DGIV RE-ENTRY TROUBLE

[cessnasoarer172]

Greetings

I have done a lot of reading on how to properly do a re-entry for the winged craft in orbiter, but I still keep having some trouble. I ran the DGIV under re-entry with the autopilots to learn, but i would really like to do my re-entries manually, to get the full experience thing =]

anyway i start off fine, have an appropriate re-entry angle, pitch up to about 40 degrees, and i am aware of what my descent speeds should be and that flight dynamics are opposite. My problem, and I just can't figure it out, is just as things start to heat up (900-1200 degrees) im pulling up as hard as possible to maintain the 35-45 degree angle, but then its not enough, and full upward power is not enough to keep the nose from rolling forward into the critical zone which overheats everything else and destroys the ship.

I've tried it time and time again, but i can't understand why im pitching forward despite my efforts. I've tried banking too, another concept i would like help on (what altitude does this occur, is it necessary, and at what bank angle) but my main concern is how to keep the nose up, which baffles me.

thank you for your help

 

[astrosammy]

Select "Atmospheric Auto" on the control switch in the top right of the center panel. Also set full trim.

 

[HiPotOk1978]

Select "Atmospheric Auto" on the control switch in the top right of the center panel. Also set full trim.

DGIV reentry w/o flight computer assistance is a pain cause the nose seems to be VERY heavy. The false sense of CoG offset is caused by the airfoil lift at hypersonic speeds. Your experience similar aerodynamic characteristics when you fly the DGIV at hypersonic speeds near the edge of the atmosphere in the 80k range using just the airfoils for pitch adjustment. Using the airbrakes during reentry (not sure how realistic that is btw, but I do it once in awhile) will also cause the nose to want to negative pitch.

Anyone here with some colleging answer the question of how realistic the DGIV reentry is?

 

[Dambuster]

You should take a look at this thread, it has a lot of helpful bits of advice in it:


http://orbiter-forum.com/showthread.php?t=4421

 

[pete.dakota]

It's quite realistic, IMO. Though, I have found that the AoA AP will hold attitude better than when flying manually. It's almost as though the flight computer can fire the RCSs harder than manual input; considering it doesn't use trim.

Also, make sure you're under 19t. Dump all your main fuel, IMO.

I would never attempt a fully manual entry in a winged vehicle. I'm sure I could, though. I just can't imagine myself being bothered to keep my hand on the stick and eye on the HSI for a full 30 minutes. So the DGIV's attitude entry AP is perfect.

 

[RisingFury]

Select "Atmospheric Auto" on the control switch in the top right of the center panel. Also set full trim.

No.

Select Elevon & Gear, hit F8 and in the upper left corner put RSC on ROT.
That way you'll have both RSC and control surfaces working.

Don't really need to dump fuel or cargo, but if you're heavy, do your de-orbit burn a few 1000 km earlier so you'll have a longer, but lower angle flight through the atmosphere.

DGIV is a dream to handle. If your slope falls under 1°, pull your nose down to 30° AOA. But a slight warning: That will raise your hull temperature, but will get you more lift and will pitch you up.

 

[HiPotOk1978]

I would never attempt a fully manual entry in a winged vehicle. I'm sure I could, though. I just can't imagine myself being bothered to keep my hand on the stick and eye on the HSI for a full 30 minutes. So the DGIV's attitude entry AP is perfect.

Well Pete, I bet if your flight computer failed, you were running out of LOX, you crew looked at ya to make sure they made it though the atmosphere, alive.... you could

 

[cessnasoarer172]

DGIV reentry w/o flight computer assistance is a pain cause the nose seems to be VERY heavy. The false sense of CoG offset is caused by the airfoil lift at hypersonic speeds. Your experience similar aerodynamic characteristics when you fly the DGIV at hypersonic speeds near the edge of the atmosphere in the 80k range using just the airfoils for pitch adjustment. Using the airbrakes during reentry (not sure how realistic that is btw, but I do it once in awhile) will also cause the nose to want to negative pitch.

Anyone here with some colleging answer the question of how realistic the DGIV reentry is?

thank you very much for your input. It doesn't seem realistic that the lift would change the CoG so significantly, but i am not aware of whether or not this would happen in real life, and this is in fact realistic, or if its just something inaccurate about the simulator. So if i get you, you are saying there really is no way to truly manually reenter the DGIV?

