Afterburners in Traveller

[phavoc]

Currently the idea is that there is a way to make chemical thrusters more powerful than grav plates, and a fuel type that stores a lot of specific impulse energy in it. It's the future, so many things are possible, but that concept has always bothered me as too silly.

So I was thinking that we could keep the idea of reactionless thrusters being powered by energy, but that the process has an upper limit (e.g. 6G) before the efficiency falls precipitiously drops off. To get the higher thrust ratings, you would use your hydrogen fuel to turn your reactionless drive into a reaction-based one. By adding the hydrogen to the thruster plates you turn reactionless into reactionless + reaction, which would allow for a higher acceleration curve using existing tech.

So in essence nothing would change, except you would not need a second set of engines, and this, to me at least, would fit better with canon - plus we move away from the magical concept of reaction-based drives. To make things easier you could simply keep the fuel consumption rules, except instead of a new chemical fuel you would be tapping your fuel tanks. One thing I haven't put pen to paper on would be what the acceleration limit would be. So could a 1G ship reach 9G by doing this, or would the upper limit be, say no more than a 100% increase in thrust output by turning on your hydrogen 'afterburners'? Could make for some interesting maneuvers, as the ship with the most fuel on board would win the acceleration battle (but hopefully not drain their tanks...).

 

[AnotherDilbert]

Wouldn't it be easier to just removing Reaction Drives from YTU?

Or rather, produce thrust any way you like, but internal compensators, and hence acceleration, is limited by TL.

 

[wbnc]

A conventional rocket burninng two fuels to generate reaction mass is a bit outdated by the time you have a fusion drive. it would be more likely that reactio drives in the #I era would be a LOT more advanced and a lot more powerful.

Since you have a fusion power plant converting liquid hydrogen to plasma then using it for reaction mass is pretty simple. the density of hydrogen As a liquid it has a density of 70.99 g/L, as a gas it has a density of 0.08988 g/L......so if converted to a superhot, charged gas it wants to expand very very badly. whihc is the source of power for a rocket.. that expansion imparts a lot of energy to the reaction mass if channeled properly. In a convetional chemical rocket that releaseof energy and rapid expansion is caused by putting to elements together and gettignn a third very hot very energetic gas/

Also plasma has a nifty qualility.....it's charged. And with enough electrical power at your disposal and you can then use an electric field of opposite charge to accelerate it even more forcefully. So if you take some hydrogen thats already highly aggtiated and lookig for the door out, and kick it in the butt with a oppositely charged electric field..it is going to be very happy to impart a good deal of energy to the ship thats treated it poorly. and it will now be free to return t it's natural state freely roaming the cosmos usig that mutual kick in the pants to propel it on its journey away from a bad relationship.

until some idjit with a Bussard scoop comes along and scoops it up, or it is drawn into a gravity well where it meets it's true love and forms an alternative relationship with an oxygen molecule to settle down and live out the rest of its days in a water molecule.....until some idiot comes along and scoops it up for fuel in the distant futre and the process starts again.

 

[AnotherDilbert]

Also plasma has a nifty qualility.....it's charged.

Good idea, but the Reaction Drives explicitly use no power, so has no energy to accelerate particles. We can design a ship with reaction drives, but without a fusion plant, so the reaction drive is not dependant on a fusion plant to work.

The Reaction Drives are extremely fuel efficient. No chemical fuel has even remotely high enough specific impulse. The only thing my limited imagination can come up with that can be so fuel efficient is some sort of fusion rocket.

 

[wbnc]

Also plasma has a nifty qualility.....it's charged.

Good idea, but the Reaction Drives explicitly use no power, so has no energy to accelerate particles. We can design a ship with reaction drives, but without a fusion plant, so the reaction drive is not dependant on a fusion plant to work.

The Reaction Drives are extremely fuel efficient. No chemical fuel has even remotely high enough specific impulse. The only thing my limited imagination can come up with that can be so fuel efficient is some sort of fusion rocket.

Hmmmmm....dern it...Okay putting on the thinking cap here. if it were a self-contained system with an internal power supply that would work. they are rather large compared to aM-drive so there's room in there for the internal power system. an MD turbine would be able to draw power from the exhaust gasses but it would strip away some of the heat and charge from the gas. a vehicle size fusion plant would be compact enough to act as a core for the drive itself since it only has to power the drive itself, not the entire craft.

 

[Condottiere]

Currently, I don't see any underlying assumptions in Mongoose Second regarding propulsion, though in Mongoose First, you can assume it was limited by inertial compensation.

And even then, accelerating above and beyond that for six minutes shouldn't be an issue, if the crew is buckled down.

 

[wbnc]

Currently, I don't see any underlying assumptions in Mongoose Second regarding propulsion, though in Mongoose First, you can assume it was limited by inertial compensation.

And even then, accelerating above and beyond that for six minutes shouldn't be an issue, if the crew is buckled down.

If I remember right the longest dogfight in history was around ten or fifteen minutes with both pilots pulling six to nine gees at a time. ttey we're able to stay in the fight..although the pilot needed some help getting out of the cockpit later.

I know Swede Vejtasa pulled nine gees for extended periods while he was engaged with several Japanese Zeroes...in a dive bomber, fighting three at a time in several passes....he won....the zero pilots (that survived) had to explain a dive bomber killing several of their flight and flying away in one piece....although I am to understand his rear gunners shorts were KIA.

 

[AnotherDilbert]

Most likely he experienced short bursts of high G during the extended dogfight. I think dive bombers were extremely well trained and experienced with high positive G forces. (Blue line below.)

Trained fighter pilots seem to have about this tolerance:

Even in the best case 9 G for several minutes is not tolerable, or perhaps even survivable. The best case is acceleration forwards.
As we can see from the green and blue lines tolerance plunges down to 2-3 G after 3 s duration in an up or down direction.

Regular untrained humans can pass out and probably eventually die under 4 - 6 G.

In Traveller space combat it would be much worse, you would experience a high constant G force in one direction (the craft's acceleration), while being spun around the craft's centre of gravity as the craft turns to manoeuvre, adding more acceleration in another varying direction.

Source: https://en.wikipedia.org/wiki/G-force#Human_tolerance

 

[Condottiere]

I wasn't thinking in terms of extreme manoeuvres, more like quick shoves such as during planetary take off.

For that, you probably do need acceleration bath tubs and highly trained and fit pilots.

 

[Reynard]

This sounds slightly like the Heplar reaction system from MegaTraveller and T4. That actually uses a fusion power system to initially create the plasma if I remember and the Heplar boosts it for the high acceleration.

By the way, how do you produce reaction mass from a reactionless system that uses electric power to manipulate gravity? Also, isn't the HG2e Afterburner system a way to boost the main maneuver system?

 

[AnotherDilbert]

Also, isn't the HG2e Afterburner system a way to boost the main maneuver system?

The HG Reaction Drives are completely independent of the Manoeuvre Drive.

 

[wbnc]

This sounds slightly like the Heplar reaction system from MegaTraveller and T4. That actually uses a fusion power system to initially create the plasma if I remember and the Heplar boosts it for the high acceleration.

By the way, how do you produce reaction mass from a reactionless system that uses electric power to manipulate gravity? Also, isn't the HG2e Afterburner system a way to boost the main maneuver system?

Heplar has always been my go to for a starships reaction drives...the "fuel" used by a reactor is only partially used to sustain a fusion reaction. Since by all theories a fusion reactor will burn only liters of fuel instead of Displacement tons of fuel a month at the absolute worst efficiency projected. The rest is heated to plasma channeled into thermocouples and MHD turbines, then used as reaction mass getting a solid boost from a systems sort of along the lines of an ION drive. if the ship is not using thrust, or other high load systems (in standby, or 'sleep" mode) the system is running at idle using only enough fuel to operate the MHDs. the exhaust from the MHD is trapped and recycled.

Although how you convince hydrogen plasma to return to Liquid hydrogen without a process that requires machinery taking up a small warehouse complex is beyond me.I'll leave that to the engineers out there.

-----------

As I understand it the Boosters are reaction based systems that work in conjunction with the Gravity based drives of a ship. the Maneuver drives deliver consistent longterm thrust and the boosters give the ship a kick in the pants during combat or emergency maneuvers.

The answer to how do you get reaction mass from a reactionless system no idea....Although I can think of all sorts of ways to use a gravity based system to impart extra energy to reaction mass generated by an attached system...

 

[phavoc]

This sounds slightly like the Heplar reaction system from MegaTraveller and T4. That actually uses a fusion power system to initially create the plasma if I remember and the Heplar boosts it for the high acceleration.

By the way, how do you produce reaction mass from a reactionless system that uses electric power to manipulate gravity? Also, isn't the HG2e Afterburner system a way to boost the main maneuver system?

Yes, the HePLAR thruster plates got me thinking of how to bridge the gap.

I, for one, have never thought of the grav M-drive as being completely reactionless. But for all intensive purposes it requires no 'fuel' to run. Instead it expels ions or some other particle in minute quantities, but enough so that actual thrust is achieved. If fits in the ST universe for their drives, so it's not unheard of. And, if you go with this sort of idea, using hydrogen to boost your thrust isn't terribly unreasonable.

 

[wbnc]

This sounds slightly like the Heplar reaction system from MegaTraveller and T4. That actually uses a fusion power system to initially create the plasma if I remember and the Heplar boosts it for the high acceleration.

By the way, how do you produce reaction mass from a reactionless system that uses electric power to manipulate gravity? Also, isn't the HG2e Afterburner system a way to boost the main maneuver system?

Yes, the HePLAR thruster plates got me thinking of how to bridge the gap.

I, for one, have never thought of the grav M-drive as being completely reactionless. But for all intensive purposes it requires no 'fuel' to run. Instead it expels ions or some other particle in minute quantities, but enough so that actual thrust is achieved. If fits in the ST universe for their drives, so it's not unheard of. And, if you go with this sort of idea, using hydrogen to boost your thrust isn't terribly unreasonable.

I actually like the concept "electric rockets" for maneuver drives.....they turn electricity into exotic particles ( Super heavy Bosons, Gravitons, what have you) which provide the energy to move the ship. It's not exactly the same as the standard grav plate but it seems a little less like magi-tech.

When I did my own setting I did include reactionless drives that do not use particles at all. they cheat by expanding pinpoints of time-space in a rapidly cycling pattern. the "plate" gets repelled by the shockwave of the bubble when it pops and transfers that nudge to the ship. a few thousand pinpoint bubbles per meter are generated. since the emitters are fixed to the hull they generate the next batch of bubbles in a slightly different position so effectively the shock wave is riding along a few nanometers from the thrust plate.

Of course this jus allows around 1-G acceleration and lower power systems provide a counter force to local gravity so ships pack large HEPLAR style drives for high impulse thrust.

 

[Condottiere]

Manoeuvre drive disadvantages pretty much confirms that it's tied to gravity manipulation.

 

[dragoner]

A rocket can have a higher acceleration (resultant force) than 6G's, it is just that the impulse winds up less because of the maneuver drive's constant thrust. It's a good place for drop tanks, to hold the reaction mass (fuel), then jettison the tank after using the fuel.

About the Maneuver Drive itself, even though not stated, it could be something similar to what Alastair Reynolds described in Revelation Space, something that affects inertial mass interactions on a quantum scale, then the actual engine could be as simple as a VASIMR, with the added benefit is that it could explain the inertial compensation that spacecraft have in Traveller.

 

[Condottiere]

If the manoeuvre drive created an inherent inertial field, you wouldn't have options of a gravitated hull, and a non-gravitated hull.