scramjet to orbit (a way to do away with rockets)

[spacefire]

ok, does anybody remember how the Dynasoar was supposed to skip over the Earth atmosphere?<br />I have an idea along that lines which could get a spacecraft to orbit without using rockets(except for the initial boost to get the scramjet running, unless a Turbine Based Combined Cycle is used)<br />Basically you get the scramjet running and go up on a ballistic trajectory, outside of Earth's atmosphere but not at orbital speeds-yet. As you dip back in the upper fringes of the atmosphere you restart your scramjet, and again go outside of the atmosphere...and keep doing so, progressively starting your burn higher and higher, getting more and more speed until at one point you will achieve orbit. <br />The advantage of this system is reduced pressure loading (Q), since you achieve most of your delta V at high altitudes.<br />Please dissect my idea and let me know your opinions. <div class="Discussion_UserSignature"> <p>http://asteroid-invasion.blogspot.com</p><p>http://www.solvengineer.com/asteroid-invasion.html </p><p> </p> </div>

 

[vogon13]

Haven't done the math, but suspect just enough air at target altitude to over tax thermal protection system, and not enough to let a practical engine concept function properly.<br /><br />Happy to be wrong on this one, but fear I'm not.<br /><br /> <div class="Discussion_UserSignature"> <p><font color="#ff0000"><strong>TPTB went to Dallas and all I got was Plucked !!</strong></font></p><p><font color="#339966"><strong>So many people, so few recipes !!</strong></font></p><p><font color="#0000ff"><strong>Let's clean up this stinkhole !!</strong></font> </p> </div>

 

[spacefire]

well I haven't done the math either. But it takes less air to run a scramjet than to burn-up an re-entry grade heatshield, otherwise the X43 would've looked much different. <div class="Discussion_UserSignature"> <p>http://asteroid-invasion.blogspot.com</p><p>http://www.solvengineer.com/asteroid-invasion.html </p><p> </p> </div>

 

[tomnackid]

This sounds like Lawrence Livermore's "HyperSoar" concept:<br /><br />http://www.llnl.gov/str/Carter.html<br /><br />An air/spacecraft with either scramjets or a mixed cycle air breathing/rocket engine skips in and out of the upper atmosphere to avoid excessive heating a la Silvebird and DynaSoar. Every time the craft skims the atmosphere it turns on its air breathing engine to pick up more speed. 25 skips can take you half around the world in under an hour. More skips and you can achieve orbital velocity.

 

[spacefire]

thanks for the link! <br /><br />He mentions the scramjet as a first stage of a LEO delivery system, I think the whole thing could make it to orbit quite easily with maybe a short rocket burst. <div class="Discussion_UserSignature"> <p>http://asteroid-invasion.blogspot.com</p><p>http://www.solvengineer.com/asteroid-invasion.html </p><p> </p> </div>

 

[cdr6]

Wasn't there a similar ("NASP"?) proposal a short whie ago? Supposed to do sort of the same thing...I remember an illustration of the thing docked to the space station... I think they were actually cutting metal on it then it sort of dropped off the radar. It was more boxy and less elegant than the picture above, had red white and blue stripes etc painted on it...?

 

[spacefire]

I'm not sure the NASP was designed to go in and out of the atmosphere to scoop air and accelerate like that.<br />I think it was proposed as an RBCC. <div class="Discussion_UserSignature"> <p>http://asteroid-invasion.blogspot.com</p><p>http://www.solvengineer.com/asteroid-invasion.html </p><p> </p> </div>

 

[scottb50]

The whole point of Scram-Jets is providing terminal maneuverability for a re-entry vehicle, read BOMB. <br /><br />To get to orbit a Scram-Jet, Ram-Jet, etal, have no use, period. <div class="Discussion_UserSignature"> </div>

 

[larper]

How do you raise your perigee? <div class="Discussion_UserSignature"> <p><strong><font color="#ff0000">Vote </font><font color="#3366ff">Libertarian</font></strong></p> </div>

 

