Milestone achieved—and surpassed! ✅TAE Technologies’ state-of-the-art fusion research reactor Norman has achieved temperatures greater than 75 million° C while demonstrating unmatched real-time control of plasma. (1/6)Norman exceeded expectations: Designed to keep plasma stable at 30M° C, the reactor was optimized to sustain plasma at more than 75M° C, 250% over its original goal. Here’s what plasma looks like inside Norman: (2/6)Our next reactor Copernicus will target 100-150 million° C to demonstrate the viability of net energy generation from TAE’s approach. (3/6)Fun fact about Norman: the plasma formed in its quartz tubes is accelerated to speeds of up to 670,000 mph—fast enough to circle the earth in 2 minutes 🌎 (4/6)The Norman reactor was named for Dr. Norman Rostoker, TAE’s brilliant technology co-founder & professor @UCIrvine, who passed away in 2014. His vision for combining plasma physics with accelerator physics at the forefront of engineering technology still drives our progress. (5/6)With a track record of over delivering on milestones and performance, TAE has attracted the support of visionary investors and to date has raised a total of $1.2 billion for its commercial fusion development using clean, safe, abundant hydrogen-boron fuel. http://bit.ly/3cdgMKK
New Atlas has an interesting, and quite detailed interview about Tri-Alpha's reactor:https://newatlas.com/energy/tae-fusion-interview/New to me is that their direct-energy-capture plans are markedly different from what Helion have talked about; They want to use more or less photovoltaic cells to capture the X-ray light off of the plasma.
I quickly skimmed through 183 pages of thread and couldn't find any math on how to harness fusion for thrust.Given the basic rocket physics, it seems like an insanely hard problem to solve, because the thermal energy waste will melt the spacecraft.The equation, from kinematics, of the power of the exhaust plume for an impulsive thrust of interval ti for a ship of mass mship for a desired deltaV vdelta is:Pe = 1/2 x mship x vdelta x vexhaust / ti And the mass flow rate is:mdot = mship * vdelta / ti / vexhaustSo for example a 2kt ship with exhaust velocity of 20km/sec and 86400 second of thrust impulse and a deltaV of 10km/sec (i.e., Mars) yields a kinetic energy in the exhaust of 2.3GW and a mass flow rate of 11kg/sec.Super efficient, yes, but the temperature of such an exhaust given an efficiency eff and specific heat cspecific is:T = vexhaust2 / 2 / eff / cspecificWhich for an efficiency of 50% and hydrogen yields 28,600K, which will be plasma that will melt everything it touches.Okay, magnetic nozzle you say.One could try an exhaust all this thermal energy out the back like chemical rockets do, but by Wien's law and Stefan Boltzmann's law, those GW are going to be almost immediately radiated as ultraviolet at about 100nm wavelengthgigawatts of ultraviolet will heat up and destroy all surrounding materials. 1/r2 won't help you because by the time the exhaust has moved a few meters a large portion of the energy will have been emitted.Forget fusion for a second. The basic laws of physics as known since the middle of the early 20th century preclude exhaust velocities of 20,000+ km/sec at gigawatts of power. It doesn't matter whether it's antimatter, fusion, or lightbulb fission or some magic source.Perhaps one can use a film of hydrogen or other material to cool the perimeter of the exhaust, but then the mass flow gets you back to about the efficiency of a NERVA style fusion rocket (that's 47kg/sec of hydrogen with a deltaT of 3000k to absorb 2GW for example, so you've just got a slightly improved NERVA rocket).Is this problem addressed anywhere in the literature?Maybe film cooling of a quickly moving exhaust will work better than as described? It just needs to get a few 10s of meters away from the ship, or 1mS. Calculating the temperature decay rate of plasma is currently beyond my skillset, though I'm working on it.NOTE: I picked the example because this is the minimum requirements to replace refueled Starships an a way that provides an economic and time-to-mars advantage.
Here is a link to my modest contribution to the field of fusion propulsion.It's a work in progress that hasn't seen much progress recently, as I've been busy with other projects, and because I've hit my limits as far as understanding the science goes.https://sites.google.com/view/worldships/accueil?authuser=0
The idea of active cooling horrifies me. To expect compressors and pumps to operate for long periods of time seems like wishful thinking. None of that stuff operates for years at a time here on Earth without regular maintenance, and they break all the time. Jet engines are as good as it gets and that's 6000 hours between overhauls, and this doesn't include minor maintenance.
Quote from: lamontagne on 10/24/2022 03:00 amHere is a link to my modest contribution to the field of fusion propulsion.It's a work in progress that hasn't seen much progress recently, as I've been busy with other projects, and because I've hit my limits as far as understanding the science goes.https://sites.google.com/view/worldships/accueil?authuser=0Good stuff, thanks!The papers you attached/linked to don't address the Stefan-Boltzmann radiation given off by the plasma. In fact they don't mention the temperature of the plasma, which would be necessary to calculate that power.Then again, I may be barking about a non-existent problem, see https://physics.stackexchange.com/questions/415028/how-do-fusion-reactors-deal-with-blackbody-radiation . I'm not sure if this applies to a fusion engine though, it's referring to ITAR.It would be helpful if your comparison table listed the exhaust velocity.I do see that aneutronic fusion was preferred, which results in less damage and heating, all of which is wasted energy.The idea of active cooling horrifies me. To expect compressors and pumps to operate for long periods of time seems like wishful thinking. None of that stuff operates for years at a time here on Earth without regular maintenance, and they break all the time. Jet engines are as good as it gets and that's 6000 hours between overhauls, and this doesn't include minor maintenance.
The ever-useful Atomic rockets has both derived formula for maximum engine power in terms of acceptable MW/m2 chamber areal heating (also arranged in terms of chamber size for a given power), along with a very extensive list of fusion engine designs.
these is a table here:https://sites.google.com/view/worldships/starshipsScroll down to the bottom of the page
Quote from: lamontagne on 10/24/2022 02:38 pmthese is a table here:https://sites.google.com/view/worldships/starshipsScroll down to the bottom of the pageI can't access the table (or in fact any table on your site):"We're sorry. This document is not published." is all I could see