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SpaceShipThree to be Orbital Spacecraft
FleaPlus writes "The president of spaceflight company Virgin Galactic has recently
stated that if the upcoming suborbital service with SpaceShipTwo
is successful, the follow-up SpaceShipThree will be an orbital craft.
Although orbital spaceflights would be much longer and could
potentially dock with orbital
space stations, they are also considerably more difficult than
suborbital spaceflights. Other private firms working on orbital
spaceflight (and potentially in the running for Robert Bigelow's $50
million America's Space Prize for orbital flight) include t/Space
and SpaceX."
There's a very interesting writeup about the potential problems related to trying to reach orbit in these "scaled composites" "spaceships" at http://www.daughtersoftiresias.org/misc/ss1.html.
Basically, the biggest problem is that due to the simplicity of the engine design (the are examples of space shuttle engine and the SS1 engine on the page above), the design would never scale enough to reach velocities needed to get into orbit.
Why would anyone pay for a suborbital flight when they expect the next version to be orbital? There will be a few no doubt who think its worthwhile to spend a hundred grand on an e-ticket to nowhere, but probably not enough to cover costs.
Seems to me the whole idea of suborbital flight as a stepping stone to bigger things is a bad one. Its like expecting DOS to scale up to a multi-threaded multi-user graphical operating system. Maybe it can be done, but is the final product safe to use? Starting with technology designed from the ground up to do the mission makes a lot more sense to me.
Then, when the materials tech becomes practical, they build a space elevator on the very same site. Makes perfect sense; at that point, they have the name and a shitload of capital to make it happen. Taxpayers have spent enough on incremental baby steps and aerospace subsidies.
May dreams such as these take wing and I'd be happy just to watch: (link)
"OH SHIT, THERE'S A HORSE IN THE HOSPITAL!"
I'm under the impression that the direct speed/altitude benefits are fairly small. Rather, the main benefits are from safer abort methods (you can parachute back down if your engines fail) and being able to build an engine optimized for the upper atmosphere and space. You also don't have to pay launch site fees, and liability insurance becomes easier to deal with. Here's a relevant quote from t/Space's site:
n =projects.view&workid=CCD3097A-96B6-175C-97F15F270 F2B83AA
http://www.transformspace.com/index.cfm?fuseactio
The major benefits of air launch come in safety, simplicity and flexibility. Crew safety is enhanced because abort-at-ignition is easier when the capsule already is high enough for parachute deployment, vs. the on-the-pad challenge of releasing sufficient energy in the correct direction to send the capsule high enough for the parachutes to deploy. Public safety is enhanced because the launch takes place over open ocean, well away from any populated areas.
Air launch also allows simpler engines, which don't need to be designed to operate at both sea-level air pressure and at altitude. The "all-airborne" operation also reduces the performance penalty of using inexpensive low-pressure tanks and engines.
Flexibility and responsiveness is greatly enhanced by air launch. Most winds and precipitation at the airport runway -- launch site -- don't delay a launch; the carrier aircraft simply flies to clear weather. In addition, responsive launch often requires matching a particular inclination and orbit phasing. The carrier aircraft over open ocean can launch the CXV to any azimuth, and by flying across longitudes, can quickly match a desired orbit phasing.
The t/Space version of air launch provides only modest performance gains, in the 10-25% range, compared to a ground launch. It does not attempt technically difficult challenges such as accelerating the launch aircraft to supersonic speeds, or reaching very high altitudes.
Getting the craft back down to earth in one piece is going to be the capability I am most interested in seeing them solve. Will it be ablative or something reusuable like the tile system but more robust? Being Rutan I full expect it to land like a plane on return so that alone will limit some of the choices he can make.
Unless he revolutionizes rocket propulsion I don't see how they are going to get anyone into orbit at reasonable costs, by reasonable I mean in the $1,000,000 range.
If space tourism would generate a good return on investment I am pretty sure the Russians would be all over it. They already have the technology to get there and have proven they would take paying customers. Since they haven't moved more aggressively I have seriously doubts if it is doable on todays technology. Look at the Kliper, the estimated costs are nearly $3 billion just to develop it! It can take 6 people and 750kg of cargo to LEV. The other issue that stands out with Kliper is that the module may only be used 25 times before retirement.