[spacefire]

you will have to use a rocket to acheive circular orbit, but the amount of propellant carried onboard will be much smaller. think about it, most of your delta V will be given by the scramjets, and the max Q will be lower than through continuous operation in the atmosphere because you will raise yourself out of the atmosphere through inertia on a suborbital parabola, then wehn you come back you fire the scramjets and go back up on another parabola, only the parabolas get flatter and flatter while each time you dip in the atmosphere (a little higher than last time) you gather speed by fring the scramjets. <div class="Discussion_UserSignature"> <p>http://asteroid-invasion.blogspot.com</p><p>http://www.solvengineer.com/asteroid-invasion.html </p><p> </p> </div>

 

[larper]

Yes, but how do you raise your perigee? <div class="Discussion_UserSignature"> <p><strong><font color="#ff0000">Vote </font><font color="#3366ff">Libertarian</font></strong></p> </div>

 

[ortemus74]

50% of the propellant used at the launch site is wasted trying to get the darn thing off the ground.<br /><br />Dealing with the shaky science of the scramjet I seriously doubt that the 'two' successful tests accellerated the scramjet to mach 7 and then mach 10. Rather the PEGASUS BOOSTER in both successful tests was actually the culprit that accellerated both scramjet tests to mach 7 and beyond...<br /><br />By the time they fired the scramjet the the X-43 was already travelling at mach 7 or beyond all thanks to the PEGASUS BOOSTERS.<br />

 

[spacefire]

larper, you do not have a perigee until you have orbit <br /><br />in order to achieve orbit, the last 'dip' back in the atmosphere-at a very high altitude and very high speed- will include a prolonged period of horizontal acceleration, then the craft will start to raise and the rocket will be fired.<br />I believe this will give you a rather elliptic orbit with a pretty low perigee, like you are probably inferring. In order to raise the perigee and eventually achieve circular orbit, you will use the rocket engines thorughout the first orbit. There's no way to get around that. However, most of your delta V would have come from the scramjets and thus you are saving weight on the oxydizer. <div class="Discussion_UserSignature"> <p>http://asteroid-invasion.blogspot.com</p><p>http://www.solvengineer.com/asteroid-invasion.html </p><p> </p> </div>

 

[najab]

<blockquote><font class="small">In reply to:</font><hr /><p>Dealing with the shaky science of the scramjet I seriously doubt that the 'two' successful tests accellerated the scramjet to mach 7 and then mach 10. Rather the PEGASUS BOOSTER in both successful tests was actually the culprit that accellerated both scramjet tests to mach 7 and beyond...<p><hr /></p></p></blockquote>Actually, the test vehicle accelerated once it separated from the booster.

 

[ortemus74]

Like I said without the PEGASUS BOOSTER it is likely the scramjet 'test vehicle' would ever acheive mach 7 and beyond under its OWN power. That's saying it still remains a two stage launch vehicle.<br /><br />Until you remove the training wheels the scramjet single-stage-to-orbit will remain a fantasy. <br /><br />Also, man usually never invents things he cannot control. At speeds reaching Mach 10 it's hard to remain in control...

 

[bobvanx]

Mach 25 (orbital velocity for LEO) is 2.5X the Mach 10 scramjet we just tested. Thermal heating won't be merely 2.5x greater. I think it follows a power law, so the energy to be dissipated is at least squared, or about 6X greater.<br /><br />Earth's gravity is just too great, and the atmosphere doesn't reach high enough, for any sort of flying to orbit scheme to be more useful than a rocket or a tether. Mars however, is a different story. A vehicle similar to the SR-71 is nearly good enough to fly into orbit at Mars. <br /><br />Skipping around the Earth at Mach 10 to 15 is pretty cool, though.

 

[scottb50]

The problem with a scramjet single stage-to-orbit vehicle is you need to be going faster than Mach 3 to even start the engine. The whole reason the Pegasus was used was to get the scramjet to a speed it could be started to begin with.<br /><br />As for remaining in control at mach10 I doubt it is much different than remaining in control at any speed. The Shuttle operates at Mach 25 as seems to be quite controllable. <div class="Discussion_UserSignature"> </div>

 

[mrmorris]

