The supply chain is gone:
To avoid any gap in providing independent repair spacewalks as a safety contingency for the space station, Congress, NASA and the ISS partners should evaluate the option of postponing the launch of STS – 135 until more external fuel tanks and other parts can be built to support additional shuttle flights in 2012.
2012? What are they smoking?
It would be at least two years, probably three, before they could resurrect the tooling and manufacturing needed to do this, and it would cost billions of dollars that NASA does not have, and isn’t going to get. Meanwhile, we’d have thousands of workers sitting around, forgetting how to launch safely. This is just crazy, and disappointing, considering the sources. Do they really so completely lack imagination that they can’t conceive of ways to do EVA and ISS repair and maintenance with what is currently coming on line, and not relying on an unsafe hyperexpensive vehicle? This is the product of emotion, not thought.
[Update early afternoon]
I have a sort-of-related bleg. I’m working on an article about the false lessons learned from the Shuttle, and how they’re continuing to screw up space policy. Suggestions in comments are appreciated. The first and most obvious one is that it proved reusables don’t reduce cost.
If they can’t get those fires under control in TX and NM that keep closing I-10 and I-40, I propose to deliver CA vegetables to the East Coast via Conestoga Wagons and trains out of Chicago and St Louis. It’s proven technology that can be re-started, re-tooled and re-ordered until we get something else ‘newer’.
Yeah, it’s a stretch, but…
They’re just at the “Bargaining” stage of the Five Stages of Grief.
They’ve been through Denial and Anger; Next comes Depression, then Acceptance.
I sounds like a living museum proposal. Where everyone can go through the motions of flight preparation but no one actually goes anywhere. That may work in Salem and Branson, but people will actually pay to watch those reenactments of by gone days.
I sounds like a living museum proposal.
What a great comparison!
Not so fast — surely the Disney corporation could build an exciting animatronic Space Shuttle Program attraction at a fraction of the cost.
Hey, give Chris Kraft a break, he’s only had seven and a half years to think about this.
“The first and most obvious one is that it proved reusables don’t reduce cost.”
I don’t think NASA has proven that reusables don’t reduce cost.
Instead I think what has been proven is a govt program doesn’t reduce costs.
The promise of socialism is it lowers costs. If socialism did lower cost, I would be a socialist.
What are the possible reasons for NASA to want to operate a shuttle?
Any government can’t operate anything and lower it’s costs.
A government can’t pass laws that lower costs.
People can’t lower costs because people don’t want to lower costs.
People or governments do want they want to do, and they want to raise costs.
If there is no consequence are there people who don’t want more money for the work they do? Do want to reduce job’s perks.
Government programs are always going to want more budget.
What group of humans doesn’t want more power?
The only thing that lower cost are markets- people who have money and want to spend less of that money.
What other possible factor could lower costs. Shame? Or other social pressure?
“The first and most obvious one is that it proved reusables don’t reduce cost.”
I’m with gbaikie, I don’t think it’s possible to make such a conclusion, the shuttle was a system designed to be expensive to operate, the fact that NASA can launch expendables more cheaply than it could the partially reusable Shuttle, is only a reflection on the fact that with expendables there’s less excuse to keep pulling them apart and then sticking them back together again.
You need to compare how a private outfit would operate expendable vs reusable launch systems, and we don’t have that, but I think if they threw 747’s away after every flight transatlantic air travel would be much more expensive.
I don’t think NASA has proven that reusables don’t reduce cost.
Neither do I. That’s why I said it was a false lesson.
Can reusable launch lower cost. Obviously.
But can launch vehicles which are reusable lower cost.
Of course we do reuse the launch tower and all the other infrastructure used to launch rocket- a launch tower is part of the rocket system.
I have mentioned a idea of a “launch tower” which adds modest amount velocity to the rocket- it would be reusable and I believe lower costs.
And/or one get more “assisted launch” by using a 0 stage which adds say 1000 mph to rocket. That could fairly easy to reuse.
Those ideas are similar to idea of mothership- and of course mothership are reused.
But one thing about any reusable thing, a launch tower, or mothership, they have to be used. The more times you use a tower tower or mothership in a given period of time, the more value it has.
I don’t know the actual costs, but I would guess that for any launch tower, the launch tower costs are higher than the cost of the first stage rocket which use that launch tower.
Or if you use the launch tower more times per year you are getting a savings equal to a reusable first stage rocket.
