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JimM

Member

From: England

Registered: 2004-04-11

Posts: 247

Re: Low-cost-reusable vehicle design-FICTION *2* - last topic got borked

I don’t see how a system that is so inefficient even under the most optimistic assumptions can possible be practical.

Quite so. What's more, it risks humans 44 times, or 65 times, or 160 times, or whatever, on space missions that are already being done today with one unmaned ELV launch.

Apart from incresing the risk of mission failure many-fold—and risking human life pointlessly which is tantamount to being criminally irresponsible—DH-1 is not even cost competitive with today's fully operational GEO delivery systems. Then there is the time it would take. You would not have to be in any sort of rush to get your satellite to GEO if you chose DH-1.

The expression "on a hiding to nothing" springs to mind.

ANTIcarrot.

Member

From: Herts, UK

Registered: 2004-04-27

Posts: 170

Re: Low-cost-reusable vehicle design-FICTION *2* - last topic got borked

For the doomsayers:
DeltaV=4400*(LN((2*B1+2*B2+B13)/(2*B2+B1+B13+D7))+LN((B1+B2+B13)/(B2+B13+2*D7)))

That's the excel formula for two orbital DH-1 stages staged together.
4400 = exhaust velocity in mps of the RL10 engine
B1 = fuel mass 37MT
B2 = empty mass 7.8MT
B13 = deployable payload
D7 = fuel mass for 1600mps. Used for GEO-GTO injection and aerobraking manoeuvres.

Using this formula two staged orbital DH-1 stages can accelerate 24MT to over 4100mps. That's roughly 50,000lb and the total deltaV required to inject into GTO and GEO.
http://www.pma.caltech.edu/~chirata/del … eltav.html

Of course these are crude calculations, and there will doubtless be some losses along the way. And of course I could have made a mistake. If I have please point it out.

Now let's do some planning:

It takes 36 flights for a DH-1 to deliver 74MT of fuel to an actively cooled cryogenic storage and drydock in LEO. Boil-off is low due to the short flight direct flight time and active cooling system. It takes ten flights to put up the cargo. Say one more flight to feed and water the astronauts at the drydock while they put the cargo through final assembly and testing. Two more for the tugs that will send the cargo to GEO.

Conservative:
That's a total of 49 flights for 50,000lb to GEO, or 1020lb per flight to GEO. $17M per launch (as per JimM) that's $16,000/lb to GEO.

Optimistic:
No boil off = two less fuel flights.
Eliminate separate drydock utility flight.
Use last two cargo flights as tugs.
That's a total of 45 flights. At $1M per launch (as per TRC)that's $900/lb to GEO, which is slightly cheaper than the current ELV cost to LEO.

It is of course somewhat difficult to get accurate up to date launch costs, but in recent years GEO launches on ELVs were around $25,000/lb. The recent influx of low cost launchers probably has not have affected this price to the same extent they have LEO cost.
http://www.domainb.com/companies/compan … ...wn.html
This page puts the cost at $11,000/lb for 2001. Probably as accurate as it gets. at that figure if you can launch DH-1s at $11M or less then you can undercut the ELVs.

Launch two 50,000lb loads to GEO per year and you have a hundred flights per year, and costs tend to the more optimistic scenario. At that price manufacturing prices for satellites come down and you can offer better value for money based upon all the things that a manned DH-1 can do in orbit (testing/repair/LRU upgrade) that an ELV cannot. Which in turn leads to a drop in insurance costs...

It's a downward spiral as the authors of TRC say. Not all at once, and not at first, but eventually, this form of system could bring prices down much further than ELVs ever could.

ANTIcarrot.

JimM

Member

From: England

Registered: 2004-04-11

Posts: 247

Re: Low-cost-reusable vehicle design-FICTION *2* - last topic got borked

OK, I looked at your stepped DH-1s from ELO to GEO. Compared with the 'traditional' refueling at LEO and moving the payload to GEO in bits, there is only a marginal delta-vee improvement, of the order of one or two earth-to-LEO fueling trips at best. In fact, given the quick way I worked it, you're talking rounding error. Like I said, Newton is not mocked.

Now for your whopper:

It takes 36 flights for a DH-1 to deliver 74MT of fuel to an actively cooled cryogenic storage and drydock in LEO.

Nope. (We already covered this.)

Because as Progress shows,even if you were right up to this point, it's going to take 36 x 2.5 or more flights, just to have all the kit you need on the ferry ship to do the transferring. That's 90 flights.

Conservatively, double all the other flights for similar reasons. You're now over 110 flights.

(And where is the pilot going to wait for the two years or more all this will take? In his itsy-bitsy cockpit on his refueling DH-1? I fancy not. Have you given any thought to his-two-year-long life-support requirements, apart from anything else? I fancy not. How about a movie called, "Mutiny on the DH-1"?)

That's a total of 49 flights for 50,000lb to GEO...

Last time I looked, you said 30,000lbs. I don't know where you got that from, never mind 50K. I'll stick with 30K thank you because ironically 50K would be too heavy for most GEO purposes(g)

Anyway ...

110 earth to LEO trips @ $17M = $1.870B = $62,000/lb.

Congratulations! Once again you've made Shuttle look cheep!

GCNRevenger

Member

From: Earth

Registered: 2003-10-14

Posts: 6,056

Re: Low-cost-reusable vehicle design-FICTION *2* - last topic got borked

"You really should stick to things you know about."

"Sorry" Jim, but I find your tone to be extraordinarily condecending... somthing that is not a good trait to have when you are on a message board. You are an intelligent person, but this is not an excuse for a bad attitude.

The "burden of proof" I do believe is entirely on you as to why the difficulty in launching a rocket doesn't scale with the size of the vehicle... Elon Musk's little rocket requires a tiny crew, where the Delta-IV is small enough to assemble semi-autonmously or Zenit-III launch with a tiny crew, but Saturn requires dozens of men to do nothing more than move and allign the launch table. Why wouldn't the cost increase? Experience shows that launching a large rocket is extremely expensive compared to a smaller one. SeaDragon, because of its massive size and need to be ocean-worthy, would be no different.

That is right, I am saying that a big rocket is fundimentally harder and more expensive to operate for no other reason than its tremendous size, and that the point of uneconomical returns for a rocket is much smaller than you think... Astronautix says that each Saturn-V shot costs about $2.22Bn each, not counting development costs. Even cutting that in half with better modern tech only leaves you on-par with the over priced Delta and Atlas HLVs, and there is not that much room for improvement since fuel performance has topped out.

