The Limits of Rocketry VS Pusher Plate Propulsion

[Spacescifi]

 

I like project Orion and wish it was more well known in the media (scifi movies/cartoons).

Consider the limitations of rocketry.

Want high thrust? Accept short burn times and the need for dropping empty rocket stages.

Want long rocket burns? Accept extremely low thrust.

Want both high thrust and long rocket burn time? Accept high heat loads that will melt your rocket engine, or require so much coolant mass as to negate the benefits of having both high thrust/long burn time. More mass usually means less burn time. Or just use antimatter, which could provide enough thrust and long burns... but also could wipe out a small nation or state.

Project Orion essentially does high thrust in short pulses of time, over and over again. It also has long burn time, due to having a lot of high thrust to weight ratio pulse units (small nukes or perhaps antimatter bombs).

There is only one scenario where in my opinion rocketry could rival a pusher plate, and even then, a modified pusher plate design could beat it.

An antimatter thermal rocket: The heat would be extreme, which is why only small amounts of antimatter could be mixed with propellant, limiting a vessel's thrust potential.

An antimatter bomb pusher plate could have higher thrust as it it's reaction happens outside the vessel and does not have to be contained. So more antimatter bomb thrust, leading to some surprisingly hefty yet speedy large vessels.

 

The only potential advantage I can see with rocketry and antimatter is that antimatter is not picky.

Even if you ran out of ALL your chemical propellant you could feed the crew's waste products in as propellant to the antimatter rocket and it would still give good thrust and long burn time. You could even grind up parts of the ship and use it as propellant. Antimatter does not care. Cannibalize the ship. You can even feed unfortunate or dead crew members as propellant for your antimatter rocket. Since it is all fuel to the rocket. Antimatter is what provides the kick and the the endurance of the rocket, less so the propellant.

 

With pusher plate propulsion this would be a lot harder to do, as all your fuel comes pre-packaged as pulse bomb units. So when you run out of fuel with a pusher plate, you're done for unless somebody is helping you refuel with more pulse units.

 

Your thoughts on pusher plates propulsion vs rocketry?

Did I miss anything?

Edited September 17, 2019 by Spacescifi
Rival

[Bill Phil]

That’s still rocketry, the propellant and its energy originate from the vehicle. They still suffer from the rocket equation.

The main reason for Orion’s spectacular performance (high thrust and decent isp) is that it isn’t trying to contain its immensely hot propellant. This allows it to get much hotter reaction mass and thus faster reaction mass - without vaporizing the vehicle (hopefully...). 

Pusher plates aren’t actually that great. Mini Mag Orion is much better than normal Orion in terms of specific impulse and has pretty decent thrust - allowing fast interplanetary transfers. Using a boosted fission system could make it even better. 

Pulse propulsion is definitely good, but pusher plates are only one sub-category. Pulsed Fission-Fusion and Mini Mag Orion are very good concepts as well.

Edited September 17, 2019 by Bill Phil

[Spacescifi]

10 minutes ago, Bill Phil said:

That’s still rocketry, the propellant and its energy originate from the vehicle. They still suffer from the rocket equation.

The main reason for Orion’s spectacular performance (high thrust and decent isp) is that it isn’t trying to contain its immensely hot propellant. This allows it to get much hotter reaction mass and thus faster reaction mass - without vaporizing the vehicle (hopefully...). 

Pusher plates aren’t actually that great. Mini Mag Orion is much better than normal Orion in terms of specific impulse and has pretty decent thrust - allowing fast interplanetary transfers. Using a boosted fission system could make it even better. 

Pulse propulsion is definitely good, but pusher plates are only one sub-category. Pulsed Fission-Fusion and Mini Mag Orion are very good concepts as well.

 

Good post.

Any pics of a magnetic orion? And I suspect the pusher plate may offer better thrust for large vessels... but I am not sure.

Care to enlighten me?