[closed] reentry question on DGIII

[twisterkid]

[ADMIN WARNING] THIS IS A 1 YEARS OLD AND OUTDATED THREAD RESURECTED BY JER11
http://orbiter.dansteph.com/forum/index.php?topic=11944.msg183583#msg183583









i did everything on the checklist including the fuel dump...i wait and wait and when it gets to about 210 ft on the
display it just goes back up to 230 then down again to 210 then back up to 230...is there something wrong with the
aircraft or is there a flaw in the way im reentrying??

thanks a lot

[twisterkid]

i 1/2 way reentered!! i just burned up in the process  ...is there a way to keep my heat down?!?

thanks

[Atom]

I sometimes use the hover thrusters to slow myself, it's not entirely realistic, but it works. On the other hand you can
always go for a more shallow re-entry.

[batat]

Where I can download GTIII?

[Atom]

I think that was a typo, I assumed he meant the DGIII.

[Maco]

I have problems with reentry too. Could someone tell me, how to do that ? How to enter the atmosphere over base
where I want to land ? Last time I appeared somewhere in Germany, instead of Florida What is the descending
angle ? What lenght of my orbit I need to get myself to the apg ? I have tried a whole period, I have tried a half of a
period, but I went to always somewhere completely different place. Please help me...

[twisterkid]

i dont have problems landing in a certain spot. i just cant even get through the atmosphere...so i will try using the
hover thrusters and then is there anything else that anybody does or uses?? thanks

[twisterkid]

ok i reentered! but now i have another question...i come in way to fast...should i use my hover thrusters or this there
any thing else i can do?? thanks in advance

[DocHoliday]

I'm not talking to you guys, until you read the manual and other relevant materials... and understand terms like
periapsis, apoapsis, reentry angle, drag, S-turns and plane alignment. No point explaining unless you read about it
first.

Reentry is hard which is why you can either, fly until you get it right and develop your own method or read what's
been written on it in the past. Plenty I might add.

[freespace2dotcom]

As harsh as doc's words sound, I'm tending to agree with him. While we're not out to get newbies, it's rather time
wasting for us to answer such simple questions. It's also time wasting for you guys too.

instead of waiting 6 hours for someone to post an answer, you could spend some time reading and you would get
the answer before then. it's not very hard.

I would recommend this as a good starting place, and it's much easier to read, imhe

http://www2.jpl.nasa.gov/basics/

[twisterkid]

ok thanks

[Pete]

Hi,

I like the DG 3 very much and use the ship for interplanetary flights without problems.
But I have still elementary problems with reentry too.
(after reading much stuff about it, not a newbie )

I dumped fuel till 1500 main and 350 rcs (<1900),

started from a 230 km (or some higher) altitude with reentry angles 0,7 or 0,5 and I´m shure to use the reentry
autopilot in the right way according to the manual.

After reaching a heigh of 100 km, the negative vertical speed is growing up till the next ascent slope and now the
descent rate is climbing up much over 1,0 - this means always "burning up" after a short time. It seems not do
depent from my  choosen reentry - angle (perhaps: "burning up" a little bit later!)

Something must be wrong with my maneuvres, if others don´t have problems with that.

Many thanks for help!!!

Peter

[Spaced]

Re-entry from Mir to CC.

1, undock
2, Dump fuel, + houskeeping (close nose cone, external doors etc)
3, select map mfd, target CC.
4 wait until your NEXT orbit will intersect with CC.
5, as you approach australia turn retrograde. On the map mfd watch the distance to CC.
6, As the distance starts dropping from around 1900 select d2 on the mini-display
7 As the distance to CC hits 1800 burn retrograde until predicted re-entry angle in d2 is 0.70
8, Switch to surface hud, Wait a while
9, As you hit about 140km alt select "pro104s40" enter and hit e to engage. select d3
10 DON'T touch ANYTHING ( maybe slide your seat back so you DON'T touch anything )
11, Around 35k alt hit "c"or spacebar, if you look out of the window WoW there's the cape right in front of you

12 land

hope this helps

[RiconSpace]

Reentry from any inclination involves proper orbital path alignment to KSC and, if necessary, one correction manuever, I
usually would perform over Hawaii, to put the spacecraft a few Klicks from the run to ensure proper runway approach procedure.

Retract Radiator and Stow HG Antenna.  I usually depressuarize the airlock and be sure the close the Spacecraft's nose cone.
 Make sure your cabin environment is set and sound and the ships strobe lights are on.

