Swoop Da Woop: The Kerbin Diving Challenge

[Reverie Planetarian]

This was a challenge borne of something that occurred to me as I was making an orbit in one of my ships one day.

Orbiting a planet is all about flying so fast that you can throw yourself at the planet or other heavenly body and miss. It seemed like you could do that as close to the surface as you dared in the orbits of the Mun and Minmus, but could you do that around Kerbin?

The wheels in my mind turned: more than messing around with gliders, this is a challenge worth finding out about, just to see if it's even possible: is it possible to approach fast enough to pull off an orbital dive into and out of Kerbin without flying apart or being unable to return by way of atmospheric drag?

I want to find out, and I invite you to find out with me.

The rules of this challenge are simple: get into an elliptical orbit around Kerbin, put your periapsis as close to the surface of the planet as you dare, and hang on tight. Dive out of the heavens, into the planet's atmosphere, then tear back into space. You have to pull off an orbit after this move to prove you've survived. If you fly apart, cannot return or otherwise can't continue into an orbit from which you can land your ship, it doesn't qualify. You have to launch, do your diving orbit, climb back out of the atmosphere, then land safely. No parts of the craft may decouple during the dive orbit, nor the second exit unless it's specifically for landing later.

Record photos of your ship, the more the better. Please try to record your flight at apogee, in the dive, afterwards and at landing. Anyone who can record a video is free to do so.

The goal is to see how close to the ground or the water's surface you can get without crashing, and how fast you can do your flyby, becoming the fastest atmospheric vehicle to ever cut the air of Kerbin.

I'll keep the score for two different classes: spaceplanes and rockets, obviously. These classes will be further split into two other classes: Stock (all stock parts) and Modified (mod pack parts are allowed). At no point is it permissible to modify any parts' values.

Now as I'm something of a WipEout fan (and since PC games don't really have a gamerscore, per se), I'll be keeping track of Achievements and ranking them using Medals. I'll be giving accolades to pilots who can do the following:

Gold Medals

Surface Tension: Get the lowest dive altitude out of all entrants without crashing.

Intercontinental Ballistic Miss: Get the lowest dive altitude out of all entrants' rockets.

Firebird: Get the lowest dive altitude out of all entrants' spaceplanes.

Double Dip: Do two successful dives in succession before landing safely.

Sky's The Limit: Have the lowest possible altitude at apogee while still exiting Kerbin atmosphere fully, then complete a successful atmosphere dive and return.

Kerb Icarus: Gain the highest possible altitude at apogee without entering solar orbit, then complete a successful atmosphere dive and return.

Going Ballistic: Exit the atmosphere after diving without using engines.

Bulls-Eye!: Land on the runway at the Kerbal Space Center.

Silver Medals

The World's Biggest Immelmann: Perform your dive upside-down at all points during atmospheric entry and exit.

Tot Rod: Have the lowest-mass possible craft to successfully dive and land in succeed at the mission.

Great Big Whiff: Have the highest-mass possible craft to successfully dive and land in succeed at the mission.

One Shot, One Thrill: Complete the atmosphere dive challenge with a single stage.

Diving Stick: Perform the atmosphere dive without using any SAS or MechJeb.

Bronze Medals

Pass Gas: Perform a dive without using RCS.

Missile With A Kerbal In It: Complete an atmosphere dive with a single-occupant craft.

Triple Swoop: Complete an atmosphere dive with a three-occupant craft.

Pow, To The Mun: Perform your dive with your apogee past the Mun, but not past Minmus.

Cold Shot: Perform your dive with your apogee past Minmus.

As one last note, feel free to share your craft files in posts, should you be successful.

Good luck, and good flying!

