[Closed] Low temperature re-entry for DGIII (outdated)

[Michelle Megan]

This tutorial is now outdated, you may have a look here:
http://orbiter.dansteph.com/forum/index.php?topic=11930.msg183373#msg183373














Low temperature re-entry for DGIII (without the need for hover thrusters).

Have a problem with re-entry for the DGIII?

The following is a time tested and refined low temp re-entry procedure that has worked for me 100
% of the time without fail.

DGIII Specs Used:
4 passenger
15 day O2 reserves
Default (iss & moon) Fuel reserve
Mark IV engine

(Please forgive the following pics that are included as they were taken at a 1024 * 768 resolution.)

I started by leaving Mir, the procedure will work from the ISS as well as long as you adjust your
orbit plane and altitude to what I have come to call the (re-entry Orbit) before the re-entry burn.

As we leave Mir the Orbit will look like this
http://www.arcadians.net/images/Orbiter/Leaving%20Mir.jpg

The first thing I do is adjust the plane to better intercept the KSC arrival so that you arrive at a 90
degree heading. (remember, this also applies for an ISS departure). The reason I chose this plane
is because it is the most forgiving as it allows 2 – 3 orbits for the deorbit burn window with the
landing zone still relatively close to KSC at the end of the re-entry interface.

To adjust the plane wait until your ship intercepts the equator as seen here
http://www.arcadians.net/images/Orbiter/Plane%201.jpg
You will also note that the topmost circled point in the orbit is below the longitude line. The goal is
to do a (orbit normal +) burn until the orbit passes just under the KSC longitude line as seen here
http://www.arcadians.net/images/Orbiter/Plane%202.jpg
Or in the case of the ISS orbit you must do a (orbit antinormal -) burn.


Now that we have the right plane for the “re-entry orbit” its time to make sure we have the right
altitude. I have refined the “re-entry orbit” to 370 km, as this has worked best for me during my
trials for a cooler re-entry as seen here.
http://www.arcadians.net/images/Orbiter/Raise%20Orbit%20370.jpg


We have the right plane and altitude for the “re-entry orbit” all we have to do now is wait until the
orbit plane is close to the KSC as seen here in the left MFD.
http://www.arcadians.net/images/Orbiter/Re-entry%20Orbit.jpg


It’s now time to place the DGIII retrograde and wait for the re-entry burn. As tested this will
occure at a distance of (19.86 M)<-- UPDATED“after you pass” KSC. And should look like this
http://www.arcadians.net/images/Orbiter/Re-entry%20burn%201.jpg
Begin the burn and stop once you have reached a 6.435 ped on the orbit screen or a re-entry
angle of 0.73 and at least a 64000 M on the deorbiting display like this
http://www.arcadians.net/images/Orbiter/Re-entry%20burn%202.jpg
Use RCS Lin to fine tune the angle.


After the burn, turn prograde and lets get the weight right. For this I have found that around 16 KT
is best. So we dump fuel until it looks like this.
http://www.arcadians.net/images/Orbiter/Reduce%20weight.jpg


Everything is looking good so far. At 130 km from the surface enter PRO104SPEC35. yep “35” not
40 as seen here. This happens as we pass just under Hawaii.
http://www.arcadians.net/images/Orbiter/PRO104SPEC35.jpg


As we continue our decent, the 35 degree angle will give us a little lift as well as apply a little
resistance to slow us down in what I like to call Phase 1 of the re-entry interface. This phase is the
longest of the 4 steps to follow and can be compared to lightly pressing on the brakes in a long
coast down a hill with a car. And should look like this.
http://www.arcadians.net/images/Orbiter/Phase%201.jpg


Eventually the DGIII will begin to fall again due to lack of speed as it is slowly reduced in Phase 1
at 35 degrees. As we get lower the heat will begin to take effect and here is where you must be
ready to alter the Angle of the DGIII. As soon as the tail section reads 310 c the overheat alarm
will sound as seen here.
http://www.arcadians.net/images/Orbiter/Phase%201.5.jpg

And you must immediately press number 2 on the number pad to increase the re-entry autopilot to
40 degrees. This will cool the tail section while increasing your drag and the Gs will begin to
increase, like this.
http://www.arcadians.net/images/Orbiter/Phase%202.jpg

