Asteroid capture craft for E-type asteroid?

[deepspacecreeper]

hello, does anyone have a design for an asteroid capture and redirect craft that meets the following conditions?

1. can redirect an E-type asteroid from a kerbin collision course with slack fuel

2. (optional) pull the asteroid into kerbin orbit

3. unmanned

4. (optional) no debris left behind

5. fully stock or stock+kw rocketry

If the craft is over 132 tons, pls. include your launcher. if it is under that, it doesnt matter if the launcher is included or not.

I prefer unmanned cause a single mistake is going to fling kerbals into kerbol orbit.

I know that asteroids wont wipe out the kerbals at .23.5 , but i just want to capture them.

If anyone could post their designs, I would be very grateful.

Edited July 2, 2014 by deepspacecreeper

[KerrMü]

I did that twice with this:

But it was manned, and it took 3 (with xtra fuel tank 4) launches and orbital assembly. So it doesn´t fit your conditions. And to be honest: It wasn´t very stable, too. Always wanted to come up with something with more than 1 claw. So I´m curious about other designs.

[deepspacecreeper]

meets two conditions, i may or may not risk a kerbal though

(depends), hopefully its gonna go well. Gives me an idea on how much fuel is needed.

Edited July 2, 2014 by deepspacecreeper

[sedativechunk]

meets two conditions, i may or may not risk a kerbal though

(depends), hopefully its gonna go well. Gives me an idea on how much fuel is needed.

Hello!

Here is the design I did just this past week to capture a class E asteroid. Ironically the night I was planning an asteroid capture, the movie "Deep Impact" was on if you've ever seen that one (great AAA movie from the 90's recommend it if you never watched it). It inspired this rocket design I came up with.

It features two nuclear engines on the side with four smaller space shuttle style thrusters (can't remember the name of them in the parts list). The nice thing about the thrusters is, firing them I get 40 minutes of burn time with .36 TWR. It's nice for catching up with asteroids. The nuclear rockets can burn for 2 hours and 30 minutes so I can safely capture and control the asteroids.

The only thing is, they are VERY HARD TO MOVE. But I did manage to capture this one and get it into a stable orbit. Kind of hard to see the shuttle design but there it is.

screenshot

[Oafman]

I just captured a class E, weighing just over 3000t. To give you an idea of what this might do to your available delta v, I had 2100m/s left on arrival at the roid, and once I had docked this became 42 m/s!

Luckily I had intercepted it a good while before it entered Kerbin's SoI, so I only needed 25m/s to push it's periapsis deep into the atmosphere. Once that aerobraking captured it I had just enough left to push the peri high enough to buy me an orbit's worth of time to move a fuel tanker in and refuel the tug.

I also took a huge amount of monopropellant, but still ran out in LKO. These things turn like oil tankers; it was painful to watch. Took the best part of 5 mins to turn to a maneuver node, and each time I did so I burned stupid amounts of monoprop.

I'm afraid I only got 1 pic, during the aerobrake. What you can see is one of the huge 3.75m tanks, with what I think is one of the KW engines (the 3.75m one that has quite a lot of thrust but is still *reasonably* efficient). There was a big booster underneath this, but I had to use a lot of its fuel to get into LKO, so I refueled it there before using it to push the capture ship out towards the roid. Then I dropped it on the way and made fine corrections with what you can see in the pic.

The thing with 4 claws didn't really work well. I had IR hydraulic pistons under each one, and the plan was to gently nudge up to the asteroid, until the first claw touched (but too slowly for it to grab). Then adjust each piston so all 4 claws are flush against the roid. Then reverse a few metres, and charge forwards with enough speed so all 4 claws lock. I tried it a few times, but the best I could get was 3 out of 4 locked. I used KAS to secure the other one to the roid with struts (ground pylons can be attached to roids), but they broke a couple of times, requiring more EVAs etc. The whole process took ages, so I would not recommend the 4 claws idea, unless you can execute it better than I was able to.

Best of luck. Take more dv than you can possibly imagine you'll need, and have a fuel tanker in LKO ready to move in fast.

