Hyper-sonic maneuvering?

[bradley101]

How would you maneuver? Ailerons and the likes would warp in the extreme airflow. Moving liquid or the likes to warp the whole shape of the aircraft?

Edited October 31, 2013 by bradley101

[Starwhip]

You could "bend" the entire vessel, manipulating the airflow without breaking the airplane. The hydraulic method seems like a good idea, if you pumped liquid into sac-like devices to minutely disrupt the airflow, they might have the same effect as ailerons.

[K^2]

Nose of the aircraft generates a shock wave. Behind the shock wave, the fluid, in this case air, is going to move at a different speed relative to the aircraft. If you look at the shape of the hypersonic aircraft, their wings are designed to be contained inside the shock wave cone. The flow there is still supersonic, since we are dealing with an oblique shock, but considerably slower.

P.S. I'm oversimplifying a lot of things. But this is the general idea behind making hypersonic flight more manageable. You still have to deal with supersonic flows near your lifting and control surfaces, and the solution is to make sure that the boundary layer is subsonic, so that you don't have separation. Then you still can generate lift and use control surfaces normally.

Edited October 31, 2013 by K^2

[SargeRho]

Thust Vector Control anyone?

[goldenpeach]

Nah,too mainstream

What about act like normal kerbals and use RCS?

[bradley101]

Thust Vector Control anyone?

That could really badly affect your bubble of air your displacing. Thrust vectoring as apposed to RCS styled various nozzles could be viable but would not provide enough maneuverability I think.

Edited November 1, 2013 by bradley101

[Agent86]

A rudder. Just have a kerbal sit on the roof with a boat oar that he can stick out into the wind to adjust the planes attitude.

[dharak1]

The Sr-71 was pretty close to hypersonic and as far asi know it only had things like rudders. I'm not sure how different mach 3.2 is from mach 5+ though.

[K^2]

I'm not sure how different mach 3.2 is from mach 5+ though.

Not as different as you'd think. The biggest difference is heating. Not only is there much more kinetic energy in the gas you encounter, but a lot more of that energy ends up deposited in the fuselage. This will mostly affect the leading edges, but it does factor into how you can use control surfaces as well. One of the consequences is that a hypersonic aircraft will not have quite such sharp leading edges as a supersonic one. Think wings and nose of the Space Shuttle compared to something like a Concorde. This helps create a protective normal shock in front of the leading edge as well as spread heat over larger area. A sharp leading edge would start overheating at these speeds.

The other obvious effect is change in overall desirable geometry for the aircraft. As I mentioned above, containing your aircraft inside the shock wave is a good idea, and at Mach 5+ the envelope is going to be narrower than at 3+. It's also not worth it trying to generate secondary shocks, generally. So unlike the 3+ (think SR-71 Blackbird here) you won't get many sharp features.

But all the other requirements are pretty much the same. You still have to deal with shock waves anywhere an edge enters a supersonic stream, and you still want to ensure that there is a subsonic boundary layer on your lifting surfaces and control surfaces or you won't get much use out of them due to separation. The transition, however, is still only around Mach 1. There are no special transitions at higher numbers, so calling a flow a hypersonic rather than a supersonic one is somewhat arbitrary. The physics is much the same.

Edit: For more details on how things are actually done in practice, take a look at Boeing X-51. It addresses most of the questions raised here. It is capable of Mach 5, and it does use control surfaces rather than rely on thrust vectoring alone.

Edited November 1, 2013 by K^2

[victory143]

Whaa? I'm confused. My solution: Don't fly that fast, no trouble. simple.

[WestAir]

IIRC, even the Concorde warped in length during each supersonic flight. One video I watched showed a pilot demonstrating this by showing the camera crew the engineering panel. On the ground, the panel was touching the wall so closely it looked connected. In flight, the aircraft had stretched sufficiently enough for the pilot to put his hand between the panel and the wall.

And they weren't even going that fast. I'd hate to imagine what type of warping occurs at Mach 5.

[Mr Shifty]

Shuttle orbiter RCS roll jets were disabled when dynamic pressure reached 10 psf, which occurred very early in the descent (about 5 minutes after entry interface) while the orbiter was still travelling above Mach 19. Pitch RCS jets were disabled about 3 minutes later (still above Mach 19.) The energy-bleed S-turns were done using ailerons for roll and elevons for pitch all at speeds in excess of Mach 6.

[Nibb31]

Even at hypsersonic speed, as long as you are travelling in a fluid, the best way to manoeuver is by using control surfaces.

