Crazy idea for air-launched Shuttle

[najab]

Crazy idea that just came to me - what would happen if we 'air-launched' a Shuttle? The idea I had was to use the basic Shuttle stack, but light the SSMEs just before SRB burnout.<br /><br />Unless I am figuring wrong, when the SRBs light, the Shuttle would leave the ground, regardless of if the SSMEs were lit (especially if we used 5-segment boosters) - the vehicle has a mass of ~4.5 million pounds and the SRB's supply ~7 million pounds of thrust.<br /><br />Just assuming that such a feat was possible, what would happen at SRB sep?

 

[najab]

Oh, yeah. The ET would necessarily be smaller.

 

[henryhallam]

I think gravity losses would lead to reduced performance... For best efficiency you should burn ALL your engines at full thrust in the shortest time possible. 5 seg SRBs could overcome this but then you'd have better performance with ground-started SSMEs + 5 seg SRBs.

 

[tap_sa]

The Stack would somersault unless you move the SRBs closer to Orbiter's belly to get thrust vector pointing through cg again.

 

[propforce]

<font color="yellow">The idea I had was to use the basic Shuttle stack, but light the SSMEs just before SRB burnout. <br /></font><br /><br />The problem is a significant reduction of launch reliability due to "air-starting" the SSMEs. <br /><br />A large part of the current starting sequence of SSME, e.g., a part of "launch-commit-criteria", is checked prior to engine start. The SRB is not lit until 3~5 sec after SSME start and ramp up to full power. This ensures a proper launch abort if something is wrong, hence greatly increase the launch reliability. <br /><br />I know, I know, you are dying to ask "but, but, but.... what about CLV ???" Hey, they don't pay me the big bucks to make these decisions <img src="/images/icons/smile.gif" />. OK, seriously, that's why Rocketdyne receive a contract to modify the current SSME to be suitable for "air-start".<br /><br />Performance wise I don't think the Shuttle would have suffer much if air-starting SSMEs, actually (though I have not run the numbers) I'd think it may even increase performance because the SSMEs would burn LONGER after the SRB separation. But then you would have to re-shape the thrust profile of SRBs which is another expensive qualification program. <img src="/images/icons/rolleyes.gif" /><br /><br />Bottomline, I think it could work but just too expensive to make these changes to make it worthwhile. <div class="Discussion_UserSignature"> </div>

 

[spacefire]

what if we used a huge balloon to raise the Shuttle to about 100,000ft and THEN light up the engines! <div class="Discussion_UserSignature"> <p>http://asteroid-invasion.blogspot.com</p><p>http://www.solvengineer.com/asteroid-invasion.html </p><p> </p> </div>

 

[tap_sa]

<font color="yellow">"what if we used a huge balloon to raise the Shuttle to about 100,000ft and THEN light up the engines!"</font><br /><br />Hey, how aboat replacing the ET completely with that balloon!? Great mass savings!<br /><br />And use only 1-segment SRBs. Just before they burn out an artillery battery at KSC opens fire shooting HTPB shells up to their throats into casings.

 

[propforce]

<font color="yellow">what if we used a huge balloon to raise the Shuttle to about 100,000ft and THEN light up the engines! </font><br /><br />That would help out less than 0.5% of total energy needed to get to orbit.<br /><br />Remember, you need <i>velocity</i> in addition to <i>altitude</i>. Otherwise, your vehicle will act just like the SpaceShipOne --- fall back to earth like a rock <img src="/images/icons/smile.gif" /><br /><br /><br /> <div class="Discussion_UserSignature"> </div>

 

[tap_sa]

<font color="yellow">"That would help out less than 0.5% of total energy needed to get to orbit. "</font><br /><br />Still, it would be nice to begin with most of the atmosphere out of the way, no?

