I will preface this by stating clearly that it departs from canon. Be thou warned! Heresy follows! :devil:
So, the typical free trader has a 500 Mw power plant and uses the bulk of that for drives that push it along at 1G. By canon, that goes into a - do I call that a reactionless thruster? A maneuver system that imparts momentum to the ship without needing reaction mass. If I understand the math, I think it's very roughly a 4% efficiency, if we assume that a 200 dT ship masses somewhere in the rough vicinity of 2000 metric tons? Presumably the life support and other ship's systems are using some power, but the fact is, we pay a high premium for the privilege of being able to move without resorting to Newton. Still, well worth the price considering the alternative.
(They're working on some microwave-based vacuum drive that's supposed to do that as well. Might just work, although the numbers are low enough that it could still be a testing error.)
So I'm thinking - I've brought this up before, I want to shape it a bit more - that's very nice, but there's all that power, and in a pinch the traditional way of doing things is way, way more efficient, under the right circumstances. You've got a fusion plant. Your fusion plant is putting out enough energy to give you 500 Mw. That can make for one wicked lot of jet thrust. In an atmosphere, you use the atmosphere itself for a working fluid. Of course, as you climb higher, the atmosphere thins and you lose your working fluid. Still, that extra thrust could make the difference between life and death -
- if for example you erred on a fuel scooping run and found yourself past the point of no return and descending into a gas giant. Such a system would at least give you thrust to maintain altitude down where the atmosphere got thick enough to be worthwhile, while you hollered for help and waited for rescue to arrive.
The other idea is, with great reluctance but it beats dying, to use your hydrogen fuel as reaction mass through the same jet system, to use it to give you the thrust you need to get yourself out of that sucking gravitational trap and back into space, and you figure you'll just deal with the spent fuel problem once you're sure you're going to survive.
Plan A is to assume this capacity is inherent in existing drives, an emergency feature for those moments when that extra boost is life. (I warned you it departed from canon. Not the slightest hint of such a feature, and a few adventure incidents where it would be very useful but is noticeably absent. Heh heh. :CoW: )
Plan B is to design a system that could be added "after market", so to speak.
Nearest prototypes I can see are the Hard Times Fusion Rocket and the Striker HP rocket with a fusion drive power plant (odd how they do that, but OK).
From Striker, I get 32,500 tons thrust out of a 500 Mw plant, at a rate of 75000 l/h (about 5 1/2 dTons per hour). Plant baffles me - it has to be designed to do the job rather than added on, so we'd have to presuppose a plant able to fill either role, either that or add a second power plant of the same size designed to behave like a reaction drive. On the other hand, 32,500 tons of thrust is something like 16 Gs, which is a bit excessive. If we want to add a separate fusion drive, one about 30% the size of a PP1 yields a 5G boost at a fuel rate of 1.7 dTons per hour (for our free trader). A bit bulky and very fuel hungry, but maybe worth it in a pinch, especially if you could get it to use the atmosphere as reaction mass instead of your hydrogen when down in an atmosphere. For around 6% the size of the PP1 (0.36 dTons at TL9), you've got a 1G booster consuming a third of a dTon per hour.
From MegaTrav, I'm going to with that 1G boost: there I need a 10 cubic meter fusion rocket (about 3/4 dTon), and it's burning 2000 l/h, or about 0.15 dTons per hour. Twice the size but a bit better than half the fuel consumption. If I want 5Gs, I need 5 such drives and consume 5 times as much fuel. But, again, handy to have if you're in atmosphere and can use atmosphere as you reaction mass.
Since they are at their core fusion drives, I can't really think of them being part of the maneuver drive system, but it is possible to think of the fusion plant as possibly being duel role, constructed to provide additional emergency thrust when the need is urgent. Or they could be installed as a separate back-up emergency drive taking some of the ship's volume. I'm leaning toward the latter because, while the fuel use is severe, it's still low enough to permit something like letting a free trader hit 6G for a few turns while desperately evading the pirate and trying to make planetfall. There should probably be some price for that interesting benefit.
