Kerbal Dynamics Railgun

[ihtoit]

The "Boffs" at KSC Command want a speedlaunch platform based on a detachable powered undercarriage and a missile that detaches for unpowered ballistic flight. For some strange reason, they call it a railgun. It's a sabot, strictly speaking, since we can't harness Lorentz forces in KSP, but in principle we're talking about the same kind of effect: instead of high current rails flinging a projectile, we're using sled-mounted propulsion.

THE CHALLENGE:

Build a "railgun" (or "sabot", or whatever you want to call it - it's a powered sled with a detachable unpowered payload) capable of launching a Kerbal.

THE RULES (subject to revision):

- NO welding, unbreakable joints, or any other anti-vehicle-shattering mod.

- NO infinite fuel or other exploits.

- No FAR or procedural fairings.

- The undercarriage may use any legal propulsion system. However, the payload (with the Kerbal on it or in it!) *must* detach *before* the undercarriage reaches the end of the runway.

- The undercarriage MAY NOT leave the ground while the payload is still attached.

- The payload *may not* possess any sort of propulsion or active aerodynamic control surface. Any aerodynamics *must* be completely static.

- SAS/ASAS permitted.

- The undercarriage doesn't have to stop safely, HOWEVER:

- The Kerbal MUST survive.

SCORING:

The distance travelled from the West end of the runway -2km. Assuming you wait until you hit the "27" marker before you launch the payload, as would be sensible to maximise your takeoff speed... and please don't cheat it by oscillating before you launch, I can tell!

LEADERBOARD:

1. sdj64 using stacked Deltas on his paper airplane looking thing, (49980m)

2. Sillychris on the Twitcher, (34601m)

3. Othuyeg doing it Richard Hammond style (video) (screenshot) (we love helmet lithobraking!), (30415m)

4. OhTehNoes in Whatevertheheckitis, (7291m) (did Bob swim a little after landing?? I make it 7941m...)

5. ihtoit in The Railgun Mk.V, (6812m)

6. ihtoit in The Railgun Mk.IV, (4133m)

7. Sillychris with an angled launcher on the Grapeshot, (2410m)

8. ihtoit in The Railgun (1000m)

SPECTACULAR FAILS:

SirJoab with this Trebuchet (static launcher, interesting mechanism...) (-1464m)

PROOF:

1000m (subtracted 2 for debarking my Kerbal)

The Railgun:

Undercarriage launch:

The instant before payload launch:

Free flight: the two SAS units at the back did a stirling job of just about keeping it horizontal:

Chutes deployed one second before impact!

Score:

Edited March 11, 2014 by ihtoit
slight but not significant rewrite of challenge parameters

[cyberklad]

This looks like a challenge to build a powered sail plane launcher. A rail gun is something completely diffrent.

[LordFjord]

So you want me to stuff a poor Kerbal into THIS?

I guess it could work though... smaller ground-based prototypes could launch the projectile up to 1.5km altitude.

Same thing, bigger, with mainsails, enhanced projectile with some wings, a seat and a chute...

Still, a cruel challenge

Its more of a Kerbal slingshot than a railgun challenge though.

Maybe a infernal robotics gigantic catapult could work as well.

Edited March 3, 2014 by LordFjord

[ihtoit]

no, a rail gun uses a propelled very large (usually captive) projectile to propel an unpowered smaller projectile.

This is a challenge to build a large projectile to launch an unpowered smaller projectile. Using rockets and wheels (or skids) instead of utilising the Lorentz effect between two high current rails. The fact that my missile has winglets merely reflects on the fact that the US Navy has had to employ such aerodynamic stabilisers, even on their teeny little 8 pound railgun projectiles (that launch at Mach 7).

(no I'm not talking about fuel-air ram accelerators or spring-piston or gas-ram airguns either. All three completely different technologies).

Edited March 3, 2014 by ihtoit

[sdj64]

Great challenge. Can't tell how well I did with the lack of entries so far but lots of wings are OP in this challenge. My craft only stalled at 10 m/s. Distance is 49980, if you subtract 2km for the runway. I'm tempted to do it again with the same design until I break 50k. I had a lot of trouble at the beginning, with it starting to wobble then shaking itself apart at high speed. My solution was only 2 landing gear, and a ton of reaction wheels on the sled. I took off at around 280 m/s.

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Edited March 3, 2014 by sdj64

[Exploding_Potato]

I guess magical flap energy glitch engines are not allowed

Also i think there should be separate categories - for gliders (wings) and for ballistic ones (no wings), maybe also 3rd category - missiles (say 1 unit of lift per ton)

[SirJoab]

Well, this isn't really a rail gun... and I didn't get very far, but I had fun! I built a trebuche using Infernal Robotics.

