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Reaction Engines To Fly Reusable Spaceplane
RobGoldsmith writes "Reaction Engines have designed a 'reusable spaceplane' to provide inexpensive and reliable access to space. The Star Wars-looking 'Skylon' reusable spaceplane has already been designed and the team are well into engine testing. They have taken some time out from building spaceships to talk about their background, their goals, and their recent engine tests. This article shows new images of their STERN Engine, an experimental rocket motor which explores the flow in Expansion Deflection (ED) nozzles. They also discuss their Sabre air-breathing engine technology. View the Skylon Spaceplane concept, the STERN Engine and much more in this in-depth interview with the team."
Can anyone find a cost per kg (or lb) of cargo estimate on that website? Not trying to detract from its value, just wanted it for comparative purposes.
I never thought that the Firefly form factor would ever actually fly, but look at the picture of the Skylon and tell me you don't see the resemblance!
Actually I see more of an SR-71 Blackbird with a fat tail. Can really see it here from above.
"You saved 1968." - Ms. Valerie Pringle to the crew of Apollo 8
Do not want shuttle 2.1. Do want Space Elevator. Now get to work.
Are you personally picking up the tab for this space elevator? Even an RLV doesn't have much of a business case to be made. There simply isn't that much demand. A space elevator needs a lot more demand than has been demonstrated to exist. A reasonable plan is to build up the demand to the point that exotic launch systems make business sense. Not develope the exotic launch system and hope someone will use it.
Reaction Engines is the name of the company. It's using conventional LOX/LH2 engines.
And for those who are calling this Shuttle 2.0, it's unmanned.
Fascism starts when the efficiency of the government becomes more important than the rights of the people.
You know, the day Sputnik went up hardly anyone was thinking about a commercial use for space, and now look at us. Space has definitely become a "build it and they will come" scenario. If you make payload lifting even cheaper, there will be more customers because things that didn't make sense before suddenly start to.
I think it looks like a cross between a SR-71 Blackbird, and a Naboo Royal Starship (the silver ship from SW episode one).
Looks like an aircraft meant for hypersonic flight to me... Dunno why it needs to look like anything else.
I may agree with what you say, but I will defend to the death your right to face the consequences of saying it.
It doesn't seem to have enough propellant mass for the task. To get to LEO, it needs something like 7.5 km/s or more in delta v (ignoring very substantial gravity and air resistance losses). If it were purely a rocket, that would be roughly 7.2 km/s (rocket equation is delta v = -4420 m/s*log(53 tons/273 tons), where 4420 m/s is perfect exhaust velocity in vacuum for LOX/LH2 burning rockets). Even if we assume we can get to Mach 5 for free (which is 1.5 km/s roughly), that leaves no more than 1.2 km/s margin. A regular rocket picks up 1.5-2 km/s or so in gravity and air resistance losses. While gravity losses might be somewhat lower (due to lift), air resistance is definitely going to be higher than the 100-200 m/s a rocket of similar size would have. So we have gravity and air resistance losses. We also have probably an inefficient nozzle design with a tradeoff between greater bell size (and efficiency in vacuum) and lower air drag. Something like drop tanks would help a little, but there doesn't seem to be the space for a lot of extra mass there. Another possibility is to use denser fuel in place of LH2 for the early parts of the flight, but that weakens the isp a little.
I don't much like the idea of a space elevator, at least for short- or medium-term applications. (Long term, is 50 years from now, is different... but also not very relevant.) Why, you ask? Simple. Give me a space-elevator class building material, and I'll make rocket tankage out of it long before it's fully developed to space elevator performance levels. Those tanks will be so vastly superior in weight performance to current materials that I can give you a rocket that is not only single stage to orbit, but does it on *pressure fed* engines. Who needs turbopumps and all their associated machinery when you can just put enough pressure in the tanks (and run at a lower chamber pressure... which is more conducive to high reliability anyway)?
For a given payload rate, my pressure fed SSTO will use somewhere between 3 and 10 times the energy (depending on which kool-aid you drink when it comes to getting the power from the ground to the elevator car). It will have a *vastly* lower capital cost. It will be faster (no radiation worries for cargo that spends days passing through the van Allen belts). Perhaps more importantly, it will scale down better. It starts with a lower investment and lower flight rate to prove out demand, and then grows as more customers appear and more rockets get built.
