40% payload SSTO- I WILL DO IT!

[quasarrgames]

Here i will document my struggles and triumphs on my ultimate quest: to create an SSTO with a 40% payload fraction!

It will be hard, but i think that it may be, just may be possible. And i aim to be the first Third.

As i do not have any screenshots of it currently, here is some other eye-candy:

This was my first large-payload SSTO. It was 90 parts, about 230 tons, and lifted a 45 ton payload to orbit, giving it a payload fraction of about 20%.

It has since acquired the nickname "The Drag Queen". I think you can see why.

I shall update progress shortly.

Edited August 14, 2015 by quasarrgames

[Majorjim!]

Hey man,

This is a bold attempt indeed. I don't know if anyone has done this before, I'm not that up on all things SSTO. There are a few guys who specialize in SSTOs. I apologize as I know only of one, Rune. There are others who are equally qualified though. I think you will need to pool knowledge to do this.

You will have to use every trick known to reduce drag. Some ways are cheatier than others. Also, wouldn't it be easier if you massively reduce the size of the SSTO and just call left over fuel 'payload'.

[PhylumCnidaria]

But that's the boring way of doing it!

[selfish_meme]

You might want to see the Stock Payload Fraction Challenge thread. Mine is currently number 11 at 38.23% in the Air Breathing ladder, but number 5 in terms of SSTO's, and maybe the highest placed of the properly practical fully reuseable SSTO's. This is my production model that is based on it for taking Orange tanks to LKO reliably and fairly easily for a 33% Payload Fraction. 40% is doable for an air breathing SSTO and I think I could maybe get mine to do it, but they would not be nice to fly or reliable and would only just make it to 70km orbits with no fuel left at all.

[Rune]

You might want to see the Stock Payload Fraction Challenge thread. Mine is currently number 11 at 38.23% in the Air Breathing ladder, but number 5 in terms of SSTO's, and maybe the highest placed of the properly practical fully reuseable SSTO's. This is my production model that is based on it for taking Orange tanks to LKO reliably and fairly easily for a 33% Payload Fraction. 40% is doable for an air breathing SSTO and I think I could maybe get mine to do it, but they would not be nice to fly or reliable and would only just make it to 70km orbits with no fuel left at all.

Yeah, I was about to write pretty much that post to reply, so +1. I will add that there is a reason I stopped at 33% also, other than the roundness of the number. Well, two. First one is that on a long enough timeline, there will always be a kerbal that tops you in any given challenge.

Second is, going over 30% requires awful TWRs, under 0.5 or so, that make the ascent both incredibly boring and difficult to boot! I mean, I like going under TWR 1 so you actually need the wings for something, and lifting a lot only using cheap fuel is nice and all... but I also enjoy not taking upwards of half an hour flying my SSTO to orbit, or having such a razor-thin margin that I can't reach anything over 70kms high, on a good day.

Rune. I guarantee you practicality will end up getting you to the same place. But you will learn a lot trying!

[quasarrgames]

Thanks for the feedback guys!

Right now I've run into a bit of a problem...

The current plane likes to shear itself in half a little too much... ...nothing agonizingly slow acceleration and way-too-careful turning won't fix!

Here's the current plane:

I've run into a bit of a rut: it doesn't have enough DV for orbit. I could start using nukes to stretch the fuel, but they're heavy. I think i need to go bigger. MUCH bigger.

Also, does it seem to anyone else like cargo bays have an unnaturally large amount of drag? Like seriously. The big one has as much exposed surface area as that delta wing, but a red line almost 10 times the size!

Edited August 14, 2015 by quasarrgames

[problemecium]

I dunno about that. The delta wing may have a large area viewed from the top, but from the edge it's really tiny thanks to being a long, thin shape whereas the cargo bay's cross-section is almost circular.

Also, a tip: it's been found that the straight adapter pieces are less drag-inducing than the slanted ones, so I'd recommend replacing the nose pieces with a straight conical nose.

[selfish_meme]

One of the worst offenders is those quad adapters. Heavy and draggy, I also found that the precoolers are useless unless you need a little more air for an engine and have no intakes. I preffered to take the radial drag hit and have more fuel.