Smallest Rocket To Orbit Challenge!

[foamyesque]

I see nobody's yet managed to beat my old 0.645t unmanned flight

I should try and see if I can replicate that in the current version. There've been changes to the rocket parts since then, I believe.

 

[foamyesque]

Ok, so, with the changes to the Spark engine back when 1.7 was released, my old design still doesn't quite manage it. The extra weight in the engine of itself increases the mass by 0.03t, and that means more fuel had to be added. Fortunately enough, the old layout deliberately had fuel removed. So, I rebuilt the machine and burned a pile of time balancing it out and re-learning the ascent profiles. The extra mass on the bottom hurts the aerodynamic stability, which was a real pain.

Also, I notice the OP says 'no clipping to exploit physics' here. For full disclosure, I used the translation tool to center a single Spider engine for my upper stage, in (roughly) the same spot as you'd use an Ant. I would consider that allowable as I am not getting anything for free, e.g. dragless parts or such.

Ascent profile was a full throttle launch, tipping to 5 degrees. At 100m/s, change the SAS to prograde. At 200m/s, throttle down to 66%. At 9km/fuel draining from the upper tank, throttle back up to 85-90%. At 11LF remaining in the upper tank, go to full throttle. At 10LF remaining, jettison the lower stage. Prograde hold to raise the apoapsis to ~68-70km, then switch to hold-attitude, and maintain a constant apoapsis of just over 70km.

Done correctly you should get the apoapsis and periapsis trading places about one second before you run out of electrical power for the probe core.

Part inventory:

1 small nosecone (0.01t)

1 OCTO2 probe core (0.04t)

2 full Oscar-B fuel tanks (0.45t)

1 Spider engine (0.02t)

1 TD-06 decoupler (0.01t)

1 Z-200 battery (0.01t)

1 Spark engine (0.13t)

Total mass: 0.67t. Total funds: 2,670 (the probe core being 1,480 of that :D)

Some screenshots -- flight was unfortunately rather busy so couldn't take 'em en route, but VAB, pad, and orbit in both map and main view are here:

 

 

-- I only realized the apsis were missing after I had reverted to the VAB. Achieved orbit was 70.5km x 88km.

 

 

 

 

 

Edited December 1, 2020 by foamyesque

[Alpaca Z]

My first submission to this challenge. 

Bill to orbit in 713 kg, and probe to orbit in 659 kg.

Mission reports and videos here.

Not sure if the OP is still around, maybe I should have started a new challenge thread?

[Alpaca Z]

Update: Bill to orbit and back in 671 kg and probe to orbit in 543 kg + probe to Minmus in 763 kg

 

I think I might re-open the challenge in a new thread, if no one replies to this one in a few weeks.

Edited July 31, 2022 by Alpaca Z

[swjr-swis]

1 hour ago, Alpaca Z said:

I think I might re-open the challenge in a new thread, if no one replies to this one in a few weeks.

Last entry before yours hasn't been processed yet in almost two years. I'd say it's quite safe to start a new one..