Oh, reusability? It gets a lot easier when you don't have to jettison a stage a third of the way there -- and when your reentry vehicle is as light and fluffy as these building materials imply, it gets even easier. Engine reusability is pretty trivial when you don't have 60,000 rpm turbines wearing out all the time.
There are plenty of engineering problems to be overcome for a space elevator. They're not impossible, but they're far from trivial. But the real problem is the competition from rockets -- it makes zero sense to compare a space elevator built with magic nanotubes to a lithium-aluminum tankage rocket; it should be compared to a magic nanotube rocket. When you do that, you discover that for any unproven market (ie, where capital costs matter) the spaceship fleet is far, far cheaper.
Sure, nobody wants to lift cargo at the current price point. Try cutting it by 90% and see what happens.
"We returned the General to El Salvador, or maybe Guatemala, it's difficult to tell from 10,000 feet"
You know, the day Sputnik went up hardly anyone was thinking about a commercial use for space, and now look at us. Space has definitely become a "build it and they will come" scenario. If you make payload lifting even cheaper, there will be more customers because things that didn't make sense before suddenly start to.
There was around an eight year lag between Sputnik 1 and the first commercial satellite. My take is that there wasn't enough business to support a commercial launch provider till sometime in the late 70's or early 80's. So it seems odd to me to build a space elevator and then wait 20 years for the elevator to become economically viable. My take is a superior approach is to increase launch demand and reduce launch costs on current and near future vehicles. That will in turn drive demand for RLVs, space elevators, and other launch systems. Some of the decisions that could be made now, don't even have to detract from development of a future space elevator.
For example, the US (so far) has missed an opportunity to transition a good portion of its manned launches to commercial vehicles, the Delta IV Heavy and Atlas V Heavy. The more demand for commercial launch, the lower the cost per launch to the launch providers. You're not going to have the market to justify a space elevator, if you don't bother to sow the seeds.
Sounds like a Skynet-Cylon joint venture. Please don't be sinister-looking....
*Opens link*
Ah, crap.
Don't put advice in your sig.
Sure, but guess what? I bet even current launch vehicles can do a lot better in cost per kg than they currently do. I figure the limit of expendable launch vehicles are somewhere around $500 per kg in very high launch volume (thousands of launches a year). RLV would drive that to somewhere around $100 per kg. At that point, you have the business to justify that next step to exotic technologies like space elevators, rail launch, etc. This is the point that I think is being missed. There's little reason to fund a lot of space elevator research now. And by the time there is enough reason, it pays for itself.
from this presentation: ... ... ...
- air intake in the order of hundreds of kg per second (400 kg/s to quote)
- passes through thousands of small tubes (resistance at that speed ?!?)
- in a few milliseconds
- cooled from + 1000degreesC to -150degreesC
Forgive me my ignorance, but are these materials physically possible ?
"Violence is the last refuge of the competent, and, generally, the first refuge of the incompetent" - Thing_1
where the crap are all the worthwhile comments from our /. readers/commentators?
I'm disappointed
Hmmm ... I would suggest GL to sue that company for (R) infringement!
And later (from a galaxy far far away) the Empire will sue GL!
Maybe Computers will never be as intelligent as Humans.
For sure they won't ever become so stupid. [VR-1988]
What the hell is an Aluminum Falcon?
http://en.wikipedia.org/wiki/TELSTAR
1962 for the first commercial satellite
Reaction Engines Ltd have been working on this for well over 10 years now (maybe closer to 20) with not a lot of actual hardware to show for it. I first heard about Skylon when I was still in uni, around 1996 or so, and not much has happened since. So while the Skylon design is inordinately cool, with some very nifty and innovative features, I'm afraid it's never going to actually fly.
Sad, really, as it's one of Europe's few contenders in the non-gov space race, and probably the most promising one, in terms of design maturity.
He who laughs last, thinks slowest.
Look into the Space Fountain instead... http://en.wikipedia.org/wiki/Space_fountain
How many "2.0" Internet businesses exist only because of the unexpected consequences of humanity building the largest peer based computer network in existence?
Slashdot itself, and other newcomers like Netflix "on demand" only exist because of the Internet. Did we build the Internet so that we could stream "Superman" in real time, or argue politics with people from around the world?