Oh and the trim controls are at the bottom mid center panel right? lol i don't really use trim, and something else that is a pain is that in FS2004, I always have the auto rudder feature activated, as i do not have foot pedals. Orbiter does not give me this luxury

 

[RisingFury]

I think DGIV reentry is very realistic and I disagree that it's got a heavy nose.
I've done 100's of reentries and can easily reenter and land on target.

I think that the DGIV fuel consumption is incredibly low and RSC fuel consumption even more so, but I think the aerodynamics is realistic.

The key is to keep your nose up at 30° to 40° AOA and not to exceed 1° slope angle and to have both RSC and control surfaces working.
I failed my reentry at the beginning quite often because I had the Atmospheric auto online.

There comes a point when RSC isn't effective enough anymore to keep the ship at the desired AOA. That's when the switch to control surfaces occurs. But at the beginning of that, the AF control surfaces aren't as affective as in the lower atmosphere and sometimes cannot hold your nose up to the desired AOA.

The thing is, if you have RSC and control surfaces online at the same time, you can drop your nose below 30° AOA and recover it with ease. If you have any of the two systems offline, your nose will drop much sooner and you're gonna die.

 

[cessnasoarer172]

I think DGIV reentry is very realistic and I disagree that it's got a heavy nose.
I've done 100's of reentries and can easily reenter and land on target.

I think that the DGIV fuel consumption is incredibly low and RSC fuel consumption even more so, but I think the aerodynamics is realistic.

The key is to keep your nose up at 30° to 40° AOA and not to exceed 1° slope angle and to have both RSC and control surfaces working.
I failed my reentry at the beginning quite often because I had the Atmospheric auto online.

There comes a point when RSC isn't effective enough anymore to keep the ship at the desired AOA. That's when the switch to control surfaces occurs. But at the beginning of that, the AF control surfaces aren't as affective as in the lower atmosphere and sometimes cannot hold your nose up to the desired AOA.

The thing is, if you have RSC and control surfaces online at the same time, you can drop your nose below 30° AOA and recover it with ease. If you have any of the two systems offline, your nose will drop much sooner and you're gonna die.

thank you! how to you get both control surfaces to operate instead of atmospheric auto?

 

[Belisarius]

Select Elevon & Gear, hit F8 and in the upper left corner put RSC on ROT.
That way you'll have both RSC and control surfaces working.

Already there

 

[SlyCoopersButt]

Of all the time I've been flying DGIV I can't believe I didn't find that trick. I've always wanted to have both on at the same time for perfect upper atmosphere control.

 

[Balladeer]

I'm still trying to learn re-entry with the DGIV and still have a long way to go. Wouldn't the PRO104SPECNN command help? Its the autopilot that is supposed to keep your attitude locked in.

 

[RisingFury]

Autopilots suck. They take every piece of fun out of Orbiter. Might as well hand control to someone else and watch them fly around.

Yes, it's difficult, yes, you die a lot, but that's the whole point of Orbiter. The learning curve is very steep and frankly it needs quite a lot of imagination to be *fun* like games made specifically for entertainment, so the whole point is to learn these complex maneuvers and then go for it.

 

[pete.dakota]

Autopilots suck.

We're talking about re-entry here, not ascent. The DGIV's entry APs don't fly the thing for you. They simply hold attitude - that's it. Hardly taking the fun out of it. And you're still applying your knowledge in the same way you would if you flew it totally manually. You still have to know which AoA and bank angles to use at certain points during the descent. And the landing certainly has to be flown manually, too.

If anything, it actually aids the learning curve. Allowing you time to observe how the ship controls and behaves at those speeds. Realistically, if the DGIV didn't have a attitude hold AP, I probably never would have learned how to fly a re-entry properly.

If you're talking about ascent, then I agree. People often claim they use launch APs for precision; but it's quite possible to fly into a very specific orbit manually using cues from MFDs.

 

[RisingFury]

I'm not just talking about the AOA hold autopilot, I'm talking about autopilots in general.
But you do bring up a good point, Pete. And I too learned how to reenter the atmosphere by observing the autopilot. But I had to learn how to land, when to do the deorbit burn and stuff like that by just crashing the ship in trial and error.

And now I do these things by the gut feeling...