DGIV Reentry hull heat problems

[Interceptor]

Hi I am really confused about the DGIV reentry autopilot. I follow the instructions to the tee,with reentry angle prediction 1.200. I use aerobrake correctly getting the green line right on KSC base .I start my burn at 17.20M like told and then correct my reentry prediction, and move time x100 till 150km alt then I switch on the reentry autopilot, and sit back and watch like told. But when I am half way through the reentry my hull temperature gets to around 1340°C and I explode. Isn't the hull temperture suppose to reach 1700°C before hull meltdown.Why doesn't the autpilot correct this. Once you set it correctly your suppose to be hands free until you are just over the Cape. What am I doing wrong? :suicide:

 

[n72.75]

Hi I am really confused about the DGIV reentry autopilot. I follow the instructions to the tee,with reentry angle prediction 1.200. I use aerobrake correctly getting the green line right on KSC base .I start my burn at 17.20m like told and then correct my reentry prediction, and move time x100 till 1.50km alt then I switch on the reentry autopilot, and sit back and watch like told. But when I am half way through the reentry my hull temperature gets to around 13.40c and I explode. Isn't the hull temperture suppose to reach 17.00c before hull meltdown what am doing wrong.:suicide:

i think that your decimal points are in the wrong places

 

[Interceptor]

i think that your decimal points are in the wrong places

Sorry not good at math.


-----Post Added-----

Sorry not good at math.

which decimal points?

 

[tblaxland]

which decimal points?

These ones (and what I think you are trying to say):

1.50km -> 150km ?
13.40 -> 1340°C ?
17.00 -> 1700°C ?

Also, I think the decimal point on this one is right but not the suffix:

17.20m -> 17.20M ?

 

[SlyCoopersButt]

The nose temperature isn't the only area you need to keep a check on. If any other area exceeds the safe level charcoal from space will be the case. Make sure to dump excess fuel and run the reentry checklist program in the ships computer

-Max temperature:
-Nose: 2200°C
-Cockpit: 1300°C
-Wings: 2200°C
-Top hull: 1300°C
-Bottom hull: 2200°C
-With doors open:
-Nose: 350°C
-Cockpit: 150°C
-Top Hull: 310°C
-Bottom hull: 350°C

 

[Interceptor]

Thanks Slycoopersbutt. I think there all corrected now,and I'll try another reentry.

 

[SlyCoopersButt]

I should add that some have claimed their DGIV's on a random basis do fail during reentry on occasion when the damage and failure simulation box is checked in the Orbiter launchpad. I think that happened to me once too. Not sure though.

 

[Tommy]

Make sure that all doors (retro, hover, etc) are closed. Use the Re-entry checklist program to ensure this. Also, there are two re-entry AP's on the DGIV. One of them (Pro105) will adjust the AoA to maintain a descent rate of about 80m/s, but doesn't actually monitor hull temps. If you are coming in from a higher orbit (over 375k) it doesn't always work. The other (Pro104) simply holds the AoA at the set angle.

Keep an eye on the descent rate shown on SurfaceMFD (shown as VS). VS should be -75m/s to -80m/s for a high (around 40 degree) AoA. Lower AoA's require a slower descent (around -20m/s) since the drag is lower and you aren't deccelerating as quickly.

Also watch ALL the hull temps shown on the re-entry display.

What AoA are you using? NOTE: when you de-orbit, AerobrakeMFD isn't taking aerodynamics into consideration. Atmospheric effects such as lift and drag are only calculated when you are under 200k altitude. Once you are below 200k, and set the initial AoA, check AerobrakeMFD's prediction again, and adjust the AoA accordingly. I find that it usually takes an AoA of around 35 degrees using the distance and re-entry angle you have indicated. At that AoA, you shouldn't burn up.

Also, I assume you are using 1x time accel once under 120k alt. Unless yo have a very high framerate, the AP will not be able to control the ship effectively.

 

[Interceptor]

Thanks Tommy, as always your a big help. I'll keep trying. I had it down to four entrys in a row last week and now I can't get one.

 

[RisingFury]

Do your de-orbit burn at lower altitudes. Below 200 km.

If you come in from too high up, it won't matter what AOA angle you hold cos you hit the atmosphere too steep.

DGIV has a small display on the right, set it to mode 2. There should be a number under Slope. That's the current reentry angle, relative to the ground. Make sure it's below 1. I usually do reentries with that number being around 0.5 so I have some room for maneuvering.

 

[Interceptor]

Thanks RisingFury I'll give it a try.

 

[HiPotOk1978]

Out of the XR1/2/5 and DGIV in my fleet, I have noticed myself that the DGIV is the most unforgiving craft out there that I use on a regular basis. I would say that the only other time I have had a problem bringing a craft down to the surface from LEO was an XR5 with near 300tons of cargo in the bay and that beat the DGIV hands down. Watch your weight when your reentering. The built in autopilots on the craft can handle 18tons, but the less fuel you bring down from LEO, the easier it will be to land

 

[-Pv-]

DGIV Autopilots (from the /Doc) manual:

PRO105SPEC40 Auto reentry (keep a low temperature reentry profile)

...

PRO105SPEC40 – Automatic reentry autopilot
Useful for reentry on earth, and can teach you also how to do a « burn proof » reentry.
This autopilot will take care to reenter you so you do not burn in atmosphere. It is not meant to land you were
you want it will just manage your AOA so you do not burn, It is your responsability to have a correct orbit
before reentry and to perform the brake burn at the right time to land where you want. (see tutorial scenario)
This autopilot will manage AOA to keep a correct vertical speed to maintain temperature within acceptable range
You can only change bank see DISP 1 (D1) display when autopilot is running for help about which keys to use.
This autopilot will disengage himself once reentry completed at about 2500 km/h (700 m/s)
TIPS: reentry autopilot work also somewhat on Mars, not tested on other planets.

 

[aus_pilot]

DGIV Autopilots (from the /Doc) manual:

PRO105SPEC40 Auto reentry (keep a low temperature reentry profile)

...

PRO105SPEC40 – Automatic reentry autopilot
Useful for reentry on earth, and can teach you also how to do a « burn proof » reentry.
This autopilot will take care to reenter you so you do not burn in atmosphere. It is not meant to land you were
you want it will just manage your AOA so you do not burn, It is your responsability to have a correct orbit
before reentry and to perform the brake burn at the right time to land where you want. (see tutorial scenario)
This autopilot will manage AOA to keep a correct vertical speed to maintain temperature within acceptable range
You can only change bank see DISP 1 (D1) display when autopilot is running for help about which keys to use.
This autopilot will disengage himself once reentry completed at about 2500 km/h (700 m/s)
TIPS: reentry autopilot work also somewhat on Mars, not tested on other planets.

Thats the one.. I have flown manual reentries, but generally needed a shower and a change of underwear afterwords. If you have it selected, random failures can cause retro doors etc to stick open, so double check all the indicators. It's not that hard to fly.. It does take some practice though..

 

[Interceptor]

Thank you