No. but they all happened because we built the Internet!
So build it! Society will profit in ways we can't today imagine today any more than Bob Metcalfe imagined Slashdot when he co-invented Ethernet!
I have no problem with your religion until you decide it's reason to deprive others of the truth.
There isn't a demand because there isn't a supply. That's like the argument, "Which came first, the chicken or the egg?"
I used to live with a little jack terrier dog that would crap all over the place. If there was a space elevator I would have used it.
I like this idea. SSTO hasn't been attainable so far. But getting an SSTO with a pressure fed propulsion system. That's extremely competitive even for a space elevator.
I checked out their video gallery. These people know what they're talking about.
-jcr
The only title of honor that a tyrant can grant is "Enemy of the State."
Doesn't look like it was a commercial satellite. NASA and publically owned European organizations were involved. Though it did belong to AT&T which was nominally a private company at the time.
Belonging to AT&T, the original Telstar was part of a multi-national agreement between AT&T, Bell Telephone Laboratories, NASA, the British General Post Office, and the French National PTT (Post, Telegraph & Telecom Office) to develop experimental satellite communications over the Atlantic Ocean. Bell Labs also built the Andover Earth Station in Andover, Maine, and it held a contract with NASA, reimbursing the agency three million dollars for each of the two launches, independent of success.
Looks like COMSAT wasn't really commercial either. It was owned by Intelsat which didn't privatize till 2001 according to wikipedia.
AM I the only one who reads the headline as 'Reactionless Engine' otherwise reaction engines sounds like another name or description of rockets to me, not a name of an unheard of company
Looking at that ship, I'm overcome with a sudden urge to fly it to Pleione to track down Mic Turner.
Real Daleks don't climb stairs - they level the building.
From what I saw at the company website, it looks like they're building the orbital equivalent of the first commercial airliner, the DC-3.
If they can get the cost to orbit even remotely close to the $200/kg number the Space Power Satellite program proposed by NASA was based on, we could either build a full system or a large proof of concept orbital power array. We're a bit more desperate for power than we were when Bush defunded the SPS project. The launch capability is the hard part of SPS, the rest is just engineering we know how to do.
That could take up enough launches to provide the company a reasonable chance at profit.
Tech Public Policy stuff
Hmm... as I'm getting old I thought I remember this concept as HOTOL, and sure enough: wikipedia Reaction engines was started by one of the HOTOL designers. Still, it's had probably 30 years of intellectual development and it looks believable to me. Go Reaction Engines.
-- For evil to triumph it is enough that good men do nothing.
Unobtainium.
another thing is that given how we humans are basically running this planet dry, there is only one way to go for future resources.
also, if we are able to spread out over the solar system, there is less of a likelihood that a single big rock will take us out...
comment first, facts later. http://chem.tufts.edu/AnswersInScience/RelativityofWrong.htm
Actually, if you want a mega-scale engineering project, my personal preference is for the launch loop.
Yeah, when you start applying space elevator class building materials to your rocket tankage, the usual assumptions simply don't apply. For example: with 65GPa tensile strength (the low end of the strength range Wikipedia gives for an elevator material) material for tankage, a 1000 psi tank filled with dense propellants (which, depending upon your models, might be better) has a mass ratio of somewhere over 1000. The exact number depends on your assumptions about anisotropic winding strength efficiency, but is probably around 1500 before you include a safety margin.
The helium to pressurize it with is actually the most problematic part -- but with that kind of tank mass ratio, it's not unreasonable to decide you're going to operate in blowdown mode (or regulated, but decaying to a lower final pressure) so that you have less helium mass at burnout. That lets you get the high initial chamber pressure (good atmospheric expansion ratio) without all the helium mass required to pressurize the entire tank. And using the ullage helium for the circularizing burn isn't hard (you could even include a peroxide monoprop heater and get a reasonable Isp out of it).
... 5 million pounds spent in developing an engine.
I see tests that have demonstrated only the precooler - not the thrust, not the reliability, ie none of the things critical to it actually working.
I see no prototype having been tested.
I see something that's a hairsbreadth from the 'I've pulled this kewl idea out of my butt!'.
-Styopa
It looks like a flying ballpoint pen.
Kaetemi
we'll never let it.
For godssake, this is NOT developed in AMERICA! It will be like the Concorde. Clever idea, could have been developed, we starved it of cash and put all the barriers we could think of in its way.
