totm june 2018 Work-in-Progress [WIP] Design Thread

[Rune]

12 hours ago, Frozen_Heart said:

Trying to build a rocket only SSTO and struggling. It can limp up to a 75km orbit and return on fumes but can't take any payload at all. Not sure how to improve it from here to make it actually useful.

Just the nature of the beast, I'm afraid. Chemical SSTOs require very high mass ratios, which means that if you spend mass on structure and wings, you are cutting your payload severely, and will need a humongous booster.

That said, a couple things might help:

-Consider that you only have to glide when empty. Less wings means less drag going up, less weight to put to orbit, and only a scarier reentry. There is a reason the Shuttle glided with a 20º slope, it didn't need to do any better.

-Vectors have a better TWR than spikes, IIRC. On chemical SSTOs, TWR is key, because engines are a sizeable fraction of the final mass in orbit. Tankage is the other big chunk, but there's little we can do for that, right?

 

Rune. Best tankage ratio is with cylindrical tanks, BTW, worst with Mk2 and the various adapter-tanks.

[Frozen_Heart]

2 hours ago, Exothermos said:

Yeah, think bigger.  Here's how I big I had to go (with your basic aesthetics) to get a full orange can to orbit, and even then margins are very tight.

5x vectors (though I think 4 would be better) and LOTS of fuel.  Reentry and landing can be entertaining too. 

Edit: Of course you don't have to go anywhere near as big for lighter payloads, I just went kinda extreme to illustrate the point.

Wow I didn't realise SSTOs had to be so big for that kind of launch. Their payload fractions seem to be closer to that of real life launch vehicles than the 10% or so I always worked from in KSP. I wonder how the fuel cost stacks up to just throwing away stages... 

1 hour ago, Rune said:

-Vectors have a better TWR than spikes, IIRC. On chemical SSTOs, TWR is key, because engines are a sizeable fraction of the final mass in orbit. Tankage is the other big chunk, but there's little we can do for that, right?

I really suspect that Vectors are going to get a massive nerf at some point so I'm hesitant to use them. They are such an OP engine atm. I'm happy with them being 1.25m as that is needed for shuttle engines, but they have the power of a launch engine with good efficiency both at 1 atm and in space.

[Rune]

3 hours ago, Frozen_Heart said:

Wow I didn't realise SSTOs had to be so big for that kind of launch. Their payload fractions seem to be closer to that of real life launch vehicles than the 10% or so I always worked from in KSP. I wonder how the fuel cost stacks up to just throwing away stages... 

I really suspect that Vectors are going to get a massive nerf at some point so I'm hesitant to use them. They are such an OP engine atm. I'm happy with them being 1.25m as that is needed for shuttle engines, but they have the power of a launch engine with good efficiency both at 1 atm and in space.

Yup, they are fat fellas. I usually go by the rule of thumb of "one Vector per 10mT of payload", and work from there to get 1.3~1.4 TWR. As to how OP they are... well, it depends. They are not that different from spikes, only they get higher TWR (but lower vacuum ISP!). They are actually not that great once you leave kerbin, being so massive, so they tend to stay on LV's, and reusable LVs at that, because of their high cost. Mammoths are really much more cost-effective. And, well... they are at the end of the tech tree, after all. Right next to the aerospikes, AKA, the engine specifically designed to build chemical SSTOs. So yeah, I'm coming around to them. Just limit the gimbals so the launch doesn't look too weird!

Cost efficiency... well, it's nowhere near what airbreathing SSTOs can get, I'll grant you that. But it is competitive with expendables, if you bring back those engines every time to the runway. VTHL SSTOs can also handle very unwieldy payloads, too:

 

Rune. Technically that's a stage-and-a-half, but it can SSTO with ~40mT without the SRBs.

Edited August 5, 2016 by Rune

[Frozen_Heart]

15 minutes ago, Rune said:

Yup, they are fat fellas. I usually go by the rule of thumb of "one Vector per 10mT of payload", and work from there to get 1.3~1.4 TWR. As to how OP they are... well, it depends. They are not that different from spikes, only they get higher TWR (but lower vacuum ISP!). They are actually not that great once you leave kerbin, being so massive, so they tend to stay on LV's, and reusable LVs at that, because of their high cost. Mammoths are really much more cost-effective. And, well... they are at the end of the tech tree, after all. Right next to the aerospikes, AKA, the engine specifically designed to build chemical SSTOs. So yeah, I'm coming around to them. Just limit the gimbals so the launch doesn't look too weird!

