Gravitic thrusters?

We know the Honorverse still uses fusion thrusters but they have considerable drawbacks. They have overall low acceleration, they have heavy fuel requirements and they have signatures visible a bazillion* miles away. But we also know the Honorverse has tractor/pressor beams. Those have insignificant fuel needs, can give high accelerations and are pretty much undetectable. So why not compromise?



The proposed drive is a powerful tractor/pressor beam in its full extension of 100.000 kilometers behind the vessel. Down that "tail" you spray a bit of gas, and the tractor/pressor presses against it, pushing the vessel forward as it pushes the gas backward; a gravitic reaction drive.

Advantages:

1) Tiny fuel needs; you need just enough for the tractor to have something to press against. Then W = F x S, where F the force applied by the tractor and S the distance during which it applies, which is the length of the tractor. The only reason fuel is needed at all is because (presumably) tractors cannot press against the interstellar medium as it's too thin. At least, we haven't seen evidence of that so far.

2) Highly stealthy. Apart from a small amount of x-rays when the fuel is accelerated to near lightspeed, you have no other emissions. Especially important is that you have no FTL emissions, meaning you're invisible to long-range sensors in combat.

3) Works through sidewalls. Since tractors can be extended through a gunport in the sidewall (as when you tractor a Keyhole), this drive can be used when you are under a bubble sidewall and thus protected from all sides.


Disadvantages:

1) Minimal fuel needs do not mean zero. Eventually you need to refuel.

2) Less stealthy than pure spider drive.

Wouldn't the gravitic arrays detect the tractor beams the same way they detect the standard drive?

Do not waste your time. Belial is just as bad as Skimper in terms of terrible, completely unfeasible ideas.

Belial666 wrote:We know the Honorverse still uses fusion thrusters but they have considerable drawbacks. They have overall low acceleration, they have heavy fuel requirements and they have signatures visible a bazillion* miles away. But we also know the Honorverse has tractor/pressor beams. Those have insignificant fuel needs, can give high accelerations and are pretty much undetectable. So why not compromise?



The proposed drive is a powerful tractor/pressor beam in its full extension of 100.000 kilometers behind the vessel. Down that "tail" you spray a bit of gas, and the tractor/pressor presses against it, pushing the vessel forward as it pushes the gas backward; a gravitic reaction drive.

Advantages:

1) Tiny fuel needs; you need just enough for the tractor to have something to press against. Then W = F x S, where F the force applied by the tractor and S the distance during which it applies, which is the length of the tractor. The only reason fuel is needed at all is because (presumably) tractors cannot press against the interstellar medium as it's too thin. At least, we haven't seen evidence of that so far.

2) Highly stealthy. Apart from a small amount of x-rays when the fuel is accelerated to near lightspeed, you have no other emissions. Especially important is that you have no FTL emissions, meaning you're invisible to long-range sensors in combat.

3) Works through sidewalls. Since tractors can be extended through a gunport in the sidewall (as when you tractor a Keyhole), this drive can be used when you are under a bubble sidewall and thus protected from all sides.


Disadvantages:

1) Minimal fuel needs do not mean zero. Eventually you need to refuel.

2) Less stealthy than pure spider drive.

We've never "seen" a tractor work on a gas. However, offhand I can't think of a reason why it would be unworkable. The only kicker would be how a tractor interfaces with matter and whether a tractor doesn't exploit some handwavium caused loophole that allows it to ignore aspects of Newtonian Mechanics for momentum transfer. It shouldn't, but... tum te tum te tum...

Belial666 wrote:We know the Honorverse still uses fusion thrusters but they have considerable drawbacks. They have overall low acceleration, they have heavy fuel requirements and they have signatures visible a bazillion* miles away. But we also know the Honorverse has tractor/pressor beams. Those have insignificant fuel needs, can give high accelerations and are pretty much undetectable. So why not compromise?

The proposed drive is a powerful tractor/pressor beam in its full extension of 100.000 kilometers behind the vessel. Down that "tail" you spray a bit of gas, and the tractor/pressor presses against it, pushing the vessel forward as it pushes the gas backward; a gravitic reaction drive.
...

Would it be stealthy though? We're not told that the reaction thrusters are extremely visible because they're the tail of a chemical reaction, for example, but keep in mind that accelerating any quantity of any kind of molecule significantly is adding insane amounts of energy to them, that is, the molecules themselves aren't particle shielded and stealthed.

I think ANY form of particle thrust would end up having the "tail of a comet" type problem, and comets aren't even travelling at a super-significant fraction of C.

And in our ongoing series of posts dedicated to finding solutions for problems noone has....

The E wrote:And in our ongoing series of posts dedicated to finding solutions for problems noone has....

And there is no textev that tractors/pressors are able to ignore gravity - in fact I believe that during the Yawata Strike, that was one of the problems that the tugs faced while dealing with the remains of Vulcan. So, in order to push your ship along, you would have to have as large a mass of gas as do do a ship, so we are not talking about small amounts of fuel here.

Potato wrote:Do not waste your time. Belial is just as bad as Skimper in terms of terrible, completely unfeasible ideas.

Ah, yes but he actually comes up with the occasional good idea and he listens to other people when they point out a problem in his ideas. Belial actually contributes.

As for his idea, even if the pressers could get the gas or dust particles up to a significant percent of the speed of light, the amount of mass they would need to act on would be pretty huge.

Now, if you could replace the reaction thrusters with spider drive tractors... [Ducks and runs]

Belial--you are using the wrong equation. The better way to examine is to say that the ratio [ship acceleration]/[ejecta acceleration] equals the ratio [ejecta mass]/[ship mass]. The 100,000 km range only tells you how long you can sustain that acceleration with a given bit of fuel.

So let's say you eject 0.1% of the ship's mass and accelerate it with a tractor beam. The ejected mass will accelerate 1000 times faster than the ship will accelerate. So if you wanted a 100 gee ship acceleration, you would have to accelerate the ejecta at 100,000 gees--a higher acceleration than a ship-killer missile.

It is highly doubtful that you get that kind of acceleration from a tractor beam that long. And 0.1% of the ship's mass is a rather large amount of fuel. If you did accelerate anything at that rate, you would only get 14 seconds acceleration from it before it left the end of the beam.

crewdude48 wrote:

Potato wrote:Do not waste your time. Belial is just as bad as Skimper in terms of terrible, completely unfeasible ideas.

Ah, yes but he actually comes up with the occasional good idea and he listens to other people when they point out a problem in his ideas. Belial actually contributes.

As for his idea, even if the pressers could get the gas or dust particles up to a significant percent of the speed of light, the amount of mass they would need to act on would be pretty huge.

Now, if you could replace the reaction thrusters with spider drive tractors... [Ducks and runs]

As the main drive it would be totally unworkable, but as a maneuvering thruster? The amount of gas needed would Be negligable - assuming you could accel it to high velocities quickly.

The question would be which is more efficient in a reaction and energy perspective fusion plasma discharge vs tractor/gas. Maybe a better solution is a combination of both - using fusion plasma with a tractor working on it?