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Another possibility:

Scorpion 3 - World's First Hoverbike.
https://www.youtube.com/watch?v=5XdbWYzM4oY

  Bob Clark

The Falcon Heavy and Falcon 9 together can launch 87 metric tons to LEO, at a launch cost of only $90 + $60 million = $150 million. This compared to the billions for the SLS.

Use the Dragov V.2 for the command module. Need a crew module and propulsion module for the lunar lander. Use the Cygnus as the crew module provided with life support. This is about 2 metric tons. For the propulsion use the Ariane 5’s EPS storable propellant upper stage:

http://www.esa.int/Our_Activities/Space … _Stage_EPS

This is about 12 metric tons gross mass at a 1.2 ton dry mass. With a ca. 320 s vacuum ISP for storable propellants this one stage would be enough to land on the Moon from lunar orbit, and also takeoff again to return to lunar orbit to rendezvous with the orbiting Dragon V.2.

For the propulsion for entering into lunar orbit and leaving lunar orbit for return to Earth, use the Dragons own Superdracos thrusters. In addition to the ca. 1.4 tons of propellant normally carried by the Dragon need about 10 tons additional propellant, for entering and leaving lunar orbit, which can be carried in the Dragon’s trunk.
With the additional propellant, the gross mass of the Dragon will be about 18 tons. Then the total mass that needs to be sent to translunar injection(TLI) is 18 + 12 +2 = 32 tons. 

Now use the rule-of-thumb that an efficient Centaur-like hydrolox stage can get a payload mass to escape velocity  equal to its propellant load. Then need a hydrolox stage of about 32 tons propellant load. A Centaur-like hydrolox stage has a dry mass about 1/10th of its propellant load, so about 3.2 tons dry mass.

Then the total mass that needs to be sent to LEO, known as IMLEO, 67.2 tons, well under the mass that can sent to LEO with FH + F9.

  Bob Clark

  You're right. I didn't consider the lift component of the reentry. The open clamshell configuration would have significant lift. So you may want to enter at the best angle of attack to maximize this. Using lift would extend the time you stay up in the atmosphere, i.e., you would not descend as rapidly into the dense lower layers, so this would reduce the heating.

  Bob Clark

GW, about reusable orbital stages, SSTO's or upper stages, I was surprised in most discussions of them it is assumed they are able to reenter to achieve an only 100 m/s terminal velocity. This is true whether horizontal or vertical propulsive landing is being discussed. See for example here:

http://yarchive.net/space/launchers/hor … nding.html

As the example of the space shuttle shows, this is not so surprising for winged, horizontal landing. But the thing is this is assumed even for vertical propulsive landing. This is surprising because this means for a cylindrical rocket stage, without wings, reentering broadside or a conical stage entering base forward, they can cancel out almost all of the ca. 7,800 m/s orbital velocity to get down to only 100 m/s terminal velocity from aerodynamic drag alone.

Actually, I haven't seen the argument for this. Anyone have a reference for the idea you can get down to 100 m/s terminal velocity even without wings?

But if so why all the big debate over vertical vs. horizontal landing? For either method nearly all the 7.8 km/s orbital velocity will already be cancelled out before either landing method comes into play, and even then they only have to account for a measly 100 m/s.

That is surprising though that without even needing wings you can cancel out nearly all of orbital velocity to get down to terminal velocity. Given that, on Earth reentry for an orbital reusable isn't even particularly hard. So why all the hullabaloo about how difficult it is to get full reusability because you also need to return the orbital stage from orbital velocity?

In fact orbital stage reusability might even be easier than first stage reusability:

  For the first stage, you need a reentry burn to cancel out forward velocity, then a boostback burn to return to the launch site then you need the final landing burn. This results in quite a bit of lost payload because of the propellant that needs to be kept on reserve.
But for the orbital stage you just let Earth rotate beneath you until the launch site is back under you before you initiate reentry, so you don't need the boostback burn. Then aerodynamic drag cancels out nearly all of orbital velocity even without wings so you don't need the reentry burn. Then you only need the landing burn and this is for only ca. 100 m/s.

Yes, I know for the orbital case you need more thermal protection than for the first stage but this is not particularly heavy anyway. Even for the space shuttle, this was only ca. 8% of the landed weight, and SpaceX's PICA-X weighs half that to only 4%. And if GW's thermal ceramic really is as lightweight as he estimates the thermal protection would be a minor portion of the vehicle weight.

Then when you consider the either wing weight or propellant weight needed for the final 100 m/s of the landing would be 5% or less, the total lost payload for the orbital stage would be less than 10%. Compare this to the 30% to 40% lost payload for the two stage Falcon 9 or BFR.

