Test BACC "Thumper" at 240,000m

[Rydium]

Hi everyone,

I've recently picked up a contract to test a BACC "Thumper" Solid Fuel Booster in a sub-orbital trajectory.

Now, I thought I had to do this at an altitude of 24,000m to 25,000m. Seemed easy enough...

After accepting it, I realised the actual altitude was 240,000m to 250,000m!

I've tried every possible design I could think of, and every trajectory said designs would allow, and I don't even come close to reaching that altitude with a Thumper attached.

Any ideas?

I've attached my current inventory. Thanks for any help!

[Plusck]

Whatever you do is going to be difficult because you probably don't have a decent probe core. Therefore you need to either send a pilot (and not have her die on reentry), or deal with added difficulty trying to get the ship to go straight with the Stayputnik..

Whatever you do, though, empty all or almost all the fuel out of the Thumper first. Then build a rocket as if you were going to go to the Mun, but with the thumper as payload instead of science and fuel.

Also, what VAB/launchpad levels do you have?

You'll need fins and very careful flying, because the empty Thumper will want to fly behind the engines rather than in front.

For the design, I'd try a relatively small tank under the Thumper with Swivel, then on the sides (with crossfeed enabled) more fuel and Reliants.

Just gonna go see if this is possible.

[Technical Ben]

Get it down to almost empty in the vab. Then use solids or fuel tanks to launch it straight up?

[Magzimum]

Well, at least the contract asks for "sub-orbital" so you really only need to go straight up.

In a quick-and-dirty test, I found that the design in the spoiler below will reach the needed altitude, with the thumper unused (i.e. available to be activated through the staging sequence):

Spoiler

 

So, you will need to build a rocket with multiple stages. I am working on the assumption that you have access to the basic decouplers. Put the thumper at the top, and put another thumper below it as a 2nd stage. Then place some more thumpers (e.g. 4 of them) radially around the bottom one. 

With the basic rocketry-violence sorted, you may want to look whether you're going to satisfy just that contract, or perhaps do a little science too. If you are already at 240,000 m altitude, and you ignite that last thumper, you may reach altitudes that you haven't reached yet. Better do some science up there! However, landing the science equipment will also be more challenging than previous missions. You will need a heat shield, and depending on the design, you may want to package the science equipment in some container to keep from exploding. 

Btw, often the contracts also demand a certain velocity (next to the altitude), which makes life more difficult. If your contract does not, don't worry about it. If it does, please update this thread, and we can see how that complicates things. 

Edited October 23, 2016 by Magzimum

[Plusck]

Ok, well this works to get you high enough - and is well within the 30 part limit. It weighs just under 18t (but you must empty the monoprop from the command pod). No fins because it has the Swivel and it's going mostly straight up anyway.

However, there is no guarantee that you'll be able to survive the return to Kerbin from there. I managed to get it up to 240km with half of that bottom tank full, but the return was very steep (I didn't really try very hard to do the mission, I must admit). Keeping everything attached until it blew up helped, but Valentina lost consciousness on separation and only woke up again about 2000m from the ground.

So ... it's guaranteed survivable, less than 30 parts and 18t, and gets you where you need to go. But it is a dangerous mission

 

Edit - just tried with a Stayputnik instead of a command pod to see if it's possible. Works fine but you must put the central fuel tank at the top of the rocket, and you need to add fins (I used elevon 1s, which are what I use all the time for low-tech stuff, if possible).

Edited October 23, 2016 by Plusck

[ForScience6686]

Launch vertical until you reach the designated altitude.  Then, to avoid frying on re entry, burn what ever you have horizontally to increase your aero braking time without going orbital.

[kurja]

14 hours ago, Plusck said:

Whatever you do, though, empty all or almost all the fuel out of the Thumper first. Then build a rocket as if you were going to go to the Mun, but with the thumper as payload instead of science and fuel.

I disagree - no need to de-fuel it, better use it as the final stage. This means you'll be firing it before reaching the required altitude you'll say, but it's no matter, once up there you can right click the part and run the test to fulfill the contract. Activating the part through staging is not necessary even when it says so in the contract description.

[Plusck]

6 hours ago, kurja said:

I disagree - no need to de-fuel it, better use it as the final stage. This means you'll be firing it before reaching the required altitude you'll say, but it's no matter, once up there you can right click the part and run the test to fulfill the contract. Activating the part through staging is not necessary even when it says so in the contract description.

Ha - well there you go.

I've always followed the instructions to the letter for the test contracts, so I haven't even tried to get around the wording.  
Which in this case is clearly wasting time and effort - a single Thumper + probe core will probably do fine if you can click test afterwards.

My most weaseling (and highly profitable) refusal to respect the spirit of contracts is the "mine ore on X and deliver ore to Y" - it's a fungible commodity so any ore'll do... ; )