Sorry Keith, but while I'm a big supporter, AFAICT Skylon remains a pipe dream. It may be slightly closer to reality with a bit more research funding, but it still exists only in a computer simulation. I've been reading about Skylon for something like 15-20 years now, and I'm not holding my breath.
Skylon needs an 'Elon Musk' to put real money into it and build a working prototype vehicle (not just an engine). Then it might be a game changer, but definitely not now.
The precooler heat exchanger is the only unique part of Skylon engines, the rest is regular turbomachinery. It enable an engine cycle that produces thrust at far higher altitudes and velocity than anything we have known before and it does it on a remarkably small amount of light weight hydrogen.
The AFRL decided recently that the engine would work as advertized, Airbus wants to build the airframe.
Lets assume Skylon works, that doesn't solve your problems. At current sorts of launch scales a hypothetical SSTO launch vehicle might be cheaper to operate than say SpaceX's launchers, but that doesn't mean launch services will be that much cheaper. Their costs are related to supply and demand, and with the initial system probably limited to a fairly small throw weight and requiring a conventional upper stage for GEO chances are slim that an SPS will make economic sense (IE GEO costs will still be far abov
Indeed, a conventional upper stage increases the cost to GEO by a factor of at least 2.5 to one. That makes the power more expensive than coal and there goes the market.
The only reasonable thing I could figure out to hold down the amount of reaction mass is to use high exhaust velocity electric engines (20-25 km/s). Unfortunately you can't power them from sunlight or they take so long climbing through the space junk bands that the vehicle gets above 2000 km
Trump is amusing, at least for some values of amusing.
The question is, then, even if you had this microwave powered electric tug, will it really be affordable? I mean its going to cost what, $10 billion to get that going? At least that much, and that'll get you what, one? So, maybe you gotta go slower and accept the hits. Don't deploy your SPS until it gets to GEO. There are creative answers.
Depending on how you do it, the tug (small change) and a ground based power plant (big bucks) could run to $20 B or more. But that's not excessive considering it about doubles the fraction of cargo delivered to GEO by a $50 B fleet of Skylons. (100 or more at half a billion each.)
Almost all the dense space junk is below 2000 km, so you could deploy a power sat at that altitude and self power out to GEO. But if the power sat is not deployed, how do you power the arcjets from 300 km LEO out to 2000 km?
I have been a fan of Nuclear Thermal Rockets since before L5 Society. But good as they are, they don't give the exhaust velocity of electric rockets and you have to lug around the considerable mass of a reactor. For where you can reach with microwave power transmission beams, that seems to be a more cost effective solution. For way out where it's too dark for solar electric propulsion, they don't give as high an exhaust velocity as you really need for missions out there. After having done a lot of work
Simple, reliable, easy to build, but not really optimum at all for a first stage. Much better for high impulse orbital transfer. Yes, nuclear electric might be more efficient, but its unlikely you're going to build a really high thrust nuclear electric design, and for lower impulse designs why not make it solar? The real advantage here though is the ease of development and deployment, you get quite a lot of bang for few bucks. The basic design of a Nerva-class system is already in the bag, it could be flying in 3-5 years if there was some impetus, and its well within the level of budget that could be realistically associated with a commercial venture.
As for not giving the exhaust velocity desired for missions to the outer solar system, there are a whole class of missions, to the inner solar system and asteroids, that would be quite feasible even using fairly primitive nuclear thermal systems. More advanced systems could be pretty interesting as well, though something of the nature of an Orion/Longshot type nuclear impulse rocket would probably make the most sense for really large manned deep space missions. We're likely at least a century away from mounting those however, so its not exactly something that relates to SPS.
Skylon? Seriously? (Score:4, Interesting)
Sorry Keith, but while I'm a big supporter, AFAICT Skylon remains a pipe dream. It may be slightly closer to reality with a bit more research funding, but it still exists only in a computer simulation. I've been reading about Skylon for something like 15-20 years now, and I'm not holding my breath.