The lack of any payload in the giant-mega-booster range also kinda kills its utility, building a large vehicle in dozens of medium pieces makes no sense ATM I grant you, but a few 100MT ones is not so bad.

------------------------------------------------------------

Now back to spaceplanes... Spaceplanes are not natural spaceships, but most of the comings and goings from Earth will be through the atmosphere, where wings are obviously superior... use of the atmosphere for its oxygen and lift is a sound concept to make launch easier.

And apparently you haven't kept up with technological advancements in the last, oh, 15-20 years... Nasa has essentially perfected composit cryogenic fuel tanks that aren't at all like the X-33's (30% lighter than Al), and slush hydrogen fuel (25-30% denser) would take care of any tank weight issues. They have tested the modified LOX/air turbine engines based off fighter jet turbines for the first stage, and the RL-60 cryogenic engine due available soon should be reliable enough for dozens of flights; its predecessor the RL-10 is good for at least 10, some models firing a hundred times. Oh yes, and modern materials should eliminate the need for glass tile nonsense on a lift-body spaceplane just fine not to mention keep the vehicle weight down.

I also don't know where you are getting your "rockets are softer" ideas from... spaceplanes by nature of their shallower trajectory require less peak thurst thrust than a ballistic rocket, whereas a ballistic rocket must lift all its weight under power quickly and exposing the vehicle to higher loads.

Oh, and I won't entertain any nonsense about you feigning to call Shuttle or Hermes a spaceplane any longer, that is clearly and patently silly... a spaceplane takes off like an aeroplane, not just lands like one with things like Hermes are just a capsule with wheels and extra lift, which makes the vehicle limitations vastly different than a ballistic launch.

And with the spacelanes shallower trajectory, an engine failure is simply not as dangerous... you have lift with airspeed, and the vehicle itself can be saved inherintly improving lifespan and safety, no 8G escape tower separation from the massive exploding booster. I digress though that the escape pod concept is not entirely unmarried from the escape tower idea, but the escape pod is jettisoned under more benign circumstances during any launch phase and is also a proven (though needing improvement) concept up to the supersonic range (F-111, B-47, Valkyrie Mach-3 bomber). With a medium-cargo class upper stage should have plenty of mass overhead for a good pod... How many times has the escape tower sucessfully worked?

A spaceplane WILL work, and it will HAVE to eventually because barring the invention of a super-fuel no conventional rocket will be practical for the large-scale development of space. Yes it will be expensive to develop, perhaps very much so, this I won't try and argue with much, but conventional rockets are simlpy not going to do in the long run, SeaDragon or not.

-----------------------------------------------------------

Now that i've vented, time for my $0.02USD about the DH-1... it ain't gonna work. Payloads. Are. Too. Small... Period. In-orbit assembly of a satellite? Fuel platform with condensing plant? Dozens of launches for one GEO payload? Manned? "Ummmm no." And nobody will buy such a vehicle either, one of the staples of TRC's finances, because only a few DH-1's would satisfy the world launch market anyway.

---

[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]

[i]The glass is at 50% of capacity[/i]

ANTIcarrot.

Member

From: Herts, UK

Registered: 2004-04-27

Posts: 170

Re: Low-cost-reusable vehicle design-FICTION *2* - last topic got borked

In fact, given the quick way I worked it, you're talking rounding error.

 

Then please, by all means, point out the actual error I made. Unlike you I posted my maths. Perhaps you'd like to do the same?

Because as Progress shows,even if you were right up to this point, it's going to take 36 x 2.5 or more flights, just to have all the kit you need on the ferry ship to do the transferring.

Is this because of the pressurised fuel transfer system, which a few posts ago you were denying the existance of? Because you might be shocked to know there are other ways to transfer fuel. Nor is there need for dozens of small tanks inside the payload bay (which would indeed eat up cargo capacity) as the 'cargo' in this case can be stored in the DH-1's LO and LH tanks. Any extra transfer equipment would be stored at the station...

In sort: We don't do it the progress way. An alternative would be to dock to the station, start the pair spinning slowly with a fly-wheel, and then transfer the fuel using conventional pumps. (Which now work perfectly because of the presence of 'gravity'.) Stop the station with the fly-wheel again and then undock. No extra weight on the DH-1 required at all. Hence no flight rate increase required.

And just because you seem to need the obvious pointed out to you: The fuel station is unmanned. No pilot waits in orbit for years. That's something you made up.

I don't know where you got that from, never mind 50K.

If you can't recognise the deltaV formula I used god knows how you did your estimate. 30klb was the ammount transportable to the lunar surface using this method. Since LTO and GTO deltaV is roughly the same I just borrowed the figure. Imagine my surprise when your tom-foolery caused me to actually do the maths and I found out it was apparently much more than that!

ANTIcarrot.

JimM

Member

From: England

Registered: 2004-04-11

Posts: 247

Re: Low-cost-reusable vehicle design-FICTION *2* - last topic got borked

Other Observations

ANTIcarrot,

The problem with delivering propellant in vehicles capable of orbiting only 5,000/lb payload at a time is obvious. Most of the payload mass is used up in the tankage, pumping, cryogenic and other control equipment needed to contain and transfer the propellant.

There's another problem. Boil-off, as you call it.

The reality is that even with what you call "actively cooled cryogenic storage", with an H2/O2 propellant mix, you can be sure to experience about 1% boil-off per week. If it takes 90 propellant delivery missions at an average rate of one per week (for example) then by the time you get to delivery no. 90 or so, boil-off will be reducing your total propellant in orbit just about as fast as you are delivering new loads of the stuff. Diminishing returns is working against this mission with a vengence by that time. And suppose you manage two deliveries a week? what then? Well, you're still going to have boil-off equal to roughly one delivery every week by the time you get near full. So even then, you can be certain of far more fueling trips. I have not worked out just how many, but we must be looking at dozens.

There is a way to make this process more efficient: deliver the propellant to LEO in bigger chunks—much bigger chunks. The bigger the payload, the smaller the portion that has to be used up in tankage & so forth. Of course, DH-1 can't deliver a bigger load. Ideally, a vehicle capable of lifting all the propellant needed in only one go would solve the problem, especially if it was just that little bit bigger and so could deliver the GEO satellite itself at the same time without all that nasty and awkward fuel pumping. And of course if it was unmanned it would not need to get back down again…

Hey! that's what we've got right now! Why reinvent the wheel, especially a new wheel with a square shape instead of a round one?

