MAR - Makeshift Asteroid Redirect Challenge

[Kasuha]

To make the wait for the ARM release a bit shorter I thought it might be good idea to offer a makeshift challenge to anyone interested in how 3000 ton payload handles in free space. Of course I cannot provide any new parts or improved maneuver nodes but if you manage to finish this challenge, you should be comfortable doing actual ARM missions

Kerbin astronomers noticed a massive object of unknown origin which will pass near Kerbin in less than a month. Kerbin is not in danger but according to analyses it might be very useful to capture and park it in nearby orbit as it appears to contain massive amounts of rocket fuel which could be used for interplanetary missions.

Official objective of the challenge is to capture the object and deliver it to Mun orbit, preferably prograde, circular, and equatorial.

The challenge uses only stock parts but you are allowed to use any mods you feel like. There will be no ladder or scoring - if you do it and are happy about it, post your result.

The object weighs 2884 t, most of which is rocket fuel. Preferred approach is to deliver the object to its final destination without draining any of its fuel but if you do, be careful about keeping it balanced.

Object has six standard sized docking ports which can be used to "grapple" the mission ship to it. All these ports are guaranteed to point through the object's center of mass unless fuel is drained from it unevenly. It has also a probe core but no propulsion or source of electricity. Docking ports are separated from fuel by parts with no fuel crossfeed so your rocket cannot drain fuel directly from it.

Warning: the object is made of about 200 parts.

To start the challenge, make a new sandbox save and copy this quicksave file into its directory (...KSP/saves/name_of_your_save/). Then deploy a any ship on launchpad or runway and press F9 to quickload. You will be brought right to the object.

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[Helix935]

couldn't you just welded the parts of the object?

[GusTurbo]

This is awesome! How stable is the "object" when moving it? Any tendency to explode?

[astropapi1]

Holy mother of [insert deity here], how massive is that thing?!

[Kasuha]

This is awesome! How stable is the "object" when moving it? Any tendency to explode?

Object has some struts that hold it together so it should be fairly sturdy for reasonable amounts of acceleration but it breaks up spectacularly under 1G on launchpad.

I did not test it too much but the docking port's connection was able to withstand over 200 kN of force on pull.

Holy mother of [insert deity here], how massive is that thing?!

2884 t

Edited March 29, 2014 by Kasuha

[Red Iron Crown]

Brilliant idea, and takes some of the sting out of not getting 23.5 this weekend.

Is the fuel in all those tanks transferable? If so the challenge is much easier than it appears at first glance.

[CalculusWarrior]

I agree with Helix, you could weld those parts together, making for a stronger final object, as well as reducing part count for those with less powerful machines.

[SlayerMcGee]

Great challenge, thank you, I will probably give it a go. I definitely want to see what happens when this thing hits Kerbin!

[Kasuha]

Is the fuel in all those tanks transferable? If so the challenge is much easier than it appears at first glance.

Yes all the fuel is transferable (I'm not sure if it can be made non-transferable) and it's up to you if you decide to use it or not. You may consider it "normal mode" using the fuel and "hard mode" not using it. Even with using the fuel the trajectory is fairly inclined.

You need about 40 m/s dv to get it to elliptic orbit inside Kerbin SOI. You need about 10 m/s of dv if you intercept it much sooner and send it to Mun slingshot with the same effect and you can get it on equatorial orbit at the same time as a bonus. But there's nothing set about what you're supposed to do with it, just have fun

I agree with Helix, you could weld those parts together, making for a stronger final object, as well as reducing part count for those with less powerful machines.

I was trying to make it stock, I'm not sure if the welding mod isn't mandatory if you use welded parts, never used it. But I believe it should not be that bad because you need to drop your lifter on the way there and with it you're probably going to drop some 200 parts anyway. Except if you really plan to use the "object"'s fuel to stop it.

Regarding the sturdiness ... well, it will probably break if you bring some mainsails to move it around. But you don't need that much thrust to move it around.

[Red Iron Crown]

Kasuha, I don't know how much effort goes into setting the save file up, but is it possible to make one with at least one 2.5m docking port?

