Reverting again (The problem with SRB's)

[SpacedCowboy]

In short, how many times do you have to revert back to the VAB to adjust those SRB's nozzles to get that perfect thrust? I know in the real world, they are not adjustable on the pad, but,,, KSP is a game. Wouldn't it be sweet if one could do so?

Not making a suggestion here (because I did so a couple of years ago) Just wanted to converse about it.

[Dfthu]

Yea, that kinda sucks. Usually I have to revert 1-3 times but I do remember once I do to revert 10 times. But would we have to revert to launch to adjust the thrust.

[SpacedCowboy]

10 minutes ago, Dfthu said:

Yea, that kinda sucks. Usually I have to revert 1-3 times but I do remember once I do to revert 10 times. But would we have to revert to launch to adjust the thrust.

Well yes. but just having to revert to launch would so much help "playability" of the game.

[Rocket In My Pocket]

I gotta be honest, I never worry about it to much.

I'd be far more likely to go back and adjust the number/type of SRB's before I tweaked the thrust settings. I'll admit, I'm impatient when it comes to rocket launches so I never mind having a TWR of 2.0 or higher.

That said, I can't see how it would hurt to let you tweak it on the launch pad, so long as you can't tweak it once the craft has been launched.

[OhioBob]

Why can't you get it right the first time?

[maccollo]

Pretty much never since I always run them at max thrust.
edit

High thrust/cost ratio is one of the advantages of solids. Reducing thrust doesn't seem to make sense. If I have more power than I need, then I balance that by switching to a weaker engine on the core, or by piling on more liquid fuel.

Edited July 3, 2016 by maccollo

[SpacedCowboy]

5 minutes ago, OhioBob said:

Why can't you get it right the first time?

If I knew that, I never would've made this post. Sorry but I play vanilla and don't rely on MJ, KER and such. Yeah, I like to "eyeball it".

[Netherman555]

Well I start to hate myself after a few times so...

But I disagree, I think it would be slightly unrealistic in an annoying way to have it.

But every man to themselves I guess.

[the_Demongod]

If you really care that much about getting a good SLTWR, use KER. I don't understand, like if you want to be able to reliably design rockets without having to test them endlessly, just use KER and that takes half of the guesswork out of the equation.

[Snark]

1 hour ago, OhioBob said:

Why can't you get it right the first time?

^ This!

1 hour ago, SpacedCowboy said:

If I knew that, I never would've made this post. Sorry but I play vanilla and don't rely on MJ, KER and such. Yeah, I like to "eyeball it".

Yes, but the math is really simple.  You don't need MJ or KER.

Seriously, it takes like five seconds with a calculator.  Take your total ship mass, multiply by 9.8 (Kerbin gravity), multiply by your desired launchpad TWR (I like 1.5, pick your own), then divide by the combined thrust of the SRBs.  That's your thrust percentage to set the SRBs at.

Bam.  Over and done.  Perfect launch, every time.

[Jetski]

Also if you don't like mods then perfect it once with lots of testing, then save it as a sub assembly. Note payload weight, and repeat a few times for various payloads. 

[nosirrbro]

uhm, ever heard of kerbal engineer?

[Madrias]

Never.  If I'm resorting to tubes full of stuff-that-goes-boom, then I'm going to use as many as I feel I need to blindly chuck my rockets into orbit.  If I've got a few extra boosters on my ship when I'm nearly in orbit, I'll drop them there.

[samstarman5]

If you are looking to be precise with burn times, power of thrust, and weight ration, then you should be more than willing to find out and do the math.  Otherwise, I fail to see the big deal to have to go back to the VAB to adjust.

[Madrias]

As any KSP player knows well:

There is nothing wrong with More Boosters.

 

(Now, if you're playing in Career mode, by all means, do the math or guess-and-check with TWR and thrust balancing.)

[GoSlash27]

Same as the others, I don't have to revert and tweak to get the thrust balanced. I do the math during the design stage so there's no guesswork.

Best,
-Slashy

[Draco T stand-up guy]

8 hours ago, SpacedCowboy said:

Sorry but I play vanilla and don't rely on MJ, KER and such.

I consider those to be essential features missing from vanilla. You don't design rockets by guesswork even in a game like KSP.

[AlamoVampire]

8 hours ago, SpacedCowboy said:

If I knew that, I never would've made this post. Sorry but I play vanilla and don't rely on MJ, KER and such. Yeah, I like to "eyeball it".

