How to best achieve a target Eccentricity?

[Kerbalnaut #55487]

KSP 1.8.1 w/ RSS, RO, RP-1 and other assorted mods.

Ok... so I finally managed the frankly epic achievement of 'simply' getting into orbit and I've unlocked a lovely array of satellite contracts.

One of these is the First Weather Satellite which is asking for an eccentricity of 0.005. If I understand this correctly, that means very, very close to a perfectly circular orbit.

Quite by fluke, I managed to hit about 0.03 (Pe @ 350km and Ap @ 830km) when I performed my first Polar Orbit (using the MechJeb orbit info window for information). Since then, i have not been able to get even close (0.074) has been my best attempt since trying this. I was expecting the eccentricity to hit zero and begin increasing again as the orbit becomes established, this doesn't seem to be happening. I think I understand why but can't articulate it...

In stock KSP, I would have found this a fairly simple task with little, low throttle burns at Ap/Pe but I am still fairly low on the tech tree and as such have no throttleable or multi-ignition final stage engines. And am essentially still using a sounding rocket on top of a launch vehicle for my satellites.

 

Are there any fool proof ways to hit a target Eccentricity? Or even any tips and tricks that would be helpful?

Thanks in advance.

[Laie]

2 hours ago, Kerbalnaut #55487 said:

I am still fairly low on the tech tree and as such have no throttleable or multi-ignition final stage engines.

RCS is both throttleable and multi-ignition.

Just wait until you get to Gemini: you'll do a lot of maneuvering on RCS then. Might as well get used to it.

[king of nowhere]

yep. if you achieved your first orbit, you should have at least the swivel. if not, it just costs 5 science to unlock. getting a precise orbit with nothing but solid rocket boosters... well, i won't say it's impossible, but it's exceedingly difficult, and impractical when you have best alternatives.

Edited July 31, 2020 by king of nowhere

[Kerbalnaut #55487]

1 hour ago, king of nowhere said:

yep. if you achieved your first orbit, you should have at least the swivel. if not, it just costs 5 science to unlock. getting a precise orbit with nothing but solid rocket boosters... well, i won't say it's impossible, but it's exceedingly difficult, and impractical when you have best alternatives.

The Swivel!? As in the liquid fuel engine from the stock version??

I'm using RSS/RO/RP-1 as stated... I don't believe the Swivel engine is included in that at all... I don't have any SRBs on this design. If you're referring to something else, please clarify.

1 hour ago, Laie said:

RCS is both throttleable and multi-ignition.

Just wait until you get to Gemini: you'll do a lot of maneuvering on RCS then. Might as well get used to it.

The setup I am currently using is a 2.2m x 14m intergrated tank with an LR79 (S-3D config) and a couple of vernier exhausts on the bottom, when the tank is staged I have an avionics package on top of that with a bunch of RCS thrusters (4x 4-way RCS blocks for directional control + 2x single jets for ullage) on for attitude control and spin stabilisation but this avionics section is staged to an upscaled aerobee (once I'm pointing the right way) on the top - AJ-10-42 and an AJ-10-37 (for better ISP). This means once I have ditched the avionics, I have no control over the satellite in any way other than running experiments.

I need to essentially, get into the target orbit (>300km) with the eccentricity of 0.005. With my final ability to adjust course being before I ignite the final 2 stages.

I have another contract that requires an eccentricity of between 0.02 and 0.04, this one I am very close to achieving (the above setup is the same as what I had been trying with but now has the next upgrade to the engines) and to do that, I just need to get my angle of ascent angle a bit better and I'll be able to just cut my engines once I'm in the desired orbit.

If i add more RCS and fuel to the aerobee, I'm not sure I'll have the dV to even get to orbit. Although i may give it a try tomorrow, these new engine configs have given me an extra 300m/s of dV. So upto 9162m/s with that design, so far I've been getting into orbit (just) with 8800m/s ish.

I may have to look at completely redesigning to a more 'traditional' satellite now I have some better first and final stage engines - perhaps multiple AJ-10 (earlies) on a larger payload with the same launch vehicle...

(By Gemini, I'm assuming you're referring to the manned missions? I'm struggling to find more science to unlock the capsules atm but yeh... looking forward to them, the contracts are unlocked!) RP-1 is a beast!

Edited July 31, 2020 by Kerbalnaut #55487

[king of nowhere]

50 minutes ago, Kerbalnaut #55487 said:

The Swivel!? As in the liquid fuel engine from the stock version??

I'm using RSS/RO/RP-1 as stated... I don't believe the Swivel engine is included in that at all... I don't have any SRBs on this design. If you're referring to something else, please clarify.

 

oh, sorry. i don't know the mods you mentioned, but i assumed they would just add some more things. if you don't have any throttable engine because the stock engines are not included, ignore my previous suggestion.