JimM

Member

From: England

Registered: 2004-04-11

Posts: 247

Re: Low-cost-reusable vehicle design-FICTION *2* - last topic got borked

The "burden of proof" I do believe is entirely on you as to why the difficulty in launching a rocket doesn't scale with the size of the vehicle...

I believe five of my earlier posts in this thread, of May 19 2004 @ 04:29, May 20 2004 @ 18:05, May 21 2004 @ 03:35, May 21 2004 @ 18:04 and May 21 2004 @ 19:56, have already addressed most of the points you bring up now, and for that reason I do not intend to duplicate my efforts now.

Instead I will try to confine myself to as few supplemental notes as possible.

On Saturn V:

“Astronautix says that each Saturn-V shot costs about $2.22Bn each, not counting development costs”

I can’t quickly find this ref. in Astronautix, but from other sources (I had reason recently to research this topic rather thoroughly) I believe this is a misleading number. My Information is that Saturn V delivered one lb to LEO for about $2,250 in 1968 money, which would be roughly $8,500 in today’s money. That’s including all development costs. So it’s about $2Bn (2004 money) per launch of a full 240,000lb payload.

However, if Saturn V were still in production, and had been developed as it was intended to be by von Braun and his team back in 1970 or so, the throw cost/lb would have fallen between 7 and 10-fold by now; the cost lb/LEO would be somewhere between $850 and $1200 and the cost per launch would be somewhere between $250M and $500M. The topic is a big one and a confusing one, because various planned future versions were differently sized, with payloads in some cases reaching over 600,000lb (300 tons!) to LEO.

On BDB:

Saturn V is not a true big dumb booster.

For one thing, it’s far too ‘high tech’!

Experience shows that launching a large rocket is extremely expensive compared to a smaller one.

Quite true with conventional design. Quite false with BDB design.

The point about BDB is that is it’s not conventional. True BDB design discards high tech, every last tiny %age performance gain design, in favor of low cost design at every turn.

I’ve already said you can go and find out what I’m going on about in detail at "LEO on the Cheap: Methods for Achieving Drastic Reductions in Space Launch Costs" by Lt. Col. John R London III (Air University Press, Maxwell Air Force Base, Alabama) (It's available from Amazon, or you can download it in pdf format from http://www.dunnspace.com/index.htm)]htt … index.htm)

SeaDragon, because of its massive size and need to be ocean-worthy, would be no different .

You are 180 degrees entirely wrong.

What you say would be true only if ships that sail on the world’s oceans are more expensive than aircraft, weight for weight. Sea Dragon is built in a shipyard, of one inch thick boilerplate steel. So:

(1) It’s built like a ship, not an aircraft.
Hence it’s cheap; dirt cheap.
(2) It’s launched from the ocean.
Hence there’s no fancy launch pad, ground crew, etc., etc. And of course this is easily doable without people fussing around the vehicle. Ballistic nuclear subs can do it from under the ocean. Sea Dragon would be sitting on the top.
(3) The bigger a vehicle like this is built, the cheaper it gets per orbited lb.
(4) The bigger it is, the lower the structure weight per orbited lb.
(5) Getting rid of turbopumps in favor of pressure feeding greatly simplifies design and construction.
(6) The cost of design is pretty much constant, whatever size
(7) The cost of navigation and other control systems is constant, independent of size.
(8) Etc., etc., etc.,…

Sea Dragon is entirely different. It’s a real, affordable way to the heavens at last. But it requires a paradigm shift to see this. Can you manage that?

Caveats:
(1) BDB is strictly cargo: no people on board.
(2) A capsule-technology vehicle is the quickest, cheapest and safest way to create a replacement man-carrier to replace Shuttle. Existing boosters are available for such a system. Therefore it should be done now on a crash basis.
(3) Spaceplanes will come one fine day, but it will take far longer and cost far more than you have been seduced into supposing, and the traffic would not bear the cost for many years yet. The technology is decades away from being ready. After the Shuttle fiasco, going for a spaceplane now would be a strategic disaster of the first order for manned space.

ANTIcarrot.

Member

From: Herts, UK

Registered: 2004-04-27

Posts: 170

Re: Low-cost-reusable vehicle design-FICTION *2* - last topic got borked

Most of the payload mass is used up in the tankage, pumping, cryogenic and other control equipment needed to contain and transfer the propellant.

Again you demonstrate an ability to ignore what I write. The 'cargo' is stored in the orbital stage's PRE EXISTING FUEL AND OXIDISER TANKS. And all the required pumping equipment IS STORED ON THE STATION. Hence there is no extra weight to eat into the cargo.

Of course there might be some boil-off on the ten minute journey from the launch site to the station (or then again maybe not because the tanks are designed to be pressurised with boiled off fuel) but even is so, I don't believe it would be enough to warrent more than one or two extra flights, and once the fiuel is transfered it becomes another story.

Boil-off, as you call it.

Well, me, the Ames Research Center, the Glenn Research Center, the Marshall Space Flight Center, most of NASA and a few other people. But don't let that stand in the way of you claiming we're all using the wrong terminology. Anyway...

http://arcoptr.arc.nasa.gov/ZBO_Page/ZB … e/ZBO.html
http://arcoptr.arc.nasa.gov/ZBO_Page/ZB … roach.html
Zero boil off has been achieved on the ground in a limited small stage test. Extending this to 30 days is currently under investigation. Doing it in space, where you don't have to insulate against a warm and heat-conductive atmosphere and ground and can hide in the shadow of a sun-shield will be much easier.

Quick physics lession: If you keep the entirety of a liquid below it's boiling tempreature, it doesn't evaporate. If you can control the amount of heat-energy entering a cryogenic tank, you can prevent the entirety of the contents from rising above the boiling tempreature.

Or at least that's what large parts of NASA thinks. No doubt you think they're wrong as well.

Why reinvent the wheel, especially a new wheel with a square shape instead of a round one?

The use of a square wheel is that it can have a hollow threaded hole placed though it's centre and be used as a nut. A device which is just as vital to the modern comercial transport industry as the wheel.

Yes ELVs can be simplier, but the past few decades has shown the only way to make them cheeper is to contract thier construction out to low pay russian workers. There has been no major break-through in technology and none is on the horizon.

BDBs of course would be very useful, but only in a sustained government-hands-off programme. Otherwise we risk doing a rerun of the apollo programme, with the whole thing cancelled after it achieves it's first/only objective.

ANTIcarrot.
PS: Certian other people might wish to try and backing up their personal opinions with either mathematical proof or reliable external sources. It does morvels for clamping down on 'facts' stated by the other person.