“Neither do I. That’s why I said it was a false lesson.”
Ok, my bad:)
That a very expensive craft would still be affordable as long as it had a high flight rate. But the Shuttle was also very expensive to operate per launch and had very high fixed overhead, so it would cost a fortune no matter how much or how little it was flown. The mantra about flight rate might as well have been, “Sure, we lose money on every sale, but we make it up in volume!”
I would argue for a reverse lesson. A high flight rate doesn’t produce a significantly lower cost per flight, a lower cost per flight produces a significantly higher flight rate.
Another false lesson is that America needs to have a single type of manned space craft that can do almost anything (and doing anything in particular only once every few years). If the goal is to boost the ISS to a higher orbit, why use the limited amount of fuel available on a Shuttle instead of a dedicated rocket stage? If the goal is to do a spacewalk, why use a vehicle with a massive cargo bay riding along? Yes, the Shuttle can use its arm and mass to make the job easier, but isn’t that like buying a Concorde so a test pilot can stand on its wingtip and have an easier job painting pinstripes on an Airbus A-380?
It’s the same lesson that hasn’t been learned by people who think buying a Prius will reduce the cost of driving, or that “renewable” energy (e.g. solar and wind) will reduce the cost of energy, because by gum you don’t have to pay for the fuel.
I submit the Shuttle is a direct result of the last time we suffered through a fad for “renewables” and a revulsion for “disposable” things: the feckless 1970s. So I would say the ignominious failure of the Shuttle to do the only thing it was really supposed to do — make LEO access cheap and reliable — is an indictment of the entire 1970s philosophy. A faddish instinctive preference for “renewable” over “disposable,” particuilarly in clear defiance of market price signals, is not only stupid, it is ultimately futile.
oops! Sorry,
“Your comment was a bit too short. Please go back and try again.”
Cargo and passengers need to travel on different vehicles.
The worst result of the shuttle program was the death of 14 astronauts.
The shuttle failed because they didn’t build the flyback first stage.
The shuttle was bad because it only went to LEO.
We have to move beyond chemical rockets, to scramjets/elevators/Orion/antimatter/antigravity/etc.
The shuttle shows we should have stuck with the Saturn V.
Those were false lessons, btw. 🙂
Oh. To answer your question. The big thing NASA has falsely proven is high costs to get into space prevent humans from going into space.
Everyone thinks we need CATS. In the sense of we need to lower launch cost to before we can mine the moon for instance.
One way to say this is NASA has been a “force” that stops free markets.
Everyone is convinced that space is dependent on lowering cost of the rockets that get us into space. Which isn’t true.
If you had markets in space for space, you would lower launch costs assuming there was also a market for rocket launches.
But even if launch cost were already at lowest cost possible- what is needed is markets in space.
And if there was market in space for space [rocket fuel, mainly] one could have market for other things- water and electrical power to make rocket fuel.
In simplest terms what is needed is for there to be a market for water in space- which leads to electrical power market and rocket fuel market
More important than launch cost is price of water on the lunar surface.
Or even having a price- being able to buy lunar water at the lunar surface.
gbaikie, the problem with the government finding water on the lunar surface is that another branch of government would declare it a wetland and put it off limits.
“gbaikie, the problem with the government finding water on the lunar surface is that another branch of government would declare it a wetland and put it off limits.”
🙂
The moon isn’t a wetland, it probably similar to dirt slightly damp.
But that is minable.
The next problem is people seem to want NASA to mine the Moon.
This very depressing:
http://forum.nasaspaceflight.com/index.php?topic=25334.0
I thought Jeff Greason of all people would understand what is wrong with such an idea.
So if NASA mines the Moon, it will have another false thing it’s proven, that Lunar mining isn’t profitable.
If NASA wants to mine the mine {could compromise, if NASA will offer to sell lunar water at a fix price- to anyone who wants to buy it, and will require a mountain of paperwork nor waiting in lines}.
False lessons.
You must use heritage parts. Heritage parts means heritage costs and you don’t get the benefits of all the industry developments since the heritage parts were first designed.
You must preserve the workforce. If you preserve the workforce you deny the possibility of achieving any efficiencies. If you can redesign your launch vehicle so that it can be launched with 50 rather than 6000 people then saving the 5950 jobs is silly. The whole basis of economics is that of creative destruction. Jobs destroyed in one place frees up labour to start a new business (or businesses) elsewhere.
