Quote from: Hop_David on 12/28/2014 11:54 pmA booster starting it's burn at 18 km altitude and a horizontal velocity of .83 km/s has some advantage over a regular booster.There's also disadvantage; it has to start with very large AoA while surviving ~8 kPa dynamic pressure or have wings.

A booster starting it's burn at 18 km altitude and a horizontal velocity of .83 km/s has some advantage over a regular booster.

AoA?

How is the 8 kPa dynamic pressure arrived at? I'd like to include the equations in my spreadsheet if possible.The 8 kPa dynamic pressure would decelerate the vehicle, correct? I am thinking the .36 km/s I have at the top is optimistic.

R7 might be referring to the atmospheric pressure of 8kPa at 18km altitude.

Too bad we can't build an angled launch platform, effectively zero out the mass of a launch payload and launcher, let Earth's centripedial force fling the pacage upwards and gradually bring the effective mass back to normal to achievel orbit either around Earth or towards another planet. Maybe the Alcubierre drive could achieve this from ground level? Be kind of interesting to see what happens if it were activated in a gravity well anyway...

Quote from: Hop_David on 12/30/2014 08:40 pmAoA?Angle of attack. If the vehicle has traditional rocket shape, pointy end forward, slim body and engines in the aft it must point the nose up and initially fly "sideways" to counter gravity and rise. That's tough on the structure.

How is the 8 kPa dynamic pressure arrived at? I'd like to include the equations in my spreadsheet if possible.The 8 kPa dynamic pressure would decelerate the vehicle, correct? I am thinking the .36 km/s I have at the top is optimistic.Quote from: R7 on 12/31/2014 09:01 amhttp://en.wikipedia.org/wiki/Dynamic_pressureq = 0.5 * rho * v^{2}Air density (rho) at 18km is 0.12kg/m^{3}, speed 360m/s, when those are plugged into above equation it gives ~7.8kPa of dynamic pressure.And yes that pressure drags the vehicle down. To calculate how much exactly you need the actual drag equation.http://en.wikipedia.org/wiki/Drag_equationNote how that begins with dynamic pressure.Also worthy of note how the dynamic pressure is denoted by "q", that's what the q in "Max Q" means, maximum dynamic pressure.

http://en.wikipedia.org/wiki/Dynamic_pressureq = 0.5 * rho * v^{2}Air density (rho) at 18km is 0.12kg/m^{3}, speed 360m/s, when those are plugged into above equation it gives ~7.8kPa of dynamic pressure.And yes that pressure drags the vehicle down. To calculate how much exactly you need the actual drag equation.http://en.wikipedia.org/wiki/Drag_equationNote how that begins with dynamic pressure.Also worthy of note how the dynamic pressure is denoted by "q", that's what the q in "Max Q" means, maximum dynamic pressure.

Quote from: Hop_David on 12/30/2014 08:40 pmAt Sea Level you will have a vehicle separating from its carrier at > Mach 1.

.5 km/s is about mach 1.5. Using the chart r7 posted and assuming a bullet shape I am guessing a drag coefficient of .4.Using a drag coefficient of .4 and a space ship of approximately Falcon 9 dimensions I get a drag force of about 300,000 newtons. Since Falcon 9 is about 500,000 kg, that comes to an deceleration of .6 meters/sec^2. The deceleration isn't as large as I thought it would be.

Quote from: R7 on 12/30/2014 11:18 amQuote from: Hop_David on 12/28/2014 11:54 pmA booster starting it's burn at 18 km altitude and a horizontal velocity of .83 km/s has some advantage over a regular booster.There's also disadvantage; it has to start with very large AoA while surviving ~8 kPa dynamic pressure or have wings.AoA?How is the 8 kPa dynamic pressure arrived at? I'd like to include the equations in my spreadsheet if possible.The 8 kPa dynamic pressure would decelerate the vehicle, correct? I am thinking the .36 km/s I have at the top is optimistic.

The spreadsheet looks OK. The simple scale height gives slightly different values for density because it assumes constant temperature. I got the number from online international standard atmosphere calculator. But in this case the scale height is quite good, simple and "close enough".

1/2 good idea....not a launch site. A space elevator build site a whole different game.

Does electric haulage (i.e. TESLA Semi) make high altitude operations and infrastructure any more viable?

So I am guessing Mars' atmosphere isn't a show stopper for an Olympus Mons rail gun.