Lightest SSTO

[ralanboyle]

This on is simple:

Put this lightest ship you can into orbit without shedding parts. 

• No need to land. 
• Weight is shown in the VAB including fuel. 
• Orbit is PE above 70km. 
• You can use the stage button to trigger events but you cannot detach any parts. 

Super simple but not super easy!

[SolarAdmiral]

Alright, here's what I put together.

4.11 Tons. It doesn't do anything, no payload or Kerbals, just a probe and a Rapier.

 

-edit-

 

Looks like smaller is possible. I figure about a 1.25 ton SSTO is possible using the Spark Engine.

Edited April 3 by SolarAdmiral

[SolarAdmiral]

Alright, this is what I got for the Spark. I tried building something a little better looking and fancier using the NCS200 nose cone tank, but couldn't get it to work. More weight and drag vs the thin stack of Oscar B tanks I guess.

1.23 Tons. This one is even less useful, having no solar panels. But I got it to orbit with 200m/s extra DV. I think this is probably close to the lowest weight SSTO possible, as there are no lighter engines with better TWR or ISP.  Are Ion powered aircraft still possible, in KSP2, or even in current KSP1 for that matter?

[Devblaze]

On 4/2/2024 at 10:41 PM, SolarAdmiral said:

Alright, this is what I got for the Spark. I tried building something a little better looking and fancier using the NCS200 nose cone tank, but couldn't get it to work. More weight and drag vs the thin stack of Oscar B tanks I guess.

1.23 Tons. This one is even less useful, having no solar panels. But I got it to orbit with 200m/s extra DV. I think this is probably close to the lowest weight SSTO possible, as there are no lighter engines with better TWR or ISP.  Are Ion powered aircraft still possible, in KSP2, or even in current KSP1 for that matter?

Your idea sparked some interest in me and made me want to give this challenge a try! I am also afraid to say that I've beat your score by 0.02 tons. Sorry not sorry!

On 4/2/2024 at 7:13 PM, ralanboyle said:

This on is simple:

Put this lightest ship you can into orbit without shedding parts. 

• No need to land. 
• Weight is shown in the VAB including fuel. 
• Orbit is PE above 70km. 
• You can use the stage button to trigger events but you cannot detach any parts. 

Super simple but not super easy!

Hey! I made you a badge! I don't typically involve myself in challenges, but this one seemed simple enough I could knock it out quite easily.

[Devblaze]

After some modifications and tweaks here's what I was able to get;
Total Mass = 1.11 t

[SolarAdmiral]

51 minutes ago, Devblaze said:

After some modifications and tweaks here's what I was able to get;
Total Mass = 1.11 t

Well seeing your improvement, I had to see if I could get it sub 1 ton.

I got 0.82 Tons.

It starts falling over on the pad so you need to launch it immediately.

[Devblaze]

2 hours ago, SolarAdmiral said:

Well seeing your improvement, I had to see if I could get it sub 1 ton.

I got 0.82 Tons.

It starts falling over on the pad so you need to launch it immediately.

It seems we've found ourselves in a good ol' fashion engineer off. 
I'm impressed with your determination, but I am afraid to say I've beaten you again!
Total Mass: 0.64 t

I also did a run without the stabilizer wings which brought it down to 0.63 Tons

Edited April 4 by Devblaze

[SolarAdmiral]

54 minutes ago, Devblaze said:

It seems we've found ourselves in a good ol' fashion engineer off. 
I'm impressed with your determination, but I am afraid to say I've beaten you again!
Total Mass: 0.64 t

I also did a run without the stabilizer wings which brought it down to 0.63 Tons

Ha yeah I can't beat that. You can make it to orbit with only 3,223m/s vacuum DV?

[Devblaze]

3 minutes ago, SolarAdmiral said:

Ha yeah I can't beat that. You can make it to orbit with only 3,223m/s vacuum DV?

Yes; however you may need launch a few times to get it perfect. I had to launch 4/5 times to make sure I did my ascent correctly.
I think you can get to orbit with around 3100 Dv as a bare minimum.

You're making it to orbit with the same amount, but you have Dv left over! Gotta ride that line!

Edited April 4 by Devblaze

[SolarAdmiral]

1 minute ago, Devblaze said:

Yes; however you may need launch a few times to get it perfect. I had to launch 4/5 times to make sure I did my accent correctly.

You're making it to orbit with the same amount, but you have Dv left over! Gotta ride that line!

Ok interesting. Yeah I don't have much experience flying so close to the minimum. But yes don't think I can beat that, at best would match it.

The only other thing I could think of to try to reduce weight is swapping some Oscar B tanks for a Baguette. As I think it has just a tiny bit better fuel to dead weight. But couldn't get any success with it, probably because of drag.

[ralanboyle]

Guys, I posted this challenge and then immediately went on vacation. I’m thrilled to come back to see you two battling it out! 

While looking at your ships I also had the thought about other tanks but obviously I haven’t built anything yet. I’ll have to see what I can do! 

 

Edited April 7 by ralanboyle
.

[ralanboyle]

Welp, I think you've found the floor. I can match the 0.64 but I can't do it at .63. You've got me beat! This was fun though, and I'm glad to see the competition! 

Given the glitches, I like challenges that push the limits of simplicity, rather than enormous, complicated ships. I'm thinking about a similar challenge to the Mun...

[SolarAdmiral]

So, upon closer examination of the rules, I believe I have a smaller, cheekier, SSTO entry.

The rules require,  "Put this lightest ship you can into orbit without shedding parts." and "Orbit is PE above 70km. "

So as such, here is my 0.13 ton SSTO

Although, technically even lighter would be a kerbal with RCS pack.

(Funny Enough, the other two possibilities I checked for this, 

-Stratus-V Minified with min fuel and 1 RCS thruster

-Two Seppatrons with min fuel

Both also came out to 0.13 tons)

 

If the 'surface' and 'orbit' don't need to be around the same body, then there's this for 0.07 tons. From Minmus Surface to Kerbin Orbit. It's single stage to 'an' orbit, and the PE is over 75km.

 

[SolarAdmiral]

2 hours ago, ralanboyle said:

I like challenges that push the limits of simplicity, rather than enormous, complicated ships. I'm thinking about a similar challenge to the Mun...

Agreed! Tiny is my Jam.

I'll keep a lookout for any future challenges.

Maybe  another larger idea would be, "Complete the Explore mode / Main missions with the lowest total tonnage"