My first (Somewhat) Successful Reentry

[Hurricane]

Hi all! :hello:

I wanted to share with you some remarkable achievment of mine (well, sort of :facepalm
So I decided that after knowing orbital insertions, ISS docks and even lunar transfers-it was time for me to go 'hardcore': trying a re-entry.
So, I used the DGIV with the 'docked to ISS' scenario. I undocked, prepared the vessel for re-entry, aligned myself with KSC (using only map- haven't got yet the hang of 3rd party MFDs). And so, I finalized my deorbit: I performed the deorbit burn at about 18Mm from KSC and waited. At about 160Km up I started preparing for the entry interface, so I activated the autopilot. Then I finalized the preparations for the reentry-making sure that I'm just a bit below 19 tons so I'll have fuel should I come short of the landing site. But then, when the flaming plasma started coming, I realized that I will overshoot-seriously. I looked out the window-just in time to see the SLF glowing away glamorously in the shadows of the night. I was about 3-7 km away from it, at about 40 kilometers up, and I knew I had no chance to fix it. So I ditched it.
I thought I'd share some of my insights out of this interesting flight:

First, Grover's excellent tutorial helped me with not getting burned-I suggest you to take a look if you haven't already.
Second, you don't have to have basesync MFD to perfectly align with your base-I could land at Brighton with no trouble without it, and also came VERY close to the KSC SLF using only map MFD.
Third, the "burn at the other side of the planet" rule of thumb is not as straightforward as it sounds. However I did think of a way to calculate the exact position for deorbit burn, I'll add it if it works.
Fourth, be sure to align your plane! In my previous reentry, the DG stopped flaming plasma right above NY, and it was somewhere after Norfolk, 25Km high, Mach 3, when I decided to ditch that reentry-I just couldn't wait to get to the SLF, EVEN if I had enough energy to perform it.

~Cheers, Oz.

 

[SystemsLock]

Congratulations. I just got the hang of reentry too, in the XR2. Really harrowing the first few times, but after that it's pretty much routine.

Sure, you don't need Basesync or even Aerobrake but I have no idea why you wouldn't want to use them. If you use them properly you'll pretty much never over/under shoot too badly and everything feels much more realistic when you plan ahead. I hate having to fudge things at the last minute (it feels unprofessional).

 

[Hurricane]

Congratulations. I just got the hang of reentry too, in the XR2. Really harrowing the first few times, but after that it's pretty much routine.

Sure, you don't need Basesync or even Aerobrake but I have no idea why you wouldn't want to use them. If you use them properly you'll pretty much never over/under shoot too badly and everything feels much more realistic when you plan ahead. I hate having to fudge things at the last minute (it feels unprofessional).

Thanks!

Now about BaseSync and Aerobrake, well, my computer is a 4.5 year old, beaten up, [and ruined by my little brother] pentium 4 machine. It won't let me install anything, it is a miracle that I even got Orbiter 2010 to install.
I will purchase a new one soon, so most likely I'll install the MFDs on the new one.

 

[TMac3000]

Well done
A proper Reentry is one of the most rewarding experiences in Orbiter, right up there with seeing Saturn up close and personal.

Now try an unpowered runway landing I have practiced these extensively, and it took a lot of trial and error to get it right. I'll be happy to answer any questions or dispense advice if you want:tiphat:

 

[Hurricane]

Well done
A proper Reentry is one of the most rewarding experiences in Orbiter, right up there with seeing Saturn up close and personal.

Now try an unpowered runway landing I have practiced these extensively, and it took a lot of trial and error to get it right. I'll be happy to answer any questions or dispense advice if you want:tiphat:

Thanks!
Like I said, I overshot the last one I tried :facepalm:
Right now I'm researching to see if I can find any formula to exactly calculate the distance from the landing site to deorbit, based on the reentry angle (0.7 degrees, right?) and the orbital altitude. Of course it won't be perfect, but at least it'll allow me to more accurately deorbit. :tiphat:
I'd love to hear your experiences and thoughts about reentries, that would be helpful indeed!

~Cheers, Oz.

