If there is a propellant, you'd need to store that somewhere first, right? Does each particle of the propellant exit the rocket with much higher energy? Or can Argon be stored in a much denser form than other fuels?
Traditional engines burn fuel, and the expanding, hot fuel pushes itself out the back of the engine at high speed, pushing the rest of the spacecraft forward. The fuel containing the energy is also the propellant.
Ion engines are the opposite in almost every way. You spend a lot of electrical energy (solar, nuclear, whatever) speeding up a tiny amount of propellant (which is usually something non-reactive like argon). You shoot a little bit of fuel at insanely high speeds out of the engine, and it pushes the spacecraft forward a little bit- so you do it for a very long time.
Yes, ion engines still need propellant, but they need a whole lot less of it.
I was at a demo for a plasma engine similar to VASIMR back in the 90's at a national lab. It was a long machine running the length of a large room. There was a window in the side where you could see the plasma. When we showed up there was a faint pinkish plasma barely visible in the window. The guy who was showing us around told us they were just getting ready for the demo and we should wait a few minutes. After a few minutes of the plasma being off, one of the engineers gave a thumbs up. Our guide pulled us close to the window and said "Watch this!". Nothing happened. "One more second!", he said. Then we smelled burning electronics. "Shit!", he said and ran towards the power supplies.
My co-founder and I looked at each other and smiled, because it was so nice to be on the other side of that situation. I knew exactly how the guys felt. Usually we were the ones trying to demo an experiment that sort-of, kind-of worked.
If I make a mistake in my code, it generally doesn't escape magnetic confinement and instantly vaporize other portions of my system with the fury of the sun.
However, this is not really 'new' tech. https://en.wikipedia.org/wiki/Deep_Space_1 used an early version in 1998.
As discussed in the article, this is a very different kind of ion thruster. That category is quite large. In particular, I believe essentially all ion thrusters flown have been electrostatic ion thrusters, including both Deep Space 1 and the Hall thrusters discussed in the article.
https://en.wikipedia.org/wiki/Ion_thruster#Electrostatic_ion...
In contrast, the VASIMR engine discussed in the article is an electromagnetic ion thruster
https://en.wikipedia.org/wiki/Ion_thruster#Electromagnetic_t...
(Apologies if you didn't intend to suggest the tech isn't that new, and just meant that the low-propellant-usage part isn't that new.)
- Specific impulse / Isp (aka how much thrust you get for a given amount of propellant)
- Maximum Thrust
Due to the rocket equation [1], adding more propellant increases the weight of your vehicle, making it harder to move, requiring more propellant, etc etc. So being efficient with your propellant is very good.
That said, given a requirement against a gravity well (e.g. a planet), there's usually a minimum total thrust required for a given maneuver to be successful (low total thrust = maneuver takes longer = more time for gravity to pull you = more propellant required).
Thus far, we generally have two types of engines. (1) High maximum thrust, lower Isp (chemical rockets) & (2) high Isp, low maximum thrust (ion/electric engines). The two are currently very far apart [2, sort by Specific Impulse decreasing, then look at the Thrust column].
As examples (Isp Vacuum / Thrust Vacuum): NEXT ion thruster 4,100s/0.236N @ 6.9 kW, VASIMR 5,000s/5.7N @ 200 kW, Space Shuttle SRBs 268s/14MN.
The hope with VASIMR is that it provides a middle ground where high Isp is available with enough total thrust to actually be useful for something other than slow orbital adjustments. An example of "something useful" would generally be anything beyond Earth orbit that covers large distances, e.g. flying to Mars.
[1] https://en.wikipedia.org/wiki/Tsiolkovsky_rocket_equation
[2] https://en.wikipedia.org/wiki/Comparison_of_orbital_rocket_e...
Sounds incredible. I wish him the best of luck.
Many commercial satellites use it for station keeping.
https://en.wikipedia.org/wiki/List_of_spacecraft_with_electr...
What a load. Aside from the repellent need by the author to inject politics into a science story, it's flat-out wrong: the rancor isn't over people who (like Chang-Díaz) pursue legal citizenship or legal residency, nor is it over people who speak a particular language simply on the basis of that language.
These controversies, taken individually, could be viewed as legitimate questions about the ethical grounds for birthright citizenship, or the appropriate scope for recusal, or the balance between mercy and safety. But in aggregate it's clear they aren't any of those things. They're expressions of a xenophobic insistence that immigrants, particularly non-white immigrants, are "the other". That they are cheaters, that they can't be trusted, that they are /dangerous/. That's xenophobia and racism, and it has nothing to do with the rule of law.
Case in point: in the last couple of months, how much have we heard the "we are a nation of immigrants" line, especially during a border security debate...as if just about everyone, including the passengers of the Mayflower, skirted customs?
The racists and xenophobes likely don't want immigrants, but I think the vast majority of Americans are happy to welcome folks from other countries who have demonstrated respect for our laws by entering the country legally. Hell, if you've spoken to naturalized citizens, they're often the most patriotic, pro-American people you'll encounter!
And many of those Americans, who have spent time, money and energy to become citizens, are strongly against the lackadaisical border enforcement that has led to the current mess.