JimM

Member

From: England

Registered: 2004-04-11

Posts: 247

Re: Low-cost-reusable vehicle design-FICTION *2* - last topic got borked

Of course these are crude calculations, and there will doubtless be some losses along the way. And of course I could have made a mistake. If I have please point it out.

Well, I’ve made some mistakes too. I’ve redone this LEO to GEO transfer business again in a manner that makes sense to me. I hope it does to you too. You’ll see that in many fundamental ways I come round to accept what you have said. I apologize, but ‘till now it was all back-of-the-envelope calcs for me.

However, all is not yet sweetness and light between us, I’m afraid.

Firstly:   When I got right down to working out the parameters under which DH-1 flies into orbit (which I had to do for the present exercise, as you will see below) I am forced to the conclusion that it’s so hyper-marginal it’s highly unlikely to make it to orbit, real world—let alone deliver a useful cargo.

Secondly:   Suddenly, there’s an orbital station you never mentioned before. Handy, eh?

Thirdly:    Taking propellant from your onboard tanks may mean you don’t need special cargo tanks, but you’ll still need all the other equipment. And transferring from your tanks will not be the dawdle you seem to dream it will be. And you’ll still have boil-off problems. And you still won’t manage to supply anything like 5,000 lbs a trip. And rotating the ship and station up and down again will not be anything like as easy as you dreamily imagine; it may help with ullage, but only at the cost of a vast number of other headaches.

And in general it’s still a real Rube Goldberg way to travel around the Solar System. If you can ever get it into orbit in the first place, which I most sincerely doubt.

Back when I was being taught these things, the Rocket Equation looked like this:

delta V = Isp(vac)*g*ln(MR)

Where…
delta V = change of velocity
Isp(vac)  = specific impulse in vacuum
g = gravitational acceleration at earth’s surface
ln = natural logarithm
MR = mass ratio

From TRC, we learn that Stage 2 is specified to perform as follows:

delta V = 24,500 fps (BUT SEE HOWEVER ON THIS)
Isp(vac)  = (?)
MR = 5.8

Gross fuelled mass at lift off is 99,000 lbs; orbited mass is (99000/5.8) = 17,000 lbs, including 5,000 lbs payload.

Because I could not clearly find the DH-1 Stage 2 Isp(vac) from a quick search of TRC just now, I decided to work it out from what I did know.

So, turning the Rocket Equation around, we get…

Isp(vac) = (delta V/g*ln(MR)) = 24500/(32.2*ln5.8) = 24500/(32.2*1.7579) = 24500/56.6 = 433

ie., Isp(vac) is 433

433 seems just on the high side of reasonable for a high-performance H2/O2 rocket in vacuum, so is accepted and used throughout below

HOWEVER

A delta-V of 24,500 fps for DH-1 Stage 2 is almost certainly insufficient in practice. It makes no allowance for orbital circularisation at LEO, no allowance for orbital manoeuvring for rendezvous etc., no allowance for de-orbit engine burn, and for contingency propellant in tanks. In my view, 26,000 fps would be a more realistic rock-bottom minimum delta-V requirement.

To achieve 26,000 fps delta V with the same MR, Isp(vac) = 26000/(32.2*ln(MR)) = 26000/56.6 = 460, which is not realistic, or with Isp(vac)  remaining at 433, ln(MR) = delta V/((Isp(vac)*g) = 26000/(433*32.2) = 1.865, hence MR = 6.45. If launch mass is unchanged at 99,000 lbs, this means orbited mass must now become (99000/6.45) = 15,350 lbs. Ship mass is unchanged, so payload has to be reduced to 2,350 lbs.

Some might say 27,000 fps delta V would be more like a true realistic minimum, in which case MR becomes 6.935 and the payload would have to fall to something like 1,275 lbs.

These calculations are based on the special case where the launch takes place on the Equator heading due east. If Florida was used, for instance, and the mission was to reach ISS, there would be no room for any payload at all(!)

BTW, and also, Stage 2 does not really start its powered flight in a proper vacuum. This would have two effects on performance not otherwise mentioned here:

(1) At first, specific impulse will not be as high as in a ‘true’ vacuum. About 1 or 2% performance degradation seems realistic on trajectory to LEO.
(2) Also because the full trajectory to LEO is not in a pure vacuum, some drag has to be allowed for, at a probable additional 1 to 2% performance degradation.

If these items were factored in DH-1 would likely reach LEO only when it carried a negative payload. (!!)…

… oh well, back to the drawing board, eh?

(None-the-less I’ve ignored all that in what follows. If I did not it’s likely DH-1 would not make it to orbit in the first place and that would be no fun, would it?)

Firstly, let’s consider Stage A. (defined here as first stage of a two stage vehicle consisting of two DH-1 Stage 2s sitting atop each other so the bottom one becomes ‘Stage A’ for the other, called Stage B.) Stage A performance is the same in each case that follows below.

Here, it’s delta V that is unknown.

Isp(vac) is unchanged at 433.

MR = (total mass of fuelled Stages A and B)/(fuel-depleted mass of Stage A + fuelled mass of Stage B)

(Note: Assumption made here—half  Stage A’s normal 5,000 lb payload mass is needed for interstaging.)

MR = (96500+99000)/((17000-2500)+99000) = 195500/113500 = 1.722

delta V = Isp(vac)*g*ln(MR) = 433*32.2*ln1.722 = 433*32.2*0.544 = 7585

DH-1 Staging Performance  – Base Case, where Stage B delivers a 5,000 payload

Stage B performs as normal Stage 2 with 5,000 payload, therefore burnout velocity is 24500

Hence the total deltaV of Stage A +Stage B at Stage B burnout is (7585+24500) = 32085 fps or 9723 mps.

Stage A
Refuelling propellant needed: 082000 lbs.
@ 5000 lbs/delivery, 017 deliveries required.
@ 3000 lbs/delivery, 027 deliveries required.
@ 1000 lbs/delivery, 082 deliveries required.

Stage B
Refuelling propellant needed: 082000 lbs.
@ 5000 lbs/delivery, 017 deliveries required.
@ 3000 lbs/delivery, 027 deliveries required.
@ 1000 lbs/delivery, 082 deliveries required.

Total
Refuelling propellant needed: 164000 lbs.
@ 5000 lbs/delivery, 034 deliveries required.
@ 3000 lbs/delivery, 052 deliveries required.
@ 1000 lbs/delivery, 164 deliveries required.

DH-1 Staging Performance  – Case where Stage B delivers a 30,000 payload

(Note: Assumption made here—Stage B trades propellant mass for increased payload.)

