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

[Pipcard]

I've never attempted it before. I want to reenter with the XR2 without burning up, and then glide to and land on a runway without breaking the landing gear.

I have Aerobrake MFD but I'm not sure on how to use it.
How do you make it so that you can do a retro burn at just the right time, so you'll land at just the right place, without guesstimation?

 

[Urwumpe]

If you have never attempted it, attempt it first so you know what awaits you.

Otherwise: aim for 16 m/s² total acceleration on your surface MFD, ignore Aerobrake MFD for a while, and keep AOA constant while using bank for controlling how fast you descent.

The faster you descend (vertical velocity), the hotter it gets and the more speed you loose. When things start to get too hot, reduce bank until you have zero bank. If you are cool and decelleration is below 16 m/s², increase bank to one side. When your ground track travels away from the base, reverse bank direction.

 

[n72.75]

The secret is practice for the most part.

I couldn't find any good reentry tutorials.

 

[Pipcard]

But how do I do a retro burn at exactly the right time, based on my altitude and the distance to the target base?

 

[Urwumpe]

But how do I do a retro burn at exactly the right time, based on my altitude and the distance to the target base?

You don't need to be exact. You can compensate a lot of error during the final reentry, if you just manage to be approximately in the right window. I prefer using IMFD for that task, since it permits plotting a deorbit towards a exactly defined entry interface. But just doing deorbit on the opposite side of earth is good enough.

But remember our words: You need to FLY to your base. Not just keeping your hands off the stick. Enable autopilot of the XR2, set AOA to about 40°, and then use the bank settings of the autopilot to glide you home. The XR2 can do this all really good for you, you just need to tell it how much it should bank.

 

[garyw]

You don't need to be exact. You can compensate a lot of error during the final reentry, if you just manage to be approximately in the right window.

Very true. I do the deorbit burn at the point furthest from the base then control the energy via the aerobrake MFD display making sure i have a little extra which i can burn off with the speedbrake.

 

[dgatsoulis]

But just doing deorbit on the opposite side of earth is good enough.

Probably the best method. Works everytime. All you have to do, is to know how "low" to set your Periapsis altitude.

--Edit--
A direct reentry is even better, but the "opposite side" method is easier to perform.

 

[Jarvitä]

As others have said, from a 350-400km orbit, de-orbit approximately from the other side of the Earth (enable tracking on map MFD, target the base you want to land on, burn when it jumps from the left side of the map to the right side of the map). Immediately after the de-orbit burn, your PeA should read around 40km. Depending on how close to the base your orbit track is, you may have to use XR2's cross-range capabilities by adjusting the bank angle during re-entry. This reduces your range, however, so if you come up short (or overshoot), you should stop the re-entry procedure at around 30km, level off and switch to powered flight (with either scram jets or rocket engines, whatever fuel you have left) to reach the base.

Seriously, with the XR2 on the default settings, it's almost impossible to fail. After an ISS mission, you should be re-entering with enough fuel to cover another 1000-2000km of trans-sonic powered flight if necessary.

After you've done a few practice flights like this, you can try more realistic settings and dumping all your fuel before re-entry for a real challenge.

 

[Cras]

Practice does make perfect. BaseSync is a wonderful tool to show how close to the base you are going to be, and can perform some basic deorbit calculations for you. So can Glideslope MFD.

Aerobrake MFD is great once in the atmosphere because it offers you a very good idea of how short or long you are going to shoot the base. You want to over shoot it so you can fly a HAC and get nice and aligned with your runway with enough energy.

I have never tried the IMFD for deorbit myself, but it did cross my mind after I used it for some rendezvous burns in LEO. I always used IMFD just for going to another planet, and the thought neve crossed my mind until Wishbone brought it up to use it for LEO things.

I never tried a powered descent myself with the XR2, always shooting for a dry and unpowered descent glide to the runway, and after some practice runs it is easy to get the hang of it.

 

[orbekler]

There may be other clips on this topic, however here are two of them (mine, BTW ). They're not perfect, but will give you a rough idea on how to perform a reentry with XR vessels.

[ame="http://vimeo.com/19787701"]http://vimeo.com/19787701[/ame]

[ame="http://vimeo.com/25592340"]http://vimeo.com/25592340[/ame]

 

[scurvydog00]

I'd recommend you watch this tutorial by oceanic and train with the DGIV until you get it down good before attempting the XR2. The DGIV reentry autopilot seems to hold it's final position as indicated by aerobrake rather well while the XR2 is more jumpy and your constantly having to adjust your AOA during reentry to stay on target.

Good luck!

 

[Jarvitä]

I should point out, the Olympus landing tutorial has no relation to reality, at all. If orbiter simulated terrain elevation properly, an Olympus landing would look more or less exactly like a lunar landing.

 

[orbekler]

I should point out, the Olympus landing tutorial has no relation to reality, at all. If orbiter simulated terrain elevation properly, an Olympus landing would look more or less exactly like a lunar landing.

Probably on top of Olympus it would be, cause pressure is 30 Pa, however in Orbiter, at Olympus base pressure is 600 Pa (the Mars mean), making lunar landing far easier.
Actually I've found Mars reentry more difficult than Earth reentry.

Let's see other opinions about this.

 

[Jarvitä]

That's exactly what I'm talking about, there's basically almost no atmosphere left up there. Orbiter puts that base 24km too low.

 

[orbekler]

I don't know if it's intentional, but Olympus Base seems to be situated about 150 km from the Olympus Mons south thrust fault.
Though it's just a guess, this would bring pressure at about the "normal" value of about 600 Pa.

 

[Tommy]

I find the XR-2 easier than the DG-IV for two reasons.

One is that the XR-2's autopilot can adjust the AoA in 0.5 degree increments, while the DG-IV can only adjust in 5 degree increments. This means that one setting will leave you short, and the next (lower) setting will leave you long. As a general rule of thumb, use the setting that leaves you short if your velocity is over 3.5k, and the one that leaves you long if your velocity is under 3.5k.

The other is that the XR-2 has a better glideslope - so you aren't coming in as steep. This makes things a bit less hectic and scary.

Also, I don't bother with the HSI - by the time you are close enough to get a signal you should already be fairly well lined up with the runway (or with your heading alignment cylinder). You can SEE the runway long before the HSI provides any guidance.

During your final approach, aim "short" of the runway, that way when you pitch up you will land at the end of the runway - not the middle. This can make a difference on shorter runways - or the XR-5 which takes longer to stop.

 

[Pipcard]

Where do you get your "heading alignment cylinder" from?

Also, most rentry tutorials are for the DGIV/DGIII for some reason. I want one for the XR2.

 

[Wishbone]

Glideslope MFD, GPC MFD for Shuttle Fleet.

 

[Fabri91]

But it's not a must-have in my opinion. I always fly the alignment "by the seat of the pants", it works quite well after some training.

 

[Jarvitä]

Agreed. Basesync MFD and Aerobrake MFD are a must if you want a perfect, upowered re-entry and landing, but eyeballing the runway shouldn't be too much of a challenge.