51–60 of 90 posts
From what I heard from industry people, overheating is an unsolved problem for VASIMR. It is 60-70% efficient, meaning that 60kW of thermal power has to go somewhere. Waste heat management for 200MW system in space is firmly outside the realm of present-day technology.
Could you use the waste heat to boil something and then spray it out the back as extra reaction mass?
https://www.spaceflightinsider.com/conferences/vasimr-plasma... http://spacenews.com/vasimr-hoax/ "Zubrin wrote in SpaceNews: “To achieve his much-repeated claim that VASIMR could enable a 39-day one-way transit to Mars, Chang Diaz posits a nuclear reactor system with a power of 200,000 kilowatts and a power-to-mass ratio of 1,000 watts per kilogram. In fact, the largest space nuclear reactor ever built, the Soviet[-…
The idea isn't ludicrous, although the torch-ship speeds of 39-day transits are definitely out of reach for now. The basic idea is, let's attach a nuclear reactor to an ion engine. Further, let's make the propellant hydrogen so we can refuel anywhere in the solar system. If we want to get serious about exploiting the solar system, we'll eventually have to give in and embrace nuclear technology, whether something like…
The real problem for a spacecraft isn't generating 700 MW of thermal heat, which is pretty small and light, but radiating it away continuously. The ISS EATCS radiates about 70 KW and each radiator is in the thousands of sq ft and thousands of pounds. So four more digits would be tens of millions of sq ft and millions of pounds, VERY superficially. However the reactor probably doesn't have to be optimized for human temps, so maybe ten times to hundred times better? It would be quite large at any rate.
There are certain engineering optimizations you make if you have an infinite liquid heatsink like a naval reactor vs incredibly expensive cooling like a space reactor. If you're willing to boil sodium your condenser can radiate a lot more per sq ft than an ammonia based refrigerator for ISS HVAC. That's a little far fetched but the VHTR/HTGR design goal was a cool 1000 C, so the radiators can run quite a bit hotter and smaller than ISS HVAC systems.
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The idea isn't ludicrous, although the torch-ship speeds of 39-day transits are definitely out of reach for now. The basic idea is, let's attach a nuclear reactor to an ion engine. Further, let's make the propellant hydrogen so we can refuel anywhere in the solar system. If we want to get serious about exploiting the solar system, we'll eventually have to give in and embrace nuclear technology, whether something like…
> The basic idea is, let's attach a nuclear reactor to an ion engine. Why do you need to attach an ion thruster to a reactor, if you can turn the reactor itself into a thruster? https://forum.kerbalspaceprogram.com/index.php?/topic/151286...
http://www.projectrho.com/public_html/rocket/enginelist.php
http://www.projectrho.com/public_html/rocket/enginelist2.php
http://www.projectrho.com/public_html/rocket/enginelist3.php
RD-600: Soviet bimodal GCNTR on page 2 is the one from that discussion
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The idea isn't ludicrous, although the torch-ship speeds of 39-day transits are definitely out of reach for now. The basic idea is, let's attach a nuclear reactor to an ion engine. Further, let's make the propellant hydrogen so we can refuel anywhere in the solar system. If we want to get serious about exploiting the solar system, we'll eventually have to give in and embrace nuclear technology, whether something like…
This boils down to theoretical vs applied. The OP approx. stated that we're basically 1/100 of the way there and this theoretical drive is currently impossible to implement. I've changed my career path because of these problems. I was a Math Major and now EE. These are the problems we need to be focusing on. Instead of using outdated and faulty technology from the 1960s. IMHO, humanity is an inflationary species (for…
But we really aren't 1/100th of the way. That's like saying a 90miles/gallon car is 1% of the way to getting 9000 miles/gallon. Getting from one to the other cannot happen through incremental improvements. It requires totally different, as yet unexplored, areas of science.
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To my understanding of physics, there is almost no amount of thrust that would actually propel us to the speed of light, in reality. The energy costs alone would simply be too enormous. "Folding space"/"Warping space", or shrinking the space in front of the craft while expanding the space, would seem to be the only theoretical way to achieve speeds that not only would match light speed but could surpass it and not br…
Alcubierre is a Mexican physicist, not Spanish.
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This boils down to theoretical vs applied. The OP approx. stated that we're basically 1/100 of the way there and this theoretical drive is currently impossible to implement. I've changed my career path because of these problems. I was a Math Major and now EE. These are the problems we need to be focusing on. Instead of using outdated and faulty technology from the 1960s. IMHO, humanity is an inflationary species (for…
>>> The OP approx. stated that we're basically 1/100 of the way there But we really aren't 1/100th of the way. That's like saying a 90miles/gallon car is 1% of the way to getting 9000 miles/gallon. Getting from one to the other cannot happen through incremental improvements. It requires totally different, as yet unexplored, areas of science.
Yeah. I think that would be apt to say.
If you're able to do some napkin math about the sheer amount of R&D to get to the other 99%, start a company ASAP because that is the billion (maybe trillion) dollar question.
Getting there is different, yes, which was entirely my original point. I'd rather not shoot an idea down before we've even started. Let's stop with the nitpicking and actually build. Incremental is probably the only way that we will get there. Think like a builder, not a complainer.
Will getting the other 99% look like how we got 1%? Of course not and if it does...then we're actually very close to a major breakthrough because we have a lot of the auxiliary technology already fleshed out.
Every journey begins with one step and we already have made a few steps. Now onto making many more.
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I think you should check your math again. 155,200mph = 69,380 m/s At 1g acceleration (10m/s/s) that is 6,938 seconds. 6,938 seconds is like 2 hours. A ship that can sustain 1g acceleration continuously for periods measured in hours, that would indeed be an interplanetary drive. Sustain that for days/weeks/months and it will take us to other stars.
How long do you need to accelerate at that pace to reach C? 299,792km/s / .01km/s => 29 million seconds? ~335 days? I'm assuming a lot of things would go wrong as you get closer to C...
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Also importantly, you have to slow down at the other end.
If your ship can only handle 1G of acceleration, would that not also mean that it could only handle 1G deceleration as well? That means starting to slow down halfway to your destination.
Bringing enough fuel to decelerate the same way you accelerated isn't usually practical, inflating your rocket by 15x its original size or more.
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How long do you need to accelerate at that pace to reach C? 299,792km/s / .01km/s => 29 million seconds? ~335 days? I'm assuming a lot of things would go wrong as you get closer to C...
Or go right. Time dilation would start working in your favor. You might get there, and back, within your lifetime. Of course everyone on earth would be long dead.
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The idea isn't ludicrous, although the torch-ship speeds of 39-day transits are definitely out of reach for now. The basic idea is, let's attach a nuclear reactor to an ion engine. Further, let's make the propellant hydrogen so we can refuel anywhere in the solar system. If we want to get serious about exploiting the solar system, we'll eventually have to give in and embrace nuclear technology, whether something like…
In all fairness modern naval reactors like the A1B are pushing more like 700 MW thermal (unclassified, probably higher) and float in what amounts to an infinite heatsink of excellent liquid coolant. Of course lifetimes and decades of experience produce the A1B, The First Torchship is not going to do as well. The real problem for a spacecraft isn't generating 700 MW of thermal heat, which is pretty small and light, bu…
Not a problem for a glowing plutonium plasma.
Here is a quote on one project from sixties:
> a spaceborne electric powerplant dubbed EU-610, with an electric output of circa 3.3x106 kWt, specific power 0.7x105 kWt/kg/sec (sic), relative mass 18.7 g/kWt, length 10000 mm.