Consider Stage B.

Total fuelled-up mass remains 99000lbs, but fuel mass is down by 25000lbs

MR = 99000/(17500+25000) = 99000/42500 = 2.329

delta V = Isp(vac)*g*ln(MR) = 433*32.2*ln2.329 = 433*32.2*0.846 = 11795 fps or 3574 mps

Hence the total deltaV of this 2-staged DH-1 is (7585+11795) = 19380 fps or 5877 mps.

Refuelling propellant needed:

Stage A
Refuelling propellant needed: 082000 lbs.
@ 5000 lbs/delivery, 017 deliveries required.
@ 3000 lbs/delivery, 027 deliveries required.
@ 1000 lbs/delivery, 082 deliveries required.

Stage B
Refuelling propellant needed: 057000 lbs.
@ 5000 lbs/delivery, 012 deliveries required.
@ 3000 lbs/delivery, 019 deliveries required.
@ 1000 lbs/delivery, 057 deliveries required.

Total
Refuelling propellant needed: 139000 lbs.
@ 5000 lbs/delivery, 029 deliveries required.
@ 3000 lbs/delivery, 046 deliveries required.
@ 1000 lbs/delivery, 139 deliveries required.

DH-1 Staging Performance  – Case where Stage 2 delivers a 50,000 payload

(Note: Assumption made here—Stage B trades propellant mass for increased payload.)

Consider Stage B.

Total fuelled-up mass remains 99000lbs, but fuel mass is down by 45000lbs

MR = 99000/(17500+45000) = 99000/62500 = 1.584

delta V = Isp(vac)*g*ln(MR) = 433*32.2*ln1.584 = 433*32.2*0.46 = 6414 fps or 1944 mps

Hence the total deltaV of this 2-staged DH-1 is (7585+6414) = 13999 fps or 4242 mps.

Refuelling propellant needed:

Stage A
Refuelling propellant needed: 082000 lbs.
@ 5000 lbs/delivery, 017 deliveries required.
@ 3000 lbs/delivery, 027 deliveries required.
@ 1000 lbs/delivery, 082 deliveries required.

Stage B
Refuelling propellant needed: 037000 lbs.
@ 5000 lbs/delivery, 008 deliveries required.
@ 3000 lbs/delivery, 013 deliveries required.
@ 1000 lbs/delivery, 037 deliveries required.

Total
Refuelling propellant needed: 119000 lbs.
@ 5000 lbs/delivery, 025 deliveries required.
@ 3000 lbs/delivery, 040 deliveries required.
@ 1000 lbs/delivery, 119 deliveries required.

Euler

Member

From: Corvallis, OR

Registered: 2003-02-06

Posts: 922

Re: Low-cost-reusable vehicle design-FICTION *2* - last topic got borked

I think that the DH-1 ended up using Pratt & Whitney http://www.pratt-whitney.com/prod_space_rl60.asp]RL-60 engines, ISP(vac)=465.

PS  Happy birthday ANTIcarrot!

JimM

Member

From: England

Registered: 2004-04-11

Posts: 247

Re: Low-cost-reusable vehicle design-FICTION *2* - last topic got borked

I think that the DH-1 ended up using Pratt & Whitney RL-60 engines, ISP(vac)=465.

This was  (is) not obvious from a search of TRC for specific impulse values. I see the RL-60 is said to manage 468 Isp(vac) in its Martian version, but that was not what I was looking for before, and by the time TRC gets to its Mars mission, it’s fast heading towards cloud-cuckoo land for other reasons anyway.

In fact, TRC mentions the RL-60 several times earlier without mentioning its performance  at all!

An exhaust velocity of 4400 mps gives an Isp(vac) of 447.
An Isp(vac) of 433 gives a exhaust velocity of 4250 mps.
An Isp(vac) of 465 gives a exhaust velocity of 4550 mps.
Since the SSME only manages 450 or so, then 433, which I remind you was derived from the other information supplied, seemed (seems) perfectly reasonable—and 465 did (does) not.

OK, so…

delta V = Isp(vac)*g*ln(MR) = 465*32.2*ln5.8 = 465*32.2*1.758 = 26323 fps

…which is just about enough to almost get clear of the super-marginal  area for orbital flight, but only if we ignore all the other problems I pointed to.

Anyway, it starts to get into real trouble when the other problems concerning getting DH-1 to orbit that I mentioned but put to one side are brought into play.

For just ONE thing, the high-altitude atmosphere DH-1 has to fly through at the start of its Stage 2 powered flight is going to have the same sort of effect as a 2 to 4% engine performance degradation. That is to say, it is equivalent to an Isp(vac) fall-off  between 9.3 and 18.6, giving an effective Isp(vac) of between 455.7 and 446.4.

Let’s get more precise:

(1) delta V = Isp(vac)*g*ln(MR) = 455.7*32.14*ln5.8 = 455.7*32.14*1.758 = 25746 fps
(2) delta V = Isp(vac)*g*ln(MR) = 446.4*32.14*ln5.8 = 446.4*32.14*1.758 = 25223 fps

In other words, the higher Isp(vac)  makes no fundamental difference.  There is far too little spare delta V for the other requirements and reasons I listed before; it is still super-marginal for achieving orbit.

THUS: DH-1 is not a viable launch system with a 5,000 lbs payload, or any payload close to it.

I can think of a number of ways to sort this problem, starting with using Stage 1 like a conventional booster instead of wasting it playing elevators. But we can come on to that topic later.

jpeachman787

InActive

From: Ohio, USA

Registered: 2004-05-30

Posts: 6

Re: Low-cost-reusable vehicle design-FICTION *2* - last topic got borked

I don't see why everyone is so pessimistic about the DH-1 on this board. Many have made a good case that if, as the authors say, 5000 lbs of cargo could be brought to LEO for $100/lb, then the company only makes $500,000 of revenue each flight, which is extremely small.

BUT, consider what would happen if we flew an airplane with the flight schedule of current expendable launchers. Ticket prices would be astronomical! Airliners are 150 million dollars or more, only made economical by flying people many times per day. So, if you could make something like the DH-1 that flew several times per day, then the launch costs would get closer and closer to a small factor of the costs of propellants... if you could find a market to justify that many launches.