The biggest false lesson of the Shuttle is that capabilities and features are more important than payload, cost, efficiency, and launch rate. A lot of the Shuttle’s most unique features, features that have had huge impacts on the Shuttle’s capabilities and costs, have been used exceedingly rarely. Given that, the smart-headed thing to do is to haul up a specialty purpose vehicle only when you really need a specialty purpose feature (like on orbit satellite repair). However, some of the Shuttle’s most famous missions have been precisely those rare occasions when those capabilities proved handy, though if people knew the full cost of those capabilities they might have a slightly different view.
True lessons from the shuttle:
1) Good engineering practice doesn’t use bleeding edge technology except when absolutely necessary. (Bleeding edge is defined as something no one has ever done before for an equivalent or somewhat similar application) If it’s needed, there should be more than one path pursued, and testing needs to be thorough indeed. One should also question carefully the assumptions that led to the seeming necessity.
2) Iteration and refinement can lead to better results and lower costs than in “perfecting” the first design before it is used.
3) Programs without clear goals lead to horrific political horse-trading that can cripple a design brief.
4) Engineering teams should be absolutely no larger than necessary, their co-location is good, and feedback between design, analysis, and test functions needs to be rapid and personal.
We seem to have drifted into valid lessons learned from the Shuttle. The request was for false ones.
Well, I’m not sure if it’s a lesson, but both Apollo and the Shuttle gave the public the impression that sending a man into space takes billions of dollars and tens of thousands of people scattered across several states, in a program that would dwarf the Manhattan project, with operating costs that exceed most country’s entire defense budgets.
The impression is so ingrained that it’s still hard for many people to believe that someone like Elon Musk could conceivably put humans in orbit. Another impression people might have is that if going to space could be simpler and less expensive then surely NASA would do it that way.
The most pernicious false lesson: It would be wasteful not to reuse as much Shuttle technology and infrastructure as possible.
The false lesson is that you have to be MORE risk averse or you’d kill more people than they did. Taking more risks can actually lower the chance of killing people.
Yesterday’s Aviation Week article on lessons from the Shuttle might be a good place to look for false lessons.
Thanks for the link, George.
How about:
Manned spacecraft require legions of people to launch them.
Space planes are bad, capsules are better.
Spacecraft need to be huge
Only government can operate a manned spacecraft.
A spacecraft needs to be able to perform every task.
maintaining jobs is more important than going to space.
You’re welcome!
A household analogy struck me about the decision to build something as complex and capable as the Shuttle, a vehicle designed to do everything, instead of building a few smaller, more dedicated craft.
A family is trying to decide what to buy for transportation. The husband wants a Ford F-150 because every now and then he needs to haul something, and he’d also like a gun rack. The wife wants a minivan because those offer a nice enclosed space for lots of passengers and the kids. The son wants a boat so he can spend time on the lake. So they compromise and buy a Marine Corps Amphibious Assault Vehicle, which met all their conflicting requirements.
@George, excellent analogy. Also, that avweek article is interesting reading. Such an incredibly shallow “critique” of the Shuttle system, and so many false lessons learned. That article also makes it seem as though the unique design blunders of the Shuttle (horizontal staging of a supercryogenic tank right next to the most vulnerable and important part of the reentry vehicle, segmented SRBs, use of SRBs at all, etc.) are somehow more fundamental safety considerations, and the solution isn’t to avoid such blunders but to just be so super diligent about safety, as the shuttle team has.
@Robin: The biggest unused capability on Shuttle is the cross-range capability the Air Force insisted on, which lead to wings that are almost freakishly oversized compared to the original concepts. That got used…when, exactly? I keep forgetting. 😛
Relates to rashomon’s True Lesson #3, I think.
@Robin: I watched an MIT Open Courseware lecture series on the Shuttle and they mentioned that the SRB’s are the escape system. If they malfunction then the result is not survivable. Of course, lots of potential malfunctions on the Shuttle are not survivable because of the basic design.
Early in the design phase they evaluated aluminum versus titanium for the airframe. The weight always came out the same because the heavier titanium airframe is offset by a lighter thermal protection system. Finally they flew out and consulted with Kelly Johnson who told them to stay away from titanium unless they absolutely needed it. In retrospect I think the titanium airframe would’ve been more thermally robust when tiles fall off and such. Plus, it’s hard to glue anything to aluminum.