Taking these facts into account a reusable SSTO may actually be more economical than a reusable two stage vehicle.

  Bob Clark

Thanks for that info. As you described its development in the video, this would certainly be patentable. Even if you don't have samples you could still patent the material, describing the process to make it.

In addition to the use as reentry thermal protection. It would also have use as combustion chamber insulation. This would have widespread applications since in this post I discussed the case of the Star 48B for which the insulation counts as a significant proportion of the dry mass of the stage.

In the video you said it weighed less than PICA-X that SpaceX uses but more than the space shuttle underside tiles. But actually if your material really is 0.03 specific gravity then it is 1/3rd the weight of the space shuttle tiles. Perhaps because you didn't realize how much lighter it would be than currently existing tech is why you didn't see the urgency in confirming its properties and patenting it.

  Bob Clark

  GW, do you have software that can do simulations of reentry, to supersonic, to subsonic flight for different wing airfoils?

I was thinking of ways to do guidance in near vacuum for small amateur built stages. Early in the space program spin stabilization was used for stages at high altitude where fins were ineffective. But this meant you had little control of the final orbital parameters. I was thinking of ways you could get this fine control at low cost and light weight for amateur built stages.

  Fins are effective at low altitude even with their relatively low size compared to the size of a rocket due to the dense atmosphere. I thought then if you made the aerodynamic surface a hundred times larger for air density a hundred times less, this should again be effective. This space shuttle wings cause significant slowdown even at reentry speeds for example because of their large size.

So how to add large aerodynamic structures to a small stage? You could use wings but this would be high drag and high disturbance at low altitude that would have to be counteracted especially for solid rocket stages that leave the launch pad at high speed.

To avoid this I thought of the curved cylindrical surface of the rocket stage that could open up like a clamshell:

In our scenario though the stage itself would not open up revealing the interior but the extra aerodynamic surface, call them clamshell wings, would be attached to the exterior of the stage. They would be closed up around the stage during low altitude flight, and opened at high altitude.

It occurred to me then that this also might be able to be used for reentry. If you can make this extra surface be lightweight then you would get low wing loading. The importance of low wing loading for reentry for spaceplanes is discussed here:

Wings in space.
by James C. McLane III
Monday, July 11, 2011
http://www.thespacereview.com/article/1880/1

At the end of the article there is this passage:

{emphasis added}

Moreover, because of their curved shape they should be even more effective at slowing down the descent during reentry, like a parachute.

I estimated the wing loading using this clamshell wing idea for the new Falcon 9 FT first stage, assuming they added a proportionally small amount to the weight. I used the specifications here:

Falcon 9 FT (Falcon 9 v1.2).
http://spaceflight101.com/spacerockets/falcon-9-ft

The dimensions given there are listed as 42.6 meters long and 3.66 meters in diameter, at a dry mass of 22,200 kg.

  Regarding the stage horizontally, you would have to put the swing points along the sides, rather than at the top, so that the clamshell wing on each side could open without blocking the opening of the clamshell wing on the other side. This means the wing area would be half that of the full surface area. So the surface area is (1/2)*Pi*3.66*42.6 = 244.9 m^2, 244.9*3.28^2 = 2634.86 ft^2.

The dry mass is 22,200 kg, 22,200*2.2 = 48,840 lbs. So the wing loading is 48,840/ 2634.86 = 18.5 pounds per square foot(psf). This is not 10 psf, but it is significantly better than the shuttle, and with the reduction in descent due to the curved surface this might still be enough to require minimal thermal shielding.

Also, we might be able to get additional wing area by putting clamshell wings on the upper surface, though not the same size as the lower ones so that all can open fully.

For attitude control we allow the swing points to be moved up or down.

  Bob Clark

GW, that info on the Star 48B is pretty detailed, such as nozzle throat size. Would that be enough under the assumption of an added on nozzle extension that brings the nozzle area ratio to 750 to 1, to calculate the thrust?

  Bob Clark

Keep in mind that the mass ratio for the stages will be significantly better than for the shuttle since it will make extensive use of carbon fiber composites.

Also unlike the shuttle, the tank will be onboard the vehicle so it could keep some small amount of fuel on reserve for maneuvering or go-around. etc.

  Bob Clark

Great. I'm looking forward to reading it. In aerospace engineering probably more than any other engineering field key facts are known by individuals in the field but not expressed in books or journals.

Thanks for revealing the "black arts" of ramjet design.

  Bob Clark