First of all, I think the DH-1's fictional 5000 lbs to LEO is somewhat small because it's not even enough to payload to launch the inflatable habitats being developed by Bigelow aerospace. So, a payload close to or larger than the capability of the Falcon V (a little under 5 tons) would seem to be a minimum. However, if any of you have the book Islands in the Sky, there's an analysis by G. Stine about an SSTO that can carry 10 tons to orbit. To make his argument valid let’s just assume  that we have a “DHx4” that can carry a 10-ton payload.

Stine assumes that a 10-ton to LEO SSTO could be built for $500,000 million, but something similar to the DH-1 with a ten ton payload is also imaginable for this price. With a life of 500 flights, requiring 1.2 million pounds of H2/02 at a cost of $0.50/lb, flying 100 times per year, having a nice debt to equity capital structure of 33% debt and 67% equity and a 16% return on investment, the required revenue for flight is
only $1.6 million or $80/lb. Assuming you could launch 40 people in a single flight, that’s 40,000 dollars per person. In the US alone, the market for this would be HUGE. Millions of people could afford a trip to space, as long as you keep the spaceship flying. Sure, there’s no market to launch that many satellites, but people are a different story.
At 40 people a flight and 100 flights a year, if there were 20 vehicles out there then you would be launching 80,000 people per year. Does anyone know the figures from the surveys taken in the United States and Japan? I seem to remember that for this price range, the amount of people that said they would pay it is in the tens of millions.

I'm sure something like the DH-1 could be built that could match or even exceed the costs of Stine's SSTO. If it’s too expensive to develop a 10-ton-DH-1 (new engines?) then a 5-ton one would be fine—just minimize the development costs. Keep in mind that if such a vehicle would truly prove to be as reliable as an airplane, the orbital stage could be modified to be used as a suborbital vehicle (no TPS, different engine bells for in the atmosphere) which is another market entirely. Businessmen would probably pay a lot to go anywhere in the world in 40 minutes or less. Also, the first stage, the “pop-up stage” can be used several times a day to launch several orbital stages, so launch costs would probably be less because u only need to buy one lower stage for 5 or so upper stages.

In summary, I just don’t understand why so many people on this board are unimpressed by the concept behind the DH-1!

jpeachman787

InActive

From: Ohio, USA

Registered: 2004-05-30

Posts: 6

Re: Low-cost-reusable vehicle design-FICTION *2* - last topic got borked

And you know what, now that I've actually looked into it more, you don't even need 5 tons to LEO to launch good-sized inflatable habitats. I admit that satellites to GEO are uneconomical with the DH-1, but most of you are assuming that the entire spacecraft would go all the way to GEO and come back. It's just a waste of energy, bringing that entire spacecraft so far up and then bringing it right back down. For that application, having an RLV with a 5 ton payload that could bring up an upper stage would be sufficient. And even if it doesn't, that doesn't matter, because satellites and going to be an overwhelming tiny part of the market for such a vehicle.

Euler

Member

From: Corvallis, OR

Registered: 2003-02-06

Posts: 922

Re: Low-cost-reusable vehicle design-FICTION *2* - last topic got borked

In summary, I just don’t understand why so many people on this board are unimpressed by the concept behind the DH-1!

Assuming that it can get that flight rate, reliability, and operating expense, and also assuming that it can carry that many people per flight, and that that many people would want to fly into space, it could work.  However, I am not sure that any of those conditions could be met, let alone all of them.

JimM

Member

From: England

Registered: 2004-04-11

Posts: 247

Re: Low-cost-reusable vehicle design-FICTION *2* - last topic got borked

Assuming that it can get that flight rate, reliability, and operating expense, and also assuming that it can carry that many people per flight, and that that many people would want to fly into space, it could work.  However, I am not sure that any of those conditions could be met, let alone all of them.

Yes, all of the above, and we can see already why DH-1 will fail on at least four out of these five conditions.

The 'better mousetrap' or the 'build it and they will come' pitch will not do and certainly will not convince anyone, such as a bank, billionaire, etc., in the project-funding business to invest a single penny. (Billionaire do not normally becoe billionaires by being carelss with their money) I'm far from being in the project-funding business, and certainly TRC does not convince me, even though I ardently want space travel moving forward again.

With TRC, the wish is father of the silly idea.

I hold the veiw that until manned spaceflight can be conducted for profit, it will never get anywhere.

The most worrying thing about manned spaceflight today is that we have to go around thinking up reasons why people should invesst money in it. Most advanced technologies have obvious and profitable applications so the venture capitalists and banks are normaly not so hard to convince. But apart from what are really nich applications like weather and TV satellite in GEO-- where the venture money has been forethcoming--there are almost zero examples of space being used to make money.

Unfortunately weather and TV satellite in GEO do not require people in space; indeed they would probably be more of a nusance than a help Similarly, they don't need RLVs either, as this thead has been showing recently.

There are only two COMMERCIAL, FOR PROFIT ideas I've hear mention of that sound as if they might just be good reasons for manned spaceflight.

Unfortunately, both have serious, possibly killer, flaws.

1: Space tourism.

Doubtless there is a market of very rich people who would pay millions, and an even larger group of not-so-rich who would pay many thousands, for a journey into space and a stay at a spce hotel, and cruises around the moom, and so on.

(Yet fundamentally, this is another 'build it and they will come' project--like Shuttle, or even DH-1. Worrying, don't you think?)

However it would take literally tens upon tens upon tens of billions to create a spce infrastructure that caters to this need. I can't see any capital provider looking at such a venture seriously in the conceivable future. Taking space's history of cost escallation into account, he'd think somewhat along the following lines--

Expenditure
Projected capital cost: $30bn (2004 money)
Development time: 20 years
Probable actual capital cost: $60bn (2004 money)
Interest accrued on capital (by completion) at 10%: $60bn (2004 money)
Debt at completion: $120bn (2004 money)
Annual capital repayments over 24 years: $5bn (2004 money)
Average annual interst on debt at 10%: $6bn (2004 money)
Annual operating cost: $6bn (2004 money)

Thus, average annual expenditure for first 25 years: $17bn (2004 money)

Income
Market A, the super-rich: 1000 @ $5M = $5B per year (2004 money)
Market B, the less rich: 10000 @$500,000 = $5Bn per year (2004 money)

Thus average annual income for first 25 years: $10bn (2004 money)

Thus average annual PROFIT/(LOSS): ($7Bn LOSS) (2004 money)

Of course, as the venture accrues debts, the debt interest due would grow, so things would just get worse year by year. In 25 years, the accrued losses and interest on them would have amounted to somewhere around $300bn. The original $60bn would be as nothing before this mountain of debt. The only question is, when do we recognise the business is bankrupt and close it down? Obviously the logical day to do that is the day before day One. Strangle it at birth, IOW.

