[Space/Spaceships] Getting the velocity/Delta V I want with the tech I want

[malloyd]

Originally Posted by scc

I've just generated data for the 4th star (Skipped the 3rd, the 4th is closer to what I've generated so far) And assuming that I've done things properly the outer two most orbits get more heating from the other stars.

If they are, your system isn't stable. If all the stars were the same luminosity/mass, the heating and gravity from each star would vary exactly the same way, and a planet getting more heat from a second star is also more strongly attracted to that second star, and thus isn't orbiting the first. That L/M ratio isn't constant, so it's theoretically possible this could happen, but the perturbations would be so huge every planetary year the orbit couldn't possibly be constant over long periods.

Your stars are still 150 plus AU apart right? Unless your "outermost" orbits are enormous you probably have a math error.

[Belial666]

Originally Posted by scc

Um, Belial666, the heat dissipation problems of lasers get WORSE in space.

First of all, free electron lasers aren't actually lasers - they don't have a lasing medium at all so the only heating problems come from the efficiency of your superconductors.

Secondly, heat pumps and radiators. This is again a brute-force approach; you pump the heat out of the FEL and into a high-temperature radiator. A highly conductive surface with a temperature of, say, 2000 Kelvin is going to be losing heat like crazy in space. With current technology you can effectively force-radiate 4 joules for every joule you spend running the heat pump or so. So the only limit to how much heat you can get rid of is the surface of your radiator and how much energy you got available - which is not going to be a problem due to a concentrated-sunlight solar plant providing it.

[scc]

Originally Posted by malloyd

If they are, your system isn't stable. If all the stars were the same luminosity/mass, the heating and gravity from each star would vary exactly the same way, and a planet getting more heat from a second star is also more strongly attracted to that second star, and thus isn't orbiting the first. That L/M ratio isn't constant, so it's theoretically possible this could happen, but the perturbations would be so huge every planetary year the orbit couldn't possibly be constant over long periods.

Your stars are still 150 plus AU apart right? Unless your "outermost" orbits are enormous you probably have a math error.

I think I said this earlier, I dropped the distances down. The mentioned star is a K2 orbiting a G4 at 51 AU, which in turn orbits and F5 at 136 AU. There's 3 other stars, a G0, G8 and a M0, but their 2000+ AU off. The other 5 stars heat the K2 a total of 94 degress

[malloyd]

Originally Posted by scc

I think I said this earlier, I dropped the distances down. The mentioned star is a K2 orbiting a G4 at 51 AU, which in turn orbits and F5 at 136 AU. There's 3 other stars, a G0, G8 and a M0, but their 2000+ AU off. The other 5 stars heat the K2 a total of 94 degress

Looks like math error to me then. Using the high end of luminosities for those (0.6, 0.8, 2.5, 1.5, 0.5 and 0.08 Lsun, the contributions of the stars other than the K2 at closest approach to the F5 should at the K2 would be 1360 W/m^2 times the sum of
1.5/2000^2
0.5/2000^2
0.08/2000^2
0.8/51^2
1.5/(136-51)^2

Or 0.889 W/m^2. Which is fairly minor. Are you adding temperature contributions instead of energies? By themselves those stars would heat something at the K2 to about 33 K, that is

The Stefan-Bolzmann constant is 5.67 x 10^-8 W/m^2K^4, and a test sphere of 1 m^2 cross section has a surface area of 4 pi, so a blackbody temperature T such that

0.889 W = 5.67 x 10^-8 W/m^2K^4 x pi m^2 T^4

For some other planet, say one at 0.8 AU from the K2 the combination would be about that 0.889 W/m^2 + 1360 x (0.6/0.8^2) = 0.889 + 1275. It should be fairly clear the other sun's contribution is minor. That extra 0.889 W/m^2 raises the blackbody temperature there by 0.006 K. As for equality, the K2 would contribute 0.889 W/m^2 at 30.3 AU, at which point that planet would have a temperature of 40K, and would sometimes be closer to the G4 than the K2 and thus not stably orbiting the K2.

[DemiBenson]

So let me see if I got this straight. The OP wants a setting where:

1. It's hard science
2. There's regular cargo shipment between very distant worlds
3. That regular travel does not use multi-stage designs
4. Fusion power is not used for spacecraft

The only way I can see this working involves either

1. Not humans, and therefore not limited by human boredom, age, economy, lifestyle, etc.
2. They devote so much of the planetary economy to this endeavor that they effectively pull themselves up a TL or two.

[scc]

malloyd, I've been using the 278*( 4th root of L / square root of R) formula, according to that G0 heats the K2 by 43 degrees, which is quite reasonable for something orbiting at 50 AU. The systems age is 3.7 billion years, so the L values of the stars are (Round to two decimal places):
F5: 4.36
G0: 1.58
G4: 0.79
K2: 0.27
G8: 0.46
M0: 0.09

[Anthony]

Originally Posted by scc

malloyd, I've been using the 278*( 4th root of L / square root of R) formula

Sounds like you're adding in the wrong place. For multi-star systems, you need to sum L/R^2 for all stars before taking the 4th root.

[scc]

Originally Posted by Anthony

Sounds like you're adding in the wrong place. For multi-star systems, you need to sum L/R^2 for all stars before taking the 4th root.

Sum L/(R^2) for all stars, then take the 4th root?

[Anthony]

Originally Posted by scc

Sum L/(R^2) for all stars, then take the 4th root?

Yes, I assume operator precedence of exponents is higher than division.

[scc]

OK, I've done that, net result is to reduce the amount of heating produced by the other stars by about half.

I've just got to figure out if it's possible/worth it to save the other habitable planets, with the older heating values I was getting two orbits inside the life zone