And speaking of basic design, the Russians, SpaceX, and others have found that horizontal assembly is far cheaper than vertical assembly. I’m wondering what would happen if we took it a step further and launched a rocket while it was still on its side. A couple extra motors that lift it horizontally, rotate it to vertical, and then detach, might be cheaper still. It would save having a giant VAB, a giant crawler, and a giant tower. Checkout would be far easier and the umbilicals would just feed up from the ground for a couple of feet. As flight maneuvers go, there’s nothing particularly challenging about it.
The Shuttle was the worlds nicest Swiss Army Knife.
What we needed was a decent toolbox of tools.
You know, I sadistically rate up all of GM’s postings on AVWeek just to f%^k with his head!
I’ve never understood the Air Force insistence on massive cross-range. The explanation I’ve seen is so that the Shuttle, launching out ov Vandenberg, could do an abort-once-around. Due to Earth rotation, the non-crossrange return point would be 600 miles or more west (earth rotates at 15 degrees per hour), in the ocean. So, wouldn’t it have been a lot cheaper and safer to build the polar orbit shuttle launch facilities on the gulf coast instead?
On false lessons learned… I’d say that the “lesson” of a one-size-fits-all launch vehicle being a good idea is a huge false lesson. Remember, they tried to kill off all unmanned US launch vehicles and shift everything to Shuttle. That was a disaster waiting to happen, and if Challenger had to happen, I’m glad it happened then and not a few years later.
Here’s a question I’ve been trying hard to find an answer to; Shuttle Endeavour is going to the California Science Center. So, how can they get it there? That’s in downtown LA, many miles from the nearest airport that can take a 747. There are freeway overpasses and many other bridges along any street route. It has an eighty foot wingspan, and a tail height of about 80 feet, so towing it on a cleared freeway would be problematic in the extreem (it’s need to go through several interchanges, too).
So, how they heck do they plan to get it there? The museum indicates it’s going to be displayed there, not at an offsite hanger (such as the Smithsonian uses). Are they panning on taking the wings and tail off?!?! I’d think that’d violate the protection stipulation.
I’m even more curious why no one in the press, or anywhere online, seems to have asked this question? (I’ve done a few searches, and turned up nothing)
@Arizona: A polar launch out of Vandenberg (120d 34m west) should take your first pass somewhere over Leningrad and Kiev with the second orbit over Poland or Berlin, covering Eastern Europe.
A polar launch from our east coast would make a first pass over Thailand and Malaysia and it would be three or four hours before potential East Bloc hot spots rolled around.
The idea was a polar launch out of Vandenberg and deploying the satellite on the first pass, I suppose opening the cargo bay doors not long after the Shuttle exited the atmosphere, and then re-entering for a landing back at Vandenberg. The Shuttle has never even attempted a satellite deployment that early, and I don’t think they’ve ever opened and closed the cargo bay doors that quickly.
Of course, the whole scenario depends on the idea that the Shuttle was just sitting on the launch pad, all ready to go, when some critical military situation flared up in Europe. In reality the Air Force could’ve flown a photographer from Vandenberg to New York on a DC-3, put him on the Queen Mary to sail to France, then ride him on Eurorail to Berlin. From there he could hitch a ride into Poland on a Trabant, then hop on a donkey cart to snap some photos of the situation, then retrace his steps to Vandenberg to deliver the critical military intelligence and find out how they’d progressed on replacing the faulty fuel sensor on the SSMEs.
The always confident, but seldom correct, Gary Church provided a succinct statement of one of the most pernicious false lessons of the Shuttle program:
Space flight is inherently expensive, there is no cheap.
On other matters, good point, George, about horizontal assembly. I’ve pointed out the same in other comments here and elsewhere. You leave the rails, however, in suggesting horizontal launch. You’d either have to fatally increase the dry mass of the vehicle to make it stiff enough not to buckle under the transverse loading of going from a horizontal to vertical attitude or you’d need more total mass – especially fuel – to compensate for spending way more of your flight profile plowing through significant aerodynamic resistance or some combination of the two. It makes a lot more sense to just slowly jack the thing upright using entirely earthbound means before you light it off. Massive giant towers aren’t required to do this. See the launch video of either Falcon 9 thus far put up; the only towers visible are some tall, but lightweight, lightning rods.
