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Posted (edited)
On 6/29/2019 at 9:01 PM, ManEatingApe said:

 

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

Craft file available here.

I thought the challenge bans rockets but you are using them? Since you propably know your challenge better than me: What's their purpose?

Edited by jost

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50 minutes ago, jost said:

I thought the challenge bans rockets but you are using them? Since you propably know your challenge vetter than me: What's their purpose?

The Kickback is only there as a structural element for the catapult hinge. Even if it did fire, it's pointing sideways and therefore of no use to launching the pod. Speaking of which, there are no rockets on the pod. Those white trails are from the shockwave, because the pod is going supersonic at launch.

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Posted (edited)
3 hours ago, FahmiRBLXian said:

Just yet another question :

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

Electric (reaction wheel, rotor, servo, hinge, piston) or gravity or both!

No gravity only powered design has made it yet, but it would be really cool if someone manages it!

3 hours ago, jost said:

I thought the challenge bans rockets but you are using them? Since you propably know your challenge better than me: What's their purpose?

What @sturmhauke said - rocket/jet power is not allowed, but fuel tanks and engines as mass or structural parts are totally fine.

The Kickback is handy as a long rigid single part to reduce strutting.

Edited by ManEatingApe

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Posted (edited)

I think it should be possible to build a rotor assembly with a supersonic tip speed, then unfurl a long tip to reach very high launch speed. Think "Ferris Wheel that spins multiple times per second" sort of thing. The problem is the craft then needs to have bullet-like aerodynamics and the ability to survive insane launch forces.

Edited by Pds314

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On 6/30/2019 at 5:01 AM, ManEatingApe said:

 

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

Craft file available here.

My only criticism of this excellent creation is that this video most definitely needs a wicked soundtrack! I suggest "Aces High" by Iron Maiden :)

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42 minutes ago, Pds314 said:

I think it should be possible to build a rotor assembly with a supersonic tip speed, then unfurl a long tip to reach very high launch speed. Think "Ferris Wheel that spins multiple times per second" sort of thing. The problem is the craft then needs to have bullet-like aerodynamics and the ability to survive insane launch forces.

Conservation of angular momentum will bite you the moment you "unfurl" the tip and it ends up subsonic, if I get what you're thinking of here.

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1 hour ago, Pds314 said:

I think it should be possible to build a rotor assembly with a supersonic tip speed, then unfurl a long tip to reach very high launch speed. Think "Ferris Wheel that spins multiple times per second" sort of thing. The problem is the craft then needs to have bullet-like aerodynamics and the ability to survive insane launch forces.

50 minutes ago, Loskene said:

Conservation of angular momentum will bite you the moment you "unfurl" the tip and it ends up subsonic, if I get what you're thinking of here.

I mentioned I was experimenting with folding wing gliders a while back. In addition to conservation of momentum, robotic parts (like my wings, or this proposed unfolding tip) are more prone to breakage under high load. I couldn't launch my glider at sufficient speed and also keep its wings intact. I'll find another use for it though.

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1 hour ago, Pds314 said:

I think it should be possible to build a rotor assembly with a supersonic tip speed, then unfurl a long tip to reach very high launch speed. Think "Ferris Wheel that spins multiple times per second" sort of thing. The problem is the craft then needs to have bullet-like aerodynamics and the ability to survive insane launch forces.

Sort of like a giant whip or something like that?

Dont have the dlc but that would be cool. A fairing bullet plus a command chair would probably work for a capsule thing to protect the kerbal....

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Posted (edited)
2 hours ago, Pds314 said:

I think it should be possible to build a rotor assembly with a supersonic tip speed, then unfurl a long tip to reach very high launch speed. Think "Ferris Wheel that spins multiple times per second" sort of thing. The problem is the craft then needs to have bullet-like aerodynamics and the ability to survive insane launch forces.

How about a heavy weight on the rim of the Ferris Wheel? The maximum speed of a rotor powered Ferris wheel is when the torque from aerodynamic drag equals the torque of the rotors. However you could _slowly_ accelerate a heavy but aerodynamic payload on the rim.

Once up to speed you would move the weight towards the center for a burst of speed (similar to ice figure skaters pulling in their arms and legs during spins)

Edited by ManEatingApe

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Posted (edited)
4 hours ago, ManEatingApe said:

How about a heavy weight on the rim of the Ferris Wheel? The maximum speed of a rotor powered Ferris wheel is when the torque from aerodynamic drag equals the torque of the rotors. However you could _slowly_ accelerate a heavy but aerodynamic payload on the rim.

Once up to speed you would move the weight towards the center for a burst of speed (similar to ice figure skaters pulling in their arms and legs during spins)

Or use many rotors in parallel, or SAS torque in the wheel and just use rotors as bearings.

A different attempt at a solution (it involves Saturn a V-sized crawler dragging around the next best thing to space elevator cables).

I somehow snapped them by going too fast. Probably low impact tolerance. The dark areas in the back are bundles of the cables, which are series of heavy telescoping pistons.