[mhoram]

You posted this challenge with a perfect timing ... less then 1 hour before I finished my first asteroid tug.

The perfect challenge to test it.

A descption of my ship is available here.

Here is my mission profile with the help of MechJeb (values in brackets denote the dV left after the burn)

Launch into a 85km orbit (6500).

Transfer burn on day 1 to the asteroid (5106)

Adjusting approach after leaving Kerbins SOI (4450)

Fine tuning with RCS

Match orbit with asteroid in 2.4km distance (3520)

Approach asteroid with RCS at 5 m/s (without timewarp, beacuse asteroid "jumped" during timewarp)

Docked (159 (adjusted to new shipmass with asteroid))

First burn retro->prograde Kerbin encounter (132)

Second burn Kerbin capture (54)

Third burn inclination adjustment (0)

I ended up with an 80876 x 16272 km orbit with an inclination of 11.45° prograde without drawing resources from the asteroid.

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Some things I would wish for:

- The asteroid clamp in the ARM update should be much more stable than the normal docking port.

- A dockingport in this challenge that is placed asymmetrically ("real" asteroids don't have dockingports which makes alignment nearly impossible).

[sgt_flyer]

@mhoram - in the ARM, the grappling device is articulated - you set the grapple into 'free move', and target the center of mass of the ship + asteroid (which is a new target mode) . Then you rotate your ship around the grapple, thanks to it's hinges (while still attached to the asteroid) to line up your ship with the center of mass, and lock the grapple in position.

So in ARM, it will be much more easier to be lined up with the CoM than you think

Edited March 29, 2014 by sgt_flyer

[mhoram]

@sgt_flyer thanks for the info. Did not look at all of the videos - the one I have seen showed some serious rotation during acceleration.

[ihtoit]

hmmm... looks like a very interesting challenge, with about as randomly unbalanced a mass as you can get without going outside and picking up the first rock you see. Yes I know it's a spherical mass of tanks, but you know what I'm saying. It's giving me ideas for an epic scenario, this is.

(BTW, my solution is to use KAS struts in lieu of large docking ports to secure the thruster to the mass, hack in some fuel transfer lines via KAS as well to drain evenly and use the fuel available to "nudge" the mass into Munar orbit. I managed to get it in a 24 degree orbit at 38kmx31km using a ring of Luvodicus super atomics. Total fuel used from the mass: 15l. I had expected to have to use a lot more since my launcher was 282 tons on the pad (mostly engines in single-stage pull configuration a la my Starflight One launcher and ditchable tanks with barely enough dV for a direct burn intercept).

[Kasuha]

I'm just in about half of the challenge myself, with one launch (500+ parts ship) and so far I have not encountered any significant problems with a 6-nuke tug. The "object" can take that load with no problems.

Edit: finished, parked the "asteroid" in elliptic equatorial prograde Mun orbit (150x400) in one launch with enough fuel left to return my kerbals back to Kerbin.

If I didn't screw up once I'd park it in circular orbit too.

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Edited March 30, 2014 by Kasuha

[frizzank]

Um you could just use one of the asteroid mods out there already?

Plug \/

[The Destroyer]

Well, I mean, you could... but this is stock!

[ihtoit]

errr... sure, which existing mod shall I dump so I don't blow my 4GB memory load limit?

[Claw]

Um you could just use one of the asteroid mods out there already?

http://i.imgur.com/1jqQMvf.jpg

Plug \/

Kasuha was making a stock challenge. Even if you only loaded the asteroid mod, you'd need another mod to grapple it.

Also Kasuha, thanks for not forcing use of the welding mod. I'm gonna have to give this a try out.

[The Destroyer]

Kasuha was making a stock challenge. Even if you only loaded the asteroid mod, you'd need another mod to grapple it.

Also Kasuha, thanks for not forcing use of the welding mod. I'm gonna have to give this a try out.

Why not put a docking port on the asteroid?

[Claw]

Why not put a docking port on the asteroid?

Sorry, I guess since I haven't used the asteroid mod I assumed you couldn't just attach a docking port with stock KSP.

[The Destroyer]

It is technically a "part" that you "build" in the VAB and then hyperedit it up.