squeakywaffle
New member
- Joined
- Oct 15, 2008
- Messages
- 4
- Reaction score
- 0
- Points
- 0
Hello, Orbiter-Forum... this is my first post here.
A couple of days ago I hauled my old PC out of the closet and got to playing some Orbiter. I don't have a whole lot of experience with the game, but I can manage to go to the moon, mars, ISS, etc... but one thing I never really managed to do was re-entry. Obviously it's not too difficult with the stock DG because it doesn't burn up and you can just dive straight in, but I really like the added realism of the DGIV and it requires you to fly a more or less realistic re-entry. I had a few successes, but they consisted of me timidly skimming the upper atmosphere for something like half an hour until I had bled off enough speed to safely dig in further, and more likely than not I would make a mistake and die due to overheating of the hull.
There were several problems I was having:
1) This is the biggest one... I couldn't keep the nose of the DGIV up. Aerodynamic forces would inevitably lower it, increasing the heat load and killing me instantly. This confused me because the AP has no trouble keeping the nose up.
2) Although I knew the appropriate entry angle was ~1 degree, I had no idea how to hold it, and always ended up either diving in too deep or skipping off.
3) I would routinely land thousands of miles from my target.
I had trouble finding answers to these questions online. Most people just seem to say 'use the autopilot', which does indeed do a good job, but I wanted to fly it myself. I managed to find a very easy (and fairly realistic, I think) way to do it. I wanted to do a thorough write-up so that all this information is available in one place.
The first step is to adjust your orbit so you will pass roughly over the base you want to land at. I do this by burning normal or anti-normal as needed, as I pass over the equator, which is indicated on the orbit display by the little squares connected by the dotted line (I think).
Once the orbit is correct, get ready to re-enter. The biggest thing is to dump fuel until you're below the maximum re-entry weight for the DGIV, which is 19 tons. The DGIV also has a checklist program on the computer which will tell you to lock retro and hover doors, which is a good idea, and kill the gear hydraulics, which is maybe not such a good idea if you're forgetful (ask me how I know). Do what you want, but you have to dump fuel.
Now, fire up AeroBrakeMFD (if you don't have it skip to the next section, and don't hit your target as precisely). Hit 'tgt' and type in the name of your target base. Now you should see the earth and your orbit, and several colored radial lines. The yellow line is the location of your target. The green line is your current location, in orbit. The gray line will be your estimated landing site, though it won't mean anything yet.
Wait until you're about a third of the way around the earth from your target. Now, perform a retrograde burn (carefully, so as not to overdo it). As your orbit shifts to take you into the atmosphere, the gray line will start to actually indicate where you would end up if you stopped your burn right now. Wait until it is right on top of the yellow line, then kill the engine. AeroBrakeMFD seems to be 'smart', and during this setup it assumes that you will be trying to fly a decent re-entry with an appropriate angle of attack, on average. Once you enter the atmosphere, however, it will dynamically update depending on your current AOA. Now check your re-entry angle (there's a program to do this on the computer). It shouldn't be higher than something like 1.5 degrees. If it is, then maybe you're in a very high orbit- if this is the case, you need to do your burn sooner, further away from your target.
Now, the most important part. To get enough control authority to keep the nose from dropping, do the following: In the cockpit panel view, switch the control switch to elevon and gear. This will enable your atmospheric control surfaces. Now, hit F8, and click 'rot' at the top left. Now, you have RCS and elevons. This will give you enough oomph to keep the nose up in the upper atmosphere, just as things start to heat up. This trick is what makes manual re-entry possible. Without it, it is very difficult, and actually impossible to fly correctly.
Now, switch your flight computer display to the re-entry data screen, HUD to surface, turn prograde, pitch up to about 35 degrees, and wait.
At some point, you will enter the upper reaches of the atmosphere (you can tell because your ship will no longer hold attitude without your help). When this happens, grab the stick, make sure you can see the re-entry data display, and get ready. This is the point of no return. You are going to be concentrating entirely on the 'slope' and hull temperatures on the re-entry display, and, of course, your AOA and roll angles.
It turns out that the workings of atmospheric re-entry are a little counterintuitive. At higher angles of attack, your hull will build up less heat, and your slope will actually increase (downwards). This is because at this AOA, the airframe does not produce a significant amount of lift, and is more or less just falling. However, if you pitch down to a more 'normal' AOA, your hull will heat up rapidly (very rapidly... so if you do this, watch out) and your slope will decrease.
You are going to use this knowledge to manage your slope, keeping it in the neighborhood of ~1.2 if you're me, or maybe a little higher if you're in a hurry, or less, if you're so inclined. If your slope is too high, you're going in too deep, and you need to pitch down to increase your lift and therefore decrease your slope (keep a close eye on your temperatures as you do this, as they will rise). If your slope is too low, you need less lift... pitch up, and you'll see your slope increase. This is all you have to do to re-enter safely. You don't have to fly s-curves or any such nonsense. You only need to do that if you are going to overshoot or miss your landing site (the shuttle is designed to enter with an extra speed 'cushion' that can be bled off as needed to make it land right where it's supposed to).
And that's it. Once you hit ~2500 m/s and 30km altitude, you'll find that you're flying more or less like a plane. Use this to your advantage, and fly in the direction of your target base. You should be within a few hundred km of it, and if you did a good job, you might be right on top of it. A few hundred km isn't good enough for the shuttle (that's why they plan to overshoot and then fly s-curves to bleed off that extra speed) but it's good enough for me, and probably you.
I hope this helps someone. I know I wish something like this had been around when I was banging my head on the wall wondering why I couldn't keep the DGIV's nose up.