Cost efficiency... well, it's nowhere near what airbreathing SSTOs can get, I'll grant you that. But it is competitive with expendables, if you bring back those engines every time to the runway. VTHL SSTOs can also handle very unwieldy payloads, too:

This is the version i'm on now. 3 Vectors but only 18mt of payload. However it glides at 25m/s so I think I can lose a wing or 50. Trouble is without them it looks awful, like a bunch of fuel tanks stuck together.

[Rune]

17 minutes ago, Frozen_Heart said:

This is the version i'm on now. 3 Vectors but only 18mt of payload. However it glides at 25m/s so I think I can lose a wing or 50. Trouble is without them it looks awful, like a bunch of fuel tanks stuck together.

And the payload bay doors are also screwing with the lines. Gotcha. Mayhaps ditch the Mk2's (they have wings installed on them, and heavy wings at that), and build with straight rocket tanks and shorter wings sections, I'd think you'd shave some weight. Also, the vertical stabilizers are really big, you don't need so much. I half-use them as wings in mine, and I'll be the first to admit it's not efficient at all, Mk3's also have bad tank ratios and the shuttle bottom is a lot of dead weight. Mayhaps you could build something with wing sections that looks as good (or better) and shave a couple hundred kgs more.

 

Rune. Also, turning Mk3s on their side makes them look much better, there is that.

Edited August 5, 2016 by Rune

[Frozen_Heart]

24 minutes ago, Rune said:

And the payload bay doors are also screwing with the lines. Gotcha. Mayhaps ditch the Mk2's (they have wings installed on them, and heavy wings at that), and build with straight rocket tanks and shorter wings sections, I'd think you'd shave some weight. Also, the vertical stabilizers are really big, you don't need so much. I half-use them as wings in mine, and I'll be the first to admit it's not efficient at all, Mk3's also have bad tank ratios and the shuttle bottom is a lot of dead weight. Mayhaps you could build something with wing sections that looks as good (or better) and shave a couple hundred kgs more.

 

Rune. Also, turning Mk3s on their side makes them look much better, there is that.

Are standard rocket tanks able to survive re-entry heat?

Also if you turn the Mk3 tanks on their side the cargo bay doesn't line up anymore. This is really making me wish that SpaceX style boosters were viable but they just end up despawning before landing.

[Rune]

9 minutes ago, Frozen_Heart said:

Are standard rocket tanks able to survive re-entry heat?

Also if you turn the Mk3 tanks on their side the cargo bay doesn't line up anymore. This is really making me wish that SpaceX style boosters were viable but they just end up despawning before landing.

Sure, if you are draggy enough 2,000º is more than enough, from LKO. Plus, being winged, you can arrest your vertical speed to stay up where you brake slowly and dissipate the heat over a longer time. A radiator next to the leading part also does wonders, I hear. The cargo bay can open sideways, but it was just a thought, I'm sure you'll come up with something great.

 

Rune. Building interesting shapes with a limited set of parts takes a lot of head-scratching.

Edited August 5, 2016 by Rune

[Frozen_Heart]

5 minutes ago, Rune said:

Sure, if you are draggy enough 2,000º is more than enough, from LKO. Plus, being winged, you can arrest your vertical speed to stay up where you brake slowly and dissipate the heat over a longer time. A radiator next to the leading part also does wonders, I hear. The cargo bay can open sideways, but it was just a thought, I'm sure you'll come up with something great.

 

Rune. Building interesting shapes with a limited set of parts takes a lot of head-scratching.

What kind of dV values are you getting from your rocket SSTOs empty btw? Atm I'm getting about 4200m/s (atm) which while enough to get to orbit, isn't enough for payload. 

[Rune]

34 minutes ago, Frozen_Heart said:

What kind of dV values are you getting from your rocket SSTOs empty btw? Atm I'm getting about 4200m/s (atm) which while enough to get to orbit, isn't enough for payload. 

