Reaction drive fuel

[thesmiths4]

Is the fuel used for reaction drives the same as the fuel used for jump drives and fusion power plants? (That is, is it all Liquid Hydrogen?)

If so, then fuel scoops and fuel processors work to refill reaction fuel, too!

 

[Reynard]

I just searched the reaction drive rules in New Traveller High Guard and there's no distinction between the fuel of Maneuver and Reaction though they mention High Burn engines are 'chemical'. The old Traveller used a much higher cost for High Burn fuel making it a separate fuel type. It's all hydrogen now I guess. The difference is Maneuver uses the power plant (and it's fuel source) whereas reaction needs a separate source. You'll still carry hydrogen but you need a lot more with a reaction drive. I also noticed the High Burn Thruster is now a secondary Reaction drive acting in conjunction with the primary Maneuver or Reaction drive for a temporary boost and is going to burn up more fuel at the same but additional rate as a Reaction drive.

 

[Chas]

It should be different. The whole point of reaction drives is that you burn out the fuel quickly and the fuel load limits how reaction drives can be applied. You can't have high jump battle cruisers screaming along at Thrust 17 or something silly...

 

[phavoc]

Well, if you want any sort of science behind it, 'burning' hydrogen as a reaction-based fuel doesn't work unless you add "oxygen' as an oxidizer. Unless there is a new way to get something to burn without the presence of an oxidizer.

I haven't looked up the numbers, but I think the specific impulse of LOX wouldn't be enough to push thousands or hundreds of thousands of tons of metal at 3G. Using "afterburners" for space craft is still silly in my view. But hey, now it's canon (or soon will be).

 

[Nerhesi]

It should be different. The whole point of reaction drives is that you burn out the fuel quickly and the fuel load limits how reaction drives can be applied. You can't have high jump battle cruisers screaming along at Thrust 17 or something silly...

Agrreeeed. Some differentiation is good here.

 

[AndrewW]

Using "afterburners" for space craft is still silly in my view. But hey, now it's canon (or soon will be).

Reaction drives already existed. Just better defined now.

 

[thesmiths4]

So, not the same fuel? The High Guard rules should make that clear. Where does reaction fuel get refilled at? Type C starports and above? Any starport? A TL7 or above world?

 

[phavoc]

Using "afterburners" for space craft is still silly in my view. But hey, now it's canon (or soon will be).

Reaction drives already existed. Just better defined now.

True. But nobody was using reaction drives to give a multi-millon ton (by mass, not displacement) ship a 3G boost. I don't know if anyone is even looking at the explanation behind all this or not. Before we had an upper limit on drives, in that they simply were incapable of doing more than 6G's thrust. And that was fine. It's sci-fi, but the entire framework fit within that limitation.

One question is how can a reaction drive push that ship faster (not even addressing the energy requirement in the fuel to physically do so), but how is that supposed to work when your drives still have an upper limit? Reaction drives are being used as afterburners (in space) in these examples. I'm assuming we're just doing a hand-wave to get around this. Which is fine, but we are going further towards space-opera (and concepts like Star Wars 'etheric' rudders and aerilons to do aerobatic maneuvers). I just wonder if anyone looks at the ramifications of this or do they just go "that's cool!". Is there any sort of thought process going into this to make sure there is at least some consistency? Some things get tossed and others don't.

 

[Reynard]

I just play and enjoy the game.

 

[AndrewW]

True. But nobody was using reaction drives to give a multi-millon ton (by mass, not displacement) ship a 3G boost. I don't know if anyone is even looking at the explanation behind all this or not. Before we had an upper limit on drives, in that they simply were incapable of doing more than 6G's thrust. And that was fine. It's sci-fi, but the entire framework fit within that limitation.

The option was still there. 6G was the limit for standard manoeuvre drives.

One question is how can a reaction drive push that ship faster (not even addressing the energy requirement in the fuel to physically do so), but how is that supposed to work when your drives still have an upper limit?