[Batz_10K]

This is one I used to capture a fairly small (900t) E-class (with 90 degree inclination change and a retrograde-to-prograde transition...ok so I slightly cheated on the inclination change with a slingshot around the Mun...) - it gives about 300ms with full tanks and a 900t asteroid. (although you get pretty long burn times with LV-Ns)

(sorry the picture is a bit small...)

One of the things I discovered was that some of the stability problems were being caused by flexing of the parts in between the engines and the claw (so having a long rocket with engines at one end and attached by a claw at the other end was quite difficult to control). This design has 12 LV-Ns close to the attachment point of the claw as possible (note you do need to be careful about where you attach the claw to the asteroid so that you can pivot properly). There's also a large docking port at the back so that you can easily swap in extra fuel/monoprop tanks without having to undock from the asteroid. As Oafman mentions, you need a *ton* of monoprop and the asteroids are very slow to turn (the best idea is to turn off sas, get the asteroid rotating and then reverse the rotation as you come up to the manoeuvre node on the navball. then turn on SAS and wait for the oscillations to dampen down (it will take a while).... good luck!

[deepspacecreeper]

do reaction wheels help reduce monoprop needed and do they do any better than monoprop in turning the craft? (i know rcs is necessary for docking with the asteroid)

[deepspacecreeper]

I've came up with a very, very rough design (far, far away from perfect, still have to refer to designs posted here). it consists of a main craft and a fuel tank, launched separately and docked in orbit.

the tank after docking with the main craft gives roughly 3000 m/s dV. The main craft gives 7000 m/s dV, acheived with LV-Ns.

Is this enough for redirecting the asteroid, on Kerbin collision couse? Please give some advice on that.

[Oafman]

I've came up with a very, very rough design (far, far away from perfect, still have to refer to designs posted here). it consists of a main craft and a fuel tank, launched separately and docked in orbit.

the tank after docking with the main craft gives roughly 3000 m/s dV. The main craft gives 7000 m/s dV, acheived with LV-Ns.

Is this enough for redirecting the asteroid, on Kerbin collision couse? Please give some advice on that.

Depends on where you intercept. I reckon it's worth burning more dv to meet it earlier, because the earlier you get to it, the less dv will be required to tweak it's path closer to the planet for an aerobrake.

If you have 7km/s you should be good. Once attached you might find that is reduced to something below 200m/s, but that will still be plenty if you meet it early.

Re. the reaction wheel question, I imagine it would make a negligible difference. You certainly couldn't hope to turn a class E roid without RCS. I used the big RCS thrusters which have a thrust of 3 (are they KW?) and it was still an incredibly slow affair.

[eempc]

If you're not a fan of rotating asteroids, then you could attach engines to burn in multiple directions. Each engine here is pointed at the centre of mass and also in one of the 6 directions you'd find on the manoeuvre node.

[Dartguy]

So, does fuel, rcs, solar power all feed throughout anything attached to an asteroid. If so, that would open up some possibilities.

[eempc]

So, does fuel, rcs, solar power all feed throughout anything attached to an asteroid. If so, that would open up some possibilities.

Asteroids are treated as a "part".

Monopropellant and electricity does feed throughout automatically. The claw does not have crossfeed so an engine can't access fuel beyond its claw, but you can still pump fuel manually from one tank to another through the claw.

[Camaron]

On the RCS v.s. SAS point mentioned earlier. Personally I prefer SAS, because it is limitless as long as you supply power. But, with an E class asteroid, you would need at least 50 of them to even dream of it, and it's best if you spread them around the surface by detachable pods. That said, you would need a whole lot of RCS thrusters to effectively move an E class as well. A real winner would probably come from an intelligent hybrid of both systems.

Last note - In my eperience, putting a truckload of SAS on the main tug or any single point at all during an asteroid grab is a HUGE mistake. Your SAS will have major issues that cause an continually increasing resonating effect which is a nightmare to deal with. I personally like to use detachable pods with SAS and clamp them all around, while having no SAS at all and the tug itself.

[Remkeau]

A little thing I did when trying to spin an E-class asteroid was to not spin it at all. What nonsense I am talking about? Decouple your craft, zip around to the side facing where you want to push, re-engage. Voila. Much less of a headache in my experience, no flexing, no long waits.