Soon the tail heat will again rise to 310 c when it does press number 2 on the number pad again
to raise the Angle to 45 degrees as seen here.
http://www.arcadians.net/images/Orbiter/Phase%203.jpg

And finally the tail heat will once again reach 310 c and for the last time press number 2 to raise
the angle to 50 degrees. Like this.
http://www.arcadians.net/images/Orbiter/Phase%204.jpg


Each step up increases your drag and stall ratio while cooling your tail section and each step
occurs faster then the last. But once you have reached 50 degree angle all we can do now is wait
for Max heat and Max G to occur as we are now at maximum breaking angle.
http://www.arcadians.net/images/Orbiter/Max%20heat.jpg  
The heat should not go past 330 c and the Gs should be around 4.7 for a few seconds before the
DGIII slows down enough to cool and complete the re-entry interface.

At around 1.000 K speed or near Mach 3 – 4 press “C” key twice to release the re-entry autopilot.
You should now be between 150 – 200 Kilometers from KSC and can prepare for your final
approach and landing.


Here is a checklist I use to help me that you can copy paste into a word file for printing.

Re-entry Orbit

-   Undock from Station
-   Adjust orbit plane at equator for KSC 90 degree approach
-   Adjust altitude to 370 km 0 ECC
-   Wait for final orbit
-   Retrograde Burn at 19.86 “after passing KSC” (Updated)
-   Burn until 6.435 PED (0.73 angle 64000 D2)
-   Prograde and dump fuel to 16 kt weight
-   At 130 km enter PRO 104 SPEC 35
-   When tail heat reaches 310 c press “Num 2”  for  40 degrees
-   When tail heat reaches 310 c press “Num 2”  for  45 degrees
-   When tail heat reaches 310 c press “Num 2”  for  50 degrees
-   Max Tail Heat & completion of re-entry interface
-   Turn off re-entry autopilot at 1.000 k speed ( Mach 3 – 4 )
-   Final Approach and landing.


I hope this helps with your future re-entry’s

Good Luck Pilots.

Michelle



Post Edited ( 02-09-05 14:44 )

[DanSteph]

Many thanks Michelle,

I'm sorry to not have the time to rework the reentry yet
I'm on others stuff anyway your tutorial is really welcome

Dan

[Cracker]

Michelle, and fellow orbinuts,


This, kind readers, is an example of a Canadian Goddess. Totally beautiful, very wise, and so kind
as to share this wisdom with US, who have been trying to crack this case for months. The DGIII is
now a perfect all-around space plane. Dan, relax a little. With minds like yours and MegaMichi, we
can plan and execute complex planetary adventures, all the while sitting in front of our monitors,
recuperating from, in my case, 13 hours of mountain climbing combined with 13 hours of applied
high-speed on-the-fly trigonometry, while dodging mountain lions, wolverines, and the occasional
grizzly (whew! another standard day), and sip a cold beer.    
Thanks, Michelle

[Michelle Megan]

Hullo

Just wanted to let everyone know that I have updated the information above and it has been tested with the 2005
version of Orbiter and DGIII.

The de-orbit works as before and if done perfectly it will drop you out of re-entry about 100 KM North of KSC. 80% of
the time I can glide the rest of the way without any engine burns. but I sometimes need to apply a little power to
main engines to keep the speed up for final approach and flaring.

I hope this helps those that are having problems with re-entry and they can use it to succeed in acomplishing the
most violent part of flying the DGIII like a pro.

I will be adding one more pic soon™ that helps the allignment phase of the proceedure using the surface display and
the Long - Lat data to assist with the burn time for allignment so it is not so "adhock" for the purist pilots.

PS. I love the 2005 upgrades. Once again Dan and Martin have outdone themselves.



Post Edited ( 02-09-05 14:45 )

[Schimz]

With my cool reentry methode, I'll also heat the dg3 around 300°C
































but in the nose
http://orbit.m6.net/v2/read.asp?id=20691

[DocHoliday]

Hey Michi,

Nice to hear from you again

[freespace2dotcom]

yeah.  I must confess though, my reentrys are much, MUCH cooler, at around 2000.

