Flight Question Reentry profiles

[StevoPistolero]

I am looking at different reentry profiles. The shuttle deorbits far away from the other side of the planet for a shallow reentry. But would a futuristic spacecraft need to do this? Could a futuristic craft deorbit right above the landing site?

Is the limiting factor G-max? And if this is a hard limit, what is the highest orbit you can descend from with a G-max<10?

 

[RisingFury]

You're looking for Gmax < 3, unless you wanna look for your eyeballs at the back of your head...

G load isn't the only problem. Heating and delta-v come into play as well.
If you have a high delta-v (really high), then you could go for a powered descent and that would allow you to begin your deorbit burn maybe a few hundred km from your target - roughly the same distance that a rocket travels before entering orbit.

 

[StevoPistolero]

Yes, I have found that the hover engines can keep the rate of descent down, lowering the g-force.

 

[Tommy]

While such a short re-entry profile may be possible, it's unlikey that it will ever be used. Even if we assume that fuel/engines will be more powerfull (and need a smaller fuel mass to achieve a given dV), the fact is that high efficiency will still be a very desirable thing.

Even in the future, fuel will not be free, and the kind of re-entry you are talking about would use a LOT of fuel. That fuel would have to have been carried during the flight from wherever-you-came-from, thus yet more fuel would have been needed to get from there to here. That could also mean a larger vessel (since the fuel tanks would need to be bigger), which means yet more mass, and therefore even more fuel needed.

A powered re-entry just isn't economically viable, and likely never will be, except in cases of extreme emergency.

Also, keep in mind that this type of re-entry doesn't necessarily save you any time. There are still going to be limits as to how fast you can slow down - especially for a manned flight. A powered re-entry may seem quicker - but only because you are de-orbiting later. The actual time when you land will end up being very close to the same either way.

 

[Bonanza123d]

This was proven in a mp race. Me and another guy were nrxt to eachother. I deorbited normally. Th did his late. I won

 

[Marijn]

In Orbiter, at least with the XR1, you can actually perform a vertical reentry, with no horizontal speed at all. If you decellerate to 0 m/s between 200 and 300 KM above the spaceport, and set the autopilot to maintain exactly 45 degrees AOA, the XR will fall towards Earth. While falling, the lift will pick up and increase, completely leveling the XR into atmospheric flight just above the ground. This is an insane manouver but it works great.

 

[Wishbone]

dV of 7 km/s will be better spent elsewhere...