Rockets not firing?

[Biker Joe]

Hello to all!

1

I'm after leaving 2 Kerbals stranded on the Mun and this is my recovery craft!

Problem is when it's on the launchpad and I turn up the throttle and press space theres a wooshing noise then nothing...

What am I doing wrong?

Edited November 9, 2013 by Biker Joe

[Rhomphaia]

After a failed launch, hit F3 to bring up the flight log.

If you see structural failure between... then moar struts.

[Kerbal01]

Elevate the engines higher off the pad, it's an annoying bug called the sticky launchpad bug it has no fix.

[Biker Joe]

After a failed launch, hit F3 to bring up the flight log.

If you see structural failure between... then moar struts.

It could be a structural thing, would that cause the rockets not to fire? I'll have to look over my design tomorrow!

Elevate the engines higher off the pad, it's an annoying bug called the sticky launchpad bug it has no fix.

Tried changing the elevation above the pad but same result!

[miketheveeg]

Problem is when it's on the launchpad and I turn up the throttle and press space theres a wooshing noise then nothing...

that sounds like the engines are 'activating' but then not firing...

have you tried hitting space again?

[Tank Buddy]

You probably could trim off some fat off of that lander...

[700NitroXpress]

If you don't have any struts supporting the center of the craft, then the force caused by it being dropped on the launch pad could be breaking a connection somewhere. If you lighten your craft and use different propulsion that should fix it. Also you don't want to have the blue decouplers, those always seem to cause more harm then good. Also, make sure the craft has power. Get rid of all the RCS, you can use SAS for turning, RCS is for docking only.

[Superfluous J]

What moon are you sending this to? One around another star?

You could cut that craft down by about a factor of 6 and probably still get to Mun and back. It's likely ripping itself apart on the launch pad.

[700NitroXpress]

Here's a better and more lightweight option. This lander has an unmanned pod so you can send it to the moon. Jet engines lift it up through the thick atmosphere, then the solid boosters push it up the rest of the way. The rest is asparagus staging with slack tanks on the outsides so you're only dropping dead fuel tanks and not fuel tanks with engines attached. This has more than enough power to get to the moon and back to Kerban and land on both.

[I_Killed_Jeb]

the above seems more like a subtle brag than a helpful suggestion...

as others have suggested OP, your rocket is probably breaking at lauchpad load, strut the sh!t out of it.

[700NitroXpress]

the above seems more like a subtle brag than a helpful suggestion...

as others have suggested OP, your rocket is probably breaking at lauchpad load, strut the sh!t out of it.

Not really, let me explain.

He's using a 3 man pod for a mission that can be done with a 2 man capacity craft + 1 unmanned module. This example craft only has one SAS unit and no RCS. When you make lightweight and compact craft, you don't need RCS for assistance, like I stated before above, RCS is really only for docking and on his craft it's just excess weight. Also, you should never stack the orange fuel tanks like that because you're pushing that excess weight for a longer period which requires more fuel. On my craft, you put the extra tanks on the outside of the craft so that you're dropping the spent tanks instead of carrying them with you longer than you need to.

The key points to take away from my example that you can use to improve your rescue craft are these:

1. Use SAS not RCS

2. Lighten your craft for the mission it's needed for

3. Don't carry excess weight with you

4. Lightweight craft won't have the issues with destroying themselves on the launch pad

5. Always support your craft properly with launch clamps if it can't support itself

In the picture of the craft in question, there's at least 120 tons of unsupported weight that's resting on the radial decouplers and that's probably what's causing the problem, they're breaking. Either that or the blue decouplers are breaking, my money's on the blue ones.

Later on I tested this, here is a back to back comparison of Red vs Blue decouplers. Red obviously wins. The blue one holds 3 grey tanks barely, red holds many. With the orange tanks, blue holds none and red holds the same as the grey tanks shown below. This tells us that the red decoupler should always be used instead of the blue decoupler whenever possible.

Edited November 8, 2013 by 700NitroXpress

[KerbMav]

It could be a structural thing, would that cause the rockets not to fire? I'll have to look over my design tomorrow!

Yes, if something detaches from the rocket an that something happens to be between fuel tank and engine, there wont be no big fire to ride on.