The unit:

Launch!

He's flying. Even Jeb's heart rate goes up a little when using this thing.

Descent is a little undignified...

Done.

My distance:

[Sillychris]

Here is my contribution:

2410 meters. And a very fun challenge.

[ihtoit]

I guess magical flap energy glitch engines are not allowed

Also i think there should be separate categories - for gliders (wings) and for ballistic ones (no wings), maybe also 3rd category - missiles (say 1 unit of lift per ton)

1. yeah, 'tis why I specifically disqualified Infiniglide from the off by not allowing active control surfaces on the missile.

2. I'm considering this, depends how many more entries we get over the next few days.

[sdj64]

1. sdj64 using B9 wingboards on his paper airplane looking thing, (49980m)

Actually, that's 4 stock delta wings on each side sort-of clipped together. I think with an even lighter craft with more wings and more engines on the sled you could get up to 100km distance.

[ihtoit]

nice... I've found with this challenge and the Spirit of Kerbin I did for the KSC Land Speed Challenge, that B9 wings have a hard drag limit. Probably best to avoid those unless you're building BIG and SLOW, stock wings do very well for keeping the sled on the ground and the missile in the air (as I discovered with a 67km throw but I forgot to get screenshots! I wonder if I can repeat the feat...?)

[Sillychris]

In case anyone was wondering:

1) Wheels are not required.

2) Capsules are not required.

3) Parachutes are not required.

My pilot bailed out on touchdown and got a little further than the wreckage. Distance: 34.6km

Note: I did not use infinite flap sploit. I also did not touch the controls after deployment of glider.

[ihtoit]

The Railgun, MK.IV: MOAR rockets and BIGGER wings!

Climbing...

Safe splashdown:

Score: 4133m

[problemecium]

no, a rail gun uses a propelled very large (usually captive) projectile to propel an unpowered smaller projectile.

Sorry to be yet another bubble-burster, but that's not a railgun either.

Railguns use the Lorentz force (a weird electromagnetic effect) to propel projectiles: two large metal rails (hence the name) pass a strong electrical current through a metal projectile and the Lorentz force causes it to be propelled along the length of the rails and (unless you built it wrong ;P) out the end of the barrel. (http://en.wikipedia.org/wiki/Railgun)

What you're talking about here is a sabot. Many railgun designs use a sabot, which is basically a big bullet with a smaller bullet inside (kinda like a multi-stage bullet?), and is as you mentioned often captive. That way the railgun can shoot small, aerodynamic bullets that wouldn't fit very snugly in the barrel by themselves. (http://en.wikipedia.org/wiki/Sabot)

Of course the challenge is still good, especially since we can't build an actual railgun in KSP.

[ihtoit]

it is, as much fun as the Thrust KSC Land Speed Challenge - except instead of brakes, you have to eject at the right time and go for distance more than speed (though a decent fling off the end of the runway helps LOADS)

[sdj64]

What sort of speeds are you all taking off from?

[ihtoit]

my last one hit 294m/s. I reckon a takeoff from a Thrust KSC challenge car would fling a missile around the planet...!

[ihtoit]

MOAR WINGZ!

The Railgun Mk.V:

Free flight:

Score: 6812m, stall speed sub-10m/s:

[ihtoit]

OK, I think I've got the hang of maximising glide distance...

climb as high as you can until you're at about twice stall speed, then heel over and keeping it just above stall speed, ride the glide slope in. Doable with SAS/ASAS, the lack of active control surfaces negates (or should do) any "infiniglide" effects.

[OTehNoes]

My current effort!

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Score of 7291m! Bob survived, the plane didn't!

[Othuyeg]

Hello, new user here. I decided to give this glider challange a try. The glider is made out of stock parts and managed to glide just about 30 kilometers from liftoff.

My proof is in the form of a video and it can be viewed here... Altough it is a long long glide. Almost 40 minutes.

http://www.twitch.tv/othuyeg/c/3862709

[Othuyeg]

Also, here is a screenshot of the flight data.

[ihtoit]

so here's me sat there wondering where the kerbal was, and he's getting ready to land it Richard Hammond style!

[Othuyeg]

Jebediah asked the scientists "How is it going to land without wheels?"

They answered, while grinning, "Use your head, dum dum."

He used his head as the landing gear.

I am already working on a new design. I believe my problem is actually that I do not have enough weight. I need more mass to achieve more kinetic energy on the runway and therefore allow me to maintain my speed for longer.

Edited March 11, 2014 by Othuyeg

[ihtoit]

ah, the paperclip weight on the nose technique. I like it.