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

[Columbia]

As far as the bomb is concerned the entire Space Center is screwed ( á° Üʖ á°)

8 fuel tanks compressed.. this could turn into a black hole.

- - - Updated - - -

And.. I made an entire runway section explode.

That was satisfying as hell.

[Thingymajigy]

550 ton 28 engine jumbo....thingy:

900 parts and counting...

[Rune]

Well apparently if you rip off the side of a Co-102 or an Fr-104, it makes an epic SSTO! Throw in a crew cabin and VTOL capability as well. Its not very long range but it can take 4 crew members to orbit.

Handling is a bit touchy. It only wants to fly upside down. Any ideas how to stop it doing this?

http://i.imgur.com/qhNphRJ.png

Selfish_meme and Commander Spock have kind of given you the right answer between them, only a bit confusing. Let's see if fancy vocabulary clears things, or I muddle the question further:

First off, "wants to fly upside down" is technically called "roll instability". Meaning when you deviate from the perfect vertical, the lift forces change slightly, and the difference tries to move the plane further from the vertical, and not against the initial movement. If the resulting forces took you back to the vertical, you would have a design which is stable in roll... and actually, this one is. Only when flying upside down! Let's see what we can do to change that.

There are two things that contribute to roll stability/instability: diheral/anhedral on the lifting surfaces, and the position of the CoL with respect to the CoM. Let's look at CoM/CoL position first, since it is probably the least contributor, and the most easy to see:

This is kind of what selfish_meme is saying. If you picture it, the CoM is always pulling "down" towards the ground, and the CoL is always pulling short of "up" (the lateral component doesn't help you fly, only turn). So what happens when they are no longer vertically aligned? Obviously, a torque appears. If you play a bit with the vectors on a paper, you will see clearly how the torque is against the movement only when CoL is above CoM, if things are the other way around the torque will amplify the movement, increasing the roll instability. This is the reason you would like high wings for roll stability.

But, you will say, airliners all have their wings low on the fuselage! And yeah, that would be unstable (but easy to build and inspect). But turns out anhedral/dihedral is a more important factor in roll stability, and here it is very much working against you! (Note: anhedral is having the wing in a "^" shape, while dihedral is having them in a "v" shape). Think about what happens to the lift vectors when you roll: one of the wings moves closer to the horizontal, increasing it's vertical lift, and the other moves more the vertical, decreasing it by the same value. The result? A torque that, in the case of dihedral wings, will oppose the movement. But with anhedral, it will increase instability and facilitate the roll. That is why airliners have no roll issues, they all have their wing with a big dihedral, 5º or more. You, on the other hand, have a huge anhedral on you lifting surfaces, that turns dihedral when you are upside down. It is rather obvious now what is happening, isn't it?

In summary: "v" wing shapes and high wings increase roll stability, "^" shapes and low wings increase instability. The solution would be to add lifting surfaces that both move the CoL upwards, and are placed with a strong dihedral. Like making the "tails" a few times liftier?

Rune. Hope that helps!

[Frozen_Heart]

Selfish_meme and Commander Spock have kind of given you the right answer between them, only a bit confusing. Let's see if fancy vocabulary clears things, or I muddle the question further:

First off, "wants to fly upside down" is technically called "roll instability". Meaning when you deviate from the perfect vertical, the lift forces change slightly, and the difference tries to move the plane further from the vertical, and not against the initial movement. If the resulting forces took you back to the vertical, you would have a design which is stable in roll... and actually, this one is. Only when flying upside down! Let's see what we can do to change that.

There are two things that contribute to roll stability/instability: diheral/anhedral on the lifting surfaces, and the position of the CoL with respect to the CoM. Let's look at CoM/CoL position first, since it is probably the least contributor, and the most easy to see:

This is kind of what selfish_meme is saying. If you picture it, the CoM is always pulling "down" towards the ground, and the CoL is always pulling short of "up" (the lateral component doesn't help you fly, only turn). So what happens when they are no longer vertically aligned? Obviously, a torque appears. If you play a bit with the vectors on a paper, you will see clearly how the torque is against the movement only when CoL is above CoM, if things are the other way around the torque will amplify the movement, increasing the roll instability. This is the reason you would like high wings for roll stability.

