Quote from: yinzer on 10/06/2009 03:35 amPeople laughed at Einstein. People laughed at Galileo. But people also laughed at Bozo the Clown.When the VASIMR guys come up with something that actually produces thrust, let me know. Hasn't Chang-Diaz been at this since the 70s?I don't recall anyone laughing at Einstein, when he published his three papers. I do recall a Nobel Prize. No one laughed at Galileo either. I think the big problem was the risk of being burned at the stake like Bruno. And people paid good money to laugh at Bozo the Clown (who thus laughed all the way to the bank). VASIMR gets to pass the same test as everything else. In the end, it has to work. To that end, I guess we'll see what happens when/if it gets lugged up to ISS and tested.
People laughed at Einstein. People laughed at Galileo. But people also laughed at Bozo the Clown.When the VASIMR guys come up with something that actually produces thrust, let me know. Hasn't Chang-Diaz been at this since the 70s?
Quote from: William Barton on 10/06/2009 01:48 pmQuote from: yinzer on 10/06/2009 03:35 amPeople laughed at Einstein. People laughed at Galileo. But people also laughed at Bozo the Clown.When the VASIMR guys come up with something that actually produces thrust, let me know. Hasn't Chang-Diaz been at this since the 70s?I don't recall anyone laughing at Einstein, when he published his three papers. I do recall a Nobel Prize. No one laughed at Galileo either. I think the big problem was the risk of being burned at the stake like Bruno. And people paid good money to laugh at Bozo the Clown (who thus laughed all the way to the bank). VASIMR gets to pass the same test as everything else. In the end, it has to work. To that end, I guess we'll see what happens when/if it gets lugged up to ISS and tested.The Nobel Prize came after Einstein was shown to be correct, not the instant he published his papers.As far as I know, the VASIMR guys have yet to demonstrate actual thrust, even with a subscale model. I would be happy to be corrected.
Quote from: alexterrell on 10/06/2009 11:43 amsnipIf VASIMR were aimed at easier traditional EP applications, then you don't need such high accelerations, and solar is fine. Why not design a VASIMR to take, say, 200-500 tons of cargo from LEO to Mars Orbit, over the course of 18 months, using near term solar power, instead of relying on someone else to make an expensive breakthrough in nuclear power?What is EP? And a 18 month cargo mission with a much smaller power requirement might be an excellent application for VASIMR. This might make solar viable. If you want the total delta of V of the planned 3 month manned mission, dig around and I bet you can find an email address for Ad-astra and someone would be glad to give you this number.Putting a uranium reactor in orbit is not high tech or high risk technically. Someone needs to teach the world a cold 235 reactor is less hazardous than the hypergolic fuels we use all the time in satellites. Danny Deger
snipIf VASIMR were aimed at easier traditional EP applications, then you don't need such high accelerations, and solar is fine. Why not design a VASIMR to take, say, 200-500 tons of cargo from LEO to Mars Orbit, over the course of 18 months, using near term solar power, instead of relying on someone else to make an expensive breakthrough in nuclear power?
He got the Nobel Prize for the work on the photoelectric effect and the quantization of light. In 1921, 16 years after he published his first revolutionary papers.Perhaps people didn't laugh at Einstein. But they thought he was wrong, about the quantization of light and about special relativity.Someone thinking you're wrong doesn't make you right.Ad Astra doesn't have a thruster, even a breadboard one. They have a fairly powerful plasma heater, some pretty pictures and math about how you might be able to build a thruster using said power heater, and an incredible PR machine. But no thruster.I'm not sure why they've spent the last ten years building bigger plasma heaters instead of an actual thruster; perhaps someone with more insight could chime in.
