Scifi Question; If Rocket Thrust Could Be Inverted...

[Spacescifi]

Scenario: This is a scifi drive, one that emits fictional extremely repulsive rays of white light from mirrored nozzles with an emitter down the throat. The effect is much the same as a normal rocket. You get the blow back effect from the exhaust and the sound of the roar of the engines in atmosphere, just minus the rocket plume even though the nozzles are lit up. Different models of drive have different operating time limits, but the protagonist's starship has 1000 hours of drive acceleration before needing an electric recharge (done at moon bases covered with tall solar panels, which combine all their collected energy to charge new drives and visiting ships that need a recharge).

Max acceleration for the protagonist ship with full payload is 5g. Which the ship cannot go past due to drive limitations.

Drive Limits: Due to weird drive physics, the highest acceleration that has ever been achieved was 9g, but the operating time was only an hour before a recharge was needed. 9g drives also take longer to recharge and are expensive to purchase. In practice manned vesssls often have drives with lowered maximum acceleration limits such as 5g.

What Happens If You Attempt To Accelerate Past Your Acceleration Limit: Your thrust will invert, meaning instead of emitting extremely repulsive light rays, you will start emitting ATTRACTOR rays. Meaning your nozzle will create a vacuum suction effect, sucking up anything nearby with the same force it was emitting extremely repulsive exhaust with.

So for example if a 500 ton vessel was accelerating at 5g, if it tried accelerating with engines beyond 5g it would find that it's engines would create an equivalent vacuum suction force.

That. Is some serious suction folks.

Advice For Pilots: Don't do that in an atmosphere. Why? It would increase air pressure inside the throat of the nozzle (which is plugged at the throat bottom because of the emitter lens), eventually warping it out wider than it should be. Too much air pressure and you would crack the emitter lens.

In space converting your repulsor drive into an attractor ray won't cause any harm so long nothing crashes into your nozzles.

Main Question: Even though I know this is scifi, I trust I got the physics on inverted thrust correct.... right?

Disclaimer: The inverted thrust only applies to the scifi drive acceleration. Obviously if you strapped rocket boosters to your ship for extra thrust you could increase your acceleration since you would not be relying purely on the scifi drive.

 

Edited February 29 by Spacescifi

[Terwin]

This is a reaction less drive, so inverting it seems like it would reverse the direction of thrust.

Then again this is a magic drive, so if you want it to, inverting the thrust could cause daisies to sprout from the control console.

[kerbiloid]

To propel the rocket, you need a propellant.

To propel it retrogradely, a retropellant.

Edited March 1 by kerbiloid

[darthgently]

I, personally, would find one hour at 9g a very hostile work environment and would be floating my resume as soon as acceleration decreased enough to allow my resume to float rather than being embossed on the aft bulkhead.

[StrandedonEarth]

2 hours ago, darthgently said:

I, personally, would find one hour at 9g a very hostile work environment and would be floating my resume as soon as acceleration decreased enough to allow my resume to float rather than being embossed on the aft bulkhead.

Depends, if you’re suspended in a buoyancy tank it may not be so bad

[KSK]

5 hours ago, Terwin said:

This is a reaction less drive, so inverting it seems like it would reverse the direction of thrust.

Then again this is a magic drive, so if you want it to, inverting the thrust could cause daisies to sprout from the control console.

Ahh, the High Impulse Propulsion by Particle InvErsion drive?

Sounds groovy!

[StrandedonEarth]

6 hours ago, Terwin said:

Then again this is a magic drive, so if you want it to, inverting the thrust could cause daisies to sprout from the control console.

Sounds more like an infinite improbability drive….

[magnemoe]

Make me think of that people did with the KAL controller in KSP 1. You could make an anti engine who produced negative trust and create fuel. Place this backward , add an normal engine on the other side.

Doing this in real world might be harder. 

[darthgently]

2 hours ago, StrandedonEarth said:

Depends, if you’re suspended in a buoyancy tank it may not be so bad

Ok, but what pressures would the fluid exert on you if the fluid is at 9g acceleration?

[StrandedonEarth]

30 minutes ago, darthgently said:

Ok, but what pressures would the fluid exert on you if the fluid is at 9g acceleration?

A person is a bag of water, so their hydrostatic pressure would balance with the outside pressure. It would be similar to deep-sea diving, without a hardsuit. The recreational dive limit is 100', with heliox mix 200' and  more is possible. So at 9 gees, being under 1' of water would be like being under 8'-9' of water, which is easily doable although it gets painful on the ears without equalization (a skill I never mastered; I even have difficulty popping them during an airliner descent).

As to how practical or effective it is, I don't know, I ran across the concept while reading Arthur C. Clarke's (with Gentry Lee)  Garden of Rama (unofficially aka Rama III in the Rendezvous With Rama series)

[darthgently]

44 minutes ago, StrandedonEarth said:

A person is a bag of water, so their hydrostatic pressure would balance with the outside pressure. It would be similar to deep-sea diving, without a hardsuit. The recreational dive limit is 100', with heliox mix 200' and  more is possible. So at 9 gees, being under 1' of water would be like being under 8'-9' of water, which is easily doable although it gets painful on the ears without equalization (a skill I never mastered; I even have difficulty popping them during an airliner descent).

As to how practical or effective it is, I don't know, I ran across the concept while reading Arthur C. Clarke's (with Gentry Lee)  Garden of Rama (unofficially aka Rama III in the Rendezvous With Rama series)

That is kind of clicking for me now.  I can see how replacing air with a non-compressible liquid would cause the 9g force to be distributed over one's surface to a large degree so I think the analogy to diving fair.  And Clarke was a stickler for the math and physics by and large.   I need to read past the first book of that series, but dang my reading list is endless at this point.  Something is still bothering me about the physics of 9g in a fish tank but I can't figure out what

[StrandedonEarth]

17 minutes ago, darthgently said:

That is kind of clicking for me now.  I can see how replacing air with a non-compressible liquid would cause the 9g force to be distributed over one's surface to a large degree so I think the analogy to diving fair.  And Clarke was a stickler for the math and physics by and large.   I need to read past the first book of that series, but dang my reading list is endless at this point.  Something is still bothering me about the physics of 9g in a fish tank but I can't figure out what

Rama II was a hard slog, I admit. Gentry added a lot of verbose social back story aspects to the story in the beginning, but it did pick once they finally reached Rama. III might even be the best of the sequel bunch, IV (Rama Revealed) went a little too far into the religious aspect IMO, which is presumably one of the reasons why the later books were generally panned.

E: And while I know the pressure at 9G wont be a problem, I still don't know how the internal organs will handle the gees, or what it would feel like.

Edited March 1 by StrandedonEarth

[kerbiloid]

6 hours ago, StrandedonEarth said:

Depends, if you’re suspended in a buoyancy tank it may not be so bad

The brain weights 9 * 1.5 = 13.5 kg inside the skull, pressing on its rear bone.

The buoyancy tanks are overestimated.

***

"You don't have a skeleton inside.
You are the brain. You are inside the skeleton.
You are a pilot of a bone machine with meat armor."

[Spacescifi]

9 hours ago, darthgently said:

I, personally, would find one hour at 9g a very hostile work environment and would be floating my resume as soon as acceleration decreased enough to allow my resume to float rather than being embossed on the aft bulkhead.

Just because a spaceship can go 9g does not mean it will, and I mentioned doing so would drain a drive's power reserve and require a recharge at a solar moon power base... which would take longer to charge than with lower max acceleration drives (like the 5g 1000 hour one).