Project High Velocity Interplanetary Passenger Spacecraft

[jedidia]

Thus if the EM wave travelling in a tapered waveguide is bounced between two reflectors, with a large velocity difference at the reflector surfaces, the force difference will give a resultant thrust to the waveguide linking the two reflectors.

er... I'm not too hot in relativistic physics, but as far as I understand it light ALWAYS has to travel at the speed of light relative to any reference frame. So where do they take the velocity difference from? The only way is to put the two reflectors in two different frames... i.e. one of them NOT on the ship.

 

[docabn]

The self propelled sail sounds about as practical as a sailboat with a giant fan .

Actually on the water I think that idea would be extremely practical except that the same energy would be better used if the propeller was in the water.
Lacking water however there is no solid object to push against. I am however unsure of how much thrust you could develop or how much push back you might get from the generator it’s self as it casts the artificial solar wind into the sail.

 

[raftdood]

Read "A Mote in God's Eye" by Jerry Pournelle & Larry Niven. Has a good section in it on Light Sails.

 

[Hielor]

Actually on the water I think that idea would be extremely practical except that the same energy would be better used if the propeller was in the water.
Lacking water however there is no solid object to push against. I am however unsure of how much thrust you could develop or how much push back you might get from the generator it’s self as it casts the artificial solar wind into the sail.

First off: please switch back to the default font color. I'm sure that the color you chose looks great for you, but keep in mind that some people use different (ie, dark) forum skins, and dark text is hard to read.

Secondly: If you're blowing a fan into your own sail, you're not really doing much of anything--the sail wouldn't generate any more thrust than the fan itself would if you just turned it around.

As for the EmDrive: I'll believe it when I see it working.

 

[T.Neo]

As for the EmDrive: I'll believe it when I see it working.

Ditto.

 

[docabn]

my appologies for the font, I think I fixed it let me know if not

and I retract my last comment I definitely had my physics reversed. The energy that struck the sail would have to somehow have more energy when reflected back into the cosmos than when it left the EM generator.:embarrassed:

 

[Zachstar]

Emdrive is bogus until they allow more independent testing. Also its not meant for anything but large craft in Geosync orbit. Its no good at propelling to moon or beyond. Thus useless for the timeframe.

I admit I have not attempted a high speed transfer in IMFD tho. Is your craft one that burns out of orbit at relatively high speed? Spirals don't really work in IMFD.

The reason NASA and other space orgs use "Windows" is because otherwise the time and energy used to arrive would be horrid. However at high speed the extra distance ought to be only a matter of how fast you want to get there. You may get there quicker and a bit less energy used in a window but either way you are flying out of the solar system at high speed if engines fail regardless. A simple distance from earth div speed ought to give you time.

 

[T.Neo]

I have a high acceleration of 1-1.5 G, so I'd imagine my flightpath would be more like that of a chemical booster than a VASIMR or ion drive.

 

[Zachstar]

Ah then it ought to not be a problem 1 burn to get on the general path then a 3 hour 1G burn to get to mars in a week or whatever.

 

[jedidia]

Heinlein did Jupiter in 6 months with 4 hours at 1 G in "farmer in the sky", if I remember correctly.

alas, that's 141,264 m/s of delta-v, most of which you have to anihilate again on arrival, so it might take this beasty a little longer. For longer distances, it might actually be faster to have less thrust and more ISP.

 

[Zachstar]

Guess it all boils down then to how much "futuristic" the engine is.

VASIMR on a fusion electric reactor is first step extremely low ISP compared to later designs. It will atleast 100 years before we are able to develop a fusion product engine that gets near the theoretical limits of ISP when it comes to fusion period. Such designs would enable colony travel to other solar systems making inner solar system travel a breeze.

 

[T.Neo]

alas, that's 141,264 m/s of delta-v, most of which you have to anihilate again on arrival, so it might take this beasty a little longer. For longer distances, it might actually be faster to have less thrust and more ISP.

I get 44 days to Jupiter (at position at time of posting) at 200km/s (not including time and distance needed to accelerate), and 5.6 hours to accelerate to that speed at 1G (3.7 hours at 1.5 G). Keep in mind though that I have the mathamatical proficiency of a goldfish.

I don't see how lowering the thrust will change much if the Dv stays the same. The ship is supposed to have a Dv of 500km/s, 200km/s is just the nominal interplanetary cruise velocity.

 

[jedidia]

The ship is supposed to have a Dv of 500km/s, 200km/s is just the nominal interplanetary cruise velocity.

Ah sorry, I misread. I thought it was to have 200km/s of delta-v. 500 is indeed pretty much all the delta-v you'll ever need.

I don't see how lowering the thrust will change much if the Dv stays the same.

well, if you sacrifice Thrust for ISP, you get more Delta-V. However, since it's now established that it's going to have 500 km/s, I wouldn't know what to do with more delta-v anyways :lol:

 

[Zachstar]

A properly designed fusion product engine isnt a VASIMR you dont really have to trade either or.

Its not pure fantasy its just far away as far as tech.

 

[T.Neo]

Indeed.

AFAIK getting a high thrust with a fusion engine (or any highly efficient engine really) is tricky at best though, most of the problems seem to be related to the exhaust vaporising the engine, hence the magnetic nozzles.

But considering where we are making just a sustained fusion reaction, it will be quite some time before we get started on any sort of fusion rocket.

Not that fusion rockets are the only concept that can have that sort of performance. Or that there is only one fusion rocket concept.

And there is always the deathspewer, uh, Nuclear Salt Water Rocket. :suicide:

 

[Sky Captain]

I think fusion rocket will be as much deathspewer as nuclear salt water rocket. Consider the fusion products will be traveling at something like 0,1 - 0,2c so anything they hit will become irradiated. A fusion engine itself also will become radioactive because of neutron bombardment.

 

[T.Neo]

Right, but the products themselves won't be radioactive (also, not all designs have such high exhaust velocity, some are lower at perhaps around 7840-8000 km/s). Needless to say, anything in the stream of the exhaust is not going to have a good day...

A fusion engine itself also will become radioactive because of neutron bombardment.

Perhaps aneutronic (or neutron-reduced) fusion would be the answer.

A radioactive engine isn't as bad as spewing still fissioning salts out of the engine. The engines could be constructed from primarily light materials too (such as beryllium or composites)- lighter elements will transmute into shorter lived isotopes.

Then again, both fusion and NSWR would probably be employed in interplanetary space, with their exhaust streams directed away from objects- at those exhaust velocities, the NSWR fission products would probably leave the solar system for good.

 

[docabn]

what about something like this?
http://www.hbartech.com/niac_sail1_final.pdf
Or is it just a bunch of bad science.

 

[T.Neo]

The science seems fine to me (I'm no scientist) but it is not an optimal propulsion system here- it seems to be very low thrust, and it relies on a uranium coated sail bombarded with antimatter. I don't really see recoating the sail (or affixing a new sail) to be practical, and I doubt the gains would warrant the inherant problems with antimatter...

It's a pity the stuff is so good.

UPDATE:

Basic structure of the front of the craft seems complete, though I have not yet added thrusters, thermal shielding or bells and whistles.

Suggestions are welcome.

 

[T.Neo]

Update

Basic structure around the propellant tanks is complete, and I've added basic docking ports to the node and the rear of the habitation module.

Now I'm moving onto the transfer tunnel, but I'm not really sure how a 200 meter long pressurised tunnel would be constructed- either a series of sections docked together like ISS modules, or sections that are fixed together in a vacuum and later pressurised, or any combination of the two.

I'm also thinking of having the truss extend over the transfer tunnel, but it may add too many polys.