Request Orbiter Space Shuttle Re-Entry

[railfanatic844]

Can anyone post a step-by-step tutorial on how to do a manual re-entry?

-AJ

 

[kevin580]

Re-entry Tutorial

Do you mean something like this one?

 

[railfanatic844]

i'm sorry but, that has to do with the delta glider....not the shuttle....

ii'm looking for a walkthrough on shuttle re-entry

 

[kevin580]

That's almost the same.
Don't make the things with the DG-IV computer, the MFDs are enough for that

 

[blixel]

I'm interested in this too. I'm almost 1-year into Orbiter now and I still don't use any additional spacecraft, not even the very popular Dan Steph DGIV or Altea Aerospace XR2. I spend the vast majority of my sim time with the standard (non scramjet) Delta-glider.

With the Delta-glider (and AeroBrake MFD), I have finally figured out how to get in the proverbial ballpark of KSC without burning up or over-stressing the craft, but I can't say the same for Space Shuttle Atlantis. The problem I run into with the Space Shuttle is that it doesn't have retro engines like the Delta-glider.

When using the Delta-glider to perform the de-orbit burn, I have already rolled the Delta-glider so that it's horizontal with the horizon, and pitched up to 1.4 degrees. I use the AeroBrake MFD's AoA hold AP to maintain the AoA. I then fire the retro engines until the graphic shows that I am on track to reach KSC. (And finally, throughout re-entry, I use translation as needed to keep me on target.)

This method doesn't work with the Space Shuttle though. You have to flip the Space Shuttle retrograde to make the de-orbit burn. Since AeroBrake reads the current orientation of your craft to makes its calculations, you don't have a good way to know when to quit burning. And then when you flip around to prograde, everything is recalculated and you're so far off track that you have to flip to retrograde again, burn again, then flip back around, etc.. Also, it doesn't seem to me that you can use AeroBrake's AoA hold AP with the Space Shuttle; It oscillates so much that it's of no use.

At least with the Delta-glider, if I come up a little short, or go a little long, I can fly the Delta-glider back to KSC like an airplane. But you don't get any do-overs with the Space Shuttle.

So, for what it's worth - I think it's a great question that railfanatic844 has asked and I really hope someone has some tips for us n00bs. I have looked at the Re-entry for Dummies tutorial, and I just don't see how it applies to the standard Delta-glider or the Space Shuttle Atlantis. (Other than the very abstract, overarching, high level principals.)

 

[Tommy]

Since AeroBrake reads the current orientation of your craft to makes its calculations, you don't have a good way to know when to quit burning.

AerobrakeMFD only takes aerodynamic effects into consideration when you are below 200k altitude. As long as you are above 200k, it doesn't matter what the ship's orientation is - it will be calculating a purely ballistic trajectory.

None of the stock vessels are capable of a realistic high AoA re-entry. For the low AoA re-entries you will have to use, the main "trick" is velocity management. To change the rate at which you are losing velocity you have to change your altitude. The lower you go (and the stock vessel's don't burn up if you go too low) the faster you will lose velocity.

The easiest way to manage your altitude is to re-enter at around 90 degrees bank, with some "up" elevator trim. This allows you to adjust the VACC with small adjustments to the bank angle. You can perform "roll reversals" and make slow "S turns" to keep yourself heading toward the target base.

By the time you get down to about 60k altitude, you should have your VS pretty close to zero, and use SMALL changes to the bank angle to change the VACC, which will in turn change the VS. Keep the VACC low - no more than 2 m/s, and keep the VS at no less than -100 m/s (between -100 and -50 m/s works well).

You'll need some practice to learn how to manage your velocity - learn what speed you should be at for any given distance from the base. Keep in mind that the last 1500 m/s of velocity will drop quickly, so it's easy to come up short. Velocity will seem to drop slowly at first, so it's easy to overshoot. With practice you can learn to "balance" the velocity and end up where you want. Early on, you want to be careful about slowing down to slowly, and towards the end you need to worry about slowing down too fast.

