Two differents ships, same techniques, not same results (Making a circular orbit)

[InF3RNo]

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Hello, I've been trying to get to the Mun and Minmus, I achieved to Mun without Mechjeb, but started to use Mechjeb questioning myself if it was cheating, as I read in some posts, it's not cheating, it's giving me info that I need in screen instead of going to map view and burning retrograde is so great with Mechjeb.

Well, here comes the question.

Ship #1:

It can reach 10km and start going 90º in 45º, reach apoapsis 70km and when 20 seconds left to reach it, burn prograde and get a nearly circular orbit, all great, but not fuel efficent, just enough to reach Mun or Minmus, with no travel back.

Ship #2:

When I reach 7km or 10km, I start doing the same thing, 90º in 45º and the apoapsis or else grows too much in lesser time, which I thought it'd be good, but no, when I try from 20seconds left to start burning prograde the calculations go crazy and I get never a periapsis, just a escaping orbit if I could match the speed needed in less time

I know Ship #2 is going faster, that could be the problem, but it lets me get higher with the liquid fuel untouched, that make me start thinking about making fuel orbiting depots around Kerbin, but the idea fades as soon as I can't put it in orbit, neither circular or not.

Any ideas what I should modify or do?

(They're the same ships but the #2 ship have larger solid fuel boosters)

Thanks!

InF3RNo.

Edited May 21, 2014 by InF3RNo

[cantab]

The only thing I can think of is that the second ship will be heavier when you're circularising (because less fuel has been used) and so require a longer burn. It may be that MechJeb's getting confused for some reason, perhaps if it's too close to apoapsis when you tell it to circularise.

[InF3RNo]

I'm trying to make a circular orbit myself, as the maneuver tool for circularise is not working well, burning prograde when near to 20 seconds to apoapsis. I'm uploading the difference between m/s when I reach 10km.

Ship #1

Ship #2

[Jasel]

Just some quick beginner tips I learned from the Scott Manley School of Exploding Rockets:

-You should start your turn when all of these are hit: 10K, with 15K app, going at 200m/s

-Look up Kerbins terminal velocities...should be a wiki page with them on it. Try not to go over too much. You can adjust the amount of thrust on your solid rockets by right clicking them. Essentially, don't go above 230 (i think) until 10K

-Your turn should should be 45 degrees

MechJeb

There might be some issues with the rockets you're using vs the amount of fuel you are trying to push up into space soooo -

-If your going to use MechJeb for anything, use it to view your DeltaV. How you use it is personal preference and how you feel it helps, or over-helps. That is your stance and no one elses. (I feel since all manned flights into space are computer controlled, it's ok to use MechJeb; that said I still started out doing everything manual just so I learned).

-Lastly - Use MECHJEB FOR DELTAV

[YNM]

A slight kind of my experience with that damned ARM SRB, and using it with MechJeb autopilot (I can do it myself too but, well... lazy hu-mans) :

1. No way to put things on low orbit (low is ~71 to 90 km), probably except if your ship is damnedly huge (that the SRB really working only for increasing applied force, that you got low TWR) - Always ending up higher than that; My sats that are launched on it as first stage will have an AP higher than 92 km.

2. Hard to be turned, even with surface control devices (winglets and such)

3. Playing with FAR and/or DRE will certainly kill your rockets. I've seen my rockets getting the reentry fire effect on ascent.

From your pictures, you can see the first craft only have an acceleration of 12 m/s^2, the second already have something like 30 m/s^2. That huge acceleration will be a huuge problem just before engine cut-off. Also, that way your circularization burn will be quite long (low TWR).

[technicalfool]

Well, I just tried ship design #2, and got into a 120km orbit with nearly 3km/sec of dV to spare. The design certainly works as far as getting into LKO is concerned. If anything, that first stage with the four big SLS boosters is overpowered. I'm getting atmospheric plasma effects going up, despite cutting all throttle on the liquid engine, and the single reaction wheel below the pod really isn't enough to tip the nose over quickly enough while those great big boosters are firing.

The extra parts are heat sinks due to the KSP Interstellar mod implementing 'waste heat' generated by the panels, also a couple of small batteries

The question I have to ask is why you've put the landing legs up there? I assume you'll be trying to land on Minmus with the thing, and you'll be jettisoning the science + pod on the way back? You might want to put the landing legs further down so you don't go landing on your engine.

