Electric Propulsion Magnets Ready for Space Tests

But not a calorie tax.

Your comment has just made me realise that when people say “woke” to mean “anything I don’t like” the subtext is “I don’t want to face up to the responsibility and effort required to participate in a decent society. I just want to do whatever I like without consequences.”

Thanks for providing the trigger for my insight.

> What rocket equation cares is reaction mass not energy: ve

Break out exhaust velocity.

Experimentally baguettes are bad for superconductor operations: https://www.theregister.com/2009/11/05/lhc_bread_bomb_dump_i...

Fill a surrounding container with a volumetric shit ton of nitrogen gas (perhaps with stepped pressure gradients) and you might be able to radiate a significantly larger amount by increasing your surface area without drastically increasing your weight (or use nuclear power to mitigate the weight concerns).

But yes, today’s design space generally prefers as low a power envelope as possible to not have to worry about dissipation.

There are several ways a spacecraft engine can be efficient. The fundamental thing is the tyranny of the rocket equation: in order to get faster you need fuel, and then you need fuel to push that fuel, into a compounding way. The best way to address this tyranny of the rocket equation is to have an engine that expels something at a very high speed. The best chemical rockets push hot gas at about 4.5 km/s. The engines discussed here are "magnetoplasmadynamic thrusters" [1]. They push plasma with a velocity in excess of 15 km/s. Some studies suggest even 100 km/s. They are basically the most efficient rocket engines our current technology can build.

The next type of efficiency is how much of the source energy is converted into the energy of the plasma jet. Is it 50%, 90%, 99%. That I don't know, and obviously you want as much as possible.

But this project is addressing a different problem. In order to create this plasma jet, you need a very strong magnetic field to contain the plasma while it is being accelerated. The field itself does not provide the propulsion, it is there only for containment. You don't want to expend a lot of energy maintaining this field. Superconducting magnets are much better than regular electromagnets, so it's no surprise that containing this plasma with superconducting magnets requires a fraction of the power of regular magnets. But someone still needed to do the actual research. What works on paper doesn't translate always in things that work in real life. These guys did just that, and now are ready to send a technology demonstrator in space.

[1] https://en.wikipedia.org/wiki/Magnetoplasmadynamic_thruster

You’d get more thrust, but lower delta-v for the same total mass, because you’re replacing propellant mass with fixed mass.

That is an economic question. What does efficiency costs vs what does providing more power cost?

It's worse than you think. Here's a really interesting article on what it would take to get Epstein drive performance:

https://toughsf.blogspot.com/2019/10/the-expanses-epstein-dr...

This thing would produce more power than all of civilization does today. No radiator could handle it. They use laser fusion, exploding D-He3 fuel pellets well behind the ship, with a giant magnetic nozzle. A tungsten heat shield protects the ship, and reaches an equilibrium temperature without active cooling.

In the Expanse though The Drive is always on, which means the ship is tossing propellant mass (efficiently) out the back of it - which means it can dissipate most of it's heat that way.

Thanks for the link.

Sometimes I wish Xanadu had actually happened. The moment I opened the article I saw something like |R^3. Honestly speaking I don't really know what |R means. And R keeps showing up all over the article.

I will dig more into this using ChatGPT with time.

But I could understand very little from reading the article.

They're only inefficient if you want them to do something other than heat up a lot of air by a very large amount very fast. :)

Agreed that I know very little about this subject.

But heat itself can be imagined as a kind of field. For eg: A candle, the closer you move to the flame, every point closer to flame, the temperature is higher. The farther you move apart the temperature reduces. Same with the Sun.

Take for eg- Sound. The closer you move to the source of it, the louder it sounds, the farther you move from it, the fainter it gets.

Now you could call this a wave. Like the wavelength stretches with distance, also decreasing frequency and amplitude. Another way of looking at this a field. Imagine 3D space with points, like a lattice. Each point has a value, and the values get denser to the center, and move farther apart as move away from center.

If Im not wrong a lot of physical phenomenon exhibit this behaviour. Including thing like light, sound, temperature, gravitation etc.

While you can make a beam of light, I doubt you can make a beam of magnetic field(ray?) or gravity for that matter?

There are many efficiency metrics. For instance, how much energy went into constructing and deploying the bomb vs. how much destruction it caused. I think large nuclear bombs would look quite ok on this metric.

I mean, if Starship works well, it could theoretically retrieve the ISS in a piecemeal fashion.