 

[TMac3000]

Thanks!
Like I said, I overshot the last one I tried :facepalm:
Right now I'm researching to see if I can find any formula to exactly calculate the distance from the landing site to deorbit, based on the reentry angle (0.7 degrees, right?) and the orbital altitude. Of course it won't be perfect, but at least it'll allow me to more accurately deorbit. :tiphat:
I'd love to hear your experiences and thoughts about reentries, that would be helpful indeed!

~Cheers, Oz.

Well, the XR-5 is a heavier vehicle than the -2 or the DG-IV, and doesn't seem to reenter accurately from 180*, so you want to start the burn at 150* from the target instead. Here are the ideal parameters I have found for an unpowered Vanguard landing:
Deorbit from 150*, not 180*
Set Periapsis to 60km

This will get you in the ball park, so you can use Aerobrake MFD to keep on target. Aim for about a 150km overshoot. You should appear on the inset screen at about mach 10-11 and go subsonic within sight of the runways. Good luck:tiphat:

Oh, and try to start from a 360 km circular orbit

 

[statickid]

Even if you come up with a formula, some small details can make variations or things you didnt plan on will not go as you think causing over and under shots, I've found the best thing to do is learn the effects of AoA and bank combinations which are not exactly intuitive and in some cases seem backwards, then you can "fly" home with skill instead of pure procedure, and not every warning light meaning catastrophic failure

 

[marcheenek]

@statickid - true. I have never done reentry that looked exactly the same, despite almost identical retro-burn procedure. What I found is better to overshoot with XR5, but not with XR2.

 

[Hurricane]

Even if you come up with a formula, some small details can make variations or things you didnt plan on will not go as you think causing over and under shots, I've found the best thing to do is learn the effects of AoA and bank combinations which are not exactly intuitive and in some cases seem backwards, then you can "fly" home with skill instead of pure procedure, and not every warning light meaning catastrophic failure

But perhaps the combination of both will come out good?
I come from the world of flight simming, so I am very familiar with the different Alpha/Bank configurations do. It doesn't change all that much from a F-16/18/35/22 to a DGIV/XR. :thumbup:

@statickid - true. I have never done reentry that looked exactly the same, despite almost identical retro-burn procedure. What I found is better to overshoot with XR5, but not with XR2.

That is kinda obvious.
By the way, I get better and better at it-I overshot by FAR less this time. I came up, 2 kilometers to the south of the cape, at an altitude of about 35 kilometers. I was 300 kilometers from the cape when I stopped flaming plasma, and realized that yet another reentry is hopeless.
Who knows, maybe I'll make a proper re-entry before getting a suitable computer to install Orbiter and those MFDs?

~Cheers, Oz. :tiphat:

 

[marcheenek]

Another trick is, if you 'undershoot' and have any scram fuel left, use it to cover the remaining distance.

 

[Hurricane]

Another trick is, if you 'undershoot' and have any scram fuel left, use it to cover the remaining distance.

Indeed, however the DGIV doesn't have scrams.
I'll continue honing my skills tomorrow, and when I'll get the hang of it-I'll post a video and perhaps write a tutorial. I'm also considering trying a skip reentry.

Cheers, Oz. :tiphat:

 

[Tommy]

But perhaps the combination of both will come out good?
I come from the world of flight simming, so I am very familiar with the different Alpha/Bank configurations do. It doesn't change all that much from a F-16/18/35/22 to a DGIV/XR. :thumbup:

It actually changes quite a lot - during re-entry. In a F-16, you decrease your descent rate by increasing your pitch. During a re-entry, you decrease your descent rate by decreasing your pitch rate.


I run Orbiter on a ten year old 900mhz Athlon - and add-on MFD work just fine. You don't install them - you just unzip them into the Orbiter folder. As long as your zip utility works, you'll be fine.

As to the de-orbit, I agree with statickid. The proceedural approach to re-entry probably won't work well in future versions of Orbiter - which will have wind simulation. Learning how to manage your energy will serve MUCH better than trying to figure out the "correct" de-orbit point (since that point will change based on vessel mass, starting altitude, wind (in future versions), etc.

 

[statickid]

yes there needs to be a general "starting point" for each specific vehicle-the formula. However I'm talking about making slight adjustments to AoA and bank while still burning in plasma. I dont know much about the fighter jets but I'm talking about high aoa causing a drop in altitude, leveling causing lift and decreasing temperature, as well as high bank angles resulting in a gradual turn..etc...etc... I usually aim my trajectory to one side or the other, ever so slightly to compensate for and take advantage of the bank drift.