I predict that, if this goes to prototype and works:
1) we will step in and buy it up, then claim the we have invented it and transfer all the production facilities to Utah
2) we will step in, buy it up and then close it down because of political pressure from our current technology production facilities
3) we will ignore it and refuse to certify any vehicle developed from it for any US launch purpose
4) we will pull what strings we can to prevent other countries from signing up to it as well
That should be enough to kill it off right now. We don't need any technical considerations. Besides, as a politician, they hurt my head....
Space has definitely become a "build it and they will come" scenario.
Except with the space shuttle, which hasn't lived up to expectations.
And the ISS, which is behind schedule.
And the way that no-one has sent a manned mission to the moon in decades.
My Karma: ran over your Dogma
StrawberryFrog
It's what the Yanks call an Aluminium Falcon.
I'm guessing that wasn't on their radar screen...
Is that what pretentious Brits call Aluminum?
I think what he's saying is that we need to know in what ways we would be using the technology, so it at least has an economically viable proposal. Jack Terrier crap is actually one of those viable proposals that would have to be figured into the whole process... but if all evidence points to very limited use, then we would just be wasting money on a fruitless endeavor. Prove to me that this is economically viable (however you want to do that), and then I'll willing hand over my money. The other way around is just bad business.
I'm sorry you misunderstood what I was trying to say. I would never send dog crap into space. I wanted to send the dog.
Rockets suck because they burn fuel. Energy goes into making the fuel one way or another and there is generally a significant environmental cost. The space elevator has a massive initial capital cost, but if you're spinning it down from orbit and making it out of something that's already up there (carbon is easy to come by, anyway) then the environmental cost is low. Once the elevator is built, it requires a fraction of the energy to operate that it takes to launch your rockets, as long as you're sending up as much mass as you're bringing down. That should be easy - we can start with hazardous wastes and power satellites. Then we can move on to masses of people going to Mars, I hope :) You are thinking of "cheaper" in terms of energy costs. But as you use the elevator, the overall cost decreases. And as you use the rockets, the overall cost increases. The more you use the space elevator, the cheaper space gets. The more you use the rockets, the more money you've spent on launches.
"You're right," Fisheye says. "I should have set it on 'whip' or 'chop.'"
And what pray tell does that have to do exactly with what the OP said, of "if you build it they will come"? No one said this stuff had to come immediately. The space shuttle is the first re-usable spacecraft the US created. Many of the first escort fighters (Allison-engined P-51 mustangs didn't live up to expectations either, nor did the first assault rifle for the US (M-16 before they lined the barrel and chamber with chrome).
First and early attempts rarely tend to their tasks as well as people hope or require. Typically you have to go through several revisions while the old models are still "in the field" as it were. Really the only difference is the expense of space exploration. NASA has been able to do some slick stuff on a low budget since the 60's or 70's, but its been a hamper.
You mention no one has gone back to the moon in the last few decades. What, may I ask, exactly would you have them do there? They still have the moon rocks from Apollo. We've gotten pretty handy with a spectrometer, being able to tell chemical compositions of planets and stars light-years away. What exactly were they to do there besides build a telescope, which we have easily done in orbit anyways (see Hubble).
The economics of space exploration are slowly changing to make it as feasible as deep ocean exploration (which is also hurting from lack of interest, outside of oil companies). The politics of it are leading to like what? Three manned missions from countries outside the US? I believe Russian, India, and China were all discussing targeting the southern end of Luna.
Anyways, manned space exploration will continue to happen and eventually we will colonize other planets. The pace of space is different. The amount of resources it takes to leave Earth and head for another system are unlike anything we've had to deal with before. The distances likewise, with it easier to measure it light-seconds and light-minutes or AU within the solar system than kilometers.
How long has it taken humanity as a whole to explore the bulk of the dry surface of Earth? You do realize I hope that there are large uncharted tracts of land. This is why we still discover new species as we cut down the rain forests. And don't even get me started on the sea, we don't even know what all is living in our oceans and can't even reach the bottom in some places.
Personally I say do as much as we can from remote without sending people out as possible. Saves lives, saves money, saves time. Voyager 1 and Voyager 2 are still sending information back occasionally. They haven't left the solar system entirely yet. In the last 10-15 years we've uncovered more information about our solar system than in the previous hundred. We're learning more about all the planets every day, and we haven't been sending out people.