If the Russians are having such issues with LEV on that budget it will take a miracle for anyone else.
Wiki link to Kliper
http://en.wikipedia.org/wiki/Kliper
* Winners compare their achievements to their goals, losers compare theirs to that of others.
Fuels that are used in space must carry their own oxygen, but when going at high speeds in the earth's atmosphere, why not make like a jet engine and get oxygen from the atmosphere? Perhaps there could be two fuels, one for use in the atmosphere and one for use in space. The engine would start using one, then as pressure dropped would slowly switch to the other. But of course with an air intake that must work from zero to hypersonic speeds, you run into some pretty nasty physics in designing the thing. End result is you end up with a non-constant flow of oxygen to your engine, no matter how well you design your system. Thus the engine must be designed with this tolerance in mind.
So, anyone trying this: good luck!
Quid festinatio swallonis est aetherfuga inonusti?
Africus aut Europaeus?
Not only had the SS1 team "done their homework and benefited from what was learned in the X-15 program".... Burt Rutan was in fact one of the engineers on the original X-15 team.
SSTO may be the holy grail, but it's wasteful from an efficiency standpoint. Multiple staging allows lower fuel mass fractions with weaker engines. It does not matter whether the stages are similar or not (though dissimilar stages could potentially take advantages of conditions in various regimes) multiple similar staging provides enough benefit to be worthwhile.
It is probably more effective, from a mass-fraction standpoint to use multiple rocket stages rather than using an airbreathing stage over a small fraction of the trip.
IMO, the real "holy grail" is not reducing the stages to 1, but increasing the stages to infinity: a rocket that consumes its own structural mass as its usefulness is spent. No piece of structural mass should be lofted higher than it needs to be. Continuous staging would be the ultimate extension of that principle. In fact, I believe I have seen engines for sounding rockets that are designed to do just that.
Can you be Even More Awesome?!
Okay ... every freaking time this subject comes up (which you all know is fairly often) at least part of the thread gets hijacked into a detour on re-entry heating and "how in the heck is Rutan going to solve that problem", etc.
... all you have to do is SLOW DOWN!
... "every action", etc. ... it takes as much energy to slow down as it took to speed up in the first place ... so it would take a LOT of fuel.) An ablative coating (on the Apollo Command Module) or the tile system (on the Shuttles) is a heckuva lot cheaper and easier than managing to get enough fuel on-orbit to slow the dang thing back down to near-zero.
... but that doesn't make it any less true!
... it just isn't so. As is the case with many science problems, there is more than one way to skin the cat.
IANARS, but I do know a thing or two about aerospace principles and technology due to the education I *do* have. What I always find amusing about this particular area of the discussion (re-entry heating) is that everyone posting seems to take for granted that re-entry heating is an axiomatic phenomenon that MUST be faced head-on. (Pun not intended but noticed.)
THIS IS NOT TRUE!
The only reason re-entry heating is an issue for us (NASA, et al) is more a matter of ECONOMICS than technology.
The simple fact is that you can re-enter the atmosphere with little or no heating
The reason we don't slow down is we can't afford to carry enough fuel to get into orbit and still have enough to slow the craft down for a cool re-entry. (Think about it
In a nutshell - if I can slow my craft down enough (think "retro-rockets" here) then I can practically "float back down" into the atmosphere with minimal heating.
There *are* possible solutions, such as *sending* fuel to orbit in a separate un-manned craft, and then re-fueling the manned craft on-station. Or *manufacturing* fuel outside Earth's gravity well so craft can re-fuel. Or having some other means of power to use for "retro-thrust" in orbit.
Now, I am going to cap the preceding comments with a BIG disclaimer:
*Of course* I realize that this opens a different set of problems and perhaps presumes technology developments in other areas
I am just tired of people assuming that no matter what you do you have to have a craft capable of withstanding all of that horrible heat
Me out!
See you space cowboy