That's a pretty weird metric, since final dV with payload would vary with Isp, but I just checked, and one of them is 4,898m/s, at 1.39 TWR, another 5,013 at 1.36 TWR. Vacuum values, of course.

 

Rune. All numbers taken from KER.

Edited August 5, 2016 by Rune

[Frozen_Heart]

11 minutes ago, Rune said:

That's a pretty weird metric, since final dV with payload would vary with Isp, but I just checked, and one of them is 4,898m/s, at 1.39 TWR, another 5,013 at 1.36 TWR. Vacuum values, of course.

 

Rune. All numbers taken from KER.

Hmm that is considerably more than mine. Barely getting 4500m/s. I changed to 3.75m tanks which improved it to about 4800 but now it prefers to glide backwards. Might try the wingless approach and do propulsive landing. Harder to hit the KSC like that though.

[RocketSquid]

I'm trying to design a working starfighter. Here's what I've got:

HEAVILY modded, using chemical rockets and jets for ascent and ion engines for orbital maneuvering. Can replenish its xenon when it enters an atmosphere.

I was originally planning for plane-style SSTO or TSTO, but that has proved to be impossible. I'm now thinking either twin-booster vertical launch:

or carrier based horizontal. Both have yet to bear fruit, but I am confident that the starfighter should work once it makes it to orbit.

[Mycroft]

So I just recently got B9 Aerospace, and promptly set out to build huge and awesome space battleships. Then I saw this military design submission thread linked to a YouTube series in progress. People could design and submit ships to the channel's author through this thread, and if the design was good enough, the craft would be used in the series. I noticed that the series used B9 and BDArmory, two of my favorite mods. So, I decided to build the awesomest ship I could, and submit it. Turns out, the series' author was no longer accepting mods for space ships. 
 So now I have this big lug hanging around my puny laptop. Today, I spotted this thread and thought, "Hey, I could put my craft there, and maybe get some likes to compensate for the five hours it took to make this ship!" So here's the album: http://m.imgur.com/a/OIwg0.The launcher required infinite fuel to get to space. Here's the KerbalX page: https://kerbalx.com/Mycroft_33/Leviathan

 

Description (from KerbalX): Be the envy of the entire system! This Omega class battleship is the pinnacle of CMAU’s finest technology!

 Guaranteed to destroy practically any opponent, this massive ship bristles with 9 heavy Abrams Tank turrets, 4 Goalkeeper 30 MM turrets, 22 BD Airborne Lasers, and the hangar capacity to house an absolute armada of medium fighters. It is 41.9 meters tall, 40.5 meters wide, and 186.0 meters long by itself. It can maintain radar locks on 6 different ships at once within a twenty kilometer radius, and weighs in at a massive 42,008.73 metric tons. It contains 3,650,650 units of ElectricCharge, 730,160 kg of MonoPropellant, 15,833.29 tons of LiquidFuel, 19,351.8 tons of Oxidizer, 460 rounds for the cannons, and 28,800 30MM rounds. At sealevel in HybridPlasma mode, TWR is 0.12. In vacuum, it is 0.20, with 10,372 m/s total DeltaV. In ClosedCycle mode, the sea level TWR is 0.54, and the vacuum TWR is 0.90-1.10 with only 3,988 m/s of DeltaV. The ship by itself is only 352 parts. It comes packaged with a massive booster that brings the mass to 110,941.1 metric tons, the width and height to 100.5 meters, and the length to 261.2 meters.

Unfortunately, the booster is unable to get the ship to orbit, so it requires you to use fuel from the cruiser, or enable infinite fuel. Our engineers currently are convinced that designing a booster with enough power and DeltaV sufficient to get it to orbit is impossible, though we are still attempting to find a solution to this problem. Once it gets to orbit, though, it can go practically anywhere and whip anything! Order today!

(Note: We also felt it was necessary to sell computers capable of running it along with the ship since it requires so many CPU resources, so for the special discount price of only 5,000 dollars plus tax, you can order one of the most impressive computers ever seen by Kerbalkind to accompany this equally impressive ship!) This is a deal beyond price! Supplies limited! Order today!

Edited August 5, 2016 by Mycroft

[david50517]

[Gman_builder]

4 hours ago, RocketSquid said:

snip

What do you mean "star fighter?"

