Looking for advice on Eve intercept maneuvers

[TanDeeJay]

I've captured an asteroid which I am planning to pull into an Eve orbit.  Now I've already pushed it into the same inclination as Eve, so all that is left is to get the intercept and then slow down to orbit.

I currently have 2 maneuvers planned that will get the asteroid into orbit, however, the AP of the current orbit takes the asteroid close to Kerbins orbit.

Would be really neat if there was a mod that would allow me to "save" a set of maneuvers so I could test out a different set of maneuvers and then switch back to the "saved" maneuvers if I can't find a better set.

Here is what I currently have with a 145dv maneuver to get the intercept and a 1550dv burn to orbit.

My ship has 6 Nerv engines and that 1550dv burn is going to take about 45 minutes game time.   (last long burn I did was 26 minutes game time which ended up taking an hour and a half real time (frame rate is down a bit  might need to upgrade my hardware... or stop tracking too many asteroids...)

My question is would it be better to do a retrograde burn at solar PE to lower the AP, and potentially have a much shorter orbit insertion burn?  but if I did that I'd be going much slower and would likely miss the encounter on this orbit?

This asteroid is to provide fuel for my eve lander which is on its way and has a scheduled orbit insertion burn in about 290 days, so it is already going to have to wait for the asteroid once it gets there before it can attempt the decent.

(I just hope I grabbed a big enough asteroid to fill the tanks on the Eve lander  )

Cheers

John

Edited February 28, 2022 by TanDeeJay
fixed spelling in title

[king of nowhere]

1 hour ago, TanDeeJay said:

I've captured an asteroid which I am planning to pull into an Eve orbit.  Now I've already pushed it into the same inclination as Eve, so all that is left is to get the intercept and then slow down to orbit.

I currently have 2 maneuvers planned that will get the asteroid into orbit, however, the AP of the current orbit takes the asteroid close to Kerbins orbit.

Would be really neat if there was a mod that would allow me to "save" a set of maneuvers so I could test out a different set of maneuvers and then switch back to the "saved" maneuvers if I can't find a better set.

You don't need a mod. Just save the game, it will save the manuevers. I usually do that, and take a screeenshot where i highlight the manuevers, and name the save stuff like "route to Jool, 1650 m/s" and perhaps references to the screenshots too. to reload the manuevers, just reload the game.

Quote

 

Here is what I currently have with a 145dv maneuver to get the intercept and a 1550dv burn to orbit.

My ship has 6 Nerv engines and that 1550dv burn is going to take about 45 minutes game time.   (last long burn I did was 26 minutes game time which ended up taking an hour and a half real time (frame rate is down a bit  might need to upgrade my hardware... or stop tracking too many asteroids...)

My question is would it be better to do a retrograde burn at solar PE to lower the AP, and potentially have a much shorter orbit insertion burn?  but if I did that I'd be going much slower and would likely miss the encounter on this orbit?

This asteroid is to provide fuel for my eve lander which is on its way and has a scheduled orbit insertion burn in about 290 days, so it is already going to have to wait for the asteroid once it gets there before it can attempt the decent.

(I just hope I grabbed a big enough asteroid to fill the tanks on the Eve lander  )

Cheers

John

 

Inefficient. the most efficient manuevers are those that lightly touch the target. Here you are crossing eve orbit instead of touching it, so the cost is going to be much higher. you can get an orbit for 400 m/s if you do this properly. For the same reason that two cars touching each other laterally are taking a lot less damage than in a frontal collision.

And the way to do it is to burn at apoapsis to raise periapsis until it touches eve's orbit. Make your periapsis the point of intercept. Of course, you won't find Eve at your next periapsis, but it's not a problem; at periapsis, you can make a small burn to change your orbital time and ensure that you meet Eve the next orbit - or in 2, or 3 orbits. You shoud be able to get into Eve orbit for less than 800 m/s total, instead of your current 1700.

The only problem with all this is that it's a lot slower, it will require multiple Eve orbits. Your trajectory is the fastest one - among those with reasonable cost. So, if you only care for speed, go for it.

P.S. if your problem is the eve lander, you can mine fuel on Gilly, it's very convenient, and unlike asteroids it doesn't run out.

P.P.S. if your ship has 6 nervs and requires 45 minutes for a 1600 m/s burn, then your ship must be around 500 tons of weight. And you have 2300 m/s, you must have about 120 tons of fuel. That you can use to feed your eve lander.

P.P.S. A 45 minute capture burn is going to be horribly inefficient; you're going to need at least 20% more than that to actually perform the manuever

P.P.P.S. Last I knew, asteroids are indestructible by heat, so you may actually aerobrake the asteroid. Of course, it's unlikely your ship would survive, but aerobraking the ship alone is going to save fuel

[TanDeeJay]

The ship has a 460ton asteroid attached to its nose.   Thats why it is on such an inefficient intercept orbit.   My previous version of this ship latched onto a 1300t Class E asteroid and I found it didn't have enough DV so I did the kerbal thing and hopefully made it big enough that no Class E asteroid could defeat it. I just found a reasonably large asteroid that had an orbit that sort of went near Eve's orbit and sent my Asteroid Catcher after it.  I didn't think of using Gilly as a source of fuel.  Hmmm... my mining ship is already enroute, and it is geared to asteroid mining not landing on a moon.  I think I'm still within the Eve transfer window, so I could send yet another ship ... All to support my efforts to land on and take off from Eve.  the problem I had with my Eve lander was that I designed it from an assumption that it was starting at a 110k orbit full of fuel (enough for it to take off) and then to get it to eve, I had to empty it of fuel... of course it would probably be much more efficient to build a space-plane, but I've never been big on creating aerodynamic vehicles, and tend towards the brute force approach  

 

And yes your right of course, just save the game and then experiment with different maneuvers.  Thankyou for that reminder   I will have a play around with maneuvers and save games and see if I can get a better burn... (although I think I have sufficient DV to do this the ineffecient way  )

 

[TanDeeJay]

Got it down to 850dv taking 3 and a bit years to orbit. 332 at AP to put the PE on eve's orbit, followed by 147 at PE to get an eve intercept, then 377 to pull into Eve orbit. some 3 years 139 days later.  what's a few years between kerbals?  The original 4 insisted they be the 1st to fly the eve lander to and from Eve. Only 3 will get to land though.  the 4th one has to do a Michael Collins and wait in orbit...

[TanDeeJay]

On 3/3/2022 at 8:04 PM, TanDeeJay said:

 I think I'm still within the Eve transfer window, so I could send yet another ship

Nope.  the "Gilly Guzzler I" is now in LKO waiting for the next Eve transfer window ... in 1 and a half years... and it will get to Eve long before the asteroid arrives 

[king of nowhere]

On 3/3/2022 at 11:44 AM, TanDeeJay said:

Got it down to 850dv taking 3 and a bit years to orbit. 332 at AP to put the PE on eve's orbit, followed by 147 at PE to get an eve intercept, then 377 to pull into Eve orbit. some 3 years 139 days later.  what's a few years between kerbals?  The original 4 insisted they be the 1st to fly the eve lander to and from Eve. Only 3 will get to land though.  the 4th one has to do a Michael Collins and wait in orbit...

well, my estimation of less than 800 m/s for this manuever was not perfect, but fairly accurate.