PROBLEMS, PROBLEMS…THEN A BLAST FROM THE PAST
On our Exodus Aerospace blog I offered a design that emulates lifting body designs of the past. The flat fat glider is short of length and fuel volume. It also needs a heavy fairing to attach it to the booster. So here I want to take a look at our history of winged warriors to see what we are learning. It may have roots in the Dyna-Soar, but the first flight demonstration was the shuttle.
This led to several light thermal protection technologies and other lessons we can still use. “The Shuttle flies at a high angle of attack during re-entry to generate drag to dissipate speed. It executes hypersonic “S-turn” maneuvers to kill off speed during re-entry.” This allows the craft to bleed off speed and keep the nose high and out of the worst heating.
This illustration shows the flat bottom as a heat shield, ejecting hotter plasma away from the sides. The delta wing is good for landings, but appears to mask air flow to the rudder. That may explain why it is such a tall vertical surface.
After the shuttle design, a proposal suggested a “fly back satellite” that would stage on a Pegasus. Look; in-line staging is not so strange after all! This was to make flight, but as a much larger vehicle; the Boeing X-37.
Now a comparison of shuttle designs reveals that the wing is moved forward. That gives the full flying tails a great supply of air flow, and makes it easier to raise the nose for a high angle of attack.
It also seems to have earned a promotion from NASA to the US Air Force. This mini-shuttle has been serving for honor with missions up to two years in duration. No crashes, and no pilot needed for total customer satisfaction in years of service.
Now this illustrates high angle of attack, and thermal distribution, possibly without all those “S” turn maneuvers.
Other reentry experiments created the Prime Lifting Body which survived a fiery reentry as shown here. Notice burns flowing over the topsides. This design continued with the X-38 crew recovery vehicle and the present Sierra Nevada Dreamchaser.
This raised the height and volume of the design to accommodate crew members and propulsion. The “duck tail” and rounded bottom cause the vehicle to gravitate to a nose high attitude. Body flaps can push the vehicle nose down for level flight at lower altitudes.
This is designed to fall well more than to fly well. A reentry vehicle is a meteorite first, and an airplane second. All’s well that falls well! It delivers the crew to a designated landing area with some degree of control and thermal survival. There may not be all the elegant control of other aircraft with limited control surfaces. There may not be elaborate landing capability here.
The X-38 was designed to land with a glide type parachute, which at least takes you to dry land instead of an ocean landing.
The Dreamchaser is a slightly wider, flatter shape, with propulsion on each side of the central pressure vessel. The bottom is still flat, and may be a bit wider. Dreamchaser may enjoy an air cushion known as ground effect on landing. This vehicle can now make a landing with conventional landing gear.
My orbiter may be too narrow in front while attempting to be sleek enough for supersonic horizontal ascent. It also lost a lot of internal volume with that heavy fairing adapter. It would rely on the “duck tail” and curvature to reach a high angle of attack.
Burt Rutan and Scaled Composites may have considered body flaps to do this at first.
For a suborbital reentry, speeds are low enough to allow an extreme “jack knife” that would be hostile at hypersonic speeds. Orbital reentry may be up around 17,000 mph!
Our suborbital design would be less extreme, but may suggest solutions that we can use in the higher speeds of orbital reentry. This too is very flat for atmospheric flight, but we may be able to thicken that for more volume. This is a long thin shape like the X-37, but lacks the feature of central wings. It could be hard to get the nose up. But there are other proposals with little or no wing surfaces.
This is based on Japanese designs and is again a nice flat airfoil. It looks like a wingless example of Burnelli’s lifting fuselage; a low aspect ratio flying wing. It is a little sleeker than Dreamchaser, but may have less volume without all that length.
Well, if you don’t mind parachutes, this ESA design will guide you to the right landing area with good volume and minimal parasite mass or drag. It is not elaborate on control surfaces for pitch, roll and yaw though!
Some thought about parachutes belong to the Soyuz recovery system. This parachute landing on the ground would be bumpy without the last minute retro rocket trick. There is one thing to remember about parachute recovery though…
Where we live in Wyoming, the wind can quickly relocate you to Kansas. Oh, this IS Kansas Toto!
No good reentry study should overlook this miracle of technology. Seriously, we do have a use for this after we consider one little issue…
If your trajectory is not high enough to severely burn things up on reentry, you still need low winds, a steady deck, and a lot of luck. Reliability engineers use statistical math to factor all the risk of multiple operations. This one poses a few challenges. And you still have to carry landing gear and extra fuel!
Our rocket man in Wyoming (Bob Steinke) does this with a wider, more stable base. Laramie rose has made several flights under challenging stability conditions. That reminds me of an aircraft that I worked on in the past…
Now THIS is a stable base for a vertical landing! Actually, this can even be done transitioning from forward motion to a dead stop. Even airliners have thrust reversers for braking. Trust me to think about laying down on the job!
Actually this is yet another ideas stolen from the British. Talk about a stable base…a four point landing! The Harrier landing, Concorde wing, and Peroxide fuels were all pioneered by the British. But then so is the art of drafting; developed to build ships to meet the Spanish Armada. Let me know if you see any redcoats coming to reclaim their stuff!
Since we are building an orbiter, it is already equipped with thrusters pointing in every direction. In a conversation with a vertical launch builder, we found no barriers to bringing a winged orbiter into ground effect, slowing, and setting gently onto skids. We don’t even need wheels if we can counter crosswinds and keep a straight line down the runway. Fewer mass parasites and another simplification. With two stages we can use air breathing propulsion and still leave the parasite engines and gear behind. More for the payload customer and redundant recovery options for the insurers.
WHAT WIL IT LOOK LIKE? ??
SO; NOW A SNEAK PEEK AT THE NEXT GENERATION. No mid stage, one large volume orbiter with a deep flat shape. These are preliminary forms that will be changing as we reflect needs for structures and propulsion.
Now we can target the optimum direction for real solutions in horizontal launch. Get ready to watch this evolve on our next Exodus Aerospace blog.