May as well find out what we can know before sending someone out since we may not have too many shots to do so.
Honestly, I'm not being pedantic here, but exactly what are the "new" commercial applications that'll magically appear in LEO? Earth imaging? Yep, we do that already. Communications relays? Yep, from both LEO and GEO. Tourism? That implies a destination that doesn't exist yet, and obviates the "cargo" bias of the launcher. Note: "scientific research" isn't a commercial application nor is it a business model. It may be a necessary component, but the research phase is usually an expensive precursor to the commercial application.
I toss this out there because I've built satellite hardware, and it really is difficult to answer the question "what are you going to do in LEO?" I understand the Catch-22 that exists - nobody considers orbital apps because you can't get there; consequently, no demand for orbital transport develops because there are no on-orbit applications. However, just creating a transport mechanism won't magically make applications fall out of the sky (so to speak.) And unless several industries are planning applications in lock-step with your launch service, there will be a sever over-capacity that will drive the launch provider into bankruptcy.
Further, if there isn't standardization for the payload-to-vehicle interface, there won't be any competition in the market. You'll choose a launch provider at the beginning of the program, and you'll be locked-in to their infrastructure for the duration. Changing providers would essentially be a "do over" from a programmatic view. This isn't a taxi where you can get out of one and into another, receiving comparable service out of either.
Can I trust my payload and/or investment dollars to a company that uses "whilst" on their site?
Once one is up it's easier to put others up.
As long as we are talking about 'magic' technology, the 'magical' space elevator is still necessarily more efficient than a 'magical' chemical rocket because however light and efficient the rocket's tank is, it still has to contain the fuel and a large part of that fuel will go into lifting the fuel itself.
The space elevator can run on fusion on the ground or solar up in the space, and all the energy goes into moving the payload.
The Brits and everybody else on the planet. ;)
There isn't a demand because there isn't a supply. That's like the argument, "Which came first, the chicken or the egg?"
There's no paradox if there's neither a chicken nor an egg.
Have you actually run the numbers on efficiency? I have. A rocket (built from space elevator class magic nanotubes, of course) is somewhere around 5-8% efficient at converting energy on the ground to energy in the payload; somewhat more if you use hydrogen instead of dense propellants, and somewhat more if you count the rocket bits in orbit as useful rather than dead weight.
How efficient the space elevator is varies depending on your assumptions about beamed power efficiency (or other means of getting power to the climber). You still have to put the vast majority of the energy into the payload directly. At geosynchronous altitude, the vast majority of your energy is in the form of gravitational potential energy that comes from your climber, not kinetic energy that comes from Coriolis forces. The climber will probably have an unexciting payload fraction (motors and energy collectors are heavy), and less than stellar conversion efficiencies. 50% overall would imply roughly 70% payload fraction and 70% conversion efficiency; that seems optimistic to me. 25% efficiency seems much more reasonable, but still a definite engineering challenge (especially if you want to climb quickly).
That says that a rocket launch uses only 5x the energy of the elevator for a given payload. The capital costs are dramatically reduced. A notional nanotube SSTO has a nanotube tankage mass noticeably less than its payload mass. It can fly several times per day, if you have an equatorial launch site or aren't too picky about destination orbit. A space elevator is *massive* compared to its payload, and has a limited number of climbers launching each day (weight limits on the lower portion of the cable are severe). The capital cost per lofted kg per day is vastly lower with the rockets than the elevator. For unproven markets, this difference is important. For current rocket launches, and any sane model for early elevator launches, the capital costs dominate the energy costs. Until there is enough of a proven launch market that you can take a business plan to investors that reasonably assumes near-100% utilization of your elevator for several years of useful life, the rockets win. The fact that the rocket version of the business plan can be made workable at much lower launch rates is a nontrivial benefit.
Sure, the space elevator makes sense many years from now, when there is a thriving space-based economy with regular demand and plenty of destinations. That world is not the one we live in today. For the near term, and even medium term, rockets will beat space elevators on price per kg launched -- especially if you give the rocket engineers space-elevator class building materials.
There's another kind? Tell me more!
Warning: this article may contain humor, sarcasm, parody, and perhaps even irony. Read at your own risk.