I think this general procedure will probably work for pretty much anything... I just use the DGIV here because I think it's the most realistic and hardest to re-enter with safely.
A couple of days ago I hauled my old PC out of the closet and got to playing some Orbiter. I don't have a whole lot of experience with the game, but I can manage to go to the moon, mars, ISS, etc... but one thing I never really managed to do was re-entry. Obviously it's not too difficult with the stock DG because it doesn't burn up and you can just dive straight in, but I really like the added realism of the DGIV and it requires you to fly a more or less realistic re-entry. I had a few successes, but they consisted of me timidly skimming the upper atmosphere for something like half an hour until I had bled off enough speed to safely dig in further, and more likely than not I would make a mistake and die due to overheating of the hull.
There were several problems I was having:
1) This is the biggest one... I couldn't keep the nose of the DGIV up. Aerodynamic forces would inevitably lower it, increasing the heat load and killing me instantly. This confused me because the AP has no trouble keeping the nose up.
2) Although I knew the appropriate entry angle was ~1 degree, I had no idea how to hold it, and always ended up either diving in too deep or skipping off.
3) I would routinely land thousands of miles from my target.
I had trouble finding answers to these questions online. Most people just seem to say 'use the autopilot', which does indeed do a good job, but I wanted to fly it myself. I managed to find a very easy (and fairly realistic, I think) way to do it. I wanted to do a thorough write-up so that all this information is available in one place.
The first step is to adjust your orbit so you will pass roughly over the base you want to land at. I do this by burning normal or anti-normal as needed, as I pass over the equator, which is indicated on the orbit display by the little squares connected by the dotted line (I think).
Once the orbit is correct, get ready to re-enter. The biggest thing is to dump fuel until you're below the maximum re-entry weight for the DGIV, which is 19 tons. The DGIV also has a checklist program on the computer which will tell you to lock retro and hover doors, which is a good idea, and kill the gear hydraulics, which is maybe not such a good idea if you're forgetful (ask me how I know). Do what you want, but you have to dump fuel.
Now, fire up AeroBrakeMFD (if you don't have it skip to the next section, and don't hit your target as precisely). Hit 'tgt' and type in the name of your target base. Now you should see the earth and your orbit, and several colored radial lines. The yellow line is the location of your target. The green line is your current location, in orbit. The gray line will be your estimated landing site, though it won't mean anything yet.
Wait until you're about a third of the way around the earth from your target. Now, perform a retrograde burn (carefully, so as not to overdo it). As your orbit shifts to take you into the atmosphere, the gray line will start to actually indicate where you would end up if you stopped your burn right now. Wait until it is right on top of the yellow line, then kill the engine. AeroBrakeMFD seems to be 'smart', and during this setup it assumes that you will be trying to fly a decent re-entry with an appropriate angle of attack, on average. Once you enter the atmosphere, however, it will dynamically update depending on your current AOA. Now check your re-entry angle (there's a program to do this on the computer). It shouldn't be higher than something like 1.5 degrees. If it is, then maybe you're in a very high orbit- if this is the case, you need to do your burn sooner, further away from your target.
Now, the most important part. To get enough control authority to keep the nose from dropping, do the following: In the cockpit panel view, switch the control switch to elevon and gear. This will enable your atmospheric control surfaces. Now, hit F8, and click 'rot' at the top left. Now, you have RCS and elevons. This will give you enough oomph to keep the nose up in the upper atmosphere, just as things start to heat up. This trick is what makes manual re-entry possible. Without it, it is very difficult, and actually impossible to fly correctly.
Now, switch your flight computer display to the re-entry data screen, HUD to surface, turn prograde, pitch up to about 35 degrees, and wait.
At some point, you will enter the upper reaches of the atmosphere (you can tell because your ship will no longer hold attitude without your help). When this happens, grab the stick, make sure you can see the re-entry data display, and get ready. This is the point of no return. You are going to be concentrating entirely on the 'slope' and hull temperatures on the re-entry display, and, of course, your AOA and roll angles.
It turns out that the workings of atmospheric re-entry are a little counterintuitive. At higher angles of attack, your hull will build up less heat, and your slope will actually increase (downwards). This is because at this AOA, the airframe does not produce a significant amount of lift, and is more or less just falling. However, if you pitch down to a more 'normal' AOA, your hull will heat up rapidly (very rapidly... so if you do this, watch out) and your slope will decrease.
You are going to use this knowledge to manage your slope, keeping it in the neighborhood of ~1.2 if you're me, or maybe a little higher if you're in a hurry, or less, if you're so inclined. If your slope is too high, you're going in too deep, and you need to pitch down to increase your lift and therefore decrease your slope (keep a close eye on your temperatures as you do this, as they will rise). If your slope is too low, you need less lift... pitch up, and you'll see your slope increase. This is all you have to do to re-enter safely. You don't have to fly s-curves or any such nonsense. You only need to do that if you are going to overshoot or miss your landing site (the shuttle is designed to enter with an extra speed 'cushion' that can be bled off as needed to make it land right where it's supposed to).
And that's it. Once you hit ~2500 m/s and 30km altitude, you'll find that you're flying more or less like a plane. Use this to your advantage, and fly in the direction of your target base. You should be within a few hundred km of it, and if you did a good job, you might be right on top of it. A few hundred km isn't good enough for the shuttle (that's why they plan to overshoot and then fly s-curves to bleed off that extra speed) but it's good enough for me, and probably you.
I hope this helps someone. I know I wish something like this had been around when I was banging my head on the wall wondering why I couldn't keep the DGIV's nose up.
I think this general procedure will probably work for pretty much anything... I just use the DGIV here because I think it's the most realistic and hardest to re-enter with safely.