I too have never had identical reentries despite strict procedure.

also I agree, you need to find specific ideas for different vehicles, even do tests to find out range after reentry burn, experiment with how many seconds of cooler level flight increase your range. Actually the post plasma flight is very lienient if you are in a hundred miles or so (vague figure). althoug a hundred miles starts to look prett small when you look at the earth and the speeds involved...

 

[Hurricane]

It actually changes quite a lot - during re-entry. In a F-16, you decrease your descent rate by increasing your pitch. During a re-entry, you decrease your descent rate by decreasing your pitch rate.


I run Orbiter on a ten year old 900mhz Athlon - and add-on MFD work just fine. You don't install them - you just unzip them into the Orbiter folder. As long as your zip utility works, you'll be fine.

As to the de-orbit, I agree with statickid. The proceedural approach to re-entry probably won't work well in future versions of Orbiter - which will have wind simulation. Learning how to manage your energy will serve MUCH better than trying to figure out the "correct" de-orbit point (since that point will change based on vessel mass, starting altitude, wind (in future versions), etc.

Actually, at an alpha of 40 degrees, the only difference is that the F-16 is still controllable at low speeds. That's because you fly fully stalled anyway.
As to the addons, my registry is corrupted and I don't deny a newer computer

yes there needs to be a general "starting point" for each specific vehicle-the formula. However I'm talking about making slight adjustments to AoA and bank while still burning in plasma. I dont know much about the fighter jets but I'm talking about high aoa causing a drop in altitude, leveling causing lift and decreasing temperature, as well as high bank angles resulting in a gradual turn..etc...etc... I usually aim my trajectory to one side or the other, ever so slightly to compensate for and take advantage of the bank drift.

I too have never had identical reentries despite strict procedure.

also I agree, you need to find specific ideas for different vehicles, even do tests to find out range after reentry burn, experiment with how many seconds of cooler level flight increase your range. Actually the post plasma flight is very lienient if you are in a hundred miles or so (vague figure). althoug a hundred miles starts to look prett small when you look at the earth and the speeds involved...

I ditched the formula thingie in that case. However I still have some technical aces up the sleeve (;

~Take care, Oz.

 

[Hurricane]

Okay, after about 10 more failures in the past few days, my ONLY problem is STILL the deorbit burn. I just can't seem to find the right place to deorbit! 17Mm is too close, so is 18Mm. But then 19Mm is seriously too far-I stopped flaming above the Pacific! :shrug::facepalm:

So, anyone wants to share his/her insights about deorbiting?

~Thanks in advance, Oz.

 

[thumper235]

Hey Hurricane,

Looks like we are in the same boat. I have made it through the atmosphere, but I have done so with absolutely no precision what-so-ever. I will check the tutorial you mentioned about as I think I am ready to really start doing this with a little class.

 

[Hurricane]

Hey Hurricane,

Looks like we are in the same boat. I have made it through the atmosphere, but I have done so with absolutely no precision what-so-ever. I will check the tutorial you mentioned about as I think I am ready to really start doing this with a little class.

At least you could use the addon MFDs... I can't do that right now. Nor do I want to...
I'll find the way to reenter, and then I'll write a 'noob's tutorial to atmospheric entry'. Until then... Trial 'n error...

~Take care, Oz.

 

[TMac3000]

Okay, after about 10 more failures in the past few days, my ONLY problem is STILL the deorbit burn. I just can't seem to find the right place to deorbit! 17Mm is too close, so is 18Mm. But then 19Mm is seriously too far-I stopped flaming above the Pacific! :shrug::facepalm:

So, anyone wants to share his/her insights about deorbiting?

~Thanks in advance, Oz.

If you are using the XR-5, try 17,200 km and burn to a periapsis of 60 km. That should put you in the ballpark, but you really need Aerobrake MFD. Your endpoint doesn't stay constant by itself: you have to keep working the nose up and down to keep it in place. This is virtually impossible without the aforementioned MFD.

