Alternate Thrusters/Maneuver Drives & Antigravity

[John Snead]

Several things have always troubled me about Traveller thruster plates. The most obvious problem is that (depending upon the exact rule system) most versions of Traveller have either thrusters or power plants sucking down simply ludicrious quantities of hydrogen for what is allegedly a fusion plant generating electricity to power a reactionless drive. Then, there are the various issues with reactionless drives themselves (including how easy it is to weaponize them).

One idea that I've always liked is to change Thrusters into reaction drives, but of a very particular (and highly efficient) sort - make them a total conversion drive that converts hydrogen into a directed beam of neutrinos - I'd make this technology related to nuclear dampers. Neutrinos are good both because the drive exhaust is not particularly visible (good for stealth) and because its harmless, allowing ships to land or dock at space stations w/o incinerating their surroundings. Running the numbers, the results also look pretty darn close to the actual figures for how must hydrogen power plants or manuever drives use. Using a loaded mass of 680 tons for a 100 DTon Scout/Courier (from TNE, and a good intermediate figure between the 916 ton mass of a a 100 DTon MT Scout and the 350 ton mass of a 100 DTon GT Scout ) & throwing the rocket equation at it

ln (ML / MB) = CB / Isp*g

ML is the launch mass, MB is the all-burnt mass, CB is the rocket velocity in metres per second at all burnt, Isp is the specific impulse in seconds and g is the acceleration due to gravity at launch in metres per second per second.

Using this, 1 ton of hydrogen accelerates the ship to a velocity of 430 km/hour, which works out to 12.25 G-hours. So, a not unreasonable 8 tons of fuel works out to 98 G-hours, which is sufficient for any remotely reasonable purpose (allowing for a 12% fuel reserve and deceleration, this gets you from Earth to Jupiter in less than a week).

While I'm at it, I'd also modify contragravity a bit too. In my idea, contragravity (aka antigravity) can be used for both lift and propulsion, but decreases in power with the inverse square law (just like normal gravity). A 6 G contragravity drive remains the most powerful gravity drive possible to build, and at 100 diameters from a 1 G world like Earth, this drive would generate a thrust of 0.0006 Gs, which nicely limits antigravity w/o making it useless.

So, for landing and take-off, ships use contragravity, while for in system travel they use neutrino thrusters.

Thoughts?

 

[Tellon]

I dont do Thuster Plates nor Jump Drives -- I know some folks are gonna complain that my STL Hard-Sci style is not Traveller -- but oh well .. lol

But yeah, Thruster Plates -- too much of a "convienence" tweak IMO

 

[Peter Schutze]

>Neutrinos are good both because the drive exhaust is not particularly visible

arent neutrino detectors a basic part of finding "high tech" civilisations ?

I'd think that being able to detect civilian reactors at several AU range would equate to detecting a starship under drive from anywhere in the system as long as you are roughly behind it

 

[John Snead]

>Neutrinos are good both because the drive exhaust is not particularly visible

arent neutrino detectors a basic part of finding "high tech" civilisations ?

I'd think that being able to detect civilian reactors at several AU range would equate to detecting a starship under drive from anywhere in the system as long as you are roughly behind it

It's still far less visible as a standard reaction drive, because you can only detect the neutrinos behind the ship, perhaps in a 30 degree wide cone, if the drive is tightly focused. That gives a whole lot of directions where the ship is undetectable. So, if a ship is coasting or accelerating towards you, there's no more chance of detecting it than there was using reactionless drives.

 

[Icosahedron]

Is there a RL scientific process by which Hydrogen can be converted entirely to neutrinos, or is this a complete handwave?

I do a similar thing with AG.

 

[Peter Schutze]

been doing a lot of research related to solar sails and other low tech maneouvre drives and a thought struck me

If we use lasers to feed power to a solar sail .... how far away would that be detectable ?

Should we have a seti program looking for lasers ?

 

[FreeTrav]

The thing about lasers is that they're very directional, so you don't see them unless they're pretty much pointed right at you. As far as detectability, that's going to depend largely on the power available to put into the laser. Robert L. Forward discusses some of the issues in the hard-science addenda to his SF novel Rocheworld (available from Baen Books).

 

[Whipsnade]

If we use lasers to feed power to a solar sail .... how far away would that be detectable ?

Peter,

As Jeff pointed out, the answer to that question is going to depend on where the lasers are aimed. It's also going to depend on how powerful the laser or lasers are.

In Niven's and Pournelle's classic The Mote in God's Eye, the Moties use a huge complex of lasers to first accelerate then decelerate a small pod across several light-years between their own system and the human inhabited New Caledonia system. New Caledonia is "behind" the Coal Sack Nebula from Earth and that nebula looks like a hooded man from it's the system's perspective with a nearby red supergiant providing a single baleful eye. The Mote system's primary could be seen as just a yellow fleck within that huge red eye.

Just a yellow fleck until the Moties built their launching laser complex.

That complex was so large, and was aimed at New Caledonia, so what had been a barely noticed yellow fleck became an easily seen green dot. The effect was so striking it triggered a religious schism on New Caledonia.


Regards,
Bill

P.S. One of the plot holes in the book, IMHO, concerns the green "mote" seen by the people of New Caledonia. Although New Cal and the Empire as a whole are going through a "Long Night", the green Mote should have been recognized as artificial and thus the product of an intelligence. The light would not have been as coherent as normal laser emissions after travelling all the distance between the two systems, but it still would have been far more coherent than naturally occurring light. While the people of New Cal had lost a great deal of technology during the Empire's collapse and a nasty in-system war with another inhabited planter New Ireland, they were still able to maintain Langston Field generators, terraforming stations, and other parts of their tech base. The idea that not one person on New Cal ran the light streaming from the green Mote through a spectrograph is quite a suspender snapper and one I noticed when I first read the book as a teen.