Recent content by tori

What kind of pressure are we talking about here? kPa, MPa, more? What volume do you need and how long do you need to sustain it? Liters, cubic meters, working for a fraction of a second or minutes? Does it need to be restartable or is it a one-time deal? If you need a single-use MPa-range gas...

You're thinking of angular (rotational) momentum. Torque you do apply "in one go" (just start the engine or whatever you have at the end of the stick), angular momentum builds up slowly and gently. Applying angular momentum in one go (e.g. by setting large roll rate in the Scenario Editor of...

Yes, but momentum != thrust. With a given amount of energy, you can either make a whole bunch of low-momentum photons, or one high-momentum one. The relationship is linear on both sides, so it cancels out. It is clear from the pythonesque math dump in my previous post. Edit: RisingFury was faster.

Well I don't know, those numbers appear to match pretty well ;). If the momentum of a single particle released is p, then in order to get a thrust of F (Δp/Δt), you're bound to release n (F/(p/t)) particles. h = 6.626e-34 (J*s, planck) c = 299792458 (m/s) L = 5e-12 (m, 5 pm gamma photon...

I don't think so, even if we do, we're still looking at 300 MW/N of thrust (as with any other photon drive). This assumes 100% efficiency of both the reaction and the reflection (producing gamma radiation of laser-like directionality). Assuming one pair gives off 1022 keV of energy, a drive...

Yes. (my result was slightly different probably due to lack of roundingapproximated SB constant)

The result is 3509.56 W. You're probably looking for specific heat radiation rate, in which case drop the Ac from the equation (82.77 W/m²).

(obligatory 2001 reference)

The PROFAC concept came close - mining Earth's atmosphere. Profac, PRopulsive Fluid ACcumulator, was described by its inventor, Sterge Demetriades, in the pages of the British Interplanetary Society's Journal as long ago as 1959. In this concept, a nuclear electric vehicle would orbit in the...

We've been using GPS in a number of stratospheric missions (the upcoming flight is called "czANSO") in well over 120,000 ft. Accuracy and stability was just as good as on the ground.

tl/dr: they can be made to be restartable, but most designers choose not to (added expense, complexity, points of failure, mass)

The energy required to break a molecule of H2O is equal to the energy released by producing it (burning hydrogen). The efficiency of both processes is not absolute however. You can e.g. electrolyze water with an efficiency of let's say 20%. Then you burn hydrogen releasing the energy and...

A lunar manufacturing outpost that posseses a mass driver for launching sats to GEO would be an attractive target to take over, for example.

There's one thing up there that is definitely worth fighting over: our assets. We have our comm sats, GPS sats, spy sats and more in the near future. Our ground forces depend on these. An enemy with very basic space technology (light lift vehicles, orbital rendezvous) has the ability to deliver...

Less than most people think. It's virtually nonexistent in the Earth-Moon system, with the exception of the deepest parts of Earth's gravity well. Heavy translunar traffic (for which it would be uneconomical to ferry H2 from Earth) and lunar outposts running on hydrogen-based propellants...