Stock Payload Fraction Challenge {1.3.x Reboot}

ATEC · December 5, 2017

@swjr-swis It was supposed to be in the rules from the start. It wasn't clear so i changed it up

@Fauble2000 Current non-nuke record is 27.6%

@SanderB I'll agree with you on the non-alikeness and have put it up on the leaderboards

@Fauble2000 You are up on the board. I like the design with the open-ended fairing, will try and use it in my next build.

swjr-swis · December 5, 2017

12 minutes ago, ATEC said:

It was supposed to be in the rules from the start. It wasn't clear so i changed it up

Ok, so just an arbitrary change compared to previous versions then. It's your challenge, so you get to set the rules - that's fair. I just thought I had missed something since it came up after there had already been several accepted entries with nukes.

So moving forward with the no-nuke rule, two corrections the OP needs:

You still have a rocket listed in the Rocket Only category that uses a nuke as last stage (Fauble2000's 27.336% fraction, at the moment in 3rd position, Nerv visible in the last screenshots). It now belongs in the Unlimited category. He still has the valid 1st entry in the rocket-only category, so it should not upset anything.
You forgot to mention 'no (...) nerv' in the Rocket Only category description. See below:

On 11/13/2017 at 7:04 PM, ATEC said:

Rocket Only: Rocket engines only (no ions, jets, or Rapiers in open cycle mode), no recovery necessary.

Rocket Only Recovery: Rocket engines only (no ions, jets, nerv's or Rapiers in open cycle) all stages MUST be recovered.

ATEC · December 7, 2017

Fixed both of those things @swjr-swis

Thanks for telling me

sevenperforce · December 12, 2017

Since no one has yet done a "rocket only recovery", allow me...

Quick and dirty, and I had a bit of margin left on both stages, but overall not a bad attempt. Comes in at 7.5% payload fraction with full recovery of upper stage (via chute) and first stage (rocket-assisted splashdown).

228.066 tonnes liftoff mass.

Spry 2.5 gees off the pad...going to try and negate as much gravity drag as possible.

Quick nose-over.

My theory is that with a lot of thrust, I'll not only get lower gravity losses, but I'll also get a high apoapse quickly, to give me more time for the upper stage to circularize.

Definitely got the "hot" part down.

Staging.

Four Darts give me a nice respectable TWR. Once I'm up to where I want to be, I'll do the final circularization with the single Terrier.

Super lofted trajectory so I'm pointed way under the horizon to circularize. More lofted than is efficient, but it was necessary in order to get enough time to recover the first stage.

The trick is to finish your circularization while the first stage is still above 70 km.

Almost there.

Orbit achieved! If I was pressed for time I'd wait to raise periapsis while I took care of the first stage, but I have plenty of time here.

There's my orbit!

Switching back to the first stage.

Transferring prop from the locked upper tank to the lower one, to improve my CoM.

Brakes out and here goes entry.

Hot!

Going to wait until I'm closer to terminal velocity so I don't waste prop.

Here goes that three-engine landing burn! Any more engines than this and it would be hard to control on the fly...especially since I'm doing this manually.