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Gravitation-aerial maneuvers are very interesting because you can choose practically any turning angle around a planet with atmosphere - unlike the pure gravity-assist where the turning angle is constrained by the planet mass and the approaching angle of the spacecraft - sparing a lot of propellant and performing high delta-v fast interplanetary travels, otherwise impossible for a chemical rocket propelled spaceship.
The only vehicle able to perform an aero-gravity assist (AGA) is the waverider
https://en.wikipedia.org/wiki/Waverider
A special delta-wing spaceplane which uses the shock wave to gain a very high hypersonic lift to drag ratio (from 4 to 8 or even more).
As a SF author I found this vehicle very interesting in a solar system colonization scenario, because I think it's unlikely that civilian spaceship owners will be ever allowed to buy spaceships powered with enriched uranium NTRs or Orion-drive nuclear pulse units.
So I have six little question about WR to submit to the experts of this forum:
1) given that the shock wave impinges the leading edges, generating lift on the lower surface, can the upper and lateral surfaces have a lighter thermal protection?
2) the main control system during the AGA may be an internal mobile ballast, like an entry capsule, but can a WR have also RCS rockets with exhaust holes on the upper, lateral and lower surfaces?
3) if the answer is no, can it have the RCS rockets placed on the aft surface like the ESA IXV?
4) can it have also two aft flaps for aerodynamic flight control like the ESA IXV
5) can it have windows on the upper surface?
6) given that some velocity is lost for the drag, the WR has to perform a burn to compensate: can it have some kind of air-augmented rocket to minimize propellant consumption?
Thanks a lot for your attention, and happy new year for all
Last edited by Quaoar (2020-01-04 06:21:52)
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There's nothing magic or new about waverider technology. Hype to the contrary is just that: hype. A waverider generates lift by the shock-induced pressure rise on a flat bottom, exactly the same effect as the component of supersonic wing lift that is generated by the bottom of a supersonic wing. It's just not a wing lower surface doing this.
It's not new at all. Some would say this dates to the 1965-vintage XB-70 Mach 3 bomber. About half its lift surface was a flat bottom, not the wings. But this was used even earlier in the 1953-vintage F-100 Super Sabre fighter jet. That aircraft raised its lift/drag ratio during supersonic dash with a flat fuselage bottom. Dash speed was Mach 1.3.
As for openings for thruster nozzles on the lateral surfaces during entry conditions, there is no reason you cannot have them, as long as you design to preclude through-flow when the thruster is not firing. The static gas column in the open port is a better insulator than any solid we could install. But the key word is "static": if vented, hot gas intrusion destroys structure. That is why shuttle Columbia shed a leaky wing with a hole, and was destroyed.
If by "air augmented rocket" you mean a mixing device that accelerates air with the jet pumping action of an embedded rocket stream, that works far better at low flight speeds, essentially subsonic, certainly not good at all at supersonic, and certainly not hypersonic/orbital-speed class.
As for windows during entry, you can have them on surfaces that are embedded in separated wake zones, where there is no scrubbing action, only very low-speed contact with hot plasma. Sometimes knowing where these locations are can be tricky. A hypersonic slipstream jet would reattach to the shuttle's nose at angle-of-attack above 40 degrees, impinging straight into the windscreen, and guaranteeing its destruction in mere seconds.
The same was true below 20 degrees. Thus the shuttle had a very tight angle-of-attack restriction during entry: 20 < AOA < 40 degrees. Loss of such control would lead to destruction of the vehicle within seconds. Nose shape details did not matter, it was true for any of the shapes considered for the shuttle's nose. This was found in Mach 5 wind tunnel tests during 1973, before shuttle's design was finalized. I helped conduct and analyze those tests as a graduate student.
GW
Last edited by GW Johnson (2020-01-04 09:58:58)
GW Johnson
McGregor, Texas
"There is nothing as expensive as a dead crew, especially one dead from a bad management decision"
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Wave riding has to do with the surface area pushing against the density of the media that you are riding on. Waves of the ocean work the same as any working fluid does. Speed at which you are pushing against the media is the other factor for how you glide as well as the attack angle against its surface that provides what looks like lift.
