Asteroid Capture questions.

[KoolBreeze420]

In 217 days and A class asteroid will fly by Kerbin I need to capture this asteroid. What I've been googling for an answer for is what should my waiting orbit ring be like should I keep the craft in a low Kerbin orbit or not?

 

[Tyko]

You'll need to set up your craft's orbit to intersect with the asteroid's path and make sure the two craft arrive at that point in space at the same time.

Are you familiar with how to perform rendezvous maneuvers? If you've already learned how to rendezvous two craft in orbit this is very much the same thing.

Edited October 31, 2018 by Tyko

[Vanamonde]

This question about how to play the game has been moved to Gameplay Questions. 

Also, welcome to the forum.

More also, asteroids can be quite massive, so the farther out you start adjusting its path, the more you'll be able to move it. When I try missions like this, I send my ship out to rendezvous with one while the roid is still out between the orbits of Kerbin and Duna. I'm not saying that closer interventions can't work, but they can be MUCH harder. So my suggestion would be to not wait in any kind of Kerbin orbit, but rather to go out and meet it as far away as you are able. 

[MaverickSawyer]

20 hours ago, Vanamonde said:

This question about how to play the game has been moved to Gameplay Questions. 

Also, welcome to the forum.

More also, asteroids can be quite massive, so the farther out you start adjusting its path, the more you'll be able to move it. When I try missions like this, I send my ship out to rendezvous with one while the roid is still out between the orbits of Kerbin and Duna. I'm not saying that closer interventions can't work, but they can be MUCH harder. So my suggestion would be to not wait in any kind of Kerbin orbit, but rather to go out and meet it as far away as you are able. 

Eh. The few times I've run a rock grabbing mission, I've waited until I get one that swings deep into Kerbin's gravity well, then use a chemical-fuel kick stage for the inclination change and the high dV transfer out to the incoming asteroid. Rendezvous under nuclear or electric propulsion, then nudge the orbit until it's just above the atmosphere. Ride down to PeA, burn enough to capture, and then worry about how to circularize and zero the inclination. 

[Superfluous J]

I literally just did this yesterday and recorded the whole thing. I don't know when I'll have time to edit it but I will do so with commentary about what I"m doing and why in every step.

Until then, though:

You want your ship orbiting Kerbin in such a way that it encounters the asteroid's trajectory and is not tilted at all relative to that trajectory. You want to meet it at or near (before preferably) the asteroid's periapsis, probably at your apoapsis because your periapsis will be wherever you burned out from LKO.

Once you have the above, you can plop a maneuver node just after the connection. Right-click the node and then use the two little buttons to go forward orbits until the encounter markers get close to each other (they jump pretty quick and can even pass each other. You want the orbit right before or right after the passing point). Then drag prograde or retrograde to encounter.

Do that burn, then rendezvous, grab, and burn retrograde to slow down. if you don't know how to do that part of rendezvous then starting with an asteroid is probably not a great idea and you should start your own personal Mercury program.

Edited November 2, 2018 by 5thHorseman

[KoolBreeze420]

Yeah I can rendezvous and all that and the asteroid is tiny and it's coming into Kerbins orbit and it shows a blue line that I suspect is the estimated asteroid path. I'm just not sure if I should line up with this path and be in orbit waiting.

[Hotel26]

I think this video is the one that tutored me:

 

It's more or less what is being said.  Once you know the inclination (I wait until the asteroid has entered the Kerbin SOI) launch into that same inclination and at some point you will raise your apoapsis such that you can rendez-vous earlier and at a slower speed.  This is especially necessary if the asteroid is on a real collision path.  I've had at least one case where the easiest r/v was at periapsis, though.

I also later posted this topic asking about making inclination changes to capture a new, incoming asteroid after the Hunter is already in orbit:

 

Edited November 3, 2018 by Hotel26

[Hotel26]

(Although it's old, this topic seems like a good one to compile similar questions...?)

Does anyone know a way to identify the inclination of an asteroid before it enters the SOI of the home body (e.g. Kerbin)?

