Mechjeb or Something Else?

[Spaced Out]

Okay so I would like to get the most efficient ascent possible, what mod could calculate the most efficient trajectory and fly that?

[kerbalfreak]

Mechjeb2 is pretty good, I don't think you'll get significantly better than that. You can edit the "Ascent Profile" if you like. The only big downside with MJ is that you need to reconfigure the ascent profile for every planet/moon, which is made for Kerbin.

A very good alternative is TCA. It can be used for hovers, to jump to other places in ballistic trajectories and much more. One function is to go to orbit, which I think is little better than MechJeb, and can be used in rockets without any gimbal or control surfaces, as long you have 3 or more non-linear engines. If you need to pitch or yaw, it throttles down the engines in that direction. Very useful for aerospikes or any vehicle with misaligned CoM and CoT .

It has an different and optimized ascend profile for every planet/moon. The default is 1 km above whats is considered space. For Kerbin, it is 71 km (70 + 1). If you want 71 km, it will act like Mechjeb. If you want higher, it follows a slight better approach.

Example, for 100 km:

MJ: Goes straight up, gravity turn, put the apoapsis in 100 km, circularize at 100km.

TCA: Goes straight up, gravity turn, put the apoapsis in 71 km. At 71 km will burn until the Apoapsis is in the other side and at 100 km. Then it goes to the other side of the planet, and circularize. TCA is slight better IMO, and seems to have a better gravity turn, but it takes more time. AFAIK, you cannot tell Mechjeb to do the same, since it will only start circularizing after reaching space (70 km). Most ships will not have sufficient time for the maneuver.

TCA profile allows to use low trust engines (ion, nuclear) early. I use it when I want to send payloads a little heavier than what my launch vehicles are capable, when going to orbit from different places other than Kerbin or for rockets SSTOs with very little spare delta-v. Mechjeb sometimes cannot control some vehicles I make, and in TCA they work normally. TCA also handles other things MJ does, but lacks many orbital maneuvers, as MJ lacks the main functions from TCA. I think the best option is to use both. You can switch between them any time you like.

Link for TCA:
 

 

Edited December 11, 2017 by kerbalfreak

[OhioBob]

I don't know which mod does the best job because I don't use them all, so I don't have a basis for comparison.  However, I sometimes use Gravity Turn.  It allows each new launch to learn from the prior one to eventually zero in on a very efficient ascent.  I think it does a pretty good job.

 

[Tyko]

28 minutes ago, OhioBob said:

I don't know which mod does the best job because I don't use them all, so I don't have a basis for comparison.  However, I sometimes use Gravity Turn.  It allows each new launch to learn from the prior one to eventually zero in on a very efficient ascent.  I think it does a pretty good job.

 

Agreed. In my latest 2.5x game I was getting bored with (almost) endlessly repeating long launch times and started using Gravity Turn. Right off the bat I was saving a couple hundred DV, which made me sad because I was pretty sure I was doing efficient manual launches (my Stock game manual launches usually took about 3300m/s, GT was doing Stock launches with closer to 3100m/s)

You can also set the target altitude and can even set launch azimuth and add roll programs - a really solid piece of coding that's easy to use.

[fourfa]

Watching GravityTurn fly and learning how it works is very educational, BTW

[theJesuit]

kOS.  I have a standard set of launchers and so have four standard launch scripts.  I let them take me to space the circularise myself because often it is to rendezvous in kerbin orbit.  I also feel it is a launcher that I developed myself and so feel justified in automating it.

Peace.

EDIT my standard launch scripts are standard launch to space with apoapsis at 80km and then repeated with a north and south variations.  

My fourth is also at the 80km but launches when the target station is at certain distance.  I know I could really get deep in the trigonometry and calculate degrees of separation but I find close enough is good enough especially as I do the circularisation or approach and docking manually and also 80km is my standard orbit for heading off to other bodies so that is where I place my stations which do orbital transfers of kerbin system personnel and refeuls.

Basically I'm saying that kOS doesn't have to be massively complicated but I use it to make the initial launch from kerbin to be more streamlined.  It also flies more accurately than I could .

Edited December 15, 2017 by theJesuit
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