Like from Star Wars? If so you should model it after a star fighter from the game. I have a exceptional X-wing on my KerbalX profile you could use as reference. It has mods and stuff but I guess that's not a big deal for you.

[RocketSquid]

1 hour ago, Gman_builder said:

What do you mean "star fighter?"

Like from Star Wars? If so you should model it after a star fighter from the game. I have a exceptional X-wing on my KerbalX profile you could use as reference. It has mods and stuff but I guess that's not a big deal for you.

Like this starfighter:

I have modified the design and it can now reach the edge of space before running out of fuel.

See here for pictures of its journey.

[Gman_builder]

4 hours ago, RocketSquid said:

Like this Starfighter:I have modified the design and it can now reach the edge of space before running out of fuel.

See here for pictures of its journey.

But how is that a star fighter? The term "star fighter" was coined by Star Wars and everything related to that term generally describes craft from the Star Wars series. So is this supposed to be a replica of something? Plus I don't really see how  it can be called a star fighter when it can hardly get to space. I don't mean to sound like a d I c k I just don't understand where your coming from.

[david50517]

[Yukon0009]

6 hours ago, RocketSquid said:

Like this starfighter:

I have modified the design and it can now reach the edge of space before running out of fuel.

See here for pictures of its journey.

Which mod part is that on the wing tip?

[Majorjim!]

2 hours ago, Yukon0009 said:

Which mod part is that on the wing tip?

I see quite a few mod parts on that craft. 

[Yukon0009]

Just now, Majorjim! said:

I see quite a few mod parts on that craft. 

The one with the texture of the RT-10 SRB?

[Majorjim!]

1 hour ago, Yukon0009 said:

The one with the texture of the RT-10 SRB?

Look at the tank textures. Looks like a few part or texture mods. And yeah the half an SRB thing too.

[RocketSquid]

8 hours ago, Gman_builder said:

But how is that a star fighter? The term "star fighter" was coined by Star Wars and everything related to that term generally describes craft from the Star Wars series. So is this supposed to be a replica of something? Plus I don't really see how  it can be called a star fighter when it can hardly get to space. I don't mean to sound like a d I c k I just don't understand where your coming from.

This is not a replica, and the term is not applied exclusively to craft from the Star Wars universe. While it is inspired by some craft from Star Wars, it is for the most part an original design.

Its inability to make orbit is why it's work-in-progress.

3 hours ago, Yukon0009 said:

The one with the texture of the RT-10 SRB?

That's an air-augmented SRB from @SuicidalInsanity's Mk2 expansion.

Edited August 6, 2016 by RocketSquid

[pTrevTrevs]

12 hours ago, Gman_builder said:

But how is that a star fighter? The term "star fighter" was coined by Star Wars and everything related to that term generally describes craft from the Star Wars series. So is this supposed to be a replica of something? Plus I don't really see how  it can be called a star fighter when it can hardly get to space. I don't mean to sound like a d I c k I just don't understand where your coming from.

I must agree with @RocketSquid here, the term "Star Fighter" is not limited just do ships from the Star Wars universe. As for it hardly being able to get to space, I would like to point out that some ships in Star Wars were incapable of reaching orbit on their own anyway. Although not a fighter, I believe the LAAT/i gunship was able to be launched from orbital altitude and land safely but it was not possible to reach orbit with one starting from the ground

Citation needed. I'm a pretty big Star Wars fan, but not quite that big.

[Gman_builder]

3 hours ago, pTrevTrevs said:

I must agree with @RocketSquid here, the term "Star Fighter" is not limited just do ships from the Star Wars universe. As for it hardly being able to get to space, I would like to point out that some ships in Star Wars were incapable of reaching orbit on their own anyway. Although not a fighter, I believe the LAAT/i gunship was able to be launched from orbital altitude and land safely but it was not possible to reach orbit with one starting from the ground

Citation needed. I'm a pretty big Star Wars fan, but not quite that big.

k

[Gman_builder]

My first half attempt at building a ship. Hull turned out great and it floats perfectly, but I have NOO clue where to even begin on the super structure. I have tried multiple different designs but nothing looked good or fit with the hull design. One thing I see that is common in all decent looking ships is a very intricate super structure, but I just don't know how to go about doing that.