But, you will say, airliners all have their wings low on the fuselage! And yeah, that would be unstable (but easy to build and inspect). But turns out anhedral/dihedral is a more important factor in roll stability, and here it is very much working against you! (Note: anhedral is having the wing in a "^" shape, while dihedral is having them in a "v" shape). Think about what happens to the lift vectors when you roll: one of the wings moves closer to the horizontal, increasing it's vertical lift, and the other moves more the vertical, decreasing it by the same value. The result? A torque that, in the case of dihedral wings, will oppose the movement. But with anhedral, it will increase instability and facilitate the roll. That is why airliners have no roll issues, they all have their wing with a big dihedral, 5º or more. You, on the other hand, have a huge anhedral on you lifting surfaces, that turns dihedral when you are upside down. It is rather obvious now what is happening, isn't it?

In summary: "v" wing shapes and high wings increase roll stability, "^" shapes and low wings increase instability. The solution would be to add lifting surfaces that both move the CoL upwards, and are placed with a strong dihedral. Like making the "tails" a few times liftier?

Rune. Hope that helps!

Thanks

I'm trying to keep the look the same but maybe I can change the tail and wing design without changing the looks too much.

[Azimech]

Well, I am still refining my walker, but i need help. I am trying to figure out a way to make something spin with lots of torque and very little speed. Turboprobs do work, however they produce such low torque it is no really working.

Any Ideas?

Use gears? Use more blowers? Without mods, a well built turboshaft engine will beat any electric motor of comparable size/mass.

[FlipNascar]

Has anyone else noticed some sort of correlation between bearings becoming floppy and the addition of a command seat to their craft? Picking up the Autogyro craft I started a few weeks back because I decided it was time to make them prettier... Built a brand new bearing, tested it. Flew perfectly. Added a Command Seat and a Kerbal, bam - bearing flops about all over the place like a wet noodle.

I need to try it with some of my other bearings to see if the command seat makes them floppy... Am I losing the plot?

And then during one of the failed bearing attempts this popped up.... The attachment points definitely seem legit right?

[Majorjim!]

Has anyone else noticed some sort of correlation between bearings becoming floppy and the addition of a command seat to their craft? Picking up the Autogyro craft I started a few weeks back because I decided it was time to make them prettier... Built a brand new bearing, tested it. Flew perfectly. Added a Command Seat and a Kerbal, bam - bearing flops about all over the place like a wet noodle.

I need to try it with some of my other bearings to see if the command seat makes them floppy... Am I losing the plot?

And then during one of the failed bearing attempts this popped up.... The attachment points definitely seem legit right?

http://i.imgur.com/UonzyG4.jpg

Dude, just save the craft twice. Also, the moment you realise this is happening, exit the editor, then reload.

[SaturnianBlue]

On Thursday I got the Space Shuttle into orbit, but I didn't get laptop time yesterday so no pics till today, I sent up an IUS with a 4 ton ballast payload, next up: can it carry a 25 ton payload to orbit? Also, I botched the landing but the kerbals survived. I had to fly a steep trajectory, more so then I usually ever do. Engines still need to thrust limit themselves during the initial liftoff and during the SSME burn only phase.

Edit: The payload made it to orbit: sadly I released the payload before the OMS burn, but it probably would work anyway.

Javascript is disabled. View full album

Edited October 24, 2015 by SaturnianBlue

[Azimech]

Has anyone else noticed some sort of correlation between bearings becoming floppy and the addition of a command seat to their craft? Picking up the Autogyro craft I started a few weeks back because I decided it was time to make them prettier... Built a brand new bearing, tested it. Flew perfectly. Added a Command Seat and a Kerbal, bam - bearing flops about all over the place like a wet noodle.

I need to try it with some of my other bearings to see if the command seat makes them floppy... Am I losing the plot?

And then during one of the failed bearing attempts this popped up.... The attachment points definitely seem legit right?

Take Command does this.