Edited September 12, 2012 by Reverie Planetarian

[MaverickSawyer]

Two questions:

1. Does Mechjeb qualify as an ASAS?

2. Can you run engines during the pass through the atmoshphere?

[Clouds]

I'm not sure I get this. It seems like it's going to be either,

A. what is the lowest you can go into the atmosphere such that you are left with just enough speed to exit the atmosphere again (and what constitutes a "victory orbit"? It's not an orbit without additional thrust; your periapsis will remain in the atmosphere even if you coast back out of the atmosphere, and I'm envisioning a dive stage that is nothing but a mk1 capsule and a non-deployed parachute), or,

B. a re-entry shuttle that is, effectively, on its own an SSTO such that you fly down in a decidedly non-orbital (ballistic) way and decide "whoops gotta go back to space" instead of landing the first time around (theoretically capable of 1m lowest altitude).

This would make more sense to me with a rule-set such as "no thrust between descent apoapsis and post-dive apoapsis; must raise periapsis above atmosphere after dive; no magic turbines".

[iplop]

Very interesting challenge!

I may take you up on this one.

[nhnifong]

I'll have to do this one, my recent simulated interplanetary rescue craft came into Kerbin for an aerobraking maneuver at around 3500 m/s and dove to about 35 km, So I know I can at least get that far. It's probably easier with wings. I'm not sure if you meant to allow engines to burn inside the atmosphere, so I'm just going to assume not, because that's a lot harder. I'll see you when I finish!

[Lemjack]

It will be interesting to see the speed that is needed to achieve this!

[cardgame]

If you can't burn engines inside atmo it will be a lot harder and IMO less fun. Dipped to ~31km and burned to nearly 3400m/s to get out of it after a failed orbit calculation

I'm glad you made this challenge, has been on my mind ever since I did that. Will try for sure sometime soon.

[Nao]

So, me first. All stock except for mechjeb and fuel fix mod. I didn't use mechjeb for more than just a reference thou. So i would personally called it "stock"

Pictures: (6)

http://imgur.com/a/NIa0D/

Lowest alt in orbit 29756m , (Pe before entry was 30637m and Ap of around 82Mm) i didn't screen-shotted that but i remember having Ap after dive close to 222 km. Landed safely after one orbit.

The only trick i used was adding 5,4 tons of ballast, i wonder what other wacky thing will you guys do, shooting out of LowKerbolOrbit? Using wings? Maybe getting along with the kraken .

Good luck!

edit: added craft file, it had much too much fuel, whole stage 4 of two tanks and areospike was unused, also i had to burn like 150l of useless fuel from stage 5 before the attempt.

Edited September 12, 2012 by Nao

[Switchblade88]

The only trick i used was adding 5,4 tons of ballast, i wonder what other wacky thing will you guys do, shooting out of LowKerbolOrbit?

SNIP

it had much too much fuel, whole stage 4 of two tanks and areospike was unused, also i had to burn like 150l of useless fuel from stage 5 before the attempt.

But; the extra fuel would help with inertia... the mass... why?? D:

Or at least burning in on your approach to raise your apogee to use the fuel for something towards the mission (this is allowed, right? I'm not clear on this scenario)

Anyhow, this challenge looks a blast. Actually reminds me of 'Farscape' (speak up if you're familiar!)

Perhaps we shall thwart the Krakensbane's good activities with our presumptuous planet-buzzing!

[Nao]

Since in KSP drag equation uses mass instead of area, more fuel (0.2 drag coeff.) would give me bigger drag losses since most of my ship mass comes from RCS thrusters 5,4t of 0,01 drag coeff. mass.

My point in this challenge was to test if ballast idea is good, i had no idea of using that fuel efficiently. In retrospect i could burn toward kerth to gain much more speed but that comes after I'm beaten haha

[nhnifong]

So, me first. All stock except for mechjeb and fuel fix mod. I didn't use mechjeb for more than just a reference thou. So i would personally called it "stock"

Where's that fuel fix mod?

[pebble_garden]

Where's that fuel fix mod?

Try here. I think that's what you're referring to?