I estimate the cables to be around 2.1 km in length each when fully extended. Each is just under 200 tonnes.

I wonder... if I make my vehicle strong enough, can it over-extend the piston to beyond its limit, thus allowing me to create super strong acceleration over long distances with a <1 tonne cable?

EDIT: yes and no. All types of motorized pistons have an ultimate breaking length of like 100 m, and a tensile strength of several MegaNewtons, yielding beyond about 25 meters. They are far stronger than their motor, but they don't retract with quite the same mechanics as, say, a rubber band.

v9Q8SC1.png

Edited by Pds314

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Posted (edited)
10 hours ago, Pds314 said:

I think it should be possible to build a rotor assembly with a supersonic tip speed, then unfurl a long tip to reach very high launch speed. Think "Ferris Wheel that spins multiple times per second" sort of thing. The problem is the craft then needs to have bullet-like aerodynamics and the ability to survive insane launch forces.

I've actually thought of doing this challenge using the supeesonic tip-ferris wheel. With a second unmanned glider mounted on the other side as a counterweight.

EDIT - It could be around almost 1 km Diameter, which would need Hangar Extender. which in turn, doesn't seem to work on 1.7.x AFAIK. Silly me, I haven't updated mine yet.

Edited by FahmiRBLXian

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Posted (edited)
13 hours ago, FahmiRBLXian said:

I've actually thought of doing this challenge using the supeesonic tip-ferris wheel. With a second unmanned glider mounted on the other side as a counterweight.

EDIT - It could be around almost 1 km Diameter, which would need Hangar Extender. which in turn, doesn't seem to work on 1.7.x AFAIK. Silly me, I haven't updated mine yet.

The biggest problem I have found with this method is that you need some other source of torque. Rotors definitely can't provide the torque for 30 meter ferris wheels to reach supersonic tip speeds unless you can find a less awkward way to run them in parallel. So 1000-meter ferris wheels are useless unless they're in space.

And even then, I tried leaving a 700-meter diameter contrarotating three-sided cable wheel in space overnight. It ripped both rotors off. Even though hypothetically it should eventually reach 460 rpm with no friction, it would need incredibly high tensile strength, as supersonic levels of tip speed would occur at just 10 RPM, and full 460 RPM would have a tip speed of 16.9 km/s. That's enough to not only escape LKO, but reach an Eve encounter. RETROGRADE.

Edited by Pds314

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Even if you could solve the tensile strength problem, I'm not sure the physics engine could handle that.

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I'm really looking forward to the release of 1.7.3. There are several new features that have the potential to considerably advance the state of the art in Kerbal siege weaponry. For example:
 

  • New turboshaft engines Could have the ideal combination of high RPM and enough torque to build an effective spinning Kerbal flinger.
  • KAL-100 Action Groups  Take the guesswork and chance out of when to release your Kerbal to their certain doom...I mean destination. Will allow precise timing of payload separation.
  • Same Vessel Interactions With this we can build gears and chains.
  • Grip Pads Could provide an ideal way to "mesh" gears or other moving parts together.

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Posted (edited)

Switched focus to rotors in order to see what mischief could be caused. Flung Jeb to the airfield in a time of 1:41

@Tyr Anasazi By popular demand a soundtrack is included this time! :)

Craft file here. This works but I've no idea why...which is much more disconcerting than something not working and no idea why :D

Removing the craft fins or changing the pod's auto-strut from grandparent to root results in the rotors reaching a limit at about 135 RPM.
With the above craft file, rotation increases steadily to about 130 RPM, then the rate increases slowly to about 150 RPM. After that there's a runaway effect, and the RPM rapidly increases until about 270 rpm when the contraption tears itself apart.

At that speed releasing the craft in the correct direction is a matter of pure luck, so there were many many attempts before Jeb hit the jackpot.

Edited by ManEatingApe

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Posted (edited)
On 7/9/2019 at 7:10 AM, ManEatingApe said:

Switched focus to rotors in order to see what mischief could be caused. Flung Jeb to the airfield in a time of 1:41

@Tyr Anasazi By popular demand a soundtrack is included this time! :)

Craft file here. This works but I've no idea why...which is much more disconcerting than something not working and no idea why :D

Removing the craft fins or changing the pod's auto-strut from grandparent to root results in the rotors reaching a limit at about 135 RPM.
With the above craft file, rotation increases steadily to about 130 RPM, then the rate increases slowly to about 150 RPM. After that there's a runaway effect, and the RPM rapidly increases until about 270 rpm when the contraption tears itself apart.

At that speed releasing the craft in the correct direction is a matter of pure luck, so there were many many attempts before Jeb hit the jackpot.

Well done - and you beat my time to touchdown too! Is it a challenge to release at the right moment?

Edited by Tyr Anasazi

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7 hours ago, Tyr Anasazi said:

Well done - and you beat my time to touchdown too! Is it a challenge to release at the right moment?

It's a lottery. During the many attempts Jeb was flung backwards over the mountains to the west of KSC, straight up to 16km altitude or straight down into the launchpad at 700 m/s! ;.;

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