It turns out that grid fins are pretty good control surfaces when you are going really fast, which is why they are used on lots of missiles and russian rockets:

http://en.wikipedia.org/wiki/Grid_fin

[Kraken tamer]

Maneuvering above Ma (mach attach) speed can be done with conventional control surfaces as there is no flow separation in the supersonic regime (this is evident by supersonic airfoils having sharp corners). More of a concern is maneuvering below Ma and above Mcr (critical Mach number). Engineers get around this by using stablators (control surfaces that only change angle of attack without changing camber). However, if you plan on using sub sonic airfoils you must sweep the wings beyond the mach number or else you will suffer excessive wave drag due to the round leading edge. The hypersonic regime is much like the super sonic regime with some minor differences being the much higher mach angle, and the Cdr (co efficient of drag) will start to increase linearly, due to more of the drag being produced by ionization of the air as opposed to wave drag.

[K^2]

Cdr (co efficient of drag) will start to increase linearly, due to more of the drag being produced by ionization of the air as opposed to wave drag.

Cool. I was actually trying to find this earlier. Do you know any references on modeling drag at hypersonic speeds and/or transonic regions? Just the general qualitative forms for each regime would be nice. I can fit the coefficients from some data.

[Nuke]

its usually written "cD" in maths, which is why its hard to search.

[K^2]

I'm quite familiar with drag coefficient and typical notation. I was looking for dependence of drag coefficient on velocity in hypersonic range, and this is the first time I see someone mention a linear dependence.

[Kraken tamer]

Follow the link: http://selair.selkirk.bc.ca/Training/Aerodynamics/Aerodynamics%20for%20professional%20pilots.pdf On page 186 is the first time it introduces supersonic theory and there is a rough graph. No numbers as this would depend on the Reynolds number as well as a couple of other things, but gives you a general overview of how things work in the near supersonic, transonic, supersonic and a brief look at hypersonic ranges. It's geared towards pilots of commercial airplanes though, so much of the book is centered around passenger airplanes.

[Lohan2008]

My solution: Don't fly that fast, no trouble. simple.

RollOFLMAOff

[Nuke]

I'm quite familiar with drag coefficient and typical notation. I was looking for dependence of drag coefficient on velocity in hypersonic range, and this is the first time I see someone mention a linear dependence.

i dont think i ever got that far. was writing a mod for freespace2 open that added newtonian physics and aerodynamics (and even orbital mechanics). unfortunately the game engine wasnt designed with this in mind and it never worked out. will probibly port the flight model into my game engine eventually, but its barely an engine so far.

Follow the link: http://selair.selkirk.bc.ca/Training/Aerodynamics/Aerodynamics%20for%20professional%20pilots.pdf On page 186 is the first time it introduces supersonic theory and there is a rough graph. No numbers as this would depend on the Reynolds number as well as a couple of other things, but gives you a general overview of how things work in the near supersonic, transonic, supersonic and a brief look at hypersonic ranges. It's geared towards pilots of commercial airplanes though, so much of the book is centered around passenger airplanes.

that will come in handy if i ever work on perfecting the flight model.

Edited November 2, 2013 by Nuke

[SpaceSphereOfDeath]

I would lean.

Really, abort, or try to slow down.

REALLY REALLY, I would attempt to steer with the control surfaces, then pump fuel back and forth to adjust my pitch

[bsalis]

I would lean.

I was going to suggest the same thing. A moveable off-centre mass. Would work for pitch and yaw, but not roll.

[Nibb31]

Some Russian missiles actually used moving weights to change their CoM for control. There is also the option of thrust vectoring.

[Yourself]

Some Russian missiles actually used moving weights to change their CoM for control. There is also the option of thrust vectoring.

On the subject of an off-center CoM, this is how the Apollo capsules controlled themselves during reentry. The CoM wasn't actually moveable, they just rolled the capsuled left or right to adjust the apparently vertical position of the CoM, which ended up changing the pitch of the capsule.

[m4ti140]

Actually STS held the 40deg AoA during reentry with CoM adjustment - to set the correct CoM they dumped fuel from front RCS tank. I wish we had such possibility for spaceplanes. If someone wrote a plugin that would automatically adjust CoM to hold given AoA (or at least allow to quickly shift CoM manualy without messing with fuel tanks) it would be extremely useful for SSTOs. Currently no matter what you do you either end up flying backwards or pointing forward at 0 deg AoA, resulting in desintegration in first case and overshooting target due to lift in second.