@ George Turner
ROFL!! That description of the “alternative ground mission” had me laughing. Thanks!!! 🙂
Thanks also for the info on the planned AF usage… yipes!!! I supposed it’s feasible to deploy a satellite that fast, if you’re just ejecting it from the cargo bay, but talk about hectic! Unless the satellite has a booster, or a lot of thruster fuel and a large thruster, it’s going to re-enter just like the shuttle, but sans a heat shield. They’d need to get the doors open BEFORE an orbital insertion burn (dangerous; without the burn, you’re re-entering, and if there’s any delay on the burn and getting the doors shut, it can ruin your whole day). Do the OMS1 with the doors open, toss the satellite now the orbit is circularized, then immediately do a deorbit burn to cancel out the delta-v they’ve just added, and hope like hell there’s no delay in shutting the payload bay doors. I’m guessing they’d only be able to think of trying a once-around launch if the sat could do its own orbital insertion burn, but even that sounds risky and hectic, at least. Maybe it’s a good thing SLC-6 was never used.
@Dick Eagleson: I think it’s feasible if you’re doing the flip to vertical within a thousand or so feet of the ground, before you’ve picked up any significant velocity, and if you’re worried about horizontal bending loads then it would be pretty trivial if your rotational launch cradle had some big aluminum I-beams. Since the extra mass is only going to be lobbed a thousand or so feet up, that extra mass shouldn’t be an issue.
I got onto the idea when I thought of the complexities of using conventional techniques to raise a horizontal rocket to vertical. It sounds easy enough, until you deal with the cradles, cranes, lock down clamps, and so forth. Then I wondered why they don’t just attach a solid rocket motor to the upper middle of the rocket and just blast it to vertical. Use a liquid rocket with some controls and the task is no more difficult than changing attitude in orbit, with an accel, decel, and final orientation. Done right and it’s potentially cheaper than a crane, especially as the vehicle size approaches a Saturn V, where anything crane capable of lifting and rotating the rocket would deserve its own episode on “Modern Marvels.”
That leads to the question of why you’d just try to rotate an empty rocket to vertical and then clamp it to a launch pad. If you can rotate it to vertical when empty why not do it while fueled, and if you can do that then why not use it as your launch method. The first complain is going to come from the structures people worried about the bending loads, but you don’t have to use just one nozzle. You can distribute them along the length and reduce the bending loads to nearly zero. And if the cradle can lift a rocket to a thousand feet or so, and rotate it to vertical, then having that same cradle land right where it took off is a trivial exercise.
So instead of an expensive steel launch pad, assembly building, and crawler you have a reusable stage 0 that can fly upward in a horizontal orientation, with a dozen or so pressure fed engines running off a single turbopump, which can be tested countless times like Armadillos hovering rockets.
Vertical launch orientation makes sense when your rocket is the size of a V-2, but as they get bigger it becomes more and more impractical, to where the construction of a new launch pad, tower, and assembly building becomes a major cost constraint that only disappears if Congress is giving you an unlimited budget.
Or as I would put it, “If we can put a man on the moon we can surely design a rocket to rotate a piece of in flight aluminum by 90 degrees.”
Asked another way, what are the odds that the Germans came up with the lowest cost launch configuration during wartime?
The dry mass of a rocket is a small fraction of it’s fully-fueled mass. Why, using whatever technique you care to name, would you rationally prefer to try tipping a rocket upright with fuel rather than without? The Falcon 9 is not exactly a bottle rocket, right? But the assembly building is basically a glorified shed. You don’t need a VAB to stick a bird together on its side. No monster crawler required either. SpaceX built a transporter-erector out of standard heavy truck and construction machinery-type parts that hauls an F9 out empty and stands it up. Pad lockdown mechanisms are no big whoop either. Ditto the fueling system.
Compared to some linear array of throttleable rocket engines that has to leap into the air and then come back down to a soft landing after (hopefully) turning a fully fueled multi-stage rocket and attached payload through 90 degrees, this other stuff is cheap.
Bending dynamics aren’t the only thing that’ll screw you up. To flip a large mass through 90 degrees of rotation about its base you need to not only accelerate it up to some radial velocity, you also have to slow it down again or it’s just going to keep rotating. So you’re looking at two arrays of throttleable engines, not just one. And every engine is going to have to be yielding a different level of thrust – the one nearest the top needs to push hardest; the one nearest the bottom needs to push least.
