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Posted (edited)
8 hours ago, kerbiloid said:

Zero thrust or zero electric power, too?

Zero thrust. Your craft should essentially resemble a glorified lawn dart coasting on momentum only. That said, using EC powered reaction wheels to keep the nose pointed the right way is acceptable, using reaction wheels to spin a prop is not.

8 hours ago, kerbiloid said:

If only the former, what about throwing back heavy parts during the flight to keep being pushed forward with recoil?

A multistage flying catapult thrown by a stationary catapult.

I had not considered the possibility of a multi-stage catapult.
That's why I love this forum! :)

To encourage creativity while keeping things fair:

  • Multistage catapults/contraptions are allowed.
  • The spirit of the challenge is to gain all momentum in one giant impulse, so the stages should be triggered immediately after one another.
  • Specifically, once the craft leaves either the boundary of the runway, or the boundary of the launchpad hex - that's it. No more adding momentum or thrust, staging to convert rotational energy to velocity etc.
Edited by ManEatingApe

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26 minutes ago, PositronLance001 said:

Does it have to be a catapult? I have a cannon that works

In the spirit of diversity and inclusion, all manner of siege weapons are welcome :)
 

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5 hours ago, ManEatingApe said:

In the spirit of diversity and inclusion, all manner of siege weapons are welcome :)
 

Mining sounds tricky, though. 

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I have a glider that is folded up on launch, and then can unfold at max altitude to travel the rest of the distance. Now I need to work on the launcher. I'm thinking an electric spinning catapult, or maybe jet-powered. There will be no engines on the glider itself.

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Posted (edited)
1 hour ago, sturmhauke said:

I have a glider that is folded up on launch, and then can unfold at max altitude to travel the rest of the distance.

Neat, I'd like to see that!

1 hour ago, sturmhauke said:

I'm thinking an electric spinning catapult

That's a good approach. I attempted a basic rotor powered spinner but couldn't get it fast enough with the weak torque. Bolting on some reaction wheels may work better....

A back of the envelope calculation shows that if you could get the craft up to ~600 m/s you could fling it on a pure ballistic trajectory to the island airfield.

1 hour ago, sturmhauke said:

...or maybe jet-powered. There will be no engines on the glider itself.

I'm afraid I'll have to dis-allow reaction engines and decoupler power...(rules have been updated). The reason is that it would make the challenge too easy!

You'll have to craftily spin, twist or flip your way to victory ;)
 

Edited by ManEatingApe

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On 6/8/2019 at 5:13 PM, neistridlar said:

Decided to try out a trebuchet today.

 Wow, the leverage on that thing is crazy.  

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2 hours ago, klond said:

 Wow, the leverage on that thing is crazy.  

Jeb: Hey Bill, I heard of this thing called a "tre-byoo-shay" that can throw a 90 kilogram projectile over 300 meters -

Bill: Hold my beer.

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Posted (edited)

I've been messing around with a piston powered trebuchet...it's extremely entertaining :D

YqHEO6n.png

On the launchpad, roughly oriented towards the airfield.

sfH3uVp.png

This is the most fun part! Timing the release is quite tricky.
It only takes ~0.5 seconds for the throwing arm to rotate this far and the craft is flung at about 220 m/s.

IBEfvCS.png

Not quite there yet...

0XnYi1a.png

 

Edited by ManEatingApe

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5 hours ago, ManEatingApe said:

I've been messing around with a piston powered trebuchet...it's extremely entertaining :D

On the launchpad, roughly oriented towards the airfield.

This is the most fun part! Timing the release is quite tricky.
It only takes ~0.5 seconds for the throwing arm to rotate this far and the craft is flung at about 220 m/s.

Not quite there yet...

 

 

Wow, that is a really neat design! with 220m/s you should be able to glide my plane to the airfield. Maybe all that is needed is to swap out the fuselage for a cone in stead, and possibly add a couple degrees of angle of incidence to the wings you can make it. What L/D are you getting?

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3 hours ago, neistridlar said:

Wow, that is a really neat design! with 220m/s you should be able to glide my plane to the airfield. Maybe all that is needed is to swap out the fuselage for a cone in stead, and possibly add a couple degrees of angle of incidence to the wings you can make it. What L/D are you getting?

Thanks!

L/D is about 11. There's some incidence on the wings, but hastily applied without tuning.

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17 hours ago, ManEatingApe said:

That's a good approach. I attempted a basic rotor powered spinner but couldn't get it fast enough with the weak torque. Bolting on some reaction wheels may work better....