Use some struts - 2-4x symmetry - to tape the rocket together at its weak part.

You can also try using more launch clamps and/or fitting them on different spots.

[Biker Joe]

Before I went to bed last nite I came up with another design! gonna give that a try first and if I can't get that to work I'll revert to my original design.

I like to massively over engineer stuff that why its so big (really I'm paranoid about running out of fuel!) but if anyone has any suggestions on what they think will do the job feel free to post up your ideas!

Thanks

[Superfluous J]

The joke about "MOAR BOOSTERS" is just that: a joke. All that fuel is doing is lifting the fuel. I hate to self promote but I *just* did a Munar mission (Part 1 is up and part 2 is uploading now, should be ready to watch in 30-40 minutes) and my ship is TINY compared to yours. Now, I cut it pretty close on purpose because I like to be efficient, but if you brought just a little more fuel than I did you could easily get there and back without shattering your connection points under the strain.

Part 1:

Part 2:

[SRV Ron]

So correct. Only take what is needed for the job. Get the efficiency into orbit down to around a 6 to 1 ratio. That takes good design. Anything way over that is just wasting fuel. (Exception is a SRB ring for the first 3,000 to 8,000 meters)

Two examples: Minmus lander in Career Mode;

Launch vehicle;

Lander;

A heavy lift to orbit.

Launch vehicle;

In orbit,

Adding a half tank in the core state and a short burn of thrusters placed the fuel can into a 100k Mun orbit.

[KerbMav]

Before I went to bed last nite I came up with another design! gonna give that a try first and if I can't get that to work I'll revert to my original design.

This will happen more than once, believe me!

I like to massively over engineer stuff that why its so big (really I'm paranoid about running out of fuel!) but if anyone has any suggestions on what they think will do the job feel free to post up your ideas!

Get KER - Kerbal Engineer Redux and look for a dV map.

Then you can design all your stages to have the thrust and fuel they need for their purpose - and still build in a safety margin if you like.

Some may call this cheating, because they like to do all calculations of fuel consumption and mass of each stage for themselves - but whatever makes anyone happy!

http://forum.kerbalspaceprogram.com/threads/56898-Eve-Rescue?p=760497&viewfull=1#post760497

Edited November 8, 2013 by KerbMav

[SRV Ron]

Another example, a bare minimum suicide launch to orbit two stage with 3 kerbals. Flown correctly, there will be fuel left for a return. Note how small this design is.

Preferred launcher is this one with the added safety of the RCS for a deorbit burn.

[DrMonte]

I think seven Main sail engines is not enough to lift the rocket. That's why it is stuck.

So no bug, just redesign.

[Spyritdragon]

Hello to all!

1

I'm after leaving 2 Kerbals stranded on the Mun and this is my recovery craft!

Problem is when it's on the launchpad and I turn up the throttle and press space theres a wooshing noise then nothing...

What am I doing wrong?

Activate the engines on the launchpad first, bring them up to full then decouple the stability enhancers, see how that happens.

Also, to see whats going on, bring your stability enhancers up to a reasonably high level. Throttle up and activate your engines, then right-click them. If you dont get a context menu, you have a structural failure on your craft even before you hit the ground and you probably need more struts. For the engines to work normally, they should be in a nominal state in the context menu.

Also, as mentioned before, those large stack seperators aren't all too strong, and you have a (very) heavy lander. Attach nukes to that instead of poodles, and you have a Jool craft. Jool and back, probably. You'd better replace them with a decoupler and try again.

Edited November 8, 2013 by Spyritdragon

[toomuchbrew]

What moon are you sending this to? One around another star?

LOL

Yeah, you are basically building this rocket to move fuel into orbit. Sometimes LESS is a lot more. It could be the connection above the orange tanks is breaking. Not catastrophically, but enough downward force to make the lower stages disconnect and become debris.

[Rhomphaia]

I think seven Main sail engines is not enough to lift the rocket. That's why it is stuck.

So no bug, just redesign.

Plent of thrust to get of the launchpad. somewhere around 1.4. problem I noticed when I tried to recreate the build is structural failures around the stack separator underneath the upper stage. replacing with a stack decoupler and strutting the upper stage to the lower better should fix that issue.