Scramjet as a Brake?

[birko]

Hi all,<br />I'm a complete civillian making my first post, and am not sure if I am in the right forums for a question that is niggling at me. I have no technical understanding, apart from what popular media feeds me, but have been fascinated with propulsion systems. The Sci-Fi section seems best to ask - as I'm wondering about something that I don't think we currently have the materials or technology to do - so my question is hyperthetical.<br /><br />Could scramjets be used to help brake a spaceplane from orbit - reducing re-entry angle?<br /><br />Thrust vectoring is currently used in most large jets when they land, with "reverse thrust". Could the forces of sramjets be redirected away from the linear, controlling the fall and giving sporadic thrust to allow a skipping "within" the atmosphere? At least until it is supersonic, and can discard it's hypersonic surfaces.<br /><br /><br />

 

[qso1]

First off, welcome to the boards.<br /><br />Space business and technology may be the place where this belongs although if you were proposing this as a part of a science fiction book or movie, this forum is fine. Aside from that.<br /><br />The answer is that its not practical. A well designed spaceplane should be built to use its body for re-entry and that includes the angle at which it comes in. The whole point of re-entry as its currently practiced is to be able to utilize something already present to get you back. Something you don't have to build and pay more money for. And that something is the atmosphere and gravity which act as the brake for returning spacecraft. This frees up the precious propellants needed to get to orbit. This is where the practicality aspect comes in. The scramjets will be needed and nearly every drop of the propellant is needed just to reach orbit.<br /><br />Eugen Sanger, a German aerospace engineer or something like that, proposed a hypersonic suborbital skip glide concept called Silverbird in or about 1944. It was designed to skip along earths atmosphere at higher altitudes like a stone skipping on water to attain lower altitudes and eventually landing. This is apparently feasible but never tried to my knowledge.<br /><br />There must be a motivation for your question and I'm just guessing, but if its to avoid Columbia type accidents in the future. Keep in mind the actual cause of the accident was not the re-entry. In fact, the TPS which includes tiles, quilted sections, and RCC did their jobs except for the RCC that was prevented from doing its job as the result of the ET foam strike.<br /><br />Adding thrusters, or even using existing thrusters to make significant changes to a re-entering vehicles flight path also complicates things and increases the risk something will go wrong. In fact, the changes could not be too drastic or the vehicle itself would break up. This also entails the increased use of that all important commodity...propellant <div class="Discussion_UserSignature"> <p><strong>My borrowed quote for the time being:</strong></p><p><em>There are three kinds of people in life. Those who make it happen, those who watch it happen...and those who do not know what happened.</em></p> </div>