Also, may I recommend going on EVA once you get to the surface, retrieving the data from the goo containers/science bay (fly up to them, click for the menu and and click to 'grab data'), and storing the science in the command pod? That way you can jettison everything, and just come back to Kerbin with a command pod full of science on a parachute. No need to bring the goo containers or science bay back at all!

I'll see if I can get to Minmus with this thing anyway. Could be entertaining.

[InF3RNo]

I added some winglets to control to put ship to 90º-45º faster, and lowered thrust to 80 from 100, and I'm able to get 70pe-80ap orbits, at last I found a way to make fuel efficency ships. Thanks!

About technicalfool said, I never achieved to return jettisoned things back to kerbin with data from science, I usually send it by transmission systems, I have to learn that too, hehe. I need to start reading something about that, any ideas where should I start from? Should I just simply google it?

Thanks again.

Edited May 20, 2014 by InF3RNo

[cantab]

I assumed the legs were for a soft touchdown when you came back to Kerbin, so that you don't risk breaking the Sci Jr by landing on it.

For returning to Kerbin from the Mun or Minmus, the trick is to leave Munar/Minmus orbit when you're heading backwards compared to its own orbit around Kerbin. That will drop your periapsis down nicely. Set down a manouvre node on a ship that's orbiting the Mun/Minus, set it up to escape, then move it round the orbit and watch how your trajectory round Kerbin changes and you'll see what I mean.

[technicalfool]

update

Made it. Your design can definitely get to Minmus.

It can also make it back with boatloads of dV to spare. 890m/s worth in this case.

Unfortunately, those legs don't do much to absorb a water landing at 8.8m/s on that single parachute. Recommend either a couple more radial chutes, or as mentioned, grab the science from the instruments while on an EVA, and dump the empty containers. Move your separator up a bit and just come back with a pod full of science.

[technicalfool]

About technicalfool said, I never achieved to return jettisoned things back to kerbin with data from science, I usually send it by transmission systems, I have to learn that too, hehe. I need to start reading something about that, any ideas where should I start from? Should I just simply google it?

Thanks again.

In most cases, transmitting science incurs a penalty. You can transmit crew reports and EVA reports and get 100% of the value. However, for surface samples, goo studies, material studies and most other things, you will not get the full value unless you return the result to Kerbin and recover it.

The good news is that you can EVA a kerbal, float over to the goo container, material bay, thermometer or whatever other sensor and use the right-click menu to "take data". This can then be returned to the command pod which can store as many unique experiments as you can be bothered stuffing in there. You can't store two of the same experiment (so you couldn't do a goo study on the same biome twice and store both results in the pod), but if you're returning the science to Kerbin, you get full science points anyway.

I also guess that English is not your first language. If it helps, there are international forums here for people whose Spanish (or Italian, French, German, etc) is better than their English!

[kidolvski]

Asparagus staging will make it more efficient. But maybe you haven't unlocked the fuel pipes yet, if you're playing career mode.

[SRV Ron]

Place the extra SAS on the second stage. You don't need it once you reach orbit.

You can also tweak the big SRBs to reduce power output and eliminate the wasteful effect of too much launch speed.

Both these early Career ships will do the Mun and Minmus flyby and orbit missions.

[InF3RNo]

update

http://i267.photobucket.com/albums/ii282/technicalfool/misc%20KSP/screenshot345_zpse7ce5f56.png~original

Made it. Your design can definitely get to Minmus.

http://i267.photobucket.com/albums/ii282/technicalfool/misc%20KSP/screenshot355_zps289b75a6.png~original

It can also make it back with boatloads of dV to spare. 890m/s worth in this case.

http://i267.photobucket.com/albums/ii282/technicalfool/misc%20KSP/screenshot366_zps9e64bf3b.png~original

Unfortunately, those legs don't do much to absorb a water landing at 8.8m/s on that single parachute. Recommend either a couple more radial chutes, or as mentioned, grab the science from the instruments while on an EVA, and dump the empty containers. Move your separator up a bit and just come back with a pod full of science.

What do you mean with boatloads of dV? I'm not that well informed about physics.

By the way how did you land on Minmus with the ship standing still? I mean, even with legs I've got problems to make it reach stable, with that, for me it'd be exploded, sure.

I assumed the legs were for a soft touchdown when you came back to Kerbin, so that you don't risk breaking the Sci Jr by landing on it.