About that... I managed to make a rotor spinner that can get up to 160 rpm with a 500 kg payload, and throw it at around 180 m/s. That's with 8 rotors driving the throwing arm, attached with some high-tech 4th dimensional struts (i.e. abuse of the lack of self-collisions). Problem is my glider design is 8t. Once I add the right counterweight to my throwing arm, it drops to like 30 rpm and launches at maybe 40 m/s at best.

I also experimented with reaction wheel spam. That does help, but is also krakenbait. You have to figure out creative ways to reinforce the rotors, and it also increases the chance of the whole thing exploding before launch. I even managed to blow up the runway a few times just getting up to speed, due to the vibrations.

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6 hours ago, ManEatingApe said:

L/D is about 11. There's some incidence on the wings, but hastily applied without tuning.

I was getting about 17.5 with my design, so you have a lot of potential for improvement right there.

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Posted (edited)

After first trying both rotors and pistons finally settled on hinges to power my catapult. Hinges "stack" very well, allowing a multiple of the maximum rotation of 180 degrees per second from a single hinge.

oQ6wo4y.png

Hinges were organized as series of 4 for speed, each placed 5 in parallel for torque. Each group of 20 was controlled by a separate KAL 1000 track editor. 12 groups overall were attached to a rigid frame of empty Kickback boosters for a grand total of 240 hinges.

HdtcsF2.png

The payload was placed at the end of a lightweight 60 meter throwing arm. Maximum theoretical speed was 4 × π × 60 ≈ 754 m/s.

T6t6vBL.png

See the catapult in action below. Jeb reached the Island Airfield in a time of 3:33

Craft file available here.

Edited by ManEatingApe

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Posted (edited)
5 hours ago, ManEatingApe said:

After first trying both rotors and pistons finally settled on hinges to power my catapult. Hinges "stack" very well, allowing a multiple of the maximum rotation of 180 degrees per second from a single hinge.

oQ6wo4y.png

Hinges were organized as series of 4 for speed, each placed 5 in parallel for torque. Each group of 20 was controlled by a separate KAL 1000 track editor. 12 groups overall were attached to a rigid frame of empty Kickback boosters for a grand total of 240 hinges.

HdtcsF2.png

The payload was placed at the end of a lightweight 60 meter throwing arm. Maximum theoretical speed was 4 × π × 60 ≈ 754 m/s.

T6t6vBL.png

See the catapult in action below. Jeb reached the Island Airfield in a time of 3:33

Craft file available here.

That is just awesome.  Have you thought about hypediting it to some of the moons?  You'll certainly get escape velocity on Gilly.  I wonder about Minmus... (Too lazy to look up the stats and do the math at the moment).

It would also be interesting to see how the lesser gravity and atmospheric density would play out distance-wise on Duna.

Edited by Klapaucius

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Posted (edited)
12 hours ago, Klapaucius said:

 I wonder about Minmus... (Too lazy to look up the stats and do the math at the moment).

Using Kowgan's trusty dV map, Minimus is 180 m/s to orbit and another 160 m/s to escape velocity, then a little extra to Kerbin intercept.

So a device to fling things from Minimus surface directly to Kerbin is within the realms of possibility.

I was thinking about trying to build an automated re-loadable ore catapult.

12 hours ago, Klapaucius said:

It would also be interesting to see how the lesser gravity and atmospheric density would play out distance-wise on Duna.

Sounds fun, if I can HyperEdit with the launch clamps intact, then I'll try it out!

Edited by ManEatingApe

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As Kerbal science marches on, the next concept to be tested was the linear accelerator, 
cAGayXL.png

where a series of rollers was intended to impart increasing velocity to the victim pilot 
BGMsLBP.png

as he/she was haphazardly pummeled mostly in the intended direction smoothly accelerated down the barrel,
LrtCv8R.png 

attaining the muzzle velocity of 15.1m/s! 
lLQTdno.png 

Though ultimately the concept had to be abandoned when the device's maximum range fell somewhat short of the island runway. 
u6LVuWl.png

 

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14 minutes ago, Dale Christopher said:

Excellent concept! @Vanamonde 

(one slight issue >_< it was pointing away from the island airfield...)

Testing did not advance to the point of an actual challenge attempt. This was the vantage point for best display purposes. 

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1 hour ago, Vanamonde said:

As Kerbal science marches on, the next concept to be tested was the linear accelerator,

Very Kerbal! I like it a lot :D
 

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Posted (edited)

Just yet another question :

Can the catapult be electric-powered, rocket / jet-powered, or must be just pure gravitational / elastic-powered?

Edited by FahmiRBLXian

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