[ghostbuzzer7]

Dawn Buggy with ultrasoft suspension combining the power of pylons and ant engines = A pleasant ride

[Bubbadevlin]

Well the second generation of my walker is done, and its a failure. I did however make a very functional gear system for providing more torque. The problem is i tried to have both sides be separate, however i could not get them synced, so it would continuously turn one way or another.

[FlipNascar]

Take Command does this.

Confirmed. I think that's also maybe why when you tried my Autogyro it didn't work for you - did you try it on an install with or without Take Command?

Anyhoos, now I need to completely rebuild the hinged rotor system now... Yay![/sarcasm]

[FlipNascar]

Awwww yeah. Apparently flying faster makes this one work better....

[Sido]

Well apparently if you rip off the side of a Co-102 or an Fr-104, it makes an epic SSTO! Throw in a crew cabin and VTOL capability as well. Its not very long range but it can take 4 crew members to orbit.

Handling is a bit touchy. It only wants to fly upside down. Any ideas how to stop it doing this?

http://i.imgur.com/qhNphRJ.png

Definitely a good design. well done

[SaturnianBlue]

Tried to make a Fletcher Class inspired Destroyer, as far as i'm concerned, it's not going so well. It has a 100 intakes and it doesn't really float. It's also top heavy, which seems very much like what the USS Sims was found to be in its early design...

[Sido]

My last Kerbin Space Station :

[Rithsom]

I'm experimenting with the narrow-band scanners. My first test, using them as wheels, did not quite work the way I wanted it to...

[Rune]

I built a tiny emergency return vehicle...

It doesn't even have a RCS subsystem, but it does put out 1.5km/s in a reentry-friendly gliding package. And it fits a Mk3 bay! If I ever put it out, it'll go in the subassembly pack I'll eventually do, with my Klaw pods and the Cuppola tug you can see grabbing it in the pic, among other things that don't deserve a thread but are quite cool.

Rune. SO cute.

Edited October 25, 2015 by Rune

[Frozen_Heart]

I built a tiny emergency return vehicle...

http://i.imgur.com/KHVA7Vw.png

It doesn't even have an RCS subsystem, but it does put out 1.5km/s in a reentry-friendly gliding package. And it fits a Mk3 bay! If I ever put it out, it'll go in the subassembly pack I'll eventually do, with my Klaw pods and the Cuppola tug you can see grabbing it in the pic.

Rune. SO cute.

I may have to steal that...

[Rune]

I may have to steal that...

You are welcome! I won't put the file up yet, but it's dirt simple to replicate if you notice that:

-The "wings" are quite sunk into the fuselage, and follow the dihedral of the underside to look cool and such.

-It only actually fits a Mk3 bay tilted 45º to make room for the wings.

-No other hidden or clipped parts (well, the front landing gear is also quite sunk to make it level with the others), 16 parts in total. I could have done it in 15, but I wanted to put an antenna in case 1.05.

Other than that, if you see that the CoM/CoL is completely wrong, don't worry: when the fuel tank is almost empty it becomes stable-ish again, and quite maneuverable at that (lots of reaction wheels, proportionally).

Rune. The more I play KSP, the simpler I build.

[Frozen_Heart]

Still stuck with this things poor performance. Made it a bit more stable but I can only just scrape 75km orbit and back. No room for docking or anything.

Any ideas? I need it to get to 500km, rendezvous, dock, and then return to space centre.

[Majorjim!]

I built a tiny emergency return vehicle...

http://i.imgur.com/KHVA7Vw.png

It doesn't even have a RCS subsystem, but it does put out 1.5km/s in a reentry-friendly gliding package. And it fits a Mk3 bay! If I ever put it out, it'll go in the subassembly pack I'll eventually do, with my Klaw pods and the Cuppola tug you can see grabbing it in the pic, among other things that don't deserve a thread but are quite cool.

Rune. SO cute.

Yup, seen thar design a lot here. Mostly people making simple dreamchasers. When those parts first came out I made one exactly like that, just a little longer.

I am so happy we have better lifting bodies now. Nothing like an unpowered descent!

[Rune]

Any ideas?

