. Hydrogen is not subject to neutron activation. Most things that are in the air aren't, either. Nuclear propulsion is quite benign when operating properly. 

 

Good points, but the real concern is thrust.

Would such nuclear thermal engines even have the thrust for orbit?

I am still thinking that asking for a solo SSTO is s bit much.

I would rather have a saucer that can hover indefinitely, and lift to an air ceiling, and then use detachable rocket boosters to reach orbit.

So where the saucer shape would really shine along with the modified SLAM engines is reentry and landing. Hover as long as you want, and land where you wish.

Eat your heart out Elon!

Edited August 10, 2019 by Spacescifi

[Guest]

Yes, in addition to a flying saucer being perfect for reentry (a biconic capsule shape is literally one step away from being one), an NTR would provide practically unlimited atmospheric endurance, helpful not only for landing, but also exploration. In fact, I had this idea about martians (descendants of human colonists) invading a post-apocalyptic Earth in flying saucers derived from their Mars/Earth landing vehicles. Nuclear powered, but with chemical thrusters for launch and landing. Such vehicles could be converted from surface/orbit transport (on Mars, the original design couldn't do it on Earth) to exploration/surface transport vehicles just by swapping propellant tank modules for cargo bays. As long as you keep it somewhat balanced, you could put in all sorts of modules into them.

The problem with liftoff is propellant, not the NTR itself. In fact, I suspect you could design a hybrid air/methane-powered saucer that would use air in atmosphere and transition to methane once it's going fast enough (kind of like Skylon, only without using any propellant when in atmosphere). The saucer isn't the most aerodynamic shape for ascent, but since you're not limited by propellant reserves, a little inefficiency could be excusable. Rocket boosters are a good solution, too. You could even go the way of the Shuttle, using rocket boosters alongside the NTR. Rockets would also save you the trouble of developing a dual-propellant NTR, so you can optimize it for atmosphere better. There is a lot you can do even with a simple, solid core nuclear engine, if you're willing to make it run very hot.

[KerikBalm]

Perhaps this thread is of interest to you?

 

[Spacescifi]

On 8/10/2019 at 1:36 PM, Dragon01 said:

Yes, in addition to a flying saucer being perfect for reentry (a biconic capsule shape is literally one step away from being one), an NTR would provide practically unlimited atmospheric endurance, helpful not only for landing, but also exploration. In fact, I had this idea about martians (descendants of human colonists) invading a post-apocalyptic Earth in flying saucers derived from their Mars/Earth landing vehicles. Nuclear powered, but with chemical thrusters for launch and landing. Such vehicles could be converted from surface/orbit transport (on Mars, the original design couldn't do it on Earth) to exploration/surface transport vehicles just by swapping propellant tank modules for cargo bays. As long as you keep it somewhat balanced, you could put in all sorts of modules into them.

The problem with liftoff is propellant, not the NTR itself. In fact, I suspect you could design a hybrid air/methane-powered saucer that would use air in atmosphere and transition to methane once it's going fast enough (kind of like Skylon, only without using any propellant when in atmosphere). The saucer isn't the most aerodynamic shape for ascent, but since you're not limited by propellant reserves, a little inefficiency could be excusable. Rocket boosters are a good solution, too. You could even go the way of the Shuttle, using rocket boosters alongside the NTR. Rockets would also save you the trouble of developing a dual-propellant NTR, so you can optimize it for atmosphere better. There is a lot you can do even with a simple, solid core nuclear engine, if you're willing to make it run very hot.

 

 

Running tbe reactor very hot is the issue, and doing thst without melting the core would require a vacuum environment and precise magnetic field strength of a degree that we do not possess today.

I saw a youtube video of one of the more powerful electromagnets, and the coils began to snap because of the current fliwing tbrough them.

We simply cannot beat material limitations without new materials to start with.

 

I also wonder if one really could pull off a magnetic nozzle SSTO. As a scifi concrpt.

Hear me out, plasma windows could screen the air like a shutter. On when engines are'nt thrusting, but off when engines are thrusting.

 

So kind of like this when engines are shuttered:

 

Only difference being that these would just have a glow, no grille panel whatsoever as it is just a plasma window.

When the engines are thrusting the plasma window would shutter off, and you would see a normall rocket engine plume, only coming from an engine port hole, as the magnetic nozzle would need to be retracted into the hull within a vacuum environment to avoid air contamination.

Once engines turn off just shutter the plasma wiindow on again. If any air molecules find their way inside the vacuum nozzle chamber there won't be many, and they will be flushed out anyways when the engine fires up.

 

The advantage of magnetic vacuum chamber nozzles with plasma shutters is that you can get the heat that would melt the nozzle otherwise and still use iy in an atmosphere because the plasma shutter would seal the nozzle when not thrusting.

Thus easier SSTO's, higher thrust, higher top speeds and all that.

I also think that if we ever manahe to generate stronget mahnetic foelds thay we can sustain without breaking the magnets, we would profit more applying it to fission rocketry thsn fusion, which seems to be far more of a challenge.