<font color="yellow">"Mars however, is a different story. A vehicle similar to the SR-71 is nearly good enough to fly into orbit at Mars."</font><br /><br />Small hitch there... two actually.<br /><br />1. The reason why a scramjet is a desirable option for reaching orbit is because it can get oxygen from the atmosphere rather than having to carry it onboard. Mars is just a bit deficient in the atmospheric oxygen department.<br /><br />2. Mars' atmosphere is too thin for the SR-71's wings to provide sufficient lift. Planes on Mars would require enormous wings. Think glider. Then think adding ramjet/scramjet to glider. Then think many many pieces of glider raining down on Martian dunes. <img src="/images/icons/smile.gif" />

 

[larper]

<blockquote><font class="small">In reply to:</font><hr /><p>I have an idea along that lines which could get a spacecraft to orbit without using rockets<p><hr /></p></p></blockquote><br />You said you could achieve orbit without rockets. Now you say you raise perigee with a rocket.<br /><br />Meanwhile, you don't seem to understand orbital mechanics. Your "last dip back in the atmosphere" occurs at the same altitude as your "first dip". <br /><br />So, you have made an incredibly inefficient vehicle for getting to orbit. I am sure it is a lifting body too, which makes it an incredible inefficient vehicle to return from orbit as well.<br /><br />Until we give up on the idea of putting wings into space, we will never return to the moon. <div class="Discussion_UserSignature"> <p><strong><font color="#ff0000">Vote </font><font color="#3366ff">Libertarian</font></strong></p> </div>

 

[tap_sa]

<font color="yellow">"Until we give up on the idea of putting wings into space, we will never return to the moon."</font><br /><br />Instead of tasteless goo from a tube I'd like to eat bbq chicken wings on the moon. Lunar henhouse!

 

[grooble]

Sure a few folks will get to the moon. But without wings in space, the masses will never get there.<br /><br />Look how much trouble it is to do one rocket launch. Can you conceive of 1,000s of launches a day?<br /><br />Even that wouldn't be much.

 

[spacefire]

what makes you think the last dip will level off at the same altitude as the first dip? <br />once you get faster and faster, your scramjet will be able to function in a lower atmospheric density. Your lifting body will generate lift in lower density as well, allowing you to level off aerodynamically. You could reach orbit using just the scramjet this way, but it won't be circular.<br />As for heating, any re-entry grade heatshield should be able to withstand the heat of the dips because the dips occur at a very high altitude with rarefied air. <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">"Can you conceive of 1,000s of launches a day? Even that wouldn't be much."</font><br /><br />What, doing same or perhaps more space launches than daily intercontinental flights wouldn't be much? Sir, you are too much!<br /><br />Even if we'd have just <i>one</i> regular manned flight per day I'd call that a pretty space fairing civilization, compared to the current pace. After that, perhaps 20 launch sites in the world, each doing a daily launch, each launch carrying 20 people and we would have a biblical amount of 144000 persons annually visiting space.

 

[spacefire]

<font color="yellow">I am sure it is a lifting body too, which makes it an incredible inefficient vehicle to return from orbit as well. <br /><br />Until we give up on the idea of putting wings into space, we will never return to the moon. </font><br /><br /><br />A lifting body with wings. What an inteersting concept. can you elaborate, please?<br /><br /> <div class="Discussion_UserSignature"> <p>http://asteroid-invasion.blogspot.com</p><p>http://www.solvengineer.com/asteroid-invasion.html </p><p> </p> </div>

 

[bobvanx]

>Mars is just a bit deficient in the atmospheric oxygen department.<br /><br />Heh. Yeah, <i>currently,</i> there's no good oxidizer in Mar's atmosphere. But after terraforming, who knows...?<br /><br /> />Mars' atmosphere is too thin for the SR-71's wings to provide sufficient lift.<br /><br />Not true! Mar's atmospheric density is very similar to the SR-71's maximum ceiling. Mars' pressure is like the Earth's at 100,000 feet; the SR-71 flew to 85,000 feet. I'd bet in a 38% gravity field, the wings wouldn't need to be any larger at all.<br /><br />The problem of what to use as a propellant in your Martian SSTO flying vehicle is a real show-stopper. Hey, waitaminute-- what was that nuclear-powered ramjet missile? The NERVA? It used <i>any</i> gas as reaction mass. So there you go, the napkin design for a SSTO flyer: an open nuclear pile with SR-71 wings flying to orbit around Mars.