There's no "easy" way to land the stock shuttle, you'll need to practice and pay attention to way your altitude affect your airspeed. There is no way to provide a "step-by-step" tutorial - it's very "seat-of-the-pants".

 

[blixel]

AerobrakeMFD only takes aerodynamic effects into consideration when you are below 200k altitude. As long as you are above 200k, it doesn't matter what the ship's orientation is - it will be calculating a purely ballistic trajectory.

Ah, I did not know this. So if you're above 200k, you can be prograde, retrograde, normal, antinormal, or any other orientation and it's not going to change how AeroBrake calculates. That's a very good tip. Do you know if it's exactly 200km? Like hard-wired into the code?

There's no "easy" way to land the stock shuttle, you'll need to practice and pay attention to way your altitude affect your airspeed. There is no way to provide a "step-by-step" tutorial - it's very "seat-of-the-pants".

I see. I have been starting to wonder if that was the case. I'm starting to think that the stock crafts like the Delta-glider and Space Shuttle Atlantis are only practical for certain tasks. The Delta-glider does well rendezvousing with the ISS and going to the moon, but for what would otherwise seem like a standard task, landing back on Earth, the Delta-glider seems like it's not quite up to the task if you're looking for a highly procedural way of doing it. And the Space Shuttle is even worse.

The default Space Shuttle can be used to learn basic orbiting stuff (apoapsis, periapsis, eccentricity, etc...), but bringing it back home from orbit feels like a dirty hack. You just know NASA has better technology and a more highly refined procedure than "seat-of-the-pants" de-orbit, re-entry, and landing.

So, perhaps it's time I expand my fleet.

 

[Tommy]

Do you know if it's exactly 200km? Like hard-wired into the code?

This is hard coded into the MFD, at least for Earth. About the only place with a real significant Atmosphere much higher than that is Titan, and you get so much crossrange there that you use MapMFD to stay on course until you can see where you want to land.

One of the nice things about a low AoA High Bank re-entry in a DG is that you don't really need to be perfectly synced with the base - in fact even if I do a Base Alignment burn, I cut it short so I'll have "room" to curve in. You can use a combo of elevator trim and bank to control the VACC very finely - much more finely than just using AoA alone.

 

[railfanatic844]

well i have the de-orbit burn done right, keep at 40 degrees, only problem i have is that i always for short of the runway site and i perform S-turns wrong i think. If i can figure out when an dhow to do the S turns the right way, then i've got it.

-AJ

 

[Tommy]

If you are significantly short of the runway (hundreds of km) it means you should de-orbit a bit closer to the base.

If you are close, but a few km short, it means you aren't staying high enough. You will lose the last 1km/s of velocity very quickly.

I try to stay above 20k altitude and until I'm on initial approach (roughly lined up with runway). I'll try to have about 400 m/s velocity at that point. I hold altitude and let the velocity drop to about 250 m/s, which I try to have happen when the 20 degree down line on the pitch ladder is just a bit short of the runway.

Unlike other flight sims, the approach glideslope will be about 20 degrees. Use a bit of airbrakes if needed to keep airspeed under 250 m/s. When you get close to the ground pull up to lower the glideslope, this will cause your airspeed to drop and you try to hit the runway at about 160 m/s - 180 m/s.

 

[jgrillo2002]

There is also the Glideslope MFD. it has worked for the shuttle so im sure it will alot easier for you to use it

 

[Numero6]

I use the BaseSync to make a deorbit burn, But i don´t know the anticipation angle, altitude and the angle of reentry ideal for the space shuttle

 

[Tommy]

ReA for the shuttle should be between 0.8 degrees and 1.2 degrees. Altitude can be from 80k to 120k. The main thing is to use the same value every time.

