[Spaceships] Alternate System Usage Questions

[DaltonS]

1. Ramscoops (SS1:p21)
   1. Can ramscoops be used to refill fuel tanks emptied while accelerating to minimum ramscoop velocity (1,800 mps) If so, what would the refill rate be?
   2. If a ramscoop is being used for this instead of feeding a reaction drive, what sort of drag (deceleration) would need to be compensated for?
2. Solar Mirrors (SS7:p18)
   1. Can a Solar Mirror be use to increase the power output of a Solar Panel Array (SS1:p25)?
   2. How can a solar mirror be used as a weapon? Or a mining tool?
   3. Shouldn't a "Solar Boiler" (SS7:p15) be a "Hull" system to access energy from the solar mirror?
3. Can Force Wings (SS7:p23) be used in conjunction with Hyperdynamic Fields (SS7:p24) to acquire the Hyperdynamic benefits of streamlining and the winged design option?

Dalton “Expiring minds want to kno....” Spence

[RogerBW]

As I see it:

I. That depends on how much you de-rate your drive. One ramscoop produces enough fuel for one drive system running at full power; if the drive is running at half power, the other half of the fuel flow can be filling the tank. This should also deal with any drag you encounter. (At least in a universe where ramscoops work at all.)

II. The panel array can probably convert all the light that hits it. Other things will be up to GM choice, but focusing will be hard.

III. Universe-dependent.

[weby]

Ramscoops: as RogerBW said, likely at reduced speed if ramscoops actually work.

Solar Mirrors: The problem with solar panels is really that the required area to get anything comparable to the other power plants is ridiculously large and that the real energy received is so variable based on distance so really solar panels would work fine as the axillary power system for things close to stars like at earth orbit, but not for high energy systems like weapons.

As example the SM +10 major battery as beam weapon outputs 3GJ and thus you likely need a lot more than that to fire it due to inefficiencies.

Total Solar radiation at distance of 1 AU is on average 1.36 kw/m^3, so with a super science 73.5% efficiency(where normal efficient solar cell today is maybe 20%) you would have 1kw/square meter and to get 1 GW(allowing you to shoot maybe every 5-15 seconds depending n your weapon efficiency) you would need a solar panel 1 km by 1 km(SM +19)

And going to mars you would need more than double the area.

So adding solar mirrors you would thus need similar areas of mirror...

A solar mirror is likely usable as weapon.. just not at any sort of range as the focusing of such is likely optimized to do the primary job. But if you want to boil someone on your ship hull, it is likely fully possible. (Also note the relatively low energy you get compared to any weapon unless your mirror that huge thing listed above for solar panels)

Yes, a solar boiler should likely be on hull, though it is possible to build heat exchanges on the hull with connections deeper, but that would likely add extra mass compared to a on the hull system.

Force wings and such: whatever the GM chooses.

[Flyndaran]

Why refill when you're using the Ram at all? I assumed you refill everything during the deceleration phase at the end of the voyage.
But that requires a more realistic modified Scoop, not the original untenable Bussard Ram.

[DaltonS]

Originally Posted by weby

Solar Mirrors: The problem with solar panels is really that the required area to get anything comparable to the other power plants is ridiculously large and that the real energy received is so variable based on distance so really solar panels would work fine as the axillary power system for things close to stars like at earth orbit, but not for high energy systems like weapons.

As example the SM +10 major battery as beam weapon outputs 3GJ and thus you likely need a lot more than that to fire it due to inefficiencies.

Total Solar radiation at distance of 1 AU is on average 1.36 kw/m^3, so with a super science 73.5% efficiency(where normal efficient solar cell today is maybe 20%) you would have 1kw/square meter and to get 1 GW(allowing you to shoot maybe every 5-15 seconds depending n your weapon efficiency) you would need a solar panel 1 km by 1 km(SM +19)

And going to mars you would need more than double the area.

So adding solar mirrors you would thus need similar areas of mirror...

1. Does that mean each solar mirror system reflecting on a solar panel array provides the same energy as another solar panel? (Mirrors are cheaper than solar panels, after all.)
2. Is there a maximum power limit that a solar panel array can handle without damage?
3. Since both are “exposed systems”, could they be made retractable like exposed radiator panels (perhaps by doubling the cost)?

Dalton “It seemed like a bright idea at the time” Spence

[RogerBW]

[QUOTE=DaltonS;1903829]

1. Does that mean each solar mirror system reflecting on a solar panel array provides the same energy as another solar panel? (Mirrors are cheaper than solar panels, after all.)
2. Is there a maximum power limit that a solar panel array can handle without damage?
3. Since both are “exposed systems”, could they be made retractable like exposed radiator panels (perhaps by doubling the cost)?

That's all up to the campaign assumptions in your world. There is no formal rules answer to this.

[Anthony]

Originally Posted by DaltonS

[LIST=1][*]Does that mean each solar mirror system reflecting on a solar panel array provides the same energy as another solar panel? (Mirrors are cheaper than solar panels, after all.)

Until you hit intensities high enough to damage your solar panels (likely considerably higher than sunlight), pretty much. The main reason we don't use concentrating mirrors for solar panels on Earth is because making it work properly with the rotation of the earth pretty much eats any savings you might get from the mirror.

[weby]

A realistic solar panel module would likely provide much less than 1 power point at Earth distance.

Current panels provide up to 300 W/kg, thus that SM +10 ship module of 500 tons would provide about 150 mega watts at TL 8, thus you would need about 6 modules to provide the estimated 1 GW for 1 power point.

But there is a large margin of error on that 1GW, thus any range between about 3 (allow firing of a high efficiency (50%) energy weapon once every 20 second turn) and 120 modules(allow a 25% efficient weapon be fired every second) would make sense.

At higher TLs the structural weight might decrease and efficiency might increase, allowing that 1 module to finally give one power point at about TL 12 as armor at that point is 4 2/3 times as protective. (Or if the panels and weapons get very high efficiency, maybe at TL 11 or 10^)


But yes, solar mirrors would definitely increase the effect of solar panels at earth distance until the panel gets too hot. That depends a lot on the cooling you have and the exact composition of your panel. (and cooling uses mass, lowering the area you get for the same mass). I do not know the exact numbers but solar cell efficiency does go down with raised temperature. (The cells I have go down about 10% between having a surface temperature of 25 centigrade to 45 centigrade at same illumination level according to their data sheet)

In fact many experimental(and few real installations) of solar cells have solar mirrors "built in" to increase the illumination level.

Conclusion:
So in game terms I would likely not allow solar mirrors as such to increase the efficiency a great deal, as the likely technologies getting anything close to the energy indicated by "1 power point" would need to have things like reflectors as part of the design. And the design would likely be optimized to work at a given energy level. (and even then you likely need the several modules indicated above at earth distance). If you use simpler panel structures you fall further and further behind from that "power point"

I would however allow things like rigging extra reflectors to compensate for being further away from the sun than the design specs for the complex panels.

As for retractable: Yes, you could build panels to be be retractable, however that tends to increase the mass(thus you would get even less energy/mass unit)

TLDR; You need a lot more mass than spaceships solar panels likely and reflectors are likely already part of advanced space based solar panel arrays.

[Varyon]

Vehicles had a retractable panel for mounting solar cells be double weight and cost. Note this is double cost and weight for the panel, not the cells. I've been working on adapting Vehicles for use in Spaceships (and throwing out abstract PP in favor of kW/ton in the process), and what I worked out there was that simply doubling the cost of the entire solar panel assembly (no change in weight or output) is sufficient to make it retractable (by using more expensive materials for the panel if it's made retractable).