So, the typical free trader has a 500 Mw power plant and uses the bulk of that for drives that push it along at 1G. By canon, that goes into a - do I call that a reactionless thruster? A maneuver system that imparts momentum to the ship without needing reaction mass. If I understand the math, I think it's very roughly a 4% efficiency, if we assume that a 200 dT ship masses somewhere in the rough vicinity of 2000 metric tons? Presumably the life support and other ship's systems are using some power, but the fact is, we pay a high premium for the privilege of being able to move without resorting to Newton. Still, well worth the price considering the alternative.
(They're working on some microwave-based vacuum drive that's supposed to do that as well. Might just work, although the numbers are low enough that it could still be a testing error.)
So I'm thinking - I've brought this up before, I want to shape it a bit more - that's very nice, but there's all that power, and in a pinch the traditional way of doing things is way, way more efficient, under the right circumstances. You've got a fusion plant. Your fusion plant is putting out enough energy to give you 500 Mw. That can make for one wicked lot of jet thrust. In an atmosphere, you use the atmosphere itself for a working fluid. Of course, as you climb higher, the atmosphere thins and you lose your working fluid. Still, that extra thrust could make the difference between life and death -
- if for example you erred on a fuel scooping run and found yourself past the point of no return and descending into a gas giant. Such a system would at least give you thrust to maintain altitude down where the atmosphere got thick enough to be worthwhile, while you hollered for help and waited for rescue to arrive.
The other idea is, with great reluctance but it beats dying, to use your hydrogen fuel as reaction mass through the same jet system, to use it to give you the thrust you need to get yourself out of that sucking gravitational trap and back into space, and you figure you'll just deal with the spent fuel problem once you're sure you're going to survive.
Plan A is to assume this capacity is inherent in existing drives, an emergency feature for those moments when that extra boost is life. (I warned you it departed from canon. Not the slightest hint of such a feature, and a few adventure incidents where it would be very useful but is noticeably absent. Heh heh. :CoW: )
Plan B is to design a system that could be added "after market", so to speak.
Nearest prototypes I can see are the Hard Times Fusion Rocket and the Striker HP rocket with a fusion drive power plant (odd how they do that, but OK).
From Striker, I get 32,500 tons thrust out of a 500 Mw plant, at a rate of 75000 l/h (about 5 1/2 dTons per hour). Plant baffles me - it has to be designed to do the job rather than added on, so we'd have to presuppose a plant able to fill either role, either that or add a second power plant of the same size designed to behave like a reaction drive. On the other hand, 32,500 tons of thrust is something like 16 Gs, which is a bit excessive. If we want to add a separate fusion drive, one about 30% the size of a PP1 yields a 5G boost at a fuel rate of 1.7 dTons per hour (for our free trader). A bit bulky and very fuel hungry, but maybe worth it in a pinch, especially if you could get it to use the atmosphere as reaction mass instead of your hydrogen when down in an atmosphere. For around 6% the size of the PP1 (0.36 dTons at TL9), you've got a 1G booster consuming a third of a dTon per hour.
From MegaTrav, I'm going to with that 1G boost: there I need a 10 cubic meter fusion rocket (about 3/4 dTon), and it's burning 2000 l/h, or about 0.15 dTons per hour. Twice the size but a bit better than half the fuel consumption. If I want 5Gs, I need 5 such drives and consume 5 times as much fuel. But, again, handy to have if you're in atmosphere and can use atmosphere as you reaction mass.
Since they are at their core fusion drives, I can't really think of them being part of the maneuver drive system, but it is possible to think of the fusion plant as possibly being duel role, constructed to provide additional emergency thrust when the need is urgent. Or they could be installed as a separate back-up emergency drive taking some of the ship's volume. I'm leaning toward the latter because, while the fuel use is severe, it's still low enough to permit something like letting a free trader hit 6G for a few turns while desperately evading the pirate and trying to make planetfall. There should probably be some price for that interesting benefit.
