Discussion Hypersonic airfoils for booster return.

[RGClark]

SpaceX prefers vertical powered landing to horizontal winged landings for their booster to do RTLS since it requires little modification to the booster and because it would also work on airless bodies. However, using wings may offer an advantage. Based on the lengths of the burns for the return portion of the boosters flight on the Orbcomm-2 mission, I estimate the amount of propellant that must be reserved for the booster RTLS as ca. 46 metric tons (mT). This results in a large performance hit of a 30% loss of payload according to Musk.

However, estimates of wing weight are about 10% of the landed weight, which probably could be reduced to 5% with carbon composites. So for a F9 booster with an estimated dry mass of 20 mT to 25 mT, you would only need an additional 2 to 2.5 mT, and likely half that with composites. This would result in large reduction of the payload loss.

But the question is could we use wings to allow a RTLS when the booster flies at hypersonic speeds, say, at ca. Mach 7? I think it might be possible, or with minimal propellant burn, if your airfoil has high hypersonic lift-drag ratio. To be sure this would be very different from the Space Shuttle's delta-wing shape. The shuttle has been described as akin to a flying brick with a hypersonic L/D ratio of only 1, though its subsonic L/D is better at about 4.5

However, airfoils of high hypersonic L/D are known:

Waverider Design.

http://www.aerospaceweb.org/design/waverider/waverider.shtml

So my challenge to Orbiter-mavens such as on the DG2 is if you have a Mach 7 L/D of about 7, could your first stage booster at a max speed of Mach 7 do a return to launch site?

Note this is a more difficult problem than just gliding down, continuing in the same direction, to land downrange. In that case you can just have large wings like the shuttle to provide high drag to slow down the speed, and then allow the wings to do a slow subsonic landing.

But to do RTLS, not just land downrange, you need to be able to turn around via aerodynamics alone, not burning engines, at hypersonic speed. That high speed means you need high aerodynamic force to turn around, hence the need for high L/D ratio.

This modeling of the descent at hypersonic speed, as the altitude reduces and air density increases while the vehicle is banking, turning all the while is non-trivial.


Bob Clark

 

[MaverickSawyer]

Okay, couple of reality checks:
Where is the upper stage going to be located?
Where are the fuel tanks?
Is the design fully VTOL, or VTHL?
How much does your thermal protection system weigh?
Does the mass savings from reduced propellant requirements outweigh the increased structural mass?

 

[Col_Klonk]

Stage 1 could be a symmetric wing with in both X and Y.. while Z has an 'adapter' on top that is ejected for flyback. Under the adapter is the rest of the nose section.

Fuel and all the other goodies are within the winged wonder, like a normal rocket.
The extra resistance area (and weight), on the way up, could be compensated for by the extra lift provided by the wing, as in the shuttle.
It's vertical take off, horizontal landing (hopefully )

I like this idea more than SpaceX's current configuration.
:thumbup:

 

[ADSWNJ]

@RGClark do you intend for it to land horizontally or vertically? I assume horizontally, right? Then do you intend for it to have its own undercarriage, or to land on a moving platform for undercarriage?

It strikes me that the design for VTOL is very different to VTO, hypersonic glide to HL. If you want the vehicle to fly like a plane (or a shuttle), then you need much more work on the longitudinal strengthening. It would be a hell of a design to behold, but I am skeptical if it would be more efficient than the current SpaceX solution.

It's the stuff of great exploration and discovery though, and kudos to all those who risk their time and capital to go after such dreams.