Realism overhaul the engines are unthrottable

[berkekrkn]

It is very hard to make an orbit. The engines are unthrottable. The engines also have limited ignition but that"s no problem for me.

Because of  the unthrottable engines  the spacecraft pulls 15 G with 1000kN engine. No I am using real fuel, real heat etc without RO.

Is it so in real life ?

Do the engines have no throttle control ?

[CitizenVeen]

Alot of engines can't, throttling an engine usually has a bad influence on efficiency, and are more expensive to develop. Some engines could (like the space shuttle, which can in RO aswell). Also, for early stages, it isnt really needed to throttle engines. With the Saturn V, they switched of 1 of the 5 F1 engines half during the first stage, to ensure that the G's on the astronauts wouldnt exceed 4g.

As for getting orbit, do you use MechJeb? It tells you your starting Thrust to weight ratio, as well as your maximum TWR per stage. 15g seems a bit much yeah. My stages hardly get above 4. Do you use multiple stages to get orbit?

Some advice:

-build a multiple stage rocket, first stage should start at arround 1.2-1.7 TWR, and get no greater then 5. Second stage can start at arround 1TWR, and should also not get much greater then 4ish.

-You need about 9.5k m/s to get orbit. Build a rocket with 10k m/s to be able to adjust for mistakes during ascent.

-Use a gravity turn!
Meaning that at arround 50 m/s (just after take-off), slowly pitch over east, and then just keep following your prograde marker, untill your prograde is horizontal arround 250km. Its no problem to archieve orbit after Ap. Again, mechjeb has an ascent guidance feature, you can set the orbit altitude (and some other functions if you wish, or let mechjeb fill them in automaticly), and let it place a target on your navball, if you keep your prograde near the target marker, you get a very smooth and efficient gravity turn.

If you have any more info on exactly where the problem lies with archieving orbit, its no problem to help you more.

Good luck!

Edited February 15, 2016 by CitizenVeen

[NathanKell]

Some tutorials:

https://github.com/KSP-RO/RealismOverhaul/wiki/First-RO-Rocket

https://github.com/KSP-RO/RealismOverhaul/wiki/Ferram's-Launch-Vehicle-Tutorial

https://github.com/KSP-RO/RP-0/wiki/Tutorial:-Reaching-Orbit

[berkekrkn]

On 2/15/2016 at 2:01 PM, CitizenVeen said:

Alot of engines can't, throttling an engine usually has a bad influence on efficiency, and are more expensive to develop. Some engines could (like the space shuttle, which can in RO aswell). Also, for early stages, it isnt really needed to throttle engines. With the Saturn V, they switched of 1 of the 5 F1 engines half during the first stage, to ensure that the G's on the astronauts wouldnt exceed 4g.

As for getting orbit, do you use MechJeb? It tells you your starting Thrust to weight ratio, as well as your maximum TWR per stage. 15g seems a bit much yeah. My stages hardly get above 4. Do you use multiple stages to get orbit?

Some advice:

-build a multiple stage rocket, first stage should start at arround 1.2-1.7 TWR, and get no greater then 5. Second stage can start at arround 1TWR, and should also not get much greater then 4ish.

-You need about 9.5k m/s to get orbit. Build a rocket with 10k m/s to be able to adjust for mistakes during ascent.

-Use a gravity turn!
Meaning that at arround 50 m/s (just after take-off), slowly pitch over east, and then just keep following your prograde marker, untill your prograde is horizontal arround 250km. Its no problem to archieve orbit after Ap. Again, mechjeb has an ascent guidance feature, you can set the orbit altitude (and some other functions if you wish, or let mechjeb fill them in automaticly), and let it place a target on your navball, if you keep your prograde near the target marker, you get a very smooth and efficient gravity turn.

If you have any more info on exactly where the problem lies with archieving orbit, its no problem to help you more.

Good luck!

Thank you very much for your answer. Which engine mod do you recommend I'm searching engines for 2nd stage. 300-400 kN thrust and more than 1 ignition. I have so many engine mods but they are either too strong or too weak.

Edited February 19, 2016 by berkekrkn

[NathanKell]

Don't have any immediate suggestions, but:

1. You often need far less engine than you think you do. 6-8 minute burn times are not uncommon for upper stages. Heck, the current EELVs have 10-20 minute burn times for their upper stages!

2. Clustering is very simple: all engines surface-attach in RO, so just add multiple engines. Bonus: roll control!

[Temeter]

2 hours ago, berkekrkn said:

Thank you very much for your answer. Which engine mod do you recommend I'm searching engines for 2nd stage. 300-400 kN thrust and more than 1 ignition. I have so many engine mods but they are either too strong or too weak.

The LR-87 has some variants with multiple ignitions, which tends to be quite useful. Go for the J2 if you need a bigger 2nd stage engine, they have 2x ignitions and have at least limited throttle. LR is in stock RO, J2 is e.g. in FASA and SXT.

In my experience, most RO rockets don't need multiple ignitions tho, it's very viable to do orbit in a single burn.

Edited February 19, 2016 by Temeter

[NathanKell]

Unless you are going to Medium Earth Orbit or higher, you definitely don't need multiple ignitions, @Temeter is very correct here. Even then, you probably can do the circ burn with the payload, it'll only be like 100m/s for a MEO circ from a 185km perigee. The key is to control your vertical velocity with pitch in order to achieve 0m/s vertical velocity at your insertion point.

[Temeter]

When it's about earth orbit, the satellite is usually my last rocket stage. It's quite cheap to get a up to additional ~3k delta-v that way.

[CitizenVeen]

@berkekrkn, did you work ik out?

The engines I used most are the RL10, and J2 engines, and bigger more powerfull one for lower stages, the F1's or so. Often multiple if 1 doesnt get me enough TWR on that stage.

Deriving from the fact that you keep asking for either throttable or multiple ignitions engines, it appears to me that the problem does not lie with choosing wrong engines or rocket design, but with the way you ascend into orbit. If you want multiple ignitions, it seems to me that you first raise your AP to out of the atmosphere, then switch of your engines, wait untill AP, and then circulize. Thats (not the most effective) but a possible way to gain orbit in stock, in RO its really a very bad way though.

What you want to do is pitch a few degrees east pretty much straight from the launchpad (I usually do this when I reach a speed op 40 m/s). Then keep following your prograde marker. You will slowly increase your AP while you gain alot of horizontal speed. I often make orbit after reaching my AP (which is usually 200km or so). If youre still having problems I can make you a imgur tutorial?

[Galile-Ho]

Lack of throttling capability makes it hard to land

Correct me if I'm wrong, but we haven't developed many real engines with deep throttling capabilities.  Maybe this is because the space programs haven't focused on landing on planets / moons for a while?  Other than the Lunar Module Descent Engine there seem to be no other options in KSP-RO.

The space-x super draco is is a non-RO part, and it is still an experimental engine.  The performance specifications indicate an Isp of 275, which is inferior to the LMDE.  

I was also wondering if the Mars Landing Engines (for the Curiosity Descent Stage) are available in RO?

Any help on landing with / without throttle-able engines would be much appreciated.