
NASA’s longshot bet on a revolutionary rocket may be about to pay off - mreithub
https://arstechnica.com/science/2017/02/nasas-longshot-bet-on-a-revolutionary-rocket-may-be-about-to-pay-off
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mreithub
One thing I don't quite get is their claim that the rocket would need "just
some solar panels" instead of a fuel tank when in the paragraph before that
they talk about exhausting argon-based plasma.

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?

~~~
Retric
Specific impulse or Isp is what you want. And yes, ion thrust takes a lot less
propellant.
[https://en.wikipedia.org/wiki/Ion_thruster](https://en.wikipedia.org/wiki/Ion_thruster)

However, this is not really 'new' tech.
[https://en.wikipedia.org/wiki/Deep_Space_1](https://en.wikipedia.org/wiki/Deep_Space_1)
used an early version in 1998.

~~~
jessriedel
> However, this is not really 'new' tech.
> [https://en.wikipedia.org/wiki/Deep_Space_1](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...](https://en.wikipedia.org/wiki/Ion_thruster#Electrostatic_ion_thrusters)

In contrast, the VASIMR engine discussed in the article is an electromagnetic
ion thruster

[https://en.wikipedia.org/wiki/Ion_thruster#Electromagnetic_t...](https://en.wikipedia.org/wiki/Ion_thruster#Electromagnetic_thrusters)

(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.)

~~~
Retric
They all need a propellant and power feed. But, you can use those same feeds
for an array of multiple engines. Thus, 'scaling up' has a wide range of
options and trade-offs. Vasimr let's you scale power output a lot from the
same engine, but so would an array of smaller engines.

With that in mind the specific techniques are important, but the gaps are
often overstated.

------
ctack
"Such an engine design offers a couple of key benefits over most existing
propulsion technology. Perhaps most notably, unlike chemical rockets, Vasimr
operates on electricity. As it flies through space, therefore, it does not
need massive fuel tanks or a huge reservoir of liquid hydrogen and oxygen
fuel. Instead, the rocket just needs some solar panels".

Sounds incredible. I wish him the best of luck.

~~~
Gravityloss
Electric propulsion has existed and been flown for decades.

Many commercial satellites use it for station keeping.

[https://en.wikipedia.org/wiki/List_of_spacecraft_with_electr...](https://en.wikipedia.org/wiki/List_of_spacecraft_with_electric_propulsion)

~~~
infogulch
The difference is this one can scale up the power/efficiency ratio on demand.

~~~
binarycoffee
I guess you mean the power-to-thrust ratio, which indeed scales roughly with
the specific impulse.

The thing is, pretty much every plasma propulsion device has the theoretical
ability to throttle specific impulse. Gridded ion engines and Hall thrusters
can for instance directly throttle specific impulse (Isp) by varying the
discharge voltage. Other plasma thrusters can do this by other means like
increasing RF heating, varying the magnetic field, etc.

Unfortunately, in real life the actual usable range of Isp always ends up much
narrower that initially predicted because of a variety of factors that are
difficult to predict theoretically (erosion and ionization efficiency in
particular).

AFAIK, due to the shear size and complexity of Vasimr, its thrust has never
been directly measured and we know very little about its actual performance. I
would therefore wait a little and discard sensationalist articles until real,
extensive testing has taken place.

------
shireboy
How are those superconducting magnets cooled?

~~~
randallsquared
In space, probably by shade.

~~~
NoGravitas
Isn't it extremely hard to dump waste heat in a vacuum?

~~~
netinstructions
I don't know how hard it is, but the ISS uses big radiators to dump excess
heat into space.

> The Station's outstretched radiators are made of honeycomb aluminum panels.
> There are 14 panels, each measuring 6 by 10 feet (1.8 by 3 meters), for a
> total of 1680 square feet (156 square meters) of ammonia-tubing-filled heat
> exchange area.

More info at [https://science.nasa.gov/science-news/science-at-
nasa/2001/a...](https://science.nasa.gov/science-news/science-at-
nasa/2001/ast21mar_1)

------
MrZongle2
FTA: _" And at a time when the national discourse assails the value of
Spanish-speaking immigrants..."_

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.

~~~
debatem1
With respect, I disagree. Derogatory terms like "anchor babies" describe
people who are, after all, US citizens of immigrant descent. Similarly, the
rancor directed at the judge in the Trump university case had nothing to do
with legal citizenship and everything to do with Hispanic ancestry. And
obviously refugees are legal immigrants granted that status by the US State
Department. But this doesn't prevent them from being the subjects of a great
deal of both fear and fury.

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.

~~~
MrZongle2
There may be some xenophobia and racism there, but I think there's also a
substantive amount of anger among a sizeable amount of the populace due to how
the rule of law is selectively applied, and how open-borders advocates
intentionally blur the lines between lawful immigrants and individuals who
illegally enter a sovereign nation.

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.

~~~
debatem1
I appreciate that you acknowledge that racism and xenophobia taint the
arguments you're making, even if you yourself are not racist or xenophobic.
It's hard to stand up for a view when it is held by people who are widely
reviled, and I suspect that courage is something our country needs more of.

However, I think the examples I provided compellingly demonstrate that issues
of legality do not sit at the core of the anti-immigration sentiment in the
US. In particular, an overwhelming concern for the sanctity of law would
likely not motivate one to demand that a sitting judge recuse themselves
because of their ancestry. Nor can it have motivated anti-refugee sentiment.

More broadly, the argument about rule of law does not have good explanatory
power for the actions and statements of those who make it. It does not explain
opposition to open borders, or to more expansive visa programs, which of
course could both be made law with comparative ease. And it seems obvious to
me that anti-immigrant militias like the Minutemen represent the height of
contempt for the rule of law, but somehow find a warm reception among those
who advance the very argument that you do.

Does this mean that nobody legitimately cares about the legality of
immigrants? Of course not. It is possible that a broad coalition of people
simply happen to agree on this wide range of narrow topics that have nothing
whatsoever to do with race or ancestry. But Occam's razor suggests that the
simpler argument is the better one: that duplicity and political convenience
are at play.

Specifically, I suspect that the broader anti-immigrant movement in the US
believes it has a winner of an argument in this one despite its lack of policy
prescriptions. As a result this argument-- the one you make-- often gets
advanced as a fig leaf for those "other" viewpoints. Which leaves you in the
awkward position of carrying water for some truly despicable people, whatever
your own views are.

~~~
MrZongle2
I can't speak for Trump's attack on the judiciary. He's barking up the wrong
tree there, and did little to help his case. It will likely be left for SCOTUS
to decide, as should be the case; judges shouldn't be cowed by politicians to
change their rulings.

We do disagree about the point about the sanctity of law. IMO selective
enforcement (engagement/detainment directives for the Border Patrol) and the
implicit support of "sanctuary cities" seem to encourage the violation of
immigration law. I think it is specifically the former that gave rise to
groups like the Minutemen.

As for carrying water for despicable people...well, so be it. I happen to
think that, as with any group, most are reasonable folks of decent character
but often overshadowed by the extremists and attention-seekers in their midst
-- an argument, I'm happy to point out, also made in the defense of foreign
individuals who come to this country under less-than-legal circumstances.

~~~
debatem1
Just to be clear: selective enforcement _is_ the law of the land. Has been
since before IIRIRA passed-- and enforcement was looser, not tighter, before
then. So when you say you respect the law, that's the law and I'd expect you
to either respect it or say plainly that you don't and why.

Regarding the Minutemen-- a gentle reminder that regardless of whether a
person is illegally in this country or not it is a felony to "point your gun
right dead at them, right between the eyes", as Chris Davis publicly advocated
for during the Minutemen's heyday. And of course, there's Shawna Forde, the
leader of Minutemen American Defense. She's an individual so law-abiding that
she has her own entry on murderpedia. And the cofounder of the original
Minuteman project was later charged with three counts of child molestation
including his own daughter, and is currently serving a nearly 20 year sentence
resulting from those charges. Then there's the allegations of influence
peddling and fraud that have embroiled the organization in litigation against
another founder, Jim Gilchrist... and the fact that Simcox cofounded another
related Minuteman project with Jason Ready, a known member of the American
Nazi party who received a BCD from the Marines, was believed by the FBI to
have been involved in the execution of at least two suspected illegal
immigrants, and finally wrapped things up with a 4-on-1 murder-suicide a few
years ago. Seriously law abiding folks, there-- and just as another reminder
_that 's the leadership_. That's who these supposedly lawful folks decided to
follow. Those are the people whose acts you compare the civil infractions of
illegal immigrants to.

You know what? I'll take the illegal immigrants, thanks.