 

[propforce]

<font color="yellow">"That would help out less than 0.5% of total energy needed to get to orbit. " <br /><br />Still, it would be nice to begin with most of the atmosphere out of the way, no? </font><br /><br />Only if you can tell me how big of a balloon and how much hydrogen or helium would it take <img src="/images/icons/smile.gif" /><br /><br />Also, how would you separate a balloon from the Shuttle? I would hate to see the balloon convers up the Shuttle such that astronauts can not see out of window !! <div class="Discussion_UserSignature"> </div>

 

[josh_simonson]

>Still, it would be nice to begin with most of the atmosphere out of the way, no? <br /><br />Only if you're trying to go orbital with a single impulse. <img src="/images/icons/wink.gif" />

 

[tap_sa]

<font color="yellow">"how big of a balloon"</font><br /><br /><i><b>Big!</b></i><br /><br /><font color="yellow">"how would you separate a balloon from the Shuttle? "</font><br /><br />That's the best part, I wouldn't! Once orbit is reached the balloon is empty and flaps behind like a giant, spent ... prophylactic, drag keeps it straight not wrapping up the Orbiter. Before reentry the balloon is re-filled with nitrogen to make it the biggest airbag in the world! The shuttle could even reenter upside down yet the miniscule ballistic coefficient would ensure safe landing, albeit slightly dent to the rudder.<br /><br />Pat.pend.

 

[propforce]

<font color="yellow">Once orbit is reached the balloon is empty and flaps behind like a giant, spent ... prophylactic,</font><br /><br />Hmmm.... we can also apply some fluids for film cooling !! <br /><br />Probably would help slow down the vehicle on reentry and save some weight on the TPS <img src="/images/icons/laugh.gif" /> <div class="Discussion_UserSignature"> </div>

 

[josh_simonson]

Better yet, instead of a balloon, use a rigid tank made out of CNT. Once in orbit one of the 4 mile tanks can be used to host the 2024 olympics.

 

[krrr]

I think the general idea is sound.<br /><br />Use them dirty big boosters to perform the thankless task of ploughing through the atmosphere, then launch your shiny rocket unsullied from a platform where it doesn't have to bother with max Q and somesuch, and has a healthy initial velocity.<br /><br />Basically, I think it would make sense to have a short-burning (60 to 80 seconds) solid first stage just to get rid of the atmosphere. Then sophisticated upper stages would chime in.

 

[scottb50]

Actually the balloon makes more sense, I doubt it would have to be 4 miles long though. A balloon filled with Hydrogen, lifts the upper stage to 100,000 feet or so. At altitude the upper stage engines draw Hydrogen from the balloon and Oxygen from LOX tanks to reach orbit. <div class="Discussion_UserSignature"> </div>

 

[scottb50]

Not to answer my own post. I just read CallicArcale's post. Never mind! <div class="Discussion_UserSignature"> </div>

 

[mikejz]

I know that people always talk about a balloon or air launching providing so little energy to orbit vs. ground launch. However, If I launch at a higher altitude, would not the lack of drag allow me to accellerate faster, and thus less gravity loss?

 

[scottb50]

I would suspect a four mile long Zepplin would get going pretty fast staight up. I doubt the momentum and altitude gained is worth the effort. <div class="Discussion_UserSignature"> </div>

 

[thinice]

To lift the upper stage the balloon should be lighter than air. In upper atmosphere hydrogen in the balloon will be at so low density that you will not be able to draw it with speed enough to feed the engine.

 

[scottb50]

I never said it would be easy. <div class="Discussion_UserSignature"> </div>

 

[propforce]

How about collecting air while the balloon is on the way up, liquidfy it and separate out the oxygen from nitrogen, and collect the liquid oxygen for the rocket engine? <img src="/images/icons/wink.gif" /> <div class="Discussion_UserSignature"> </div>

 

[john_316]