Of course, by cool, I mean awesome, and not cold.

In any case, keep truckin'

[Atom]

13 hours of mountain climbing

That sound fun.

[DanSteph]

Awesome post Michelle, I'll put a link in the FAQ to this post

Dan

[Drono]

There's something I'm missing.    What you call "tail temperature" in the DGIII manual is told to be the
upper hull
temperature. Maybe I'm wrong, it makes no sense. The cone temp is the first, and is useful. The second is the cokpit
external temp, and I like it too. The third, the bottom one, has to be the temperature of the lower part of the hull,
who would be concerned with the upper side?
Ok, whatever, in the DGII manual I see the limits are as follow:

            2620°
2510°  1380°   2510°
            1520°

The 310° limit for the tail is far below the 1520° wrench limit, and I've got no warning, it's my nose to break apart.
Could you help me Mishelle? Please, be patient

Federico aka Drono

PS Great job evrebody!

[duttas]

Thanks a lot Michelle for sharing the re entry knowledge. I had a perfect re entry with DGIII and a successful landing.
I made it to home safely from the Moon.

[SiberianTiger]

A fine reentry manual, but too strict for my taste.

[StarLost]

Ah, my good friend from the Rodina, when baking a cake for the very first time, one always follows the recipe exactly. After
one is accomplished in the kitchen, variation and creativity may be added.

[Mole]

Well said, StarLost. Real spaceships are flown by the numbers, just like jet aircraft. I know that I was always burning
up until I started following Michelle's instructions. Now I vary them a little, and I find:

usually 35 or 40 degrees nose up will work
usually a re-entry angle between 0.70 and 1.00 will work

The toughest part is now timing the re-entry burn so that I wind up right above the base, so I can glide down shuttle-
like without power. I use the BaseSyncMFD and it is nearly perfect in getting me over the base horizontally (so I don't
need to go left or right) but it is not so good in indicating the point of re-entry burn (sometimes more than 500 km
off). I am going to compile a table with altitude-vs-distance, using a constant reentry angle such as 0.70.

[StarLost]

Mole, I've not tried it so I don't know for sure, but have you tried it using LandMFD? It may be more accurate for the timing
of the retro-burn (and it wasn't available when Michelle wrote up her tutorial, I believe).

[Mole]

I've still not tried LandMFD but I seem to remember it's for landings on planets/moons with no atmosphere.

[brodie]

ok something weird is going on, i did this yesterday and for the 1st time i actually got the DG on the runway without
using the engines ( -11 m/s and the gear collapsed, but its a HUGE milestone for me).. wen i got home today i
thought i wud try it a few more times to get the landing right.  Now whenever i fly this de-orbit wen my tail temp
reaches 310 i press num pad 2 to increase AOE to 40 deg, but it struggles.  The RCS doesnt fire evenly, the number
moves so quickly its to hard to make out and the pitch up is around 0.5 deg per second (compared to the 2-3 deg per
second i got yesterday).  Even using my stick to aid the autopilot doesnt work, its still terribly slow... this struggle
occurs every time i increase the AOE to reduce temps and the result is an Overshoot, G-excess and burn up (90% of
the time, I have once or twice banked the wings and killed the G's and power flown back to CC)! yesterday as with
every time i try something new I always quicksave at important points so i dont have to wait around to practice
certain things, i used a quicksave from yesterday's succesful de-orbit which puts me at 120km above the earth and
ready to engage the autopilot and now this RCS problem ...!!! It almost feels like the autopilot is contradicting itself
(like wen u try to fire thrusters when locked prograde etc..).  All i dont understand is why it worked fine yesterday
and now its not :S, ive checked my joystick etc... It's very annoying, this is the 1st succesful de-orbit profile that has
got me on the runway at KSC HELP ME!!!!

[Mole]

Brodie,

Usually when I press "Num-2" while in the atmosphere the DGIII doesn't completely raise itself by 5 degrees. I
always figured it's the atmospheric pressure that tries to "straighten" the craft, which is too strong for the RCS
rockets to overcome. The point is that the temperature SHOULD still lower from 310 (usually for me it goes down to
about 280 degrees, then goes up again, I get about a 30-40 seconds before it's back to 310).