It’s closing time, George. You’ve had a few too many and you’re talking crazy. Trust me, George, you do not want to take that woman home with you. And you don’t want to drive. You’re gonna hurt yourself.
Just a quick note on aluminum vs. titanium: I’ve seen it stated before that it turns out to be a wash in more reasons than one: yes, the titanium has higher temperature resistance than the aluminum, but it’s not high enough to withstand a burn-through from the heat shielding. Plus what it gains in ability to withstand temperature it loses from lower thermal conductivity.
@Dick Eagleson: Hey, I wasn’t that drunk! ^_^
Yes, the idea sounds insane at first blush, but consider the common idea of using a stage 0 carrier aircraft, something like a massively upsized B-1. Say its dimensions were scaled up by about a factor of 3 and its engines by 10, perhaps some derrivative of GE power plant turbines, to allow it to carry at a fully fueled Atlas V to mach 2 for an air launch. The structural loads on the Atlas would be the same as my crazy horizonal launch suggestion, with 1 to 1.4 G’s while its held horizontally in the carrier’s cargo bay.
If the horizontal launch cradle has similar structural properties to the carrier’s bomb bay, then the lifting force can be applied at one point, as if it came from a wing instead of a rocket engine. If the single point is slightly offset from the center of mass, the center of percussion relative to the point of application would define the instantaneous center of rotation of the system, allowing a simple solution for the control system. (We’ve been solving such center of percussion, rotation problems at least since the late 1500’s or early 1600’s). If the rotation rate is fairly slow, say 9 degrees per second for a 10 second stage 0 ride, the rocket could stop the rotation using it’s own control system. Otherwise just add a single solid motor to kill most of the rotation, or a pair to apply a pure torque.
I think the advantage would be that once you haul the vehicle out of the horizontal assembly building and over to the launch pad, you hook up the fueling lines and get clear, eliminating the erection and pad check out, shaving days if not weeks off the launch cycle.
I think this relates to a lesson from the Shuttle. If there’s a critical component that can be re-inspected after a major configuration change, people will be assigned to inspect it. Provide enough such opportunities and you’ve got thousands of people burning up hundreds of thousands of man hours. So launch the rocket before they get the chance. ^_^
But yeah, it does sound a little crazy.
@Phil: Titanium will eventually burn through, but I’m wondering how a penetration or TPS failure like Columbia’s (or perhaps somewhat smaller) would’ve been different if the inner wing structure would’ve been vastly more heat tolerant. Would it have gotten far enough through the re-entry to make a survivable abort, perhaps due to only a tire rupture?
I suppose I’m wondering if an airframe with a more robust thermal limit would make for more of a layered TPS system, allowing for a more graceful failure. For example, a tile thickly epoxied to a titanium skin, so that if the tile breaks off you still have the epoxy layer as an ablator which will buy a little more time before the titanium is directly exposed. It will take a little more time for the titanium to heat up to burn through, and even longer for the wing’s internals to heat up to the point of structural failure. As an added benefit you wouldn’t have aluminum burning like a torch.
It’s hard to remember that the NRO was actually considering replacing all robotic satellite imaging with humans on the shuttle launched out of Vandenberg. But when you consider that they were still using film canisters captured by hooks hanging out of the back of planes (with no automatic capture systems), it’s not that crazy.. ok, it is.
If you want to go with an air-breathing stage 0, there’s a simpler way than building an uber-bomber with a bomb bay big enough to swallow an Atlas 5 or Falcon 9. You go with an annular cluster of afterburning jet engines that wraps clear around the base of the rocket like a donut. You need to have enough engines in the cluster to impart the requisite acceleration to the whole vehicle. The annular aerostructure needs to carry enough fuel to provide useful boost with enough remaining after separation to return to a vertical back-down landing at the point of launch.
The most powerful aircraft engine made is the GE90-115B which, at full chat, can crank out 127,900 lbs. of thrust (lbt). This is a civil aviation engine so no afterburner has ever been designed or fitted, but this is quite doable. For short-duration operation, in fact, the GE 90-115B would be ideal for this application as it has the highest or near-highest bypass ratio of any engine in commercial service so its exhaust stream is almost entirely plain old air. If you’re planning to burn most of your fuel load in, say, 60 seconds, then you want to have the maximum volume of oxygen available with which to burn it.
