Payload Efficiency Challenge

[Laie]

Nukes to the rescue:

This baby takes 137.3 tons to orbit, consuming 13.23t of solid fuel and 575t LF/O. That should amount to 392funds per ton but adding up the actual recovery values as displayed on the screen, I ran at 390.5 funds. Riddle me this.

I'm too lazy to make a gallery that will be viewed five times at most, though. Craft file is here, ascent profile is visible on the screen.

Note that the booster's parachutes do not deploy from staging (they'd fold up/get cut); so wait until after the nukes have been ignited, then switch vessels and deploy chutes (ABORT action group -> backspace). You can watch them land if you feel like it, MJ will look after the lifter in the mean time. But MJ will not stage while you're watching other vessels, that's why you have to wait for the Nervas first.

Also note that no matter how many struts I put on that thing, it won't survive a chute-only landing. The given ascent profile should leave you with ~200m/s of nuclear delta-V after discharging the payload, but don't use more than half of that for your de-orbit burn. Remaining fuel should be moved to the quad clusters for landing at 8m/s.

Discussion: The boosters are the kind of shenanigans one does for a challenge. You can take away the boosters at the bottom, remove the small tank from the payload, and cost will go up only slightly. Nukes shouldn't be ignited on the ground, though, but only after 12-15 seconds of flight. The main purpose of the boosters is to provide that delay.

Edited February 4, 2015 by Laie

[ttnarg]

You can watch them land if you feel like it, MJ will look after the lifter in the mean time. But MJ will not stage while you're watching other vessels, that's why you have to wait for the Nervas first.

Dose MJ Keep the the stages loaded when they are apart? if so thats a big advantage over stock. I was thinking of using the "Flight Manager for Reusable Stages" mod to do this. The reson why I used such a big engine on my upper stage is so that I could get the burn done in time to sech back to the first stage and land it.

[Laie]

Dose MJ Keep the the stages loaded when they are apart?

Nope. They're staged so early that they're safely back on the ground before the rocket is really underway. Which just worked when I tried it the first time, but then found to be unreliable because of the folding parachute thing. So now there's probe cores on them and one has to switch vessels and whatnot, all that only so that the nukes don't ignite before you've gained at least some altitude (1000m would do).

Fun part is that I since have noticed that a simple 12 second pre-delay on MJ's staging would do just the same.

Those boosters save me a whopping five funds/ton; the losses from just igniting the Nervas on the ground would be in the same ballpark. But for the purposes of this challenge, give or take ten funds is a lot.

[Right]

@KCS Thanks for pointing out the typo. And way to make my eyes bulge with such a massive SSTO payload! Perhaps the most impressive aspect is that you did it with so few parts! Those B9 engines and giant intakes are a big help I'm sure. Still, a plane that size in FAR is equally impressive. Kudos indeed!

@Laie I've been waiting for someone to bring the nuke engines into the big leagues! I experimented with it myself, but to no avail. I must be flying your craft wrong though. I can't get the boosters stage to land for recovery before reaching the 2.5k bubble, even without arming the chutes until just before landing.

Funny enough though, I'm working on a design which uses the same idea as your booster 'shenanigans'

[kcs123]

@Right, thanks, building that plane was challenge by itself, but numbers shows that it is worth to do it - 57.43 cost/t and wide 24m cargo bay offers room for 2.5 m space station parts with some stuff attached to sides like solar panels and similar.

Doubt that I will carry more than 100t at time, but with ability for more than 300t will give some extra dV for reaching higher orbit in space.

[Laie]

@Right: I don't know why it doesn't work for your or how to debug this. Could you please assume "dumb" boosters (no probe core, chutes, etc) that were simply discarded? That would increase the price by 10 funds/t, to something like 402funds/t.

Running on nukes alone would be slightly cheaper in that case, but requires a different ascent profile. I'll report back with figures for MJ.