I believe the key to not burning up is a very shallow re-entry angle (look at DISP 2, the angle is determined when you
do your de-orbit burn). I usually use 0.70 and I almost never burn up (any more    )

[brodie]

i do the orignal posters de-orbit to the number.  i get a big drop in temp wen i go to 40 deg but then after the pitch
up is too slow and the temp just keeps raising, above 310 ':(

[SiberianTiger]

brodie wrote:
i do the orignal posters de-orbit to the number.  i get a big drop in temp wen i go to 40 deg but then after the pitch
up is too slow and the temp just keeps raising, above 310 ':(

Try to keep the pitch up key pressed for a while, it will work.

[matthew1]

I can't view those pics (links) in the first post, above. It just says "unable to connect" (I'm using firefox, but IE doesn't
work either).

Can anyone help please?

[Atom]

This is a very old post, it's likely the host has gone down.

[Michelle Megan]

Yep

My site is down now and I lost hosting ability.

I still have the original pics for this tutorial though and if someone can provide me with a folder at their site I can ftp
them up and redo the above tutorial.

I also plan to improve upon the proccedure so that it works a little smoother with orbiter 2006. I made 3 perfect re-
entries using my time tested proccedure and it still works great. the DGIII emerged very close to KSC.. so close that
no engines were needed for final approach. The Deltaglider was gliding all the way to the ground with plenty of
momentum to spare. Good thing DGIII has air brakes  

[reekchaa]

No Takers Yet?

C'mon... Michelle's tut was GREAT... all these newbs would stop bugging if only we could redirect them
here.

If Dan himself doesn't have the space/time, we could always settle for a free/banner site, Michi.  Sorry I can't help...
I'm between hosts.

[Michelle Megan]

reekchaa wrote:
No Takers Yet?

C'mon... Michelle's tut was GREAT... all these newbs would stop bugging if only we could redirect them
here.

If Dan himself doesn't have the space/time, we could always settle for a free/banner site, Michi.  Sorry I can't help...
I'm between hosts.

Thats ok

I been trying some station building.. Using Kulch's energia, with those neat modules. It's the first time I use the
dragonfly to build this station - o - mine.

Hardest part has been the energia setup's for launch with each part of the station. Im starting to get the idea for pin
point positioning. but it's still trial and error untill it's perfectly placed for launch. I been keeping all the setups as I go.
Can't wait till Kulch completes his editor and other neat stuff hes working on.

I did notice a few quircks with Orbiter when building a station part by part in this way. As more and more items are
attached the less acurate the orbit holds when time accelerating.  I used to be able to view my station and *100
untill the station is nearest the launch window. which usualy takes 24 minutes. But with a larger station, or " more
stuff in orbit " I now have to *10 or the orbit falls apart real bad.  So if Im now waiting for my launch window it now
takes 2 - 3 real hours to wait till my next part can launch.

I guess since each station part is classed as an independant ship or object the demands on my system grow beyond
a point where I can speed up time too quickly else the orbit decays.. but not in a way where the station will burn up..
but rather the station tends to clime higher and higher.

I wonder if the station will get so big that ill be restricted to real time only flying

I am amazed at some of you that fly real time all the time. I know my system fans perk up when I have orbiter on. So
to fly a real mission to the moon or even a full day's obiting in LEO it sure puts a strain on any computer. then theres
the threat of a power outage. I perish the thought of someone flying a real time earth to mars flight. imagine you just
had your computer on for 4 - 6 months then.. ooops power outage for an hour and any battery pack fails mid flight..
icky..  :P


hmmm I think I need to launch a fuel module soon.


btw. This is what im using atm.

- Orbiter 2006 (Earth lvl 9)
- Dragonfly
- Orbiter sound
- DGIII
- Kulch's Energia booster kit
- Selene B (fuel delivery)
- gregburch's Station building blocks 2006

Pentium 4 - 3 ghz
2 gig Ram
ATI Radeon X850P 256 meg vid

and possibly way too much tasks running on me system for all it's protections. ( PF usage on clean boot = 255 ish )