 

[Hurricane]

If you are using the XR-5, try 17,200 km and burn to a periapsis of 60 km. That should put you in the ballpark, but you really need Aerobrake MFD. Your endpoint doesn't stay constant by itself: you have to keep working the nose up and down to keep it in place. This is virtually impossible without the aforementioned MFD.

It's the DGIV. I saw Samuel Edwards has a reentry chart for it but I can't get it to open the .zip file. Perhaps my new [uncorrupted] computer will be able to run it.
I'm gonna give it another shot, I'll tell you if it works. :tiphat:

---------- Post added at 08:13 PM ---------- Previous post was at 07:19 PM ----------

Okay.
"Houston; Delta, Golf, India, Victor Zero-One here, main gear touchdown!"
"-Copy DGIV 01, main gear touchdown"
"Okay, nosegear touchdown"
"-Copy"
"Houston, Delta, Golf, India, Victor Zero-One here, wheelstop!"
"-Copy, welcome back, congratulations on return to the blue planet!" :tiphat:

[:bananadance::banana::speakcool::woohoo::woohoo::headbang::headbang:]

This is pretty much the summary of the (Imaginary) chatter of my DGIV with Johnson Space Center, Houston on my first fully successful reentry.
(Well, sorta successful: I derailed from the runway threshold on the other side because I flared too soon. No more night landings for me ).

Now, several notes:
1. I find the "range" output on the DGIV second mini-HUD very useful and accurate, try to have it at about 1.5-2.5 times the current distance to your target the entire distance, it'll prove useful to have that spare energy.
2. Next, I made a mistake that almost cost me a safe landing: I steepened my glideslope at about 60 km up. Instead, I could have just made that slight overshoot and made a HAC or some S-turns prior to landing. Conclusion: always oblige to note No.1!!!

Uhm, that's all I can say. Tomorrow I'll make another one, using Aerobrake MFD as an aid, after I'll feel comfortable with reentries I'll stop using it, and write a tutorial, so that my (currently unpolished) technique will be revealed to the public, where all may be able to use it. :tiphat:

~Take care and hail The Probe [], Oz.
[Again: :bananadance::banana::speakcool::woohoo::woohoo::headbang::headbang:]

---------- Post added 02-06-12 at 07:39 PM ---------- Previous post was 02-05-12 at 08:13 PM ----------

Okay, second fully successful reentry: this time I overshot by a bit because I took over the controls just a tad bit too early. I was aiming down by about 20* when I noticed my hull temperatures were as high as almost 1500*. So I pitched up immediately and waited for the plasma to stop, then I waited until the hull temperature went down below 400* and pitched down to -5*. I was about 60 km away and at Mach 5 when I initiated my HAC (should've just made some S-turns instead, so I'd come at a bullseye). After my HAC I was already subsonic, so I decided to make a short burst with full thrust till I get to a reasonable altitude/speed configuration, that happened at 400 m/s and 35 km away from the runway. My landing went perfectly good aside from the fact that the DGIV is a hard ship to maintain centerline alignment with. So I almost went off the runway (all that in dark and no landing lights, hail me! :hail: )

Now, some other notes:
1. The first note that I mentioned in my other post isn't fully correct: Only use it when you're starting to cool down considerably and only fully rely on it when the runway is in viewing distance but you still can't use your instincts to land.
2. If you're going to overshoot, but not that much (That is, you're going to be about Mach 5 when you're above your landing site, that should happen at 20-30 km high,) just deploy your airbrake and make some S-turns, DO NOT EVEN CONSIDER A HAC! At those kinds of speeds, you're going too fast to make a HAC and will never make it, you'll overshoot your landing site and when you're finally aligned you'll come short. MAKE S-TURNS! HACs are for when you're about 10km high, and about to go subsonic AND you're ALREADY above your landing site. That doesn't necessarily settle with the above condition (Mach 5, 20-30km), unless you've got some REALLY good piloting skills and awesome guts. My silly HAC stressed the DGIV to its limits, it was a 3.5 g turn, not something you want to feel for more than several seconds (unless you're an astronaut (

Okay, that concludes this thread. I can now change experience level to "Advanced", accounting for the fact that I did 2 successful reentries and 8 semi-successful reentries without the help of addon MFDs!

I'll write a tutorial soon, so expect one!

~Take care, Oz. :tiphat: