Reaction Drives fuel consumption in MGT
- Thread starter Sturn
- Start date
Rikki Tikki Traveller
Cosmic Mongoose
It IS hydrogen! heated in the Fusion reactor to a Plasma state (very high temp, but just below the point of fusing to helium) and then shot out the back of the ship at a varying velocity based on the velocity of the ship (that is the only way to keep the efficiency up). Don't ask how they do it (just squint and nod your head).
The reaction mass is the 2.5% of ship's volume per G-Hour of thrust. That is in addition to the normal requirements of the fusion power plant.
If you want to use a different fuel, such as Anhydrous Ammonia, then you can. The numbers might be a bit different, but probably still "close enough".
The reaction mass is the 2.5% of ship's volume per G-Hour of thrust. That is in addition to the normal requirements of the fusion power plant.
If you want to use a different fuel, such as Anhydrous Ammonia, then you can. The numbers might be a bit different, but probably still "close enough".
Rikki Tikki Traveller
Cosmic Mongoose
I think they were thinking Chemical Rockets, like we have today, but that is incorrect. The numbers given were from TNE, which used a Plasma Drive called HePlaR.
If you really tried to use a Chemical Rocket, your fuel usage would be HUGE. Something on a the order of 10% of the ship's volume per G-TURN.
Look at modern rockets, it takes something like 80% or more of the volume of the ship for the fuel to get a payload to low orbit. That only takes a few minutes; granted at several G's of acceleration, but you get the idea.
Even in space, where the rocket doesn't have to overcome that 1G gravity field and the drag from the atmosphere, it still requires a huge amount of fuel to accelerate a payload anything close to 1G for even just a couple of minutes.
No, the Reaction Drive in HG HAS to be a Plasma or Fusion rocket, no chemical rocket would work.
Avenger wrote a book on under the Golden Age Starships series on Primitive Spacecraft and Space Stations, it has a nice section on Chemical Rockets and their fuel usage.
If you really tried to use a Chemical Rocket, your fuel usage would be HUGE. Something on a the order of 10% of the ship's volume per G-TURN.
Look at modern rockets, it takes something like 80% or more of the volume of the ship for the fuel to get a payload to low orbit. That only takes a few minutes; granted at several G's of acceleration, but you get the idea.
Even in space, where the rocket doesn't have to overcome that 1G gravity field and the drag from the atmosphere, it still requires a huge amount of fuel to accelerate a payload anything close to 1G for even just a couple of minutes.
No, the Reaction Drive in HG HAS to be a Plasma or Fusion rocket, no chemical rocket would work.
Avenger wrote a book on under the Golden Age Starships series on Primitive Spacecraft and Space Stations, it has a nice section on Chemical Rockets and their fuel usage.
Another way to do it is have the first grav drives only work in a gravity well. If grav drives were limited like this up to say TL 12 that would leave a large window where ships intended to land would carry a grav drive for liftoff/landing and a reaction drive for deep space manoeuver.
That could lead to some very interesting design options and tradeoffs to ballance. Some ships would be 'hybrids' while others would specialise as orbital shuttles or deep-space vessels.
Simon Hibbs
That could lead to some very interesting design options and tradeoffs to ballance. Some ships would be 'hybrids' while others would specialise as orbital shuttles or deep-space vessels.
Simon Hibbs
simonh said:
I started this thread while doing planning for a campaign with almost this exact mechanic in mind. I'm going to use, "Lifter" limited grav drives that allow only up/down performance very near a gravity well along with a reaction drive for forward thrust in space or atmosphere. "Grav" vehicles that require any kind of good speed or thrust include a combination of thruster and lifter. They can hover with lifters but only obtain faster speeds with thrusters. Starships require reaction drives for space travel and thus more fuel considerations. Spacecraft intended to land on non-vac planets will most often include lifters for help. They could do it without (thrusters + streamlining), but lifters make it much easier.
Sturn said:
Another option is a G-Field effect that neutralises or greatly weakens gravity fields within a bubble-like region by altering the local gravitational constant. A vehicle with such a field is effectively in freefall when it's active, so the crew will float about, etc. Any thruster system only has to work against the vehicle's inertia (and wind resistance) and can ignore gravity.
Further extensions of this idea would be a C-Field that manipulated the local speed of light, and an I-Field that manipulates inertia to make thruster drives more efficient. It's a totally different technology paradigm from Traveller though.
It's also occurred to me that if gravitic thrusters work in a gravity well, and can give significantly more thrust than just cancelling local gravity, they could be used to boost a ship during takeoff enough to achieve an interplanetary trajectory. Further course corrections or additional boosting would still require a deep-space thruster drive though. Even if this effect wasn't enough for fast interplanetary travel, it could still be a useful trick.
Simon Hibbs
simonh said:
An idea I put much work into, before discarding it for something else, was somewhat similar. I replaced MD's and JD's with only a Gravity Drive, a device that could greatly enhance gravity to the point a craft would even begin to, "warp". Handwaves needed of course. This allowed a craft to, "push" off from a planet while having the GD set to reverse gravity. Aim this push towards another planet. When getting closer to the target, use the same method (anti-gravity vs the planet's grav well) to slow down and be, "caught". For interstellar travel, the same method could be used, but from star to star instead.
This created all kinds of fun in-game ideas. Planets/stars of larger mass would result in quicker trip times (a.i. use the smallest mass of the 2 objects as a base for determining speed, larger better). Sling-shotting around a planet/star takes a little more skill (-1 DM astrogation or pilot?), but also creates a quicker travel time. In an emergency, you could actually pull your craft at great speed into a planet (GD set to amplified gravity), then reverse at the last moment (GD set to reverse gravity). This would greatly amplify the speed of your launch, but the forces could damage your ship and a failed roll means you are forced into a crash landing!
More fun then a simply jump roll.
These Gravity Drives were only good for trips between stars or planets. You couldn't deviate. Thus, spacecraft also needed a MD of some sort for flight at the end of the trip.
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