For returning to Kerbin from the Mun or Minmus, the trick is to leave Munar/Minmus orbit when you're heading backwards compared to its own orbit around Kerbin. That will drop your periapsis down nicely. Set down a manouvre node on a ship that's orbiting the Mun/Minus, set it up to escape, then move it round the orbit and watch how your trajectory round Kerbin changes and you'll see what I mean.

Roger that, will try next, but usually when landing to Minmus or Mun I decouple the thrusters and there's no way back, don't know how to land with thrusters and all that.

In most cases, transmitting science incurs a penalty. You can transmit crew reports and EVA reports and get 100% of the value. However, for surface samples, goo studies, material studies and most other things, you will not get the full value unless you return the result to Kerbin and recover it.

The good news is that you can EVA a kerbal, float over to the goo container, material bay, thermometer or whatever other sensor and use the right-click menu to "take data". This can then be returned to the command pod which can store as many unique experiments as you can be bothered stuffing in there. You can't store two of the same experiment (so you couldn't do a goo study on the same biome twice and store both results in the pod), but if you're returning the science to Kerbin, you get full science points anyway.

I also guess that English is not your first language. If it helps, there are international forums here for people whose Spanish (or Italian, French, German, etc) is better than their English!

Good to know, will test it on my next flight. And yes, english is not my first language, it's spanish, but not so many spanish that know answers so fasts obtained than english forum.

Asparagus staging will make it more efficient. But maybe you haven't unlocked the fuel pipes yet, if you're playing career mode.

I've checked some videos about that Asparagus, it doesn't work with solid fuel boosters, right? I thought that asparagus was about placing and dropping some fuel containers in order, but also seen that's about fuel transfering or something like that? Haven't tried it even when I played only sandbox long time ago.

Place the extra SAS on the second stage. You don't need it once you reach orbit.

You can also tweak the big SRBs to reduce power output and eliminate the wasteful effect of too much launch speed.

Both these early Career ships will do the Mun and Minmus flyby and orbit missions.

http://i.imgur.com/GO5zTmR.jpg

If SRB you mean the solid fuel boosters, yes, already advised me to modify that so I don't waste the fuel so much, because it seems I'm not able to get at 100% thrust power from them to a nearly circular orbit, but with 80% I can do that fine.

-----

Thanks for all the answers, I'll put your tips to good use right now, that I'm going to try fly more efficently, and obtain science much more!

Edited May 20, 2014 by InF3RNo

[technicalfool]

What do you mean with boatloads of dV? I'm not that well informed about physics.

By the way how did you land on Minmus with the ship standing still? I mean, even with legs I've got problems to make it reach stable, with that, for me it'd be exploded, sure.

dV (or Delta V), also means "change in velocity". If your craft has 890 metres per second of dV remaining, and it is travelling in one direction at 890 metres per second, then burning in the other direction until the fuel depletes will leave you stood still. It's the way that rocket scientists calculate how much fuel is remaining.

As for how I landed on the engine, partly I came down really gently (under 1 metre per second), and partly I landed on one of the Minmus flats. The gigantic green "ocean" areas on Minmus are perfectly flat, and great for landing on for your first time.

[InF3RNo]

Again I've got a problem, now it's when trying to burn 90º - 45º, I can see my prograde a bit far from where it should be, I think it could be the ship mass is higher and the prograde is moving because that reason. In the picture you can see that I changed it to 90 - 65 and the prograde is way down from the 90 - 45, should I change it a bit more like 90 - 80 to make the prograde fit where it should be to get a good apoapsis in time?

Thanks!

[cantab]

Surface prograde will tend to drop below your heading because gravity is pulling the rocket down. The effect is greater for low TWR rockets, which may indeed want less of a pitchover to compensate. That said your screenshot above is showing a respectable TWR and speed so I'm not sure if it's the issue here, unless the stage before or the start of that stage had low TWR.

Orbit prograde will be below surface prograde in a standard eastwards launch because it has an extra horizontal component from Kerbin's rotation, but you're showing Surface velocity above.

Though unlikely, it could be that your command module is mounted askew on the rocket. I'd have thought you'd notice that on launch though, unless you're switching command modules during the ascent.

[InF3RNo]

Thanks again for the answers, I achieved to get to Minmus with enough fuel 2500 m/s on Vacuum, that's what the ÃŽâ€V says, I hope I can get back to Kerbin without any problem.

Never achieved so much Science Points at once

Thanks!

Edited May 21, 2014 by InF3RNo