So let's see. I'm supposed to find $60bn to finance this venture, which won't be operational for 25 years, then watch another $7bn (plus interest) indebitness increase annually for another 25 years until I owe something like $300bn. Is this someones idea of a joke?

… at which point you would politely be shown the door, with the parting words, "Don't call us,we'll call you."

2: Space Power.

As we face an ever-growing risk of a serious disruption to oil supplied, the practicallities and the economics and the necessity of SPS seems poised to become much better than they have up to now.

SPS is a project that would cost far more than space tourism to get started, but sands every chance of make profits in the long term. Nowever the money needed (2,3,4,5 hundred billion dollars?) is way beyond the pockes of private investors. It HAS to be funded by government. That's the difficulty, and it's not minor.

The side effects are good, however. Apart from what it does to get out of the clutches of OPEC, it also gives us a solid, enduring space infrastructure as a major spin-off. And space tourism might be economic too, as another sort of spinn-off.

Euler

Member

From: Corvallis, OR

Registered: 2003-02-06

Posts: 922

Re: Low-cost-reusable vehicle design-FICTION *2* - last topic got borked

2: Space Power.

As we face an ever-growing risk of a serious disruption to oil supplied, the practicallities and the economics and the necessity of SPS seems poised to become much better than they have up to now.

SPS is a project that would cost far more than space tourism to get started, but sands every chance of make profits in the long term. Nowever the money needed (2,3,4,5 hundred billion dollars?) is way beyond the pockes of private investors. It HAS to be funded by government. That's the difficulty, and it's not minor.

The side effects are good, however. Apart from what it does to get out of the clutches of OPEC, it also gives us a solid, enduring space infrastructure as a major spin-off. And space tourism might be economic too, as another sort of spinn-off.

By space power, you mean solar pannels in orbit (or on the moon) that send microwaves to Earth which are then converted into electricity, right?  I don't see how this could be economical, considering that it is a lot cheaper and easier just to build solar panels on Earth.  Also, the  oil shortage should not affect the practicality of this much, especially since very litle of our electricity comes from oil.

JimM

Member

From: England

Registered: 2004-04-11

Posts: 247

Re: Low-cost-reusable vehicle design-FICTION *2* - last topic got borked

By space power, you mean solar pannels in orbit (or on the moon) that send microwaves to Earth which are then converted into electricity, right?

I don't favor the moon, because you reduce power output 50% right off, during the lunar night. There are other problems about the moon. I favor GEO, where the time out of sight of the Sun would be miniscule, so you get full efficiency for your investment
 

I don't see how this could be economical, considering that it is a lot cheaper and easier just to build solar panels on Earth.

M^3 by M^3, orbital panels are about eight  times as efficient as ground panels. First, they can operate 100% (almost) of the time. Second, they don't have the solar enegry dissipated by the atmosphere before they 'gather' it. Third, they can be directly facing the Sun all the time, so there is no sunrise/sunset effect. Fourth, there are no clouds to block the Sun.

Ground solar power has other problems too. It is very difficult to transmit power vast distances by power line. Superconducting might make this practical one fine day, but we can't  wait. So, the only practical way to transmit power over continental differences is (would you believe) send it up into space, 'catch it' and re-transmit it back to where you want. Better just to generate the power in orbit in the first place. And it is necessary to have a global system for transmitting the stuff. Otherwise, where comes the power to light our lives at night, or keep us warm in the winter, etc., etc?

And they leaves us open to political blackmail, just like oil does.

Also, the  oil shortage should not affect the practicality of this much, especially since very litle of our electricity comes from oil.

But all our gasoline, diesel, etc. does. Solar power can be used to electrolize water and so get us into the hydrogen economy.

From our point of view, of course, the attraction is that SPS requires a vast and permanent space infrastructure. But the real beauty is that it stands up for itself; it can be argued for convincingly even if you were not interested in getting into space as such. It gives space travel a real purpose at last.

Euler

Member

From: Corvallis, OR

Registered: 2003-02-06

Posts: 922

Re: Low-cost-reusable vehicle design-FICTION *2* - last topic got borked

Being 8 times more efficient is not enough if they are 100 times more expensive.

JimM

Member

From: England

Registered: 2004-04-11

Posts: 247

Re: Low-cost-reusable vehicle design-FICTION *2* - last topic got borked

Being 8 times more efficient is not enough if they are 100 times more expensive.

But that's only part of it, as I pointed out.

Any anyway, who says it's 100 times more expensive?

Yes, it certainly would be pricey to start with, but with real mass production (in space, on the moon) with real low-cost heavy lift (yes, BDB!) and all the rest of it, it won't be more expensive for long.

And we have the first real breakthrough into space on a sustainable, economic basis.

(Serving sugestion:- don't let NASA near this.)

Euler

Member

From: Corvallis, OR

Registered: 2003-02-06

Posts: 922

Re: Low-cost-reusable vehicle design-FICTION *2* - last topic got borked

Well, I decided to run some numbers, and while it turned out to be a little less impractical than I thought, it is still not an economical way of generating power.

Solar panels cost about $4 per peak watt.  In a somewhat sunny location, the solar panels will receive about 5 sun-hours per day.  This comes out to $19.2 per average watt.  If space solar panels are 8 times more efficient, they panels themselves will cost $2.4 per average watt.  The difference is $16.8/watt.  If solar panels can get 146 W/kg, then you must have a launch cost of $2450/kg (to GEO), which is significantly below current launch cost.

However, in reality the system is not nearly as competitive as that.  For instance, the mass of the support structure is neglected in the above calculations.  It also does not take into account that the space-based solar panels will have significantly shorter lifetimes than the ground based ones.  Furthermore, it assumes that there will be a free, massless, 100% efficient transmission system, when in reality the transmission system would be expensive to develop and have a low efficiency.  Also, solar panels are getting cheaper at a faster rate than launch costs are reducing, thereby increasing the competitiveness of ground based systems.  Solar power is not your only competition either; coal, natural gas, nuclear, hydropower, biomass, wind, etc. will be even tougher for your system to beat.

ANTIcarrot.

Member

From: Herts, UK

Registered: 2004-04-27

Posts: 170

Re: Low-cost-reusable vehicle design-FICTION *2* - last topic got borked

Solar power is not your only competition either; coal, natural gas, nuclear, hydropower, biomass, wind, etc. will be even tougher for your system to beat.

Costs for building conventional power stations always leave out the cost of the fuel over the fifty year lifespan of the plant. Nuclear power stations also leave out the cost for safeguarding the nuclear waste for the next thousand years.