[Reverie Planetarian]

I'm not sure I get this. It seems like it's going to be either,

A. what is the lowest you can go into the atmosphere such that you are left with just enough speed to exit the atmosphere again (and what constitutes a "victory orbit"? It's not an orbit without additional thrust; your periapsis will remain in the atmosphere even if you coast back out of the atmosphere, and I'm envisioning a dive stage that is nothing but a mk1 capsule and a non-deployed parachute), or,

B. a re-entry shuttle that is, effectively, on its own an SSTO such that you fly down in a decidedly non-orbital (ballistic) way and decide "whoops gotta go back to space" instead of landing the first time around (theoretically capable of 1m lowest altitude).

This would make more sense to me with a rule-set such as "no thrust between descent apoapsis and post-dive apoapsis; must raise periapsis above atmosphere after dive; no magic turbines".

B was my intent, honestly. But I wanted to see if this could be done at all first, so I didn't specify...

At first I did think that it was possible to do it entirely ballistically though.

[nhnifong]

Alright! My strategy was to hit the atmosphere as fast as possible, and aim as low as I could while my apoapsis after aerobraking was still above 70 km per second. (mechjeb predicts this for you)

I used mechjeb and the fuel bug fix. I did use mechjeb's smart A.S.S. for manueving. but besides that it's stockish.

Further comments are in the imgur album.

http://imgur.com/a/5YuNu

My lowest point, 23,303 meters altitude, travelling at a whopping 4356.8 meters per second! That's Mach 12.8!

Now shower me in medals!

[Ekku Zakku]

I'm actually quite interested in this challenge, as I was considering using this method to slow down and orbit some of the new planets in .17 while saving fuel. I might give it a shot later if I have the time XD

[nhnifong]

I'm actually quite interested in this challenge, as I was considering using this method to slow down and orbit some of the new planets in .17 while saving fuel. I might give it a shot later if I have the time XD

Aerobraking is nice when the landing autopilot predicts your final apoapsis for you.

[Ekku Zakku]

Oh nice! I'm definitely going to use that, thanks for letting me know XD

[Reverie Planetarian]

Alright! My strategy was to hit the atmosphere as fast as possible, and aim as low as I could while my apoapsis after aerobraking was still above 70 km per second. (mechjeb predicts this for you)

I used mechjeb and the fuel bug fix. I did use mechjeb's smart A.S.S. for manueving. but besides that it's stockish.

Further comments are in the imgur album.

http://imgur.com/a/5YuNu

My lowest point, 23,303 meters altitude, travelling at a whopping 4356.8 meters per second! That's Mach 12.8!

Now shower me in medals!

Right then. So far that's Surface Tension, Intercontinental Ballistic Miss, Pow, To The Mun, Kerb Icarus, Missile with a Kerbal In It and-whoa, hold on a tic, you crashed into the Mun? Hmmm...

But you've proven it's possible, so this one I'll give a pass.

There's your bar, everyone. Now try to clear...erm, go under...over? Whatever. You want to take the Gold? Beat this!

[nhnifong]

Woohooooo!!!

[nhnifong]

Whether you can burn your engines in the atmosphere is almost meaningless. The drag slowing you down is orders of magnitude more powerful than any engine.

[Lemjack]

wow that's crazy that you lost over 3500m/s speed, that is some serious drag, poor Mr Kermin musta had his face squished on the windshield

[Trebuchet-Launch]

I was doing a test run to see if it was even possible, and accidentally (because of overshooting grossly and then hitting the wrong button while on the fastest warp) left Kerbin's SOI entirely, went into Kerbol orbit, dropped my perapsis to roughly Eve orbit levels (I assume, I don't know exactly where the orbit will be), and managed to re-intercept Kerbin. I now really wish I had taken shots - maybe you need a prize for that sort of overkill too! I will probably take an official shot at the prize tomorrow if I remember with this rocket - it does a good job.

EDIT: I didn't bounce back out. On the other hand, the whole exercise was an excellent practice run for an interplanetary mission with a fairly gentle re-entry, for whenever that gets added to the simulation.

Edited September 14, 2012 by Trebuchet-Launch