The BACC Haul thumper Contract has changed

[Rhombeus]

Altitude 46,000m to 49,000m

Speed 200m/s to 260m/s

This is a very tough nut to crack.

All my large craft seem to just fly off at angles from launch, even totally symetrical rockets with fins.

The only way I managed to get up at that altitude was with a load of stacked hammers but I had no way of slowing my ascent so my speed was way to high.

Anyone got any build ideas?

 

[sal_vager]

Welcome to the forums Rhombeus

This contract is possible with careful adjustment of the Thumpers fuel load, ideally you'd burn out early and coast up to 60 or 70km, hitting 200/260m/s as you hit 46km.

Not easy, but you can keep recovering the craft and only pay for the fuel if you add enough parachutes and some landing legs

[Snark]

Welcome to the forums!

Can you post a screenshot of what you tried?  Then we can give some specific advice.

It sounds like you have two problems, one general and one specific:

1. General problem:  "How do I keep my rocket stable so it doesn't flip out?"
2. Specific problem:  "How do I get a Thumper where I need it for this contract, under these conditions?"

Regarding #1, it would really help to see a screenshot so we can offer specific advice.  "Add fins" is good advice, but they have to be in the right place; poorly placed fins can actually make the problem worse.  So I'll defer addressing that one until you post a screenshot.  The general guideline is "pointy in front, draggy in back, make sure center of mass is as close to the front of the rocket as possible."

Regarding #2:  there are a few things you can do:

• You can reduce the fuel content of the Thumper in the VAB (i.e. launch it partially empty, or even completely empty).  This will make it a lot lighter and therefore easier to lug into the right spot using other rocket engines.
• If you're flying using SRBs as engines to lift you, and they're too powerful and making you go too fast:  you can adjust their thrust.  Not with the throttle (the way you can with liquid-fuel engines), but you can set the thrust amount in the VAB by right-clicking on them.  Note that reducing the thrust doesn't mean you're giving anything up-- it's not wasting fuel, it's just burning the fuel more slowly.  For example, if you set the thrust to 50%, it means the rocket will get half the thrust but will burn twice as long.

Screenshot would really help.  Post them on some site like imgur.com, then use the "insert other media" button at bottom right here and choose "Insert image from URL", and paste in the URL of the screenshot.

[Reactordrone]

Something like this should do the job. Fly almost straight up and cut engines when your apoapsis hits 49km. You should slow down to the test speed range inside the altitude limits then ride the thumper into a sub-orbit

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Edited January 3, 2016 by Reactordrone