Economics of space flight/2nd Stage reusable orbiter

[tap_sa]

<font color="yellow">" Well what happens when a hi drag body comes into the atmosphere? "</font><br /><br />The body slows down, dives faster into the atmosphere because gravity wins over centrifugal force, the body slows down even faster, dives even faster and burns up if not equipped with a hefty heatshield. Do you think that high drag gives the deceleration free without the body heating up?

 

[holmec]

>dives even faster and burns up<<br /><br />In the atmosphere hi drag produces lift. That's why airplanes fly. It is also the reason why when you drop out of an airplane you stop accelerating at a certain point. Sure you have heat with viscosity, the key is to slow down below the compustion threshhold without killing crew or equipment.<br /><br />It may not be possible, but it may be. Who had done a study on this? <div class="Discussion_UserSignature"> <p> </p><p><font color="#0000ff"><em>"SCE to AUX" - John Aaron, curiosity pays off</em></font></p> </div>

 

[spacefire]

I think the Venture Star had minimal thermal protection compared to the Shuttle, and the reason seems to me that, being a big empty shell coming back from orbit, it would slow down without generating that much heat per unit area. <div class="Discussion_UserSignature"> <p>http://asteroid-invasion.blogspot.com</p><p>http://www.solvengineer.com/asteroid-invasion.html </p><p> </p> </div>

 

[holmec]

>I think the Venture Star had minimal thermal protection compared to the Shuttle, and the reason seems to me that, being a big empty shell coming back from orbit, it would slow down without generating that much heat per unit area.<<br /><br />nice! <div class="Discussion_UserSignature"> <p> </p><p><font color="#0000ff"><em>"SCE to AUX" - John Aaron, curiosity pays off</em></font></p> </div>

 

[tap_sa]

<font color="yellow">"I think the Venture Star had minimal thermal protection compared to the Shuttle"</font><br /><br />I wouldn't call multilayer Titanium/Inconel sandwiches and C-C leading edges 'minimal'.<br /><br />LINK

 

[spacester]

mmmm . . . titanium sandwiches . . . . <br /><br />I love that TPS, to me by far the best system yet, largly because the maintenance is managable compared to carbon tiles.<br />***<br />At the risk of stating the obvious . . . <br /><br />It ain't the velocity, it's the energy.<br /><br />Kinetic Energy of the vehicle = 1/2 m * v^2<br /><br />All the Kinetic Energy has only one place to go: Heat energy.<br /><br />It ain't the temperature, it's the heat flux. The faster you come in, the higher the rate of turning the KE into heat. So at some point the flow of energy becomes too great for any known method / material.<br />***<br />My idea is to design a craft that can come in hot or warm. You take on propellant on orbit, burn it to disipate a lot of KE before hitting the thick stuff and you come in warm. If you fail to make the rendezvous with the orbital filling station, you come it hot.<br /><br />By design, a warm re-entry would require much less (zero?) refurb. A hot entry would raise costs, establishing a value for that on-orbit propellant. <div class="Discussion_UserSignature"> </div>

 

[spacefire]

However, most of the skin is aluminum, if I remember correctly. <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 slower you want to re-enter the better, I would thing you could reduce your velocity as much as you wanted to, with enough propellant. Somewhere the economics come into play. <br /><br />Slow up as much as you can to 400,000 feet, there the atmosphere takes over. The Shuttle is going 17,000 mph, reduce that to 10,000 or so and heating would be even less, which would take a lot of propellant, but would reduce the level of TPS needed.<br /><br />Perhaps an orbital based re-entry vehicle that delivers a lander to about 200,000 feet, releases it, returning to orbit. <br /><br /> <div class="Discussion_UserSignature"> </div>

 

[soccerguy789]

I think that reusability of the crew vehicle on any space mission saves time. if you are concerned about reusability of a heat shield, you can have a disposable, removable heat shield.

 

[scottb50]

All I was talking about was a vehicle that carries the payload to about 200,000 feet and 8,000 mph or so, and returns to orbit for re-use.<br /><br />You can't dispose of heatshields, that would be pretty expensive. <div class="Discussion_UserSignature"> </div>