Thanks for replying... I think some people forget just how complicated (and time-consuming) it is to design a vehicle for space travel when you don't have billions of dollars in your budget.
The rocket is not perfectly efficient; neither is the elevator. As I explained above, plausible estimates put the efficiency difference at about a factor of 5. That number can vary by a factor of at least 3 (in either direction) depending on which kool-aid you prefer. The implication of this is that for the short and medium term, the reduced capital cost of the rockets dominates. For the long term, where energy costs are actually relevant, the elevator wins -- but that problem is properly classed as "a very nice problem to have." It will be a long time before we do, and until then, rockets make more sense.
On the other hand, when we went to the moon it was emotionally a "giant leap for mankind," but it really didn't lead to anything or change anything in practice. Neither has the ISS paid off. Motorolla's Irridium communications constellation seemed incredibly awesome and well-timed, and promptly went out of business. How do we know which situation we're looking at with a space elevator?
"Is that what pretentious Brits call Aluminum?"
Our language - if you don't like it you're free to use another one...
I was always a fan of the surface-to-orbit 30km long rail gun.
Hey, if you think you can get those numbers, go ahead. I haven't seen anything other than a skyhook that does $100/kg. Also, once you have 2 skyhooks, you can build 20 while lifting cargo.
"We returned the General to El Salvador, or maybe Guatemala, it's difficult to tell from 10,000 feet"
Hey, if you think you can get those numbers, go ahead. I haven't seen anything other than a skyhook that does $100/kg.
To be honest, nobody has seen anything that can do $1000 per kg much less $100 per kg. But once you get any launch system to the point where virtually all of the cost is reaction mass and energy, then it's going to be $100 per kg or lower. RLVs, skyhooks, and space elevators can do that. If your launch system only runs mass up to orbit, then RLVs remain rather competitive. The only weakness is that chemical motors have a much lower isp than what you can use in vacuum (where most of the space elevator and skyhook would be). That means a lot more reaction mass and somewhat more energy.
Space elevators and sky hooks have an additional advantage over RLVs. All three can economically drop mass from orbit, but the tether systems can harvest the energy and momentum of orbital mass going to Earth's surface. This removes the last big restriction to cost to orbit. If there's some large quantity of sufficiently valuable mass in orbit to return to Earth, it might actually yield a negative cost to orbit for material coming from Earth. Eg, if putting a kilogram in space meant a kilogram of gold or other PGMs (with an expenditure of say a few dollars per kg for tether operations and upkeep) was returned to Earth, then that would create a massive economic engine for putting stuff in space from Earth.
Our website - if you don't like it you're free to use another one...
The resemblance to Queen Amidala's "Naboo Cruiser" is remarkable.
http://www.galacticempiredatabank.com/NabooCruiser1.jpg
Coincidence?
That that is is that that that that is not is not.
Watto like!
http://starwars.wikia.com/wiki/J-type_327_Nubian_royal_starship
I'm more of a fan of the laser launcher concept myself. Problem is, it takes a lot of energy to make one of these work right, so we're probably looking at a couple geosync power sats feeding microwaves to the site. Talk about bootstrapping. Development costs would be a helluva lot lower than 'magic materials' to build a loop or a fountain, I'd think, and if something screwed up, you've still got a nice shirtsleeve environment to work on...
Understanding the scope of the problem is the first step on the path to true panic.
Ok, I've had enough.
You don't want me here? I'm taking my language and I'm leaving.....
You don't have to hang it up there; it stays up by itself. The ribbon is moving faster than orbital velocity (14 km/s -- orbital is a bit over 7), so its natural tendency to go in a straight line means that the Earth's surface curves away from it. You then have to apply tension with cables to hold it down and make it follow the curvature of the Earth (from 80 km up, of course). The problems with the launch loop lie in things like the control systems and the quantity of stored energy, not the basic physics. Wrapping your head around it takes a little work, but in many ways it works for the same reason that the space elevator counterweight does -- both the ribbon and the counterweight are moving at a higher velocity than orbital velocity for their altitude, so they try to "fall" away from the Earth and thus maintain tension in the cable[s].
