Best way to redirect Class E asteroid

[Crusher48]

I recently had a mission to redirect an asteroid that ran into a speed bump when I realized it was a class E. Though I gave up on redirecting it for now (my ship did not have that much fuel), how would I redirect it later on when I want to have the bragging rights for a huge asteroid around Kerbin?

[Spheniscine]

If all you need to do is to capture it into Kerbin orbit, you can try redirecting it into an aerobraking trajectory. I'm not exactly sure how much ∆v you'd need to stabilize the orbit though; I think ~200 m/s or so; maybe more if you need to redirect it a lot to get the right trajectory.

Really though, class Es can easily go over 2000 tons, so you'd have a hard time moving it anywhere else, short of using a mod like Asteroid Recycling Technologies to mine/hollow it, or being extremely good/lucky with gravity assists etc.

Edited January 24, 2015 by Spheniscine

[capi3101]

Claw's tutorial will give you some good guidelines, though since you're up against a class E you're going to need a craft with a lot more oomph.

I'd give you the exact range of masses for Class E rocks - the information is on the wiki - but the wiki is spazzing out at the moment. It's definitely up there though.

[cantab]

Meet it in solar orbit. Though it takes a bit more delta-V to reach it that's delta-V without the asteroid. Once you meet it it only takes a small correction to line up a gravity assist or aerocapture. And of course use nuclear engines.

For manouvering them, one approach is to simply fly the tug around the asteroid as needed, rather than even try and rotate the massive rock.

[Spheniscine]

The wiki gave asteroid masses as e^1.5x, where x ≈ 1 for A, x ≈ 2 for B, etc.

Assuming a variation of ±.5 for x, this gives

A: 2.1 ~ 9.5 tons

B: 9.5 ~ 42.5 tons

C: 42.5 ~ 190.6 tons

D: 190.6 ~ 854 tons

E: 854 ~ 3,828 tons

[Frozen_Heart]

Can you use multiple claws on the same ship to stabilise the asteroid? I'm eyeing up a class E but have been having wobble issues with just one claw.

[cantab]

You can, but multiple claws are known to attract game bugs.

An approach I've used is to dot small control sections around the asteroid, like this: https://flic.kr/p/nVTQZ7 But I never tried it on anything bigger than that 500-ton D class, which has four of the control sections you can see.

The tug, incidentally, only gave about 100 m/s of delta-V with the asteroid, but that was enough to aerocapture into an elliptical Kerbin orbit.

[Raptor9]

I did it once. Would not care to do it again. Getting it redirected to penetrate Kerbin's SOI isn't so hard if you do it really far out. But keeping it in there is a nightmare. Definitely try to pull off a solid aerobrake. And don't even ask about adjusting it's orbit once you do capture it....ugh (Multiple trips to get more fuel).

HOWEVER, it serves as a really good anchor point for stations beyond Minmus. A slight bump during docking that far out can really throw your orbit.

[Frank327]

Can you use multiple claws on the same ship to stabilise the asteroid? I'm eyeing up a class E but have been having wobble issues with just one claw.

I had a go with a class E asteroid too.

That's a tug with a skipper engine on the end for reference. I had a lot of trouble keeping it stable at the start too. The trick is to have a really good probe core. Once you're docked to it with your manouvre node lined up with the centre of mass, just free the pivot of the claw and tell your SAS system to aim at the target (being the centre of mass of the asteroid). Then lock the pivot and it should fly straight without wobble or tilting. This way your engines will be aimed exactly right.

If the asteroid is already passing by kerbin very close (or colliding) then the mission should be doable. In my case its kerbin periapsis started at 16.000km and I had 2/3rd of the fuel to get it into the atmosphere for aerobrake. Of course that's still not counting with the circularization burn you have to do once you've aerobraked.

[purpletarget]

For Class E's I will use a small ion probe with a claw to intercept the asteroid in solar orbit. Once attached, you can find out exactly what the mass of the asteroid is, as well as setup possible flight plans, which will tell you exactly how much dV you need in order to do the job.

Then, you can custom build your intercept ship to with the dV reserves needed for the capture, as well as the initial oomph for a Kerbin SOI intercept just shy of the asteroids Pe. (Generally I found this required NASA sized parts, and multiple LVNs as a good combination...the burns are long (several minutes for only 1-200m/s) but most capture orbits are far enough out for that to not be an issue.

The rocket equation is your friend.

[capi3101]

The wiki gave asteroid masses as e^1.5x, where x ≈ 1 for A, x ≈ 2 for B, etc.

Assuming a variation of ±.5 for x, this gives

A: 2.1 ~ 9.5 tons

B: 9.5 ~ 42.5 tons

C: 42.5 ~ 190.6 tons

D: 190.6 ~ 854 tons

E: 854 ~ 3,828 tons

I got a thread locked down on me on Saturday going after this information...thanks for posting it. So yeah, a class E ranges about that much. You can plan for 1808 tonnes but it sucks if the rock turns out to be heavier. Frankly the notion of sending a sounding probe first makes sense for Class D and E given the wide range of possible masses, less so for Class A through C.

An approach I've used is to dot small control sections around the asteroid, like this: https://flic.kr/p/nVTQZ7 But I never tried it on anything bigger than that 500-ton D class, which has four of the control sections you can see.

I've done that sort of thing on an E before; added Vernors to it to steer the thing. They wobbled hard enough I thought they'd break off, but they did do the job.

Definitely try to pull off a solid aerobrake.

This link will definitely help on that particular score.

[Laie]

Lucky you all... I got a mission to take a class E... To EVE ORBIT.

I'll have to build an Imperial Star Destroyer for that

No you don't -- not anymore. Just include an ISRU kit and turn the asteroid into fuel. If you bring an engineer, your drill will probably run a lot faster than your converter. This leads to spillage: a lot of the asteroid's mass will just vanish. If you want to avoid that, you need to micromanage the drill and turn it off when the ore tank is full. Though in this case, you probably don't want to avoid it: an E class asteroid can shrivel to less than 50t. But it will still be the same size and is considered an E class for purposes of the contract.

You can also drill to fill up your ore tanks, then jettison the ore. Or just drill for fuel and use that to move the asteroid (you'll be surprised at how much remains), but handling E classes is a tricky endeavour. If you have no other use than just to fulfill a contract, you should lighten your load.

Incidentally, you don't have to accept every mission.

[Kryxal]

I could see drilling for fuel as VERY useful for those missions where you build a station into an asteroid and take it insanely far away...