Once properly aligned, give attention to your altitude and distance from the landing site to determine the best timing for
deorbit procedure: retrograde burn (or prograde burn using retro-thrusters; this involves longer burn window/time so you must
compensate for reduced motor performance. I have been extremely successful with both procedures)

Typically, if you're returning from ISS at an altitude of about 200 miles and inititially aligned to KSC, you will commence
deorbit procedure in the vicinity of 16.60M (somewhere over AUS) until your PED is about 6.400 and predicted reeentry angle
(command: D2) is somwhere  in the neighborhood of 1.15 - 1.19.  

As mentioned earlier, if your alignment is off, safely make a normal or anti-normal burn (depending or your situation,
probably a anti-normal burn) to exact your approach to KSC.

Is is said that the DGIII should have a mass of no more than 19000kg (I've made successful landings with near full tanks but
I find it more interesting to stick to the covets of the craft's creator.  So do your main fuel dump, if necessary, so to
ensure you do not burn up in Earth's thick atmosphere.

Set the Reentry Program: P104S40 then Enter.  Set seatbelt sign.  Continue to observe the MFD (D3) for signs of increasing
atmospheric pressure indicated by rising temperature at each sensored point of the spacecraft.  Execute 'E' the Reentry
program at an altitude of about 70-75 miles (Just off the West Coast of the US).  Allow the ship to decend without further
handling until you are well within the airframe operating conditions in the atmosphere (Your cool and aerodynamic).

This procedure should provide a safe reentry in the vicinity of KSC.  In fact, you should see visable hull cooling typically
somwhere over the panhandle of Florida if your Inclination is around 58.80 degrees inbound.

Happy Orbiting

[Pete]

Hi,

many thanks for help!

Reentry is working well now (especially with the values of Michelle Megan!)

and to Spaced:
this was the main advice:

"10 DON'T touch ANYTHING ( maybe slide your seat back so you DON'T touch anything )"

if you don´t touch anything , you are not in danger to destabilize the process - i think this was my prior fault!!

Greetings!!

[Bob Denny]

I'm getting frustrated too

While I have mastered the re-entry itself without burning up, rather well, I cannot get the retro-burn timing right. It is,
of course, a function of your orbit. Assuming you are already in an orbit that passes over the base (I got all of that!), how
do you time your retro burn? There are all sorts of "seat of the pants" suggestions on various forums -- the two here (start
16.6M and burn for -1.15 to -1.19 re-entry angle -- or -- start 18.0M and burn for -0.7) are obviously for some orbit that
I am not in! The advice seems to be for some orbit that that person is in.  The 18.0M/-0.7 suggestion has me
whizzing over  the cape at 60KM altitude and doing over 6Km/sec. Wrong. And yes I started Pro104Spec40 way back before entry
interface.  The AFCS MFD always burns waaaaay to early and leaves me out of energy over  the Gulf of Mexico. By the way, I
start from the DG III Docked to Mir scenario, and do a plane change at the next node to get the orbit just touching the KSC
circle, and sure enough it ends up passing right overhead when I am approaching Australia. That part I got well, as well as
the thermal control.

There must be a better way... a way to calculate the timing and delta-V of that retro burn, given your orbit. It's
probably "too complicated" without an MFD, but... the closest thing is AFCS MFD and all it has is a table of
altitude/speed/distance that it shoots for. For the DG flavor, the speed starts out too fast, and the MFD can't ever get
locked on to the table.

The Disp-2 display on DG-III always shows an estimated re-entry speed that is much faster than it ends up being.

Finallly, in the Disp-3 display, what is the Range: suppoosed to be to? It seems to refer to something I can't relate to, and
seems different. It's definitely never the range to the base you're headed for.

[Wilko_]

This post was made exactly a year ago (yes, just about to the date) by Arkalius, and I've used it's advice a lot since
then. It seems to work perfectly, but I haven't done tests since the new version of Orbiter was released. In general,
this gets me to the base I want to be at on Earth (with a few mid flight corrections, so always have enough fuel left
in the tanks). The entire thread can be found here: http://orbiter.dansteph.com/forum/index.php?topic=10005.msg160748#msg160748

Well I did a few test runs... The distance travelled is the degrees of distance from the end of the deorbit burn to
the
point when speed drops below mach 3 (this is the point where I disable the autopilot and take control).

200km alt, 0.70 reentry angle, 133.11 degrees travelled
250km alt, 0.70 reentry angle, 152.03 degrees travelled
300km alt, 0.70 reentry angle, 163.37 degrees travelled

0.70 degrees for reentry angle seems to work quite well, as in each instance the max G's from deceleration was 2.9
which is well within tolerance.

