SSTO with the littlest parts

[Pds314]

Build an SSTO using:

Only the smallest crewed cockpit (the lawn chair),

Only the smallest jet engine (the Juno)

Only the smallest rocket engine (the Spider and/or the Ant)

Only the smallest fuel tank: the R4 "Dumpling" tank. Yup. That means no Mk0 LF, and no Oscar-B.

All other components may be any size. And you may use as many of a component as you wish. However, you must use at least one of each of the above.

The goal is to minimize the part count for an SSTO that can reach a 70 km periapsis and return safely.

Edited October 15, 2020 by Pds314

[camacju]

This is a creative challenge but I'm not sure if this is possible. I'll give it a shot though

[camacju]

I have realized that I have no idea how to properly fly a Juno

[Corona688]

TL/DR, this challenge will require at least 300, perhaps thousands of parts.

I've actually done ultra-light stuff with spiders before:  It helps that the spider is actually one of the better in-atmo engines.  (The ant, on the other hand, is uniquely terrible.)

Comparing the weight of an occupied command seat to the weight of an okto+accessories, I think that a pair of spiders and berries can probably circularize an orbit.  It's in the ballpark.

But getting high enough to do that requires a hammer - that is, at very rough underestimation, 30 berries of fuel plus 100 spiders of thrust.  That's 2 tons of dead weight an SSTO can't get rid of. Tripling the payload requires tripling the thrust.  Call it 300 spiders and 100 berries.

Of course, that's the direct approach.  With the juno...  Well.  It weighs a quarter-ton for what's basically no help at all.  It will get you a few hundred meters height, but basically no velocity.  The spiders still have to do all the work of lifting and circularizing.  You'd get more benefit from launching from the abandoned airfield than from carrying a juno.

Edited October 15, 2020 by Corona688

[Pds314]

1 hour ago, Corona688 said:

TL/DR, this challenge will require at least 300, perhaps thousands of parts.

I've actually done ultra-light stuff with spiders before:  It helps that the spider is actually one of the better in-atmo engines.  (The ant, on the other hand, is uniquely terrible.)

Comparing the weight of an occupied command seat to the weight of an okto+accessories, I think that a pair of spiders and berries can probably circularize an orbit.  It's in the ballpark.

But getting high enough to do that requires a hammer - that is, at very rough underestimation, 30 berries of fuel plus 100 spiders of thrust.  That's 2 tons of dead weight an SSTO can't get rid of. Tripling the payload requires tripling the thrust.  Call it 300 spiders and 100 berries.

Of course, that's the direct approach.  With the juno...  Well.  It weighs a quarter-ton for what's basically no help at all.  It will get you a few hundred meters height, but basically no velocity.  The spiders still have to do all the work of lifting and circularizing.  You'd get more benefit from launching from the abandoned airfield than from carrying a juno.

Come now, the Juno can do 18000 meters and Mach 2. And yeah carrying it will be bad for your health to be sure. But you can definitely get more than "a few hundred meters of height" with it.

 

As for the high part count, well yeah. I specifically said minimum part count for a reason.

Edited October 15, 2020 by Pds314

[Corona688]

3 minutes ago, Pds314 said:

Come now, the Juno can do 18000 meters and Mach 2. And yeah carrying it will be bad for your health to be sure. But you can definitely get more than "a few hundred meters of height" with it.

...which only leaves 60km and 2000m/s left to go.  Besides which, 30 tons in dead spiders is hardly "ideal conditions"

 

Edited October 15, 2020 by Corona688

[Pds314]

10 minutes ago, Corona688 said:

...which only leaves 60km and 2000m/s left to go.  Besides which, 30 tons in dead spiders is hardly "ideal conditions"

 

As for preferring the spider, I'm not so sure I would. The spider can only radial attach and has significantly inferior ISP in a vacuum. Sure, you can't operate ants on the ground (well not very well), but above 12 kilometers the ant has superior ISP.

 

I am not saying this is an easy challenge by any stretch.

Edited October 15, 2020 by Pds314

[camacju]

Normally for challenges it's good practice to include your own submission so it can be proven that the challenge is possible.

[Gordon Fecyk]

Back in 2018 a challenge came up to build an orbit-capable craft with 'weak' engine parts. The Spark engine isn't part of Pds314's challenge, but I thought I'd share anyway.

 

This craft stays at 131 parts, and uses Junos and Sparks. It's also a pretty good trainer craft to learn how to fly again with Ferram Aerospace.

https://kerbalx.com/gordonf/Weak-Engine-SSTO

To adapt this craft for this particular challenge, consider swapping the cockpit with a service bay and command seat, the Sparks for Ants, and see what happens.

Edited October 16, 2020 by Gordon Fecyk

[Corona688]

Was that before or after the spark was nerfed?  The spark used to be game-breakingly good.

[Gordon Fecyk]

1 minute ago, Corona688 said:

Was that before or after the spark was nerfed?  The spark used to be game-breakingly good.

I did this in KSP 1.3.1, before the Spark's texture revamp.

I suspect one could cram sixteen Ant engines in place of those eight Sparks, and two Ants in each place where a Spark was on those nacelles. That should still keep it around 150 parts. Swapping the cockpit for a service bay / command seat would reduce the mass quite a bit, though a small reaction wheel would be a good idea somewhere too.

[Pds314]

1 hour ago, camacju said:

Normally for challenges it's good practice to include your own submission so it can be proven that the challenge is possible.

I'm working on it xP

[Corona688]

11 minutes ago, Gordon Fecyk said:

I did this in KSP 1.3.1, before the Spark's texture revamp.

It had phenominal TWR and ISP back then.  I could get a three-spark asparagus arrangement to orbit.  A few updates later it stopped working.  I was quite annoyed. 

Turns out, the TWR was so good, it was more efficient than the terrier for nearly all purposes despite its minor disadvantage in ISP, and much better in-atmosphere besides.  What engine to use?  Sparks.  But its not strong enough - so use ten.

I still think they nerfed it a little too much.

Edited October 16, 2020 by Corona688

[Pds314]

48 minutes ago, Gordon Fecyk said:

Back in 2018 a challenge came up to build an orbit-capable craft with 'weak' engine parts. The Spark engine isn't part of Pds314's challenge, but I thought I'd share anyway.

 

This craft stays at 131 parts, and uses Junos and Sparks. It's also a pretty good trainer craft to learn how to fly again with Ferram Aerospace.

https://kerbalx.com/gordonf/Weak-Engine-SSTO

To adapt this craft for this particular challenge, consider swapping the cockpit with a service bay and command seat, the Sparks for Ants, and see what happens.

Very cool. Although if you want a spark SSTO, the simplest way to do it, IIRC even in current version, is just 2 oscar B tanks, a spark, an octo2, and a heaping dose of aero shenanigans.

Or you can replace the shenanigans with an extra oscar B.

The spark is *MUCH* better than the spider/ant.

It has 5s superior sealevel ISP to the spider, beating it in its home territory.

It has 5s superior vacuum ISP to the ant, beating it in its home territory.

It has a vacuum TWR that's 53% better than either.

And it places inline which means minimal drag, especially with aero node shenanigans.

Every time I've looked into using ants for something like a caveman Tylo lander to save weight, the spark has proven the superior option. The Spark is meta below a certain size and in fact beats the not meta Swivel at everything but part count and cost per thrust. The Ant/Spider on the other hand... Pretty much solidly beaten BY the swivel. The only reason they're ever meta is in something too small for a twitch or spark, where their main competition is RCS thrusters.

Edited October 16, 2020 by Pds314