[Laie]

53 minutes ago, Kerbalnaut #55487 said:

The setup I am currently using

Your description doesn't tell me much anymore.

However, it seems that you simply don't have the technology to complete that contract yet. RCS will provide enough thrust / dV to get the job done, but it will be so much easier if you can also rotate your satellite.

Arguably, you can still do it without control as long as you can still open and close the throttle. That used to be possible even with the sounding rocket core, but i don't know if it still is. It's been a long time since I played RP-0, and and didn't like most of what has been added in RP-1. Way back when, you could rake in enough science points with only 2-4 sounding rockets, also enough funds to finance the first building upgrades. It would take a while until it was finished, of course, but without running costs you could just fast forward, launch a few satellites, and timewarp again. IMO the game doesn't really start until you have Atlas/Agena.

[Kerbalnaut #55487]

14 hours ago, king of nowhere said:

oh, sorry. i don't know the mods you mentioned, but i assumed they would just add some more things. if you don't have any throttable engine because the stock engines are not included, ignore my previous suggestion.

RSS - Real Solar System (KSP in our solar system)

RO - Realism Overhaul (More realistic physics and stuff I believe - moar boosters isn't necessarily a quick fix for extra dV)

RP-1 - Realistic Progression 1 (the name says it all - realistically progressive contracts)

I'd highly recommend all of them, but be warned, the challenge is extreme compared to stock but FAR more customizable.

Stock = Lego Duplo

RP-1 = Lego Techniks

I will add this link in case you fancy the challenge as there is alot more than just those 3 mods involved - https://github.com/KSP-RO/RP-0/wiki/RO-&-RP-1-Installation-for-1.8.1 - this is an excellent guide to use and covers alot more than just the installation. It'll give you some very welcome notes on how to get started with RP-1.

13 hours ago, Laie said:

Your description doesn't tell me much anymore.

However, it seems that you simply don't have the technology to complete that contract yet. RCS will provide enough thrust / dV to get the job done, but it will be so much easier if you can also rotate your satellite.

Arguably, you can still do it without control as long as you can still open and close the throttle. That used to be possible even with the sounding rocket core, but i don't know if it still is. It's been a long time since I played RP-0, and and didn't like most of what has been added in RP-1. Way back when, you could rake in enough science points with only 2-4 sounding rockets, also enough funds to finance the first building upgrades. It would take a while until it was finished, of course, but without running costs you could just fast forward, launch a few satellites, and timewarp again. IMO the game doesn't really start until you have Atlas/Agena.

It took alot of experimentation and time wasting making that step up to getting into orbit and as this is the first career playthrough I've managed it on (been using rp-1 for a month or two, KSP only since March). I may just play this until funds run out then start a new one up taking from the lessons I've learned.

I'm also using Kerbalism so there is no click for all science type abilities, the cosmic Ray experiment for example takes 90 days to complete and the only satellite I've had last that long was in the polar orbit one that lasted about 130 days before the battery ran dry but due to the eccentricity I accidentally hit with it (0.03) that experiment wouldn't run - needed minimum of 0.04 if you can believe that!? Fml lol. Same goes the the micro meteorite detector!

 

So yeh... challenges galore! I'm thinking I just need the nose cone (which is a smaller avionics unit) to separate and have some attitude adjustment abilities on it... After all... i don't need the fuel tank or engine once the fuel is expended.

....saying that.... all my solar panels are on the tank DOH

Edited August 1, 2020 by Kerbalnaut #55487
added rp-1 install guide link

[Kerbalnaut #55487]

@Laie Thanks for the idea... 4x4way rcs on the nose cone, solar panels transfered to nose cone. Engines cutoff with 0.006 eccentricity and i haven't even separated the nose cone yet.

Seems I got that just right angle of ascent and now have the attitude control to complete the current contract and should be able to accept and complete the weather satellite one at the same time! And hopefully enough dV in the rcs to get a higher eccentricity for the experiments to run... win - win! 

Edited August 1, 2020 by Kerbalnaut #55487

[Laie]

2 hours ago, Kerbalnaut #55487 said:

Stock = Lego Duplo

RP-1 = Lego Techniks

To stay in your picture, it's really Realism Overhaul that corresponds to Lego Techniks.

Reenactment Progression 1 is the career mode for RO and last time I tried, there was way too much busywork for my taste.

7 minutes ago, Kerbalnaut #55487 said:

@Laie Thanks for the idea...

Not my idea, and please do not believe that this is just a crummy workaround: that's how it's done, period.

Edited August 1, 2020 by Laie

[MacLuky]

What I did is put a decoupler between the lv avionics and the payload. It will suck the battery dry in a couple of hours but that is enough to use rcs to trim the orbit, then dump it and the rcs leaving the science node in orbit.

use a decoupler set to zero impulse or it still gets messed up