7 ms·

NASA’s longshot bet on a revolutionary rocket may be about to pay off

74 points by mreithub 10y ago

ctack 10y ago
"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 10y ago
  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_electric_propulsion https://en.wikipedia.org/wiki/List_of_spacecraft_with_electr...
  - infogulch 10y ago
    The difference is this one can scale up the power/efficiency ratio on demand.
    - Gravityloss 10y ago
      There's basically four inputs to electric propulsion: power source mass efficiency (W/kg), required delta vee (m/s), required acceleration (m/s/s), and exhaust velocity (m/s). (Well there's efficiency too.) You can approximately minimize total mass with this info. Turns out, your spacecraft will in total be heavier, if you go to higher exhaust velocities. You save on propellant but you need bigger solar arrays. Not worth it. All this talk about "Mars in x days" assumes a fantastic power plant. It's a little bit like you're starting a car company and showing wheels and saying "my car company enables range and acceleration three times that of Tesla" while you don't have any kind of battery or motor yet.
    - binarycoffee 10y ago
      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.
- nthcolumn 10y ago
  You would need two of these ion engines side by side, with solar panels say outside those and a bubble cockpit in front center with... :P
MrZongle2 10y ago
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 10y ago
  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 10y ago
    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.
mreithub 10y ago
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 10y ago
  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.
  - ethbro 10y ago
    (IAN a physics major) But to elaborate per my understanding, there are 2 important variables you're playing with in rocket engines: - 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 https://en.wikipedia.org/wiki/Tsiolkovsky_rocket_equation [2] https://en.wikipedia.org/wiki/Comparison_of_orbital_rocket_engines https://en.wikipedia.org/wiki/Comparison_of_orbital_rocket_e...
shireboy 10y ago
How are those superconducting magnets cooled?
- randallsquared 10y ago
  In space, probably by shade.
  - NoGravitas 10y ago
    Isn't it extremely hard to dump waste heat in a vacuum?
    - netinstructions 10y ago
      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/ast21mar_1 https://science.nasa.gov/science-news/science-at-nasa/2001/a...
    - dragonwriter 10y ago
      There's hard theoretical limits on the rate at which you radiate heat, so without contact with an external medium or dumping mass, you're pretty much stuck with limits based on how big your radiators are

74 points by mreithub 10y ago

ctack 10y ago

"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 10y ago
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_electric_propulsion https://en.wikipedia.org/wiki/List_of_spacecraft_with_electr...
- infogulch 10y ago
  The difference is this one can scale up the power/efficiency ratio on demand.
  - Gravityloss 10y ago
    There's basically four inputs to electric propulsion: power source mass efficiency (W/kg), required delta vee (m/s), required acceleration (m/s/s), and exhaust velocity (m/s). (Well there's efficiency too.) You can approximately minimize total mass with this info. Turns out, your spacecraft will in total be heavier, if you go to higher exhaust velocities. You save on propellant but you need bigger solar arrays. Not worth it. All this talk about "Mars in x days" assumes a fantastic power plant. It's a little bit like you're starting a car company and showing wheels and saying "my car company enables range and acceleration three times that of Tesla" while you don't have any kind of battery or motor yet.
  - binarycoffee 10y ago
    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.
nthcolumn 10y ago
You would need two of these ion engines side by side, with solar panels say outside those and a bubble cockpit in front center with... :P

MrZongle2 10y ago

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 10y ago
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 10y ago
  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.

mreithub 10y ago

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 10y ago
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.
- ethbro 10y ago
  (IAN a physics major) But to elaborate per my understanding, there are 2 important variables you're playing with in rocket engines: - 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 https://en.wikipedia.org/wiki/Tsiolkovsky_rocket_equation [2] https://en.wikipedia.org/wiki/Comparison_of_orbital_rocket_engines https://en.wikipedia.org/wiki/Comparison_of_orbital_rocket_e...

shireboy 10y ago

How are those superconducting magnets cooled?

randallsquared 10y ago
In space, probably by shade.
- NoGravitas 10y ago
  Isn't it extremely hard to dump waste heat in a vacuum?
  - netinstructions 10y ago
    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/ast21mar_1 https://science.nasa.gov/science-news/science-at-nasa/2001/a...
  - dragonwriter 10y ago
    There's hard theoretical limits on the rate at which you radiate heat, so without contact with an external medium or dumping mass, you're pretty much stuck with limits based on how big your radiators are