One Way to Capture An Asteroid

[Vezbot]

 Capturing asteroids have always been difficult for me. No sphere of influence, small target, but the closest approach nodes help greatly. Over time I developed my own way to catch one of these as they pass.

My way of rendevousing with an asteroid, there are other ways but I am familiar with this one the most, if you would like to discuss different techniques of capturing an asteroid that would be cool. Here is my way of doing it: First you launch from kerbin in a prograde orbit and change your inclination later to match the asteroid. Usually I launch a rocket and it at an orbit of 6000 km above kerbin before I track an asteroid. That way I have it readily available and can change the orbit later on when the asteroid's orbit is determined. 99% of the time it will be on an escape trajectory out of Kerbin's SOI. The key to doing this would be to match your inclination with the orbit and then put your apoapsis near it's perapsis. Or even on the same altitude. Now it's time to wait, the encounter can range between 50 days up to 200 days, but once it is reached Kerbin, time warp until it's right at the beginning of passing Kerbin, right after it entered kerbins SOI. Depending on how high the orbit is the orbital period can range from less than an hour to several days, if its in a high orbit, then do the rendevous burn earlier if burning prograde or burn retrograde when making an orbit and meeting up with it in less time. I usually burn prograde because with a retrograde burn, speeding up your orbital period to encounter the asteroid at the right time can sometimes not work out, with the orbit needed going into kerbins atmosphere at perapsis. When burning prograde, hover your mouse over asteroid perapsis to find out when it will reach there, then burn prograde to match that time when you make one orbit to meet up with it. It's not always perfect so fine tune it if you have to. At this point the closest approach should be under 100 KM and you can do the relative velocity burns, cancelling out the velocity you already have and then burning towards it. Don't make the velocity too slow, because it can make both your craft and the asteroid drift away from kerbin before you can do the capture burn to prevent the asteroid from escaping. I recommend 50 m/s a second for more powerful engines or 20 m/s for ions. 

Congratulations you have docked with the asteroid and are able to do further research and maybe set up a mining base (although the returns in fuel aren't that good for anything under class E) .Good for science in career mode and you can bring these in orbit just for fun in sandbox. Have fun!

Discuss this with me others if you want.

Edited April 16, 2020 by Vezbot
Spelling mistakes, there are probably still some. Typing this on a phone lol

[Vanamonde]

When I want to capture an asteroid, I send a low-thrust/long-duration pusher probe to the region between Kerbin and Duna, where small nudges can make big changes. I then arrange a low pass and rely heavily on aerobraking to get a capture, then go back to long, weak burns to adjust to the desired orbit. 

[Vezbot]

That's cool