Flight Question PRO104SPEC Assistance DGIV

[PaulG]

Hello. This is not a post asking how to re-entry. I got that covered and I re-enter well every time. This question pertains on how to use PRO104SPECxx either correctly or more efficiently.

I deorbit opposite the base and I control the AoA using PRO104SPECxx and by watching Aerobrake MFD. I control this quite well so that I'm very close to the base and then I use the OPS MFD (the one for the shuttle, not sure if I have the name right) to use the alignment circles for a perfect landing every time.

But, the problem is, PRO104SPECxx only allows AoA increments of 5 degrees. Often, very often, I need only a degree or two to make adjustments and keep the total G rating reasonable. Is there some hack that will allow 1 degree changes? As it is, I drop the sim rate to 0.1x so I can reload PRO104SPECxx a degree lower and after engaging, I bring it back up to 1x. I do this so I don't go out of control whilst typing.

Or, is there some better way? Or, should I just use PRO105SPECxx and deorbit a lot closer to the base? If that is the answer, is the a graph for earth available that shows the relationship between deorbit altitude and distance from base for the PRO105SPECxx setting?

I'd prefer PRO104 if possible..

Thanks,
Paul

 

[insanity]

Honestly, 5 degrees is good enough. If you want to make small adjustments, pitch up and down for short periods of time, then adjust back to your original setting (probably 40ish).

 

[PaulG]

Well, not really. Depends. What is the maximum realistic Gs? 5 degrees can bump it quite high if you are dropping at a high rate. Actually, my AoA is generally around 25° when I deorbit from 120k opposite the base. That puts me to about 15km altitude at the alignment circle.

---------- Post added at 04:53 PM ---------- Previous post was at 07:24 AM ----------

Hmm...it seems as though there are not many options when it comes to this. How many use PRO105 versus PRO104? I may try to map out an indirect equation using a response surface design for PRO105. I assume the two input variables would be deorbit altitude and reentry angle and the output variable will be distance from base. What do you think?

 

[insanity]

It depends on what you mean by maximum realistic Gs. The human body can take a bit of a punishing, if it is for brief periods of time. How steerp of a reentry are you going for here? The DGIV also has a high range of tolerance for G forces. Usually on re-entry I pull about 4.5 when I transition from braking to landing phase. Linear RCS and small attitude changes are your best friends when going about reentry in the DGIV.

 

[PaulG]

Yes, but, when running PRO104SPECxx how do you do small attitude changes?

 

[insanity]

you don't need to. You make the 5 degree ones for short periods of time to adjust your slope. I wait until I'm lower than 200km to fine tune my approach with Aerobrake. The basic procedure is create an inital reentry profile when you're about on the other side of the world and lower than 400 km or so. Then when you get close to 200km turn on pro104s40. Below 200km, make a few small burns to get your profile in aerobrake to make you fall short by about 60km. Turn off the autopilot and make small RCS adjustments to fine tune it (holding the aoa manually) then switch it back on and just make little pitch adjustments here and there to hold that. When you get to 100km and closing switch off the autopilot and make a small dive for the runway. If done correctly you should deadstick with less than 5 Gs pulled for the entire reentry.

 

[PaulG]

Well, essentially, I do that. But how do you hold the AoA manually? Perhaps its because I fly with the keyboard and not a joystick. Heh, I know. I've just been lazy to put it on.

 

[insanity]

I've got a video of it if you want it. When you're above the thicker atmosphere (150km+) there is negligible resistance so once you kill the autopilot you shouldn't have to give any inputs to adjust attitude. Just make a few small setup burns and turn the AP back on.

 

[Shadow Addict]

Orrr switch to the XR1 and use its attitude hold AP. It has increments of .5, IIRC.

 

[PaulG]

Hmmm...XR1...tempting....

In regards to upper atmosphere. Generally, the changes I make are below 80km altitude.

 

[Tommy]

I find the 5 degree increments are usable. Begin by using whichever AoA gets you closest to target. You can go a bit long (a couple hundred kilometers) but not to far. Early on especially you'll want to end a bit short. As you descend, your path indicated by Aerobrake will shorten, and you can lower the AoA in 5 degree increments to keep the endpoint close to target.

As for the de-orbit, I find that the DGIV prefers a steeper re-entry than you'll get by de-orbiting on the opposite side of the planet. Coming in from the ISS, try de-orbiting about 17M from base. From a low parking orbit (about 200k) try about 15M.

You can also use banking to control the descent rate, making S turns.

 

[PaulG]

Thanks Tommy. I remember you saying something similar in one of my previous posts on a similar topic. Perhaps, it is just in my approach from deorbiting so far from the base. Unfortunately, someone mentioned the XR1 which looks quite cool. Now I have an itch to try that.

 

[Sar]

I usually do a deorbit burn around 17-16M or so from ISS altitude (~350K) and aim it with aerobrake mfd then at around 200K I hit P104S40. After that it shouldn't take too much to hit the sweet spot and land unpowered if you've done the synchronizing with base well enough, usually takes only one to six attitude changes that last less than two seconds or so.

I use this to figure out where to deorbit burn. (Don't know who put this in OF the first place, but thank you who ever you are)

d = h / tan(alpha)

d : distance from base
h : altitude
alpha : desired reentry angle

Also there's a video reentry tutorial in the forums somewhere that's very good!