IMHO the laser launcher is yet another result of the common fallacy that mass ratio actually matters. It doesn't; cost does. If you save a lot of mass while making the whole thing more expensive, that's not a win. I should add the caveat that I'm not current on the detailed numbers, so I may be mistaken, but that's my general impression of it. (Obviously mass ratio matters to the extent it has an impact on cost; but that is the *full* extent to which it matters.)
Either way, I'm saying there is a market there... just prove the viability before we start spending money.
Except for Canada... so... we've got the cannucks.
Hell, how do you catch up to the loop moving at 50k km/hr? If you can do that, why bother with the tube at all?
With the laser launcher, the big investment is in the lasers, mirrors, mirror guidance & controls and all the stuff that stays on the ground. The cheap part of it, the capsual, reaction mass & payload, is what goes up. So, once you get the system into place and working, the more you use it, the more you amortise the cost across each launch until someday you get down to a per-launch cost of the capsual, payload, maintanance, and electricity to push that sucker up.
Understanding the scope of the problem is the first step on the path to true panic.
Surprising as it may seem, every one of your questions is addressed in published papers. Many of them can be found in the references section of the Wikipedia article I linked to.
Your argument in favor of laser launchers has no meaning without either some numbers to back it up or at least some sound logic as to why the expensive capital investment is less than for a [launch loop|space elevator|rocket fleet] or is made up for by reduced operating costs (including but not limited to energy consumption).
This tells me it's going to need 'magic materials'. 'Magic materials' cost money to develop, time to learn to manufacture, machine, assemble, etc.
Did I mention that this launch loop is almost the size of the Great Wall of China?
Understanding the scope of the problem is the first step on the path to true panic.
What part needs magic materials? The ribbon is made of soft iron iron or steel, probably woven in a manner not unlike normal cables, or possibly in solid sheets. That's not exactly difficult to make. The sheath is a kevlar or carbon fiber composite with an aluminized mylar liner. The control magnets are copper windings over soft iron. You didn't actually read any of the papers, did you?
What part of "mega-scale engineering project" made you think this would be small?
The tethers holding that sucker to the ground. Did you think of doing a back-of-the-napkin calculation on the tensile strength needed to hold this sucker down???? We're talking orders of magnitude beyond the best artificial spider silk to hold this thing down, and I don't think you can quite order that up in industrial quantities yet.
What part of 'too goddamned big and expensive to be economically feasible in our lifetimes' do you not understand? Especially since you'd have to build the sucker in order to test its viability. I'd guestimate it'd only cost a couple trillion dollars, so wait a few weeks for the economy to finish pancaking before writing the check; you'll get your money's worth then. I'm supposing this will be a government project, nobody else would have the cash and the desire to pull this off (although there's bound to be a few private sector entities that could concievably get the cash together, I wouldn't count on their stockholders allowing them to spend it on something like this), which means it won't come in anywhere near budget or on schedule. Yes, I've done heavy construction in my younger crazier days; it put me through college.
Oh, and don't count on selling this to Congress unless you can do like Ike did with the interstate highway system that came about in the 60's & 70's.
Contrast this to a laser launching system. For a few million, you can do a real-world feasibility study. Hell, Lightcraft Technologies already did a feasibility study using a 10 kw laser to push a 25 gram weight to 200 feet as a test. The test worked. Show me a comparable feat with your launch loop.
Understanding the scope of the problem is the first step on the path to true panic.
The first paper includes cost estimates. There's nothing hard about the cables to hold it down; they can be as thick as they need to be. The original paper has numbers for them using ordinary steel cable -- they're tapered, so they're a little abnormal, but strength certainly isn't a problem. The weight problem is more likely to be keeping the sheath light enough that the ribbon can stay up. Each kg of ribbon can lift a little less than 1 kg of other stuff, including sheath, cables, and payload. Seriously, the materials science is not the hard part, and neither is the physics.
Building a test model is actually a place where the launch loop does well in comparison to the other mega-scale engineering proposals. A small scale launch loop is useful, unlike an elevator. A launch loop that's an arch capable of lofting your payload to 50km and 2km/s is decidedly useful -- that's an excellent starting point for the second stage of a rocket.
I'll have to get back to you on a lab bench scale test. I don't know of any that have been done; I do, however, have some magnets in the mail for exactly that purpose. It's very much a back burner project, though, so don't expect results for a couple months. (Try building a laser launch demonstrator in your garage by yourself on a 3-digit budget...)