The GE 90-115B has a specific fuel consumption of 1/4 lb./lbt/hour. 1/4 lb. x 127,900 lbt = 31975 lbs. of fuel, but we only need to make maximum thrust for one minute, not one hour. Dividing by 60 we get 533 lbs. of fuel. Now afterburners add thrust at the cost of efficiency. I figure we should look at afterburning sufficient to produce a rough doubling of thrust to, say, 250,000 lbt. This would likely boost total fuel required by a factor of roughly three, so we’re talking 1600 lbs. per engine. You’d also need to allow for the hover back to base and back-down soft landing – say another 400 lbs. That makes a nice round one ton of jet fuel per engine.
The GE90-115B weighs a bit over nine tons. Adding a ton for fuel and a probably too pessimistic allowance for tankage, structure and all other elements of a remotely pilotable flying donut, it seems quite reasonable to suppose we’d wind up at roughly 14 tons per engine for our stage zero. Each engine can produce 64 tons of thrust so we have a net plus of 50 tons of thrust per engine at liftoff and rising quite modestly as fuel burns off over the first 60 seconds of flight.
How many engines do we need, then? Taking a fully-loaded Falcon 9 as our target for assisted boost, we’re looking at a launch weight of right about 735,000 lbs. We need to have enough engines in our flying donut to boost this mass, plus itself, at an acceptable acceleration. The Falcon 9’s nine Merlins put out roughly 1,125,000 lbt. at launch. We should look to keep to roughly this 3:2 ratio of thrust to mass.
Three afterburner-enhanced GE 90-115B’s will do to balance the Falcon 9’s mass. one and a half more will give us the 3:2 ratio we’re looking for. Round up to five and we have 735,000 lbs. of rocket, 140,000 lbs. of donut booster and 1,250,000 lbt. Not quite 3:2. Add a sixth engine and we are now at 735,000 plus 168,000 versus 1,500,000 lbt., slightly above the desired 3:2 ratio for the combination of the rocket being boosted and the annular booster.
The diameter of the GE 90-115B engine is roughly the same (12 ft.) as the diameter of a Falcon 9 first stage so the packing geometry of a six-engine donut is optimal.
You haul the rocket out flat and stand it up, as per current practice, then you wrap the donut around its base using a hinged joint that lets it open up in two semicircles and lock the whole thing together with suitable quick-releases and you’re ready to go.
At T-minus Zero, the donut lights up, the whole shebang rises majestically into the air and 60 seconds later, the Merlins light off, the donut cuts the afterburners and – assuming it’s robot avionics are able to either avoid being tumbled by the Falcon’s backwash or are able to right a tumble that occurs – flies back to base and down to a soft landing on its struts.
Not saying this is necessarily a desireable thing to do, but it’s a feasible thing to do and doesn’t involve any brobdignagian airframe development or the need for five miles of runway to get it airborne.
@Dick Eagleson: I’ve thought about using the GE-90’s in the scheme you propose, but some of the power generation turbines are much, much larger. They of course haven’t been optimized for a lower mass, but GE, Siemens, and other companies shouldn’t find it much of a challenge to do that if there was a customer for an aero derivative of their existing designs, some of which should produce something in the neighborhood of a million lbsf.
It might be simpler for them, however, to just upscale their existing aero engines. One of the advantages of increasing their size is that the angular accelerations drop linearly with radius, since optimum blade tip speed is fairly constant, somewhere near Mach 1.
Given the vastly higher ISP of jet engines, my horizontal orientation at lift-off would simplify to just carrying the rocket up, horizontally, and then letting it drop as soon as the its boosters ignite. That would give good seperation between the stage 0 and the exhaust stream from stage 1, and swinging a rocket from horizontal to vertical at altitude is no harder than swinging it from vertical to horizontal, something every rocket already does.
Didnt see it explicitly called out, but one obvious false lesson is that you can design an operational space shuttle on paper, and call the first generation design the ultimate one.
Three Skylifters (150,000kg ea.) aught to do the job of taking a fully loaded F9 to some high altitude? The F9 could assist with it’s own partial thrust and throttle up when the Skylifters are unable to make greater altitude.
ken,
That would be an impressive spectacle and one with no fire and noise.
If they build that thing, the UFO Hotline phone is going to ring off the hook.
Commander Straker will never get any sleep!