I like the idea with a modified 747-400 with either 1 or 2 X-40/X-37 type of vehicles.<br /><br />These vehicles dont even have to be military in nature. I think if that if a 747 carrying one or 2 of these aloft could place a modified space plane into low orbit and even be able to fly to the ISS.<br /><br />I just dont see why they dont take a page from the X-15 and SS1 book here? <br /><br />My point is this. Lets say that we use one of these vehicles just as rescue vehicles for say a stranded crew or ill crew member who needs serious medical attention.<br /><br />Wouldn't that be sufficient as well? <br /><br />Even a non military application of one of these special craft far outweights no access to space what so ever...<br /><br />A enlarged X40/X37 with a ISS docking adapter and suffient station on-time to rescue a crew of say 3 plus the 2 pilots. So yes a 5-6 man crew vehicle like the H-20 but air launched.<br /><br />The SS1 can launch 3 crew. So an enlarged version could launch 6 but what if it had added systems and dropped from a 747-400??? I dont imply using the SS2 I am implying using a x40/x37 variant. <br /><br />I just dont see why Boeing or Lockmart don't see any commercial applications? Oh perhaps because they used to have a monopoly on space access... <br /><br />HAHAHAHA Not anymore!<br /><br /><img src="/images/icons/smile.gif" /><br /><br /><br />P.S. Hey if you want I'll take over the X-40/X-37 projects and turn them into Air Launched Vehicles with space station access.<br />

 

[mlorrey]

"I know that people always talk about a balloon or air launching providing so little energy to orbit vs. ground launch. However, If I launch at a higher altitude, would not the lack of drag allow me to accellerate faster, and thus less gravity loss? "<br /><br />Yes and no. Your gravity losses would be slightly less, and if, for instance, you were lifted by balloon to 100,000 or more feet, you'd gain significant velocity while dropping which you would be able to translate into lateral velocity, so you'd be using your gravitational potential to get velocity, but only if you had sufficient aerodynamics to do so (such as having wings of some sort). However if you drop too far, you lose a lot of that energy in aerodynamic losses.<br /><br />The lack of drag at altitude does reduce your aerodynamic losses, not your gravity losses. Your gravity loss savings are because you are less deep in the gravity well, so, for instance, if your balloon is floating east at 100,000 feet at a few miles/hr, you calculate the boost you get from the earth's rotation differently: instead of launching 4,000 miles from the earth's center, you are launching 4,020 miles from the earth's center, so the force of gravity is slightly less AND your flight path circumference around the earth means you are going faster in absolute terms than you would walking along at a few mph on the ground. Thus:<br /><br />4,000 mile diameter X 2 X Pi = 25132.741228718345907701147066236 mile circumference <br />25132.741228718345907701147066236 / 24 hours = 1047.1975511965977461542144610932mph angular velocity at the equator at sea level.<br /><br />Conversely, at 4,020 miles, or 100,000 ft above the eath's surface:<br />4020 x 2 x pi = 25258.404934861937637239652801567 miles circumference<br /><br />25258.404934861937637239652801567 / 24 hours = 1052.4335389525807348849855333986 mph<br /><br />Thus, at 100,000 feet you are going 5 mph faster than being on the ground, when launching from the equator.<br />Not much difference.<br></br>

 

[henryhallam]

Er, that makes no sense. There would be zero advantage to dropping from a stationary balloon at any height and then trying to convert your falling velocity into horizontal velocity. You are only throwing energy away as drag by doing this. Instead just keep it as grav. potential energy and accelerate forwards + a bit upwards.<br /><br />Gravity losses have nothing to do with the Earth's rotation and aren't really due to how deep you are within a gravity well, they can best be explained by the following thought experiment:<br /><br />A rocket hovers on the pad weighing 100kg and producing 1000N of thrust. It will go nowhere and be wasting energy because it's using all its thrust to support its own weight. Eventually some propellants will be used up and the rocket will slowly accelerate upwards.<br />If the same rocket with the same amount of propellants and initial mass had an engine that produced a lot more thrust, say 5000N, it would immediately leap off the pad at an acceleration of 40m/s^2. For the same amount of initial propellants you end up with better delta V or more payload into the same orbit. So gravity losses depend almost solely on how rapidly you can accelerate, which is usually limited by three things - atmospheric drag, vehicle structure and the human body. Launching from a high altitude balloon gets rid of most of the atmospheric drag so you can accelerate a bit more rapidy and reduce the gravity losses a bit. But it is still a silly idea.