Skylon needs an 'Elon Musk' to put real money into it and build a working prototype vehicle (not just an engine). Then it might be a game changer, but definitely not now.
- Necron69
Re: (Score:1)
The precooler heat exchanger is the only unique part of Skylon engines, the rest is regular turbomachinery. It enable an engine cycle that produces thrust at far higher altitudes and velocity than anything we have known before and it does it on a remarkably small amount of light weight hydrogen.
The AFRL decided recently that the engine would work as advertized, Airbus wants to build the airframe.
http://www.reactionengines.co.... [reactionengines.co.uk]
Skylon, or something with similar performance is the only way economical power
Re: (Score:2)
Lets assume Skylon works, that doesn't solve your problems. At current sorts of launch scales a hypothetical SSTO launch vehicle might be cheaper to operate than say SpaceX's launchers, but that doesn't mean launch services will be that much cheaper. Their costs are related to supply and demand, and with the initial system probably limited to a fairly small throw weight and requiring a conventional upper stage for GEO chances are slim that an SPS will make economic sense (IE GEO costs will still be far abov
Re: (Score:1)
" requiring a conventional upper stage for GEO "
Indeed, a conventional upper stage increases the cost to GEO by a factor of at least 2.5 to one. That makes the power more expensive than coal and there goes the market.
The only reasonable thing I could figure out to hold down the amount of reaction mass is to use high exhaust velocity electric engines (20-25 km/s). Unfortunately you can't power them from sunlight or they take so long climbing through the space junk bands that the vehicle gets above 2000 km
Re: (Score:2)
Trump is amusing, at least for some values of amusing.
The question is, then, even if you had this microwave powered electric tug, will it really be affordable? I mean its going to cost what, $10 billion to get that going? At least that much, and that'll get you what, one? So, maybe you gotta go slower and accept the hits. Don't deploy your SPS until it gets to GEO. There are creative answers.
Re: (Score:1)
Depending on how you do it, the tug (small change) and a ground based power plant (big bucks) could run to $20 B or more. But that's not excessive considering it about doubles the fraction of cargo delivered to GEO by a $50 B fleet of Skylons. (100 or more at half a billion each.)
Almost all the dense space junk is below 2000 km, so you could deploy a power sat at that altitude and self power out to GEO. But if the power sat is not deployed, how do you power the arcjets from 300 km LEO out to 2000 km?
The
Re: (Score:2)
I only have one thing to say, Nuclear Thermal Rocket.
Re: (Score:1)
I have been a fan of Nuclear Thermal Rockets since before L5 Society. But good as they are, they don't give the exhaust velocity of electric rockets and you have to lug around the considerable mass of a reactor. For where you can reach with microwave power transmission beams, that seems to be a more cost effective solution. For way out where it's too dark for solar electric propulsion, they don't give as high an exhaust velocity as you really need for missions out there. After having done a lot of work
Re:Skylon? Seriously? (Score:2)
Simple, reliable, easy to build, but not really optimum at all for a first stage. Much better for high impulse orbital transfer. Yes, nuclear electric might be more efficient, but its unlikely you're going to build a really high thrust nuclear electric design, and for lower impulse designs why not make it solar? The real advantage here though is the ease of development and deployment, you get quite a lot of bang for few bucks. The basic design of a Nerva-class system is already in the bag, it could be flying in 3-5 years if there was some impetus, and its well within the level of budget that could be realistically associated with a commercial venture.
As for not giving the exhaust velocity desired for missions to the outer solar system, there are a whole class of missions, to the inner solar system and asteroids, that would be quite feasible even using fairly primitive nuclear thermal systems. More advanced systems could be pretty interesting as well, though something of the nature of an Orion/Longshot type nuclear impulse rocket would probably make the most sense for really large manned deep space missions. We're likely at least a century away from mounting those however, so its not exactly something that relates to SPS.