Hotel26

Wangari Maathai KSC-Return Mission

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Posted (edited)


The Wangari Maathai KSC-Return Mission
 

iwEZXLR.jpg

 

This mission stems from a discussion in the topic: Describe your "standard" Kerbin re-entry profile...

The mission is about your technique as a spaceplane pilot, not about spaceplane design(Please note this very carefully to avoid off-topic distractions!)

Your mission, should you accept it, is to launch Wangari Maathai east-bound from the KSC pad, circularize between 70 and 75 km and then complete the lap of Kerbin, landing again, intact, on KSC R9/27.

You will then, to participate, lodge a submission within this thread containing:

  1. a screenshot of your vehicle, whole and undamaged (showing particularly wings, engines, heat shield and speed brakes, all intact), at its final resting point on the runway
  2. Pilot Procedure for flying the same re-entry profile.  (Please think of this as a detailed and precise 'recipe': if other pilots cannot fly and endorse your instructions, "it didn't happen".)

Anyone interested, whether or not they have entered a submission, is most welcome to discuss Pilot Procedures submitted and anything related to spaceplane descent and approach-to-land profile technique.  In particular, it is hoped that Pilots will try any and all Procedures of interest submitted; and comment, with or without endorsement, as this feedback/validation is critical to success.

 

rSID0jw.jpg   CulIeh6.jpg

4rYxFI1.jpg   vrMByPm.jpg


Please observe the following:

  • time taken and fuel used do not matter
  • fuel may be pumped during flight, but not dumped
  • the vehicle MAY NOT be modified/tweaked
  • full fuel load must be carried at launch
  • you must circularize within the limits of 70-75 km
  • the use of autopilots (e.g. Atmospheric Autopilot) is permitted
  • mods that effect aerodynamics, e.g. FAR are prohibited
  • settings that effect thermodynamics or damage limits may not be altered from their defaults
  • gear may not be extended at any speed in excess of 150 m/s and may not then be retracted
  • liftoff and return should be in daylight
  • final resting point must have all landing gear on the runway asphalt


Most importantly, let us please acknowledge and respect @Brikoleur 's generosity in subjecting his magnificent Wangari Maathai to the beatings you space jocks are likely to give it.  Do remember that this Mission is about your skill (or lack thereof) and not about his design.  (My deep gratitude to Professor Brikoleur for his permission to run this mission with focus on his most interesting craft.)

Also bear in mind that this Mission, while a Challenge, is NOT a Competition; it is a Collaboration.  There are no points awarded, no leaderboard, no Judges and no winners.  Nor is there necessarily "One Right Way" to bring this machine home.

This is an opportunity to hone or, perhaps, to teach, our skill and/or techniques as a spacepilot jockeys.

The primary objective is that we all learn something and we all have fun.
 

pwMhYiy.jpg

 

Good luck!!                                                     (The fire trucks are standing by...!)

 

P.S. de-orbiting WM with lots of fuel has its challenges but may ultimately be easier than bringing it home after it's launched a payload close to its max tonnage.  Potentially, if this mission stimulates interest, we may run a sequel with a precisely-defined payload, to be deposited into orbit, before returning WM to KSC.

Edited by Hotel26

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Looks like too much fun to not try!  :cool:

On 3/11/2020 at 6:22 AM, Hotel26 said:

gear may not be extended at any speed in excess of 150 m/s and may not then be retracted

^^ This rule is pretty cool and a nice accuracy touch.

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Posted (edited)
1 hour ago, Death Engineering said:

This rule is pretty cool and a nice accuracy touch

Yes, I actually have played with the gear speed limit self-imposed since my first KSP airplane, except of course, I can retract during, say, a go-around.  I use 150 m/s and it is very, very generous!  It's not so much for 'realism' as to enforce good approach planning and to prevent myself getting lazy and using the gear as airbrakes to save an approach.

VLE: see V-speeds

I really do hope pilots get interested in this challenge because Wangari Maathai has a kind of Coffin Corner that will break the mould for lots of "standard" procedures.  If you enter too steeply, you risk 1. burning up, 2. auguring into the ground or 3. pulling the wings off.  If you don't enter too steeply, you will likely just 1. burn up.  :)

I do think it requires a novel approach to land.  But I am not sure I have it entirely figured out, either.  At least, I haven't fully tested how reliable my theory is in performance.  WM appears to present a Puzzle fit for a Mastermind?

It would be most interesting to see what people come up with.

Edited by Hotel26

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1 hour ago, Hotel26 said:

It would be most interesting to see what people come up with.

Will take a run at it this weekend.  :D

As to the 'realism' comment, I'm referring to the 'real' space shuttle (Space Shuttle..) that could only retract when doing reconditioning. It reminded me of playing the old (okay ancient) Shuttle that had that restriction and my button-pushing-knob-turning couldn't resist deploying the gear in space. Oh, I can't retract? We go boom.

"The nose landing gear is retracted forward and up into the lower forward fuselage and is enclosed by two doors. The main landing gear are also retracted forward and up into the left and right lower wing area, and each is enclosed with a single door. The nose and main landing gear can be retracted only during ground operations."

https://science.ksc.nasa.gov/shuttle/technology/sts-newsref/sts-gear.html

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Needless to say I'm flattered.

I built this craft because I needed it, and used it in a career game for a quite a few operations with a fairly wide variety of payloads. I came up with the design because I got fed up tweaking balance, packaging, and aerodynamics on HTOL SSTOs with underslung payloads. This one goes up like a rocket and has drag at the back so it's quite straightforward to fly out, and it's always the same on the return trip so once I got that figured out, it was pretty simple to bring back too. 

