Flight Question Reentry and landing with XR2 and other spaceplanes - is there a secret to doing it?

[orbekler]

BaseSync is the completely wrong program there, you have the right mode among the "Course" menu, but I am currently not sure how it was properly called...need to start Orbiter.

If you planned, let's say, Moon to Earth, you can straightly use (IMFD) Base Approach /Surface Launch, and when you reach LEO, you're already base synced.

 

[Urwumpe]

If you planned, let's say, Moon to Earth, you can straightly use (IMFD) Base Approach /Surface Launch, and when you reach LEO, you're already base synced.

Yes, it was base approach and the one under Course was Planet Approach, which does a similar role, but not for reentry.

The problem is disabling the lateral components of the deorbit burn, you need to trick a little there finding a really good solution, but if 1000 fps or 300 m/s (depending on IMFD mode) are too much for you in a bad orbit for landing anyway.

 

[Cras]

You will get better results from BaseSync if you use it properly. The final alignment burn should be made AFTER you de-orbit (you should still be around 150k when you get to the last quarter orbit). When you de-orbit, it changes your velocity and period, so the "old" prediction is no longer correct.

I dont think a final alignment burn is at all neccessary when re-entering with a winged spacecraft. It certainly can make things easier if you do an alignment burn after deorbit, but this is really only an option for the fantasy space craft. I certainly have never had enough propellent left in the tank for a final alignment burn when say flying the Space Shuttle, but of course if flown correctly that is not a problem. Flying the space shuttle, if Basesync says I will pass by the base by 400k, I still conisder that a valid pass, as I can make that up with S-turns.

 

[Pipcard]

What's the proper airspeed when landing the XR2? (not vertical speed)

 

[Jarvitä]

What's the proper airspeed when landing the XR2? (not vertical speed)

Around 200 m/s, preferably in the 180-220 m/s range. Above that, it's dangerous to deploy the landing gear, and below, it basically turns into a falling brick.

 

[blixel]

Do you guys have a good method for getting lined up with the runway? Or do you just "eyeball it"? As Tommy mentioned, the HSI MFD is pretty useless. By the time you are in range, it's too late to do anything with the information (unless you are already lined up.)

My non-scientific approach for getting lined up is to try to aim 20k (or so) "in front" of the runway. For example, I was coming down from orbit intending to land at Wideawake International. My de-orbit maneuver had me coming in at a heading of about 40 degrees. Knowing that the runways at Wideawake have a heading of 120 degrees, I tried to keep myself west of Wideawake by 20k (according to BaseSync MFD).

That sort of helps ... but I still run into the problem of not being able to see the runway, so I don't know when to begin banking to make the landing. In my most recent attempt, I waited too long to bank, so I ended up coming back toward Wideawake at a sharp angle - in the other direction. It was too sharp to land ... (so I blew the whole scenario as far as making an unpowered landing goes.)

I was able to apply power and get myself aligned with the runway as I flew past it. Then I flew down range, did an Immelmann roll, and landed at Wideawake on the 300 degree runway. But it's incredibly disappointing to spend all that time on de-orbit and re-entry just to have it all fall apart in the last few kilometers because you can't see where you're going.

I was watching this guy's video:

It looks to me like he has an MFD (on the right) that tells you how to turn so that you'll be lined up with the runway. I looked on OrbitHangar.com and couldn't find the MFD he is using.

 

[Cras]

The MFD in the video is the GPC MFD that comes with Shuttle Fleet. It is very useful during re-entry fas it helps you judge not only runway alignment, but also the HAC and energy management during decent.

I also have Glideslope MFD running as well, which just gives further guides on managing energy and alignment with the runway.

But I come from the flight sim world, so when it comes to turning out of the HAC, I have no real trouble "eyeballing" it and banking out of the turn and straight onto the runway. Eventually, after enough tries, you will get the feel for when to roll out of a turn. But in the mean time, try Glideslope MFD, as it offers a more precise indication of where the spacecraft will be in the immediate future by way of displaying little green "x"s on a horizontal situtation display. This makes flying the HAC very easy to do, and will give you a very good idea of how to roll out of the turn.

Once on final heading with the runway, I try to fly the nose of the spacecraft with the threshold of the runway, and if I have done my energy management right during the descent, it will result in quite a bit of a nose down attitude to keep the speed up around 300 kts. At about 2000 feet AGSL, begin to flare, slowly bring the nose up. This is the critical point, in any DG type craft, from the Space Shuttle to the XR2. The vertical speed prior to the flare is going to be very high. The flare will help kill that down to something the gear can survive, about -5 m/s or less, but the key is to no to do it too soon, or you will kill all lift and end up having the spacecraft stall and just fall straight out of the air at a speed that will certainly do some damage. Shuttle Fleet you do not need to worry about, as it is indestructable (although Orbiter sound will make a crash sound and the speed brakes do seem to display some sort of damage), but the XR2s or the DGIVs will have the gear buckle, and in the XR2, further damage will ensue, such as damage to the wings, the hover engines.

 

[Didaskalos]

I found that if you use IMFD BaseApproach with the right settings, you can use it to deorbit close to your target base from anywhere in LEO. Here's what I did. I loaded the stock In Orbit Undocked from ISS XR2:Ravenstar scenario. I punched up BaseApproach in IMFD and fed it the following: Alt:80k, ReA:1.00, and the trial and error number, Ant:18.00. I use ApT for the Hint (usually about 2k) and that finds a solution that will get you close in Aerobrake. Then after that autoburn I used BaseSync to tidy up the distance on the first orbit. The benefit is that you can use the first orbit without burning to align to the second or third orbit and waiting until 90 degrees away to deorbit. I ran the XR2 out of fuel trying to set that up.

I also discovered that with the XR2, an AoA over 45 won't keep you under -100 m/s vs. (Fire in the sky!) So what I did after performing the deorbit was to go ahead and set the XR2 to 45 AoA and uncap the retros and use the engines (RCS to fine tune) to adjust the projected landing. Not the most efficient use of fuel, but I believe Aerobrake bases its predictions on your current AoA? I also discovered that it's a good idea to undershoot a bit and fly it in rather than overshoot and flip the brick.

Keep in mind, these are the results of my first attempt from the ISS in a stock scenario. I'll try other orbit and other places and see what happens.

~D