Quote from: yinzer on 10/06/2009 08:51 pmHe got the Nobel Prize for the work on the photoelectric effect and the quantization of light. In 1921, 16 years after he published his first revolutionary papers.Perhaps people didn't laugh at Einstein. But they thought he was wrong, about the quantization of light and about special relativity.Someone thinking you're wrong doesn't make you right.Ad Astra doesn't have a thruster, even a breadboard one. They have a fairly powerful plasma heater, some pretty pictures and math about how you might be able to build a thruster using said power heater, and an incredible PR machine. But no thruster.I'm not sure why they've spent the last ten years building bigger plasma heaters instead of an actual thruster; perhaps someone with more insight could chime in.Huh? It is an actual plasma thruster, just not in space! (And charged particles are only "stuck to magnetic field lines" on a large scale where the magnetic field is constant, like the solar corona. If they were stuck even on small scales, then synchrotrons wouldn't work, would they? Yup, all those charged particles would be stuck in the magnetic fields!) I guess most of the reason they haven't flown smaller demonstration thrusters is that there is a minimum size needed for the refrigeration requirements of the superconducting magnets. Hall thrusters and other ion thrusters have much, much smaller minimum sizes.
However, while experiments proceed, a major physics objective continues to be the demonstration of plasma/field detachment after expansion in the magnetic nozzle.
Quote from: Jim on 10/06/2009 06:03 pmQuote from: Star-Drive on 10/06/2009 06:01 pmSomeone needs to teach the world a cold 235 reactor is less hazardous than the hypergolic fuels we use all the time in satellites."That isn't trueJim:Are you referring to the very thermally hot RTGs and their Pu-238 fuel or a cold, never-used U-235 fueled power reactor? There is a big difference between the two. Danny:Cleaning up a cold and intact U-235 reactor after an accident is no big deal. Cleaning up a hot U-235 NERVA reactor being used as the first stage of a rocket was examined by intentionally redlining and blowing up a NERVA engine at Jackass Flats, NV, back in the 1960s. This was described in James Dewar's two books on the NERVA program entitled “To the End of the Solar System” and “The Nuclear Rocket”. Just go to Amazon book section and type in Dewar’s name. Bottom line was that the NV clean-up crew waited about three weeks for the really radioactively hot core materials pieces to abate their radiation outputs, then they moved in donned in their bunny suit PPE and had the test stand ready to go again in a couple of weeks. Using KSC for a cold U-235 launch should be safer than supporting an RTG powered payload. However, for a first stage NERVA launcher I’d move these operations to a Pacific Ocean island until enough operational experience is obtained.http://www.amazon.com/End-Solar-System-Nuclear-Rocket/dp/189495968X/ref=pd_sim_b_1
Quote from: Star-Drive on 10/06/2009 06:01 pmSomeone needs to teach the world a cold 235 reactor is less hazardous than the hypergolic fuels we use all the time in satellites."That isn't true
Someone needs to teach the world a cold 235 reactor is less hazardous than the hypergolic fuels we use all the time in satellites."
My understanding is that the physics and especially the engineering of their magnetic nozzle are still not completely solid. It certainly has not been demonstrated.
I think they were trying to prove that it WASN'T that big of a deal to clean up. Nowadays, the anti-nuke crowd makes it seem like it would always take "infinite" resources to clean something like that up (which it would after their endless, frivolous lawsuits).
Quote from: Robotbeat on 10/07/2009 04:12 amI think they were trying to prove that it WASN'T that big of a deal to clean up. Nowadays, the anti-nuke crowd makes it seem like it would always take "infinite" resources to clean something like that up (which it would after their endless, frivolous lawsuits).Having to wait three weeks to approach it should not have been a surprise. We knew enough to not have to have done the test. What type of isotope and what its half life is was well understood before the first reactor was built.Danny Deger
Quote from: yinzer on 10/06/2009 11:32 pmMy understanding is that the physics and especially the engineering of their magnetic nozzle are still not completely solid. It certainly has not been demonstrated.Like your other statements here, you are just showing your ignorance. You saw that video posted by the other fellows here? See how the plasma has a diverging spread to it? That is because it is following the magnetic field lines of the nozzle on exit, like an electromagnetic de laval constriction.
The question on clean up comes down to this. If you have Uranium, enriched to say 20% U235, scattered across the floor of the Atlantic, do you have to retrieve the pieces?How many Soviet nuclear subs are down there?