I don't find it particularly hard to fly, the main issue is that it is big and fragile and somewhat draggy when empty, which means you need a light touch when bringing it down.

Spoiler

If there's any fuel left on re-entry, I do pump it around to maintain a suitable balance and re-entry attitude -- too nose-heavy and you come in too hot, too tail-happy and you lose control. I look at the attitude control with SAS on and the craft pointed up at my desired angle, and when it starts creeping too far up (or down), I pump fuel back (or forward) to keep it where I want it. With that fuel pumping trick, burning up or tumbling out of control never was a problem for me. 

 

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Okay, 

I like reusable missions and the realism of landing back at KSC so I make a habit of doing it often. This plane flies pretty well for a big heavy beast but it's drag coefficient is higher than I'm used to. I went ahead and landed it with the left over fuel from a mission without payload so it was about as heavy as possible, and I did not move fuel around. 

I use Trajectories, which estimates your landing location on atmospheric bodies. The version that was just released seems to do a better job.

I've added some captions to the video but here are the basics: 

I aim for KSC using Trajectories, it is better to come up short than to over shoot it. Also, I like about a 2100m/s insertion. 

Then I hold an Angle of Attack (AOA) of 15-25 degrees. That's the difference between where you are going and where you are pointed. (Relative Wind vs Chord Line). That increases both lift and drag, so it halts the descent once atmospheric resistance is enough and kills off speed. This is why I don't burn up. 

Once I am flying relatively level I adjust attitude to affect my landing spot. Lift/Drag Max is the best glide angle and I can increase drag by increasing angle beyond this point in order to shorten my glide distance without diving - diving would increase airspeed - and I'd burn up.  So, counterintuitivly, pitch up to land sooner. 

Once I am in sight of the airfield I maneuver into a position from which I can have a 5-10 degree approach. 

I intentionally aim short and come in low so that I can bleed off airspeed. Big heavy birds don't like to slow down. Real airlines use a 3 degree glide-slope.  

Ideally, I flair for landing as I pass over the threshold. 

Enjoy

 

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Posted (edited)
On 3/16/2020 at 9:03 AM, ralanboyle said:

Then I hold an Angle of Attack (AOA) of 15-25 degrees.

Very nice job.  I'm gonna go fly it and see how this feels.  (I had been avoiding AoA > 0 to avoid the heat from the extra drag but it's a kind of "immunization", I suppose!)

I sense an argument in the greater reliability of returning a craft to the KSC that a spaceplane has, in The Great Rocket vs Spaceplane debate.  (Not that I want to re-open worms for supper...  :) )

"It's the Fun, silly!"

Edited by Hotel26

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Posted (edited)

This was a very fun mission. I screwed up a few things.  I overshot and then foolishly tried to compensate and got into a spin. Fortunately, just hanging on got me in thick enough atmosphere to regain control. The leftover fuel was a life saver.

I'm just now going back to rockets so despite the number of hours I have put into KSP, I am still a newbie as far as rockets are concerned. Planes, however, I know well.  Once I regained control, I found the aircraft incredible easy to fly.  

Also, I think I disqualified myself because I put down my gear at about 170. I rarely think about speed, I just put down my gear at the time that seems right to me, so I was not even thinking about it.

 

 

 

Here is a speeded up video: I did hit quicksave a few times just in case, but never used them. The game also got briefly paused due to the cat.  I did not edit anything, however.  I made a second attempt which was far, far better except I should have flared up a bit. I came in a bit too hot and blew up at about 35,000 meters, almost within sight of the KSC.

 

Edited by Klapaucius

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Posted (edited)

Just for fun, I did another attempt, except this time I launched retrograde from the Dessert Launch Site.  Again, I overshot, and this time was 17 k short of the runway when I landed.  Oh well.  Valentina is fit. She can walk.

 

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@ralanboyle  Impressive textbook run.  What's the funky red line on your maneuver at 0:25?

Edited by Klapaucius

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2 hours ago, Klapaucius said:

This was a very fun mission

You did a good job.  I felt sure you were going to lose a wing somewhere during that turbulence but you held it together!

 

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3 hours ago, Klapaucius said:

 

@ralanboyle  Impressive textbook run.  What's the funky red line on your maneuver at 0:25?

Dude, If you like atmospheric flight you've got to try the "Trajectories" mod. It's a game changer for landing at KSC, or hitting specific islands on Laythe, or building a re-serviceable base on Duna or Eve. It doesn't really do the work for you but it estimates your landing area better than stock. 

Also, good job with the recovery but, as a pilot IRL, I'm not sure I'm man enough to take on an Approach Procedure that includes a flat spin recovery. :o

 

4 hours ago, Hotel26 said:

Very nice job.  I'm gonna go fly it and see how this feels.  (I had been avoiding AoA > 0 to avoid the heat from the extra drag but it's a kind of "immunization", I suppose!)

I sense an argument in the greater reliability of returning a craft to the KSC that a spaceplane has, in The Great Rocket vs Spaceplane debate.  (Not that I want to re-open worms for supper...  :) )

"It's the Fun, silly!"

Thanks, all I know is that this is how the Space Shuttle and the X-37B bleed off speed. The Commanders of the Shuttle would also perform the same maneuver to the side rather than up if they wanted to increase drag without increasing glide distance, it would change the course to the left or right so they would have to roll and perform an equal maneuver in the opposite direction to get back on course. This created an S shaped approach if the shuttle was above nominal speed and altitude. So, if you find yourself coming in too hot AND too high you might try that. If you increase your AOA too far, the plane will stall (yes, even at supersonic speed) and you may enter a spin like @Klapaucius did. 

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