Biomass is problomatic as it stinks. Hydroelectric destroys large tracts of the enviroment for little short term gain. And we're going to run out of coal and natural gas eventually.

Unfortunately at current launch costs SSPS systems are EXPENSIVE! Nasa put the mass estimate at 100,000MT. At current bargin-basement launch costs that works out to around $100B. At $200/kg that works out to a 'mere' twenty billion dollars. Of course a better way would be to build a nasa asteroid tug. A 10,000MT tug costing $2/10B could put a 500,000MT rock into GEO, which could build 5 SSPSs, and bring the minimum price down to between $400M and $2B.

High risk and high cost, but governments have taken greater risks in the past and spent more money on power stations. One is  currently spending significantly more than that on an oil war.

SPSS though should be seen in the same context as the colorado dam. It wasn't built as an end in itself but as a means to settle an otherwise uninhabitable stretch of land. Building an SSPS would make space flight truely routine, require a space based workforce that force the defacto colonisation of space.

At which point going to Mars would be easy.

ANTIcarrot.

JimM

Member

From: England

Registered: 2004-04-11

Posts: 247

Re: Low-cost-reusable vehicle design-FICTION *2* - last topic got borked

In a somewhat sunny location, the solar panels will receive about 5 sun-hours per day.  This comes out to $19.2 per average watt.  If space solar panels are 8 times more efficient, they panels themselves will cost $2.4 per average watt.  The difference is $16.8/watt.

I did not realize it was as bad as that. On that basis, space panels are not 8 times more effective, but more like 16 times better, so based on what you say, solar power panels cost $1.40/watt and the difference is $18.00/watt.

If solar panels can get 146 W/kg, then you must have a launch cost of $2450/kg (to GEO), which is significantly below current launch cost.

And of course that means the target launch cost is now $4900/kg/LEO, well within current capability.

And even that only applies if you insist on shipping everything from earth. Mine and manufacture on the moon, save a fortune and develop the space infrastructure. A win-win situation.

the mass of the support structure is neglected in the above calculations.

As it has been with your ground-based price, and in 1G, you need more massive support than in 0 G. It may be possible to use the solar wind to hold the panels open like a sail, and use the solar wind for station-keeping into the bargain. The mass of current orbital solar panels has got more to do with the unraveling mechanisms and support structures for panels attached to spacecraft and satellites than the intrinsic needs of the panels themselves.

(BTW, I don’t recall any solar panels or indeed any other on-orbit power source for the famous DH-1. I think their mass, whatever the technology, could be the final straw that breaks that camel’s back.)

space-based solar panels will have significantly shorter lifetimes than the ground based ones.

Sez who? Surface ones are exposed to more environmental damage-causing factors that are space ones, not least weather.

Furthermore, it assumes that there will be a free, massless, 100% efficient transmission system, when in reality the transmission system would be expensive to develop and have a low efficiency.

Have you any idea how expensive and inefficient—and short-range-- existing surface power transmission is? (So inefficient that beyond about 500 miles it’s so poor (about 10%) it’s not practical.) Have you any notion of how efficient micro-wave power transmission through vacuum can be? (About 90%)

Solar power is not your only competition either; coal, natural gas, nuclear, hydropower, biomass, wind, etc. will be even tougher for your system to beat.

The fundamental trouble with coal & gas are the same as oil; they’re going to run out.
Nuclear and hydropower will never get past the treehuggers.
Biomass and wind are not serious sources of mass power.

That leaves us with… space power.

JimM

Member

From: England

Registered: 2004-04-11

Posts: 247

Re: Low-cost-reusable vehicle design-FICTION *2* - last topic got borked

Unfortunately at current launch costs SSPS systems are EXPENSIVE! Nasa put the mass estimate at 100,000MT. At current bargin-basement launch costs that works out to around $100B

That number rings a bell… yes… yes… $100bn is the cost of the ISS.

In that light, SPS is so cheap how can anyone say no?

dicktice

Member

From: Nova Scotia, Canada

Registered: 2002-11-01

Posts: 1,764

Re: Low-cost-reusable vehicle design-FICTION *2* - last topic got borked

Short run, just to gain time: Consider, if every city's traffic were composed exclusively of today's technology hybrid gasoline/electric motor vehicles. . . .

GCNRevenger

Member

From: Earth

Registered: 2003-10-14

Posts: 6,056

Re: Low-cost-reusable vehicle design-FICTION *2* - last topic got borked

Solar power in space is nearing competitive with advanced cookie-cutter nuclear and such, except for an achillies heel or two... transmission and reliability.

Unfortunatly you aren't beaming it from only a few miles away through a vacuum, but rather through a wall of water and dust laden air thats over fifty miles thick, and from an altitude of many thousands of miles away from GEO as you propose. Transmitting substantial energy down to a spot thats under a kilometer wide (for practical to manage reciever areas) from 36,000km away with a microwave will probably require a "dish" of great size and still have substantial loss. Then you have the atmosphere to contend with, which will also cause scattering or absortion of the energy, especially with all the water and the pesky ionization. This is not like a communications satellite, not in any shape form or fasion at all, the energies you are talking about for the beam are really quite large, and disruption by the atmosphere, beam spreading, and the trouble of keeping it alligned are real issues.

And about the solar wind... being that it is positivly charged and can induce ionization and such that would be hard to deal with on such a scale, I also imagine that it will eat into the efficency of and eventually ruin a large solar array chemically in GEO with no Van Allen belts to protect you... The ISS solar pannels are protected, and they will experience a 10-20% loss of efficency over the years it operates only from radiation sources (which you wouldn't have Earth's shadow to block half of). One good solar flare might be enough to cook a massive GEO array.

These are not issues that you can casually ignore and gloss over, which strongly influence the effectiveness of such an SPS system versus simply making a larger array on Earth with ultra-efficent nanocomposit/Gallium Arsenide cells or ultra-cheap polymeric ones, questions that need to be answerd before you can make such assertions about the "sure thing" of solar SPS. Solar cells in the world today are expensive because they aren't mass-produced, but if they were, I bet they would slap solar SPS silly.

And if it does break... how do you intend to fix it? What if the beam drifts where you don't want it to? What mechanism will you deliver power during blackout? How reliable is the attitude control system?... Or you can just put the cells on the ground near the end customer, or do the one thing France should be admired for; build cookie-cutter reactors and recycle spent fuel.

---

[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]

[i]The glass is at 50% of capacity[/i]