You are the kinda person who scares the heebie jeebies outta me. How can you not use autopilot? How can you manually fly the same profile hundreds of thousands of times? How do you have saint like patience to manually babysit huge burns? You have more patience than I. Now, <runs off mid thought as impatience takes over again>

[Madrias]

I don't typically auto-pilot, either.  I've had MechJeb installed a few times, only to find out that about the only things I use on it is the landing assistance and the docking assistance.  That, and I usually had no problem letting it handle burns for me.  But, time and time again, I found MechJeb wasn't really helping me get into space.  Might have to do with the fact that I'm a spaceplane pilot, or that I'm an idiot who doesn't know how to configure MechJeb properly, but basically, I fly to orbit, Mechjeb handles any dockings, helps me with landings, and flies my ship between point A and point B.  When I remember to install the silly thing.

[pandaman]

All opinions are valid. 

 I use KER, but revert to assembly is an option I often use in my R&D saves, for whatever reasons, when stuff goes to pot.

However, I don't see why being able to adjust SRB thrust on the pad is, in game play terms, any different  to going back to the editor.  It saves a click or two and a few seconds maybe, but that's about all, so I don't see why it shouldn't be an option apart from perhaps a programming perspective where on the launchpad or runway under physics load counts as 'in play'.

[Champ]

I think the reason you can't adjust SRB thrust percentage on the launchpad is because if you can adjust it on the launchpad, then you can also adjust it in flight. And this is really impossible with SRB.

[Vaporized Steel]

What is perfect thrust? Can you tell me? Mine is over 9000 TWR, what's yours?

The way I see it you want maximum thrust to get out the atmosphere ASAP, because that saves you your Delta V to orbit, especially if the rocket is aerodynamically shaped.

SRBs are auto set at max. I'm not sure why you would even want to readjust them. Math or no math, Ker or no Ker, Mj or no MJ.

Unless your care about the Kerbals and their precious G meter, which shouldn't matter anyway. Because Kerbals can survive prolonged G's in ways that doesn't allow me to break a Kerbal body, with any of the SRBs btw. That said, I haven't fully tested it.
 

[THX1138]

47 minutes ago, Vaporized Steel said:

What is perfect thrust? Can you tell me? Mine is over 9000 TWR, what's yours?

The way I see it you want maximum thrust to get out the atmosphere ASAP, because that saves you your Delta V to orbit, especially if the rocket is aerodynamically shaped.

SRBs are auto set at max. I'm not sure why you would even want to readjust them. Math or no math, Ker or no Ker, Mj or no MJ.

Unless your care about the Kerbals and their precious G meter, which shouldn't matter anyway. Because Kerbals can survive prolonged G's in ways that doesn't allow me to break a Kerbal body, with any of the SRBs btw. That said, I haven't fully tested it.
 

I don't know what the sweet spots are but I do know that it's not fuel efficient to go too fast because of air resistance. It used to be most efficient to stay at terminal velocity but everything changed after an update in the past.

[Vaporized Steel]

Terminal velocity is not a constant, it is based on the aerodynamics of your rocket. Terminal velocity used to be a thing to gauge speeds during takeoff in the old soup atmosphere, where it simply didn't matter whether your vessels was aerodynamic or not. So for every layer of altitude there was a constant terminal velocity regardless of what vessel you were using. Ofcourse I'm going overboard by saying that you should always want the thrust set at max, in some cases your going to get over terminal velocity, which depends on your design. That would only be for a short while in the lower atmosphere. Since the lower atmospheric layer of Kerbin is negligible in size, your going to lose little if you go over terminal velocity, just make sure you don't go over it to much. And I don't think that would happen in most cases, unless it's a pod with a SRB directly underneath.

In which case your probably playing very early career, the only point in the game where I would even want to touch the thrust limiter on the SRBs.

The most efficient Kerbin launches Delta V wise are those with very high TWR and a very narrow ascent path.

[cantab]

Calculate twice, fly once.

The maths isn't that hard, provided you know how to use and rearrange formulas. That's like year 7 stuff, learn it when you're about 12, but I suppose you might have forgotten it.

Depending on my rocket design, thrust limiting SRBs may be called for. In particular if I use a core stage that's already low TWR, and boosters to get it going off the pad, lighting all engines from the start, then when the boosters drop I need the core TWR to have risen enough thanks to fuel burnoff and the higher altitude, and that may mean running the boosters at lower than max thrust so they last longer.