The thrust limits are to the drive, that drive can only go at whatever thrust it is rated at, but you can stack different drive types.

I just wonder if anyone looks at the ramifications of this or do they just go "that's cool!". Is there any sort of thought process going into this to make sure there is at least some consistency? Some things get tossed and others don't.

As for though process. Some stuff has been added to make it easier to simulate different universes. Just providing more options, it is up to the group/individual or whoever if they wish to make use of them or not.

 

[tolcreator]

In TNE, which had reactrion drives as standard, it was the same "fuel", for jump drives, power plants, and reaction *mass*. The reaction drive doesn't use the liquid hydrogen as fuel (except in that it powers the fusion plant that powers the reaction drive), the drives runs off electricity and shoves the liquid hydrogen out the back as reaction mass, not fuel.

In a chemical rocket, it is the byproducts of combustion that are expelled as reaction mass. In this case, "fuel" is the correct term, the same stuff (or its combustion byproducts) also being the reaction mass.
The reaction drives are not chemical rockets: The "fuel" is not burned, it is heated (to plasma and then some) and expelled out the back. Heated by lasers/magnetic fields/whatever you're having yourself.

 

[phavoc]

In TNE, which had reactrion drives as standard, it was the same "fuel", for jump drives, power plants, and reaction *mass*. The reaction drive doesn't use the liquid hydrogen as fuel (except in that it powers the fusion plant that powers the reaction drive), the drives runs off electricity and shoves the liquid hydrogen out the back as reaction mass, not fuel.

In a chemical rocket, it is the byproducts of combustion that are expelled as reaction mass. In this case, "fuel" is the correct term, the same stuff (or its combustion byproducts) also being the reaction mass.
The reaction drives are not chemical rockets: The "fuel" is not burned, it is heated (to plasma and then some) and expelled out the back. Heated by lasers/magnetic fields/whatever you're having yourself.

So it would make them more like plasma or fusion drives. Reaction drives are also at the lower levels (the same as rockets today). The higher TL drives would be better served with a different name to differentiate them (they are still being used like afterburners, but that's not the issue - just ensuring the underlying logic flows with the rest of the system)

 

[madmike]

Have a look at Gypsy Knights Games Anderson and Felix Guide to Naval Architecture. There is a full module for reaction drives offering different types of drives, explaining the fuels they use and modifier tables to enable ships to be designed with them.

 

[thesmiths4]

I think that for game purposes, reaction drive fuel should be considered the same as jump/powerplant fuel. It simplifies the logistics for players, and it can be explained as the drive using some sort of high output plasma torch drive, but self contained, with enough power to operate itself only. As a rocket guy, I'd love to have a real drive like that! I wouldn't want it to lift off from my back yard, of course...

 

[MongooseMatt]

I think that for game purposes, reaction drive fuel should be considered the same as jump/powerplant fuel. It simplifies the logistics for players,

This is the assumption we are making, precisely for this reason.

 

[phavoc]

I think that for game purposes, reaction drive fuel should be considered the same as jump/powerplant fuel. It simplifies the logistics for players,

This is the assumption we are making, precisely for this reason.

There's a giant logical hole here - reaction drives are what power lower-end non-gravitic spacecraft. They are the Saturn-V and Soyoz rockets of today. Now we are leaping past that into gravitics and special drives... and yet the same TL6 technology is integrated into TL15?

So why not, for example, apply the same bookkeeping ease to life support costs? Why are we having fixed AND flexible costs to calculate and keep track of? Why is one worthy of this simplification and the other not? I am all for less bookkeeping, but there's no rhyme or reason to it... it's like there is a bulletin board at MGT headquarters and you throw darts at topics to do stuff like this to.

 

[phavoc]

So if we aren't going to change the nomenclature of things, can we at least add in a sentence like "At TL9 and reaction-based engines transition into fully-function fusion rockets". That's a little more sciency and separates the lower TL conceptual drives from the future ones. And it still allows for using the same fuel source.