My kind of question! Let's see what I come up with...

-It looks like a tad high TWR. I'll allow it, because I suspect the engine configuration is one of the things we like about this, right? It does look cool. If push comes to shove, you can always put a single RAPIER on the middle, but then I suspect low wing loading will hurt you increasing drag.

-You don't have any LF tanks that I can see. If you are keeping it on rocket fuel tanks, you are wasting space and mass badly, since they are much less dense when half-full and thus have awful tankage fractions. And these days, you need a lot of gas to properly milk airbreathers.

-Vernors are heavy, and draggy. And you already carry a monoprop tank in the form of that docking port... how about switching to place-anywheres?

-Other than those building tricks, we can work on your ascent path. Have you seen Val's runs on the payload fraction challenge? Point is, if you go shallow, you pick up speed so fast that you actually climb faster. Try breaking Mach 1 with a 10-15º form the runway to start climbing supersonic quickly, then don't let it pitch up too much to hit >1,300m/s on airbreathers at 15-20kms. From there you don't need that much dV to make orbit.

Rune. And if all else fails, send me a link and I'll take a look at it and cheat it into submission, I like the lines and don't want to see it die.

[selfish_meme]

Still stuck with this things poor performance. Made it a bit more stable but I can only just scrape 75km orbit and back. No room for docking or anything.

Any ideas? I need it to get to 500km, rendezvous, dock, and then return to space centre.

http://i.imgur.com/AYdqsHv.png

These are probably ruled out for aesthetics sake, besides Runes suggestion on ascent path (with Rapiers always get fast down low and then hold it on the edge of exploding till you hit space). Shock cone intakes are less draggy than ram air intakes, they also work well on the back of rapiers clipped in a bit, open nodes on the back of rapiers are draggy. A pointier nose (a shock cone works best) would also reduce drag. This would allow you to accelerate quicker, reach a higher speed and requires less dV to orbit. As Rune said also you have too many engines, two would probably do, which probably means you don't need to run off the end of the runway and can climb quite steeply to mach 1, but it also means you are wasting fuel.

[Frozen_Heart]

My kind of question! Let's see what I come up with...

-It looks like a tad high TWR. I'll allow it, because I suspect the engine configuration is one of the things we like about this, right? It does look cool. If push comes to shove, you can always put a single RAPIER on the middle, but then I suspect low wing loading will hurt you increasing drag.

-You don't have any LF tanks that I can see. If you are keeping it on rocket fuel tanks, you are wasting space and mass badly, since they are much less dense when half-full and thus have awful tankage fractions. And these days, you need a lot of gas to properly milk airbreathers.

-Vernors are heavy, and draggy. And you already carry a monoprop tank in the form of that docking port... how about switching to place-anywheres?

-Other than those building tricks, we can work on your ascent path. Have you seen Val's runs on the payload fraction challenge? Point is, if you go shallow, you pick up speed so fast that you actually climb faster. Try breaking Mach 1 with a 10-15º form the runway to start climbing supersonic quickly, then don't let it pitch up too much to hit >1,300m/s on airbreathers at 15-20kms. From there you don't need that much dV to make orbit.

Rune. And if all else fails, send me a link and I'll take a look at it and cheat it into submission, I like the lines and don't want to see it die.

-Yeah I want to keep that engine configuration. Reminds me a bit of the Normandy and is somehow balanced by magic.

-I did have a LF tank but they each had 400LF. Twice what I needed. Though I do lose some oxy but have less mass like this. I'll fiddle with both so see what is optimum.

-I was getting better performance with the RCS. I was thinking that using a single fuel would be more efficient. Proved wrong there though.

-I pretty much head up at 20 degrees and switch to jets between 1300 and 1400 m/s. I think its rocket fuel I'm low on as I still have a tiny bit of LF left on landing. Its still a bit unstable but much better than it once was.

Here is the craft in case you want a look: https://www.dropbox.com/s/jh4oqvobs6knhf9/VT-104A.craft?dl=0

Its the first SSTO I've been happy with how it looks in a long while. All I did was pull the side off a Co-102, then give it rapiers and wheels!