Asteroid mining

[juanml82]

I was planning to capture E class asteroids to set up a refueling station in LKO, since I find that procedure, once the asteroid is in LKO, less of a chore than a Minmus refinery (as I don't need to land and take off rovers which then go to aerocapture at Kerbin).

So, I grab an E class and use it to keep refueling the asteroid catching as I capture it. Once that's done, I set up a maneuver node to change the inclination from 95 to 0, warp while mining to refuel the tanks and engage mechjeb to handle the 8 minutes burn.

And then I find out that all that refueling had emptied the asteroid!

So, is it worth it, or how is it worth it? I was thinking of grabbing the asteroid while it's still on solar orbit, so it can be directed to an aerobreak with Kerbin. Or is it better to try to capture D or C classes, since their slower weight means less fuel to maneuver them? But even then, if refueling something like three MK3 fuel tanks three times (plus monoprop and oxidizer for the vernors) can empty an E class asteroid, are asteroids worth it as refuelling stations?

[Warzouz]

If you couldn't do with a E class, that would probably be the same for a D class. Less fuel expenditure, but also less ore to mine.

Yes I tried to get a D class asteroid to do that, but I was too late (rendez-vous would have occur 1day after periaps). The asteroid had also a nearly polar orbit which would have taken a very long time to set to LKO.

I think the best hope is to meet the asteroid out of SOI and change it course there. It should get to a most equatorial hyperbolic as possible.

Maybe aero braking is an option, I don't know. The problem is we have to wait to find a suitable candidate and have a try. Meanwhile, launch windows occurs and we don't want to miss them.

[SanderB]

you have to begin maneuvering the asteroid before it hits your SOI, preferably even 90° ahead of its encounter with kerbin to alter its close approach inclination and 180° to close its approach to kerbin, ideally. More than likely 45° ahead of the encounter is more realistic. What it seems like that you're doing is maneuvering the asteroid at its highest relative velocity to kerbin and that is extremely expensive and generally unfeasible. Changing its orbit well before its encounter will allow a much cheaper option of hitting the atmosphere at a Pe of 15-40km and aerobrake it from there. I haven't done it before myself. You may have to decouple your ship until it has passed the kerbin atmosphere to prevent your asteroid redirection vessel from burning up in the atmosphere.

Once attached to your asteroid at 45° or more from the encounter (relative to Kerbol) it should be easily possible to change an asteroids periapsis to 20-30km. In my sandbox test, the 2,500t asteroid needed to be at a Pe of 25km to aerobrake enough velocity to be captured. Any lower than that and it re-encountered the atmosphere too soon and it did not allow the redirect vessel to reattach and raise its Ap fast enough. ~10km higher and it would escape.

Edited May 24, 2015 by SanderB

[juanml82]

The other thing I was thinking was to fully mine the asteroid. The asteroid "dry" mass would be lost (but that's compensated by the ore container's dry mass) and, essentially, the ship should be far easier to maneuver

[Foxster]

Yup, found the same thing. By the time I had it near Kerbin it was almost out of juice and that was with a very long burn from a long way out. Was a bit of a pointless exercise really. Even if you got it back without using any ore the amount of mineable ore is limited and you'd only get a couple of mission's worth out of it.

There's certainly little, if any, scope to set up a useful in-space refuelling station using an asteroid. Now, if it recovered its ore over time...

[juanml82]

And fully mining the asteroid instead of capturing seems like a bad idea: you need capacity with some 100,000 units of ore. Which I built, using tweakscale to increase the size of the 2.5 m ore container, and it ended up with a ship with some 300 tons of weight and less than 1,000 m/s of dv because of that.

Now, I used hyperedit to RV it to an E class in solar orbit and the procedure works like a charm: I needed four days to deplete the asteroid and the fully loaded ship is incredibly comfortable to manuever. But the dry mass of the ore container kills it. And you're getting ten MK3 long lox tanks worth of fuel.

[CaribouGone]

another factor to consider is what % of the asteroid's mass is ore.

unfortunately, you won't know that till you're there.

from what i understand, even a high % class A can give you more fuel than a mediocre D or E.

while 9 mk3 is a lot of fuel, you may have grabbed a dud asteroid.

also, towing is often easier than pushing.

[n0xiety]

I was fortunate enough to get a 3500t %92 ore E class and only mined 250t to bring it into 800km kerbin orbit. I must say it seems like a great source of fuel to me in my career.lets say 3000t minable left inside the asteroid that would make 300000ore right since each ton creates 100ore as i see it? And 300000 ore turns into quite alot of fuel.