These are all of the factors when we enter an atmosphere before landing which apply to the EDL...
Shuttle in many a movie was said to be a flying brick for that reason as it road the air in a spiral path until it could land as it was going slow enough.
The gravity aspect is the arc along which the craft is following but its assuming that you are not coming in faster than the pull of the planets pull. The craft is then riding along the arc rate gradually slowing as it gets towards the surface following the arc until it reaches the planet at near zero speed..Its free fall that we see cause the ship speed up as it gets closer as it follows the path to the planet.
So if reverse retro rockets are fired to compensate for the increasing pull then you can slow and follow that path but the fuel consumption will steadily increase as you try to keep it from going faster.
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There's nothing magic or new about waverider technology. Hype to the contrary is just that: hype. A waverider generates lift by the shock-induced pressure rise on a flat bottom, exactly the same effect as the component of supersonic wing lift that is generated by the bottom of a supersonic wing. It's just not a wing lower surface doing this.
It's not new at all. Some would say this dates to the 1965-vintage XB-70 Mach 3 bomber. About half its lift surface was a flat bottom, not the wings. But this was used even earlier in the 1953-vintage F-100 Super Sabre fighter jet. That aircraft raised its lift/drag ratio during supersonic dash with a flat fuselage bottom. Dash speed was Mach 1.3.
As for openings for thruster nozzles on the lateral surfaces during entry conditions, there is no reason you cannot have them, as long as you design to preclude through-flow when the thruster is not firing. The static gas column in the open port is a better insulator than any solid we could install. But the key word is "static": if vented, hot gas intrusion destroys structure. That is why shuttle Columbia shed a leaky wing with a hole, and was destroyed.
If by "air augmented rocket" you mean a mixing device that accelerates air with the jet pumping action of an embedded rocket stream, that works far better at low flight speeds, essentially subsonic, certainly not good at all at supersonic, and certainly not hypersonic/orbital-speed class.
As for windows during entry, you can have them on surfaces that are embedded in separated wake zones, where there is no scrubbing action, only very low-speed contact with hot plasma. Sometimes knowing where these locations are can be tricky. A hypersonic slipstream jet would reattach to the shuttle's nose at angle-of-attack above 40 degrees, impinging straight into the windscreen, and guaranteeing its destruction in mere seconds.
The same was true below 20 degrees. Thus the shuttle had a very tight angle-of-attack restriction during entry: 20 < AOA < 40 degrees. Loss of such control would lead to destruction of the vehicle within seconds. Nose shape details did not matter, it was true for any of the shapes considered for the shuttle's nose. This was found in Mach 5 wind tunnel tests during 1973, before shuttle's design was finalized. I helped conduct and analyze those tests as a graduate student.
GW
Great GW!
I'll put thermal screen over the window close them during atmpspheric flight and open them in deep space.
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Quaoar:
The Mercury, Gemini, and Apollo capsules all had windows located on the lateral surfaces in the wake zone. The AOA restriction for them was AOA < lateral wall "tumble home" angle, so that separated flow could not re-attach along the lateral wall. The separation line was essentially at the periphery of the heat shield.
With no attached flow, there is no scrubbing action, and the heat transfer coefficients are low. The driving temperature is the same plasma effective temperature as for the heat shield, but with extreme scrubbing, the heat transfer coefficients on the heat shield are an order of magnitude larger.
I think, if memory serves, these windows were quartz panels, which could run rather hot, cooling essentially by conduction, laterally into the window frame structure as the heat sink. With a transmissibility near 100%, there is about 0% emissivity for hot quartz, so radiation cooling is not an option.
GW
GW Johnson
McGregor, Texas
"There is nothing as expensive as a dead crew, especially one dead from a bad management decision"
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