From 200km to 250km alt, the distance travelled jumps nearly 20 degrees (around 2000km) but, from 250km to
300km alt, the distance travelled only jumps around 10 degrees. My guess (and I will test it) is that the distance
travelled for an alt of 350km will be around 168 degrees. Also, if this pattern of halving the extra distance every 50ish
km is correct, then by extrapolation, the distance travelled for an altitude of 225km would be around 146 degrees,
and for an altitude of 275km, it would be around 158 or 159 degrees. I will test these altitudes and see what I come
up with.

-Arkalius

[Wilko_]

(Sorry about the double post but just an afterthought. Use the MAP MFD to see how many degrees you are from 180.
You'll see the degrees either counting up to the magical figures, or counting down. Only commence the retroburn
when they are counting down towards 0. Hope that isn't confusing. Use common sense)

[Murdock]

Maco wrote:
I have problems with reentry too. Could someone tell me, how to do that ? How to enter the atmosphere over base
where I want to land ? Last time I appeared somewhere in Germany, instead of Florida What is the descending
angle ? What lenght of my orbit I need to get myself to the apg ? I have tried a whole period, I have tried a half of a
period, but I went to always somewhere completely different place. Please help me...

I have tried to spot the reentry too,  I do start deorbit burn with the ship in opposition to the point I want to land
(roughly), that means when you are on the opposite side of your orbit curve in map MFD then I make just enough
burn time so as to lower perigee altitude to about 30-40 km. Once I descent to an altitude were I can read enough
atmospheric pressure I engage reentry autopilot with a standard 40 degrees angle (see DG III docs) and adjust the
angle to maintain predicted range within the range indicated in map MFD once you select you destination as target
base.
Sounds complicated but it worked for me. The challenge remains not to burn your ship in low atmosphere before
depleting enough speed!

[Me]

does any body have any good reentry plans for landing on mars or are the figures basically the same?

[oversoul]

Mars has a very low density atmosphere compared to Earth's. Using the Martian atmosphere to slow down a spacecraft "is like
using a frozen lake to slow down a bowling ball" I once read somewhere, and that's close to the truth.

You can use your engines, which is fuel expensive, or you can put into a highly elliptical orbit so that periapsis dips down
into the "thicker" parts of the atmosphere so that each orbit you are braking a little more. Eventually you'll have a
somewhat circular orbit and then you can brake some more or use engine burns. That's what NASA plans to do with the Mars
Recon Observer.

http://en.wikipedia.org/wiki/Mars_Reconnaissance_Orbiter

[oversoul]

ooh man I just fried my pants off ... it was a long approach, too.

heh

[Mole]

Did Arkelius or anybody else ever finish the table he started?
BTW  I've tried the deorbit from 250 km and 300 km as stated above; the 250 km worked almost perfectly but I got a
significant overshoot (by about 650 km) on the 300 km value -- only tried it once, will keep on trying.

[markl316]

Maco wrote:
I have problems with reentry too. Could someone tell me, how to do that ? How to enter the atmosphere over base
where I want to land ? Last time I appeared somewhere in Germany, instead of Florida What is the descending
angle ? What lenght of my orbit I need to get myself to the apg ? I have tried a whole period, I have tried a half of a
period, but I went to always somewhere completely different place. Please help me...

I have actually created a playback for orbiter 2006 that demonstrates a complete dgIII reentry, starting docked with
the ISS, all the way to touchdown.  It is available at http://orbithangar.com/searchid.php?ID=2453.  Copy and paste
this url.

[jer11]

too hard for me to make a good reentery, I jettison the fuel and i did a reentery  autopilot but it still fails. And it
makes
the crew die. I need some help to make a good reentery. I did 15 attempets but all fails help me whih this. I did a
reentery attempt at 12-09-06 when im on L.A.. I was almost there! So helpme with this!

My health before andafter reentery
Before reentery:



After reentery!


-----Messages--------
Jeramie Long.:Hello San Francisco.
San Francisco,CA: Hi whos this
Jeramie Long.: Its the pilot of DGIII
San Francisco: What is the problem pilot?
Jeramie Long: I going to make a reentery and i will die if it burns.
San Francisco: Are you going to land at the airport?
Jeramie Long.: Altitude 95km...90...Uh oh! im prepared.
San Francisco: I loated you, you are south of Florida. His Altitude is 87 km
Jeramie Long: Computer Reads Cockpit 500c.
Jeramie Long: Alt 80..75....70....65...[static]
Jeramie Long: Yes i will land at the airport
San Francisco: he burned PILOT?? PILOT?? YOU THERE???
Jeramie Long.: uhhhh....buh...(cut off in mid word)
San Francisco's company: Did the pilot burn?
San Francisco: Yes he did!
ON TV: The Deta gliderIII burned at Key West after a metting to the ISS. Unfourtinley, all people died. He was going
to land at the airport to come back home.



((((((



Post Edited ( 01-10-07 05:14 )