Ant is trickier, and will depend on how you set the ReA and Alt, and will vary quite a lot depending on how you fly the atmospheric portion of thr re-entry. It will vary with the vessel - and with the mass of the vessel (ie, fuel load and payload - more mass means larger Ant) and with the pilot. I would start with an Ant of at least 60 degrees.

You will want to make some test flights. Select some values, such as ReA 1 degree, Alt 120k, Ant 60 degrees, and then make at least 3 attempts using those values. Then, you can see how short (or long) those values leave you and adjust the Ant. Make at least 3 attempts using the same values - this will help you become more consistent during the atmospheric portion, and help you "average" out the variations from one attempt to another. Focus on being consistent - if you come up 500k short on the first attempt, then 200k long on the second, etc, you won't be able to re-enter on target with any reliability.

This is one of the hardest things to do - much harder than launching or docking - so expect to practice quite a bit before you can do it with any regularity.

 

[Scav]

Another way to achieve that consistency throughout your deorbit is to standardize your weight. One of the procedures followed in real life is to dump unnecessary fuel, for three reasons I can see right away:

#1: Less fuel means less weight. The dry weight of the spacecraft is a constant value; the variables involved include how much fuel you have and how heavy your payloads are returning dirtside. NASA runs the shuttle almost completely dry of propellant (+/- 3% in the main tanks) after the initial deorbit burn. I've had a practice of running the DGIV down to +/- 1,000 kg in the mains, and +/- 150 in the RCS tanks. This reduces the glider's weight down to +/- 14,000 kg.

Of course, I've run my DGIV's re-entries a lot more conservatively; I've shot re-entries of a .5 angle, 1.0 ReA, with an altitude of 80km and had enough crossrange to run a serious HAC to final, all the while not heating the spaceframe up past 1,200C at the nose. Your mileage may vary.

#2: Less fuel on the ground means a safer situation for any dirtside workers who handle the vehicle after the flight crew have left. Propellant is often hypergolic, which means if one chemical comes in contact with another, a very big boom can result. :blink:

#3: Less weight on the spaceframe means less physical stress, and less heating on the hull. Imagine a rock skipping across a pond or river. You threw that rock so that the flat side was in-line with the water, right? That means the rock will hit the water, come back up, and hit the water again. It will continue to do this until it loses enough forward velocity that it can't come back up again. Then it sinks to the riverbed.

Now, if you threw that rock so that it hit the water with an angle, the rock would immediately splash into the water, lose all of its forward velocity, and sink. I guess this is the best analogy I can come up with.

Anyway, my apologies if I'm reiterating stuff previously said. Just trying to be helpful.

 

[Numero6]

Thanks to all your advices, I manage to do a reentry with the space shuttle.
I used the Space Shuttle from Shuttle Fleet 4.7, mainly because of the auto DAP wich you engage with the B key. That maintain your AoA during all the reentry and when you perform the S turns.
I know that the AuotFCS is not working for orbiter 2010, but is actually fun for me, do the reentry manual

 

[Blacklight]

The Shuttle is REALLY hard for me to de-orbit from the ISS. For some reason, I NEVER have enough main engine fuel to drop my orbit into the atmosphere. Even when I leave the ISS with a full tank. I always end up as a permanent satelite. (and of course, I launch a shuttle mission to rescue the crew... and then they too end up stranded. :facepalm

 

[blixel]

The Shuttle is REALLY hard for me to de-orbit from the ISS. For some reason, I NEVER have enough main engine fuel to drop my orbit into the atmosphere. Even when I leave the ISS with a full tank. I always end up as a permanent satellite.

Are you trying to de-orbit by burning prograde?

Seriously ... you're doing something very, very wrong. If you orient to the retrograde position and burn 1/2 away around the planet, you will easily drop your PeA into the atmosphere with a relatively small burn.

 

[ky]

My problem with de-orbiting is where I do the de-orbit burn.Does anyone have a strategy of where to perform it?

 

[garyw]

As far away from the landing site as possible. The other side of the planet is good.

 

[ky]

Ok thanks!