I have to set an alarm for its entry into Kerbin SOI; then identify its inclination; then scramble a 'Roid Hunter Mission with less time available...

 

[Superfluous J]

59 minutes ago, Hotel26 said:

(Although it's old, this topic seems like a good one to compile similar questions...?)

Does anyone know a way to identify the inclination of an asteroid before it enters the SOI of the home body (e.g. Kerbin)?

I have to set an alarm for its entry into Kerbin SOI; then identify its inclination; then scramble a 'Roid Hunter Mission with less time available...

 

Track it in the tracking station, and then click Kerbin or use tab to cycle through all worlds until you're at Kerbin. You will see the asteroid's path.

If you want to see it on the launch pad, put your ship there, then go into map mode and target the asteroid. Its orbit will show up when you hit ~ to center back on your ship.

I actually do this in the first few minutes of my post popular video, linked in my signature, including an attempt to launch into the same plane as the asteroid. I don't exactly nail it but hey.

Also don't try anything else in that video. It was before they changed the atmosphere in 1.0 and you can NOT do that with an asteroid anymore

Edited August 9, 2019 by 5thHorseman

[XtraChrisP]

Go out and grab it while it's still in Kerbolar orbit! I made my first grab of a Class A a while ago and I was able to nudge it  enough to get a great gravity assist from Mun. I was able to cancel out about 70 degrees of inclination with that assist! So yeah, the earlier you grab it the less you have to move it to make big changes, and def look for that Mun assist.

[bewing]

On the basic theory that inclination changes cost almost nothing when you're going slow, I always intercept my asteroids at the outer edge of Kerbin's SOI. I don't bother with inclination or an orbit at all. Just spend 30 days or so flying out to where the asteroid's orbit pierces the SOI. If I get there early, I burn to a stop and start very slowly falling toward Kerbin. Make sure I have a close flyby with the asteroid. Then burn like crazy as it gets near. I always have a drill and converter on my asteroid catchers -- so I don't bother worrying about fuel.

[Geschosskopf]

Intercepting in Solar orbit is worth some World's First points but it's a lot easier in Kerbin's SOI.

To intercept in Kerbin's SOI, I put my catcher on the launchpad, target the asteroid, warp until the asteroid's trajectory within Kerbin's SOI passes over the launchpad, then launch into that inclination (AND direction!) as closely as possible.  Then I put the catcher ship into an orbit at that inclination that's about 1/2 to 2/3 of the distance from Kerbin to the asteroid's eventual trajectory through the Kerbin system.  Once the asteroid is within Kerbin's SOI, it's just plotting a maneuver same as going to Mun or Minmus.  In general, this strategy gets you to the asteroid well before it's Kerbin Pe so you have plenty of time to do whatever you want with it.

Intercepting in solar orbit requires making a plane change with respect to the sun and that's always quite expensive.  I haven't found the best way of reducing this dV cost.  The method I generally use, which is better than nothing (IOW, leaving Kerbin's SOI in the same plane as Kerbin), goes like this....

• You will always leave Kerbin's SOI on the night side as you need to get into a higher orbit than Kerbin to be slower than both it and the asteroid coming up from behind it.
• If the asteroid is coming down from above Kerbin's orbital plane, you want to leave Kerbin's SOI going down on Kerbin's night side.  If the asteroid is coming up at Kerbin, you want to leave Kerbin's SOI going up.  This determines whether you launch north or south in the next step.
• Wait until KSC is more or less on the line between the sun and the center or Kerbin.  It doesn't matter if KSC is on the day or night side of Kerbin, just launch into a polar orbit going north or south depending on whether you need to leave Kerbin's SOI going up or down.
• Burn to leave Kerbin's SOI on the night side with a bit of outward velocity so you'll end up in a  slightly higher, slightly slower solar orbit than both Kerbin and the asteroid with respect to the sun, but mostly up or down relative to Kerbin to get the closest you can to the asteroid's inclination.
• Match planes with the asteroid, then rendezvous with it.  This will usually take several burns as you get closer and closer to the asteroid, and none of them will be particularly cheap.