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K.S.P Fastest Runway Speed

MajorGosnell
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ElMenduko

ElMenduko

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Posted (edited)
When trying to edit a post in a cell phone they get deleted!

So, after 2 accidental deletions here you go

A crazy 1143.2m/s!

This hasn't ended, rcgothic! Link: [URL]http://m.imgur.com/a/XBelj[/URL] (embedding isn't working for some reason)

It was very difficult to get this screenshot because:

* It goes so fast that you can't get it perfect
* I had to tweak ALL the serpratrons' thrust limiter to prevent the most of the diminishing returns. Still I didn't get it perfect, ran out of solid fuel just before the screenshot
* It would get attacked by the kraken and explode 90% of the time
* The speed varied a bit between succesful tests

However, after further testing I realized that it was so unstable that it invoked the kraken. And it was kraken phantom forces that caused the speed to change between tests. (And the rapid unplanned dissassemblies)

It must have been the accidental weak kraken drive that gave me some 140m/s extra speed. That means this is a hybrid car, and it helps the environment! (a little bit, if you ignore the srb exhaust)

I also did a few experiments with bigger things, and with lots of space shuttle engines. Those bordered insanity, and were way worse than this one Edited by ElMenduko
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Friethjoph

Friethjoph

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My tests using a quad coupler of the new spaceplane engines all detonate at passing 300 m/s, even if they could deliver an acceleration of 140 m/s²... Well, it IS ridiculous... Couldn't there be some kind of rails or sleds be allowed to make it less hard to stay on the runway? Well, we technically COULD create rails from H-Bar, but it would involce several rovers to place those, and they have to be re-placed for each test and they have to be placed perfectly...
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ElMenduko

ElMenduko

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[quote name='Friethjoph']My tests using a quad coupler of the new spaceplane engines all detonate at passing 300 m/s, even if they could deliver an acceleration of 140 m/s²... Well, it IS ridiculous... Couldn't there be some kind of rails or sleds be allowed to make it less hard to stay on the runway? Well, we technically COULD create rails from H-Bar, but it would involce several rovers to place those, and they have to be re-placed for each test and they have to be placed perfectly...[/QUOTE]

Oh, I tried with many things to appease the kraken, but none worked well enough... Actually, I could imagine a rail made from H-bars would create a lot of problems.
In the end though, I might have created a hybrid kraken drive... Now if I can get this to work in a vaccuum...

Also, there's no need for quadcouplers, you can surface attach the Vector engines (and the aerosìkes too!)
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herbal space program

herbal space program

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[FONT=Times New Roman][SIZE=3][COLOR=#000000] [/COLOR][/SIZE][/FONT][COLOR=windowtext][FONT=Arial][FONT=Arial][SIZE=3]I’m wondering why folks are even bothering with the Vector engines. It seems like all Sepratrons, with a mean TWR of 31 vs. the Vector’s 21 with even a T100 tank, would be the way to go. [/SIZE][/FONT][/FONT][/COLOR]

[FONT=Times New Roman][SIZE=3][COLOR=#000000] [/COLOR][/SIZE][/FONT]
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Gaarst

Gaarst

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[quote name='herbal space program'][SIZE=2][FONT=verdana][COLOR=windowtext]I’m wondering why folks are even bothering with the Vector engines. It seems like all Sepratrons, with a mean TWR of 31 vs. the Vector’s 21 with even a T100 tank, would be the way to go.[/COLOR][/FONT][/SIZE][/QUOTE]

The Vector gives 1000kN of thrust against 18kN for the Separatron. It is easier to put one inline Vector than dozens of Separatrons. Also, due to the weak thrust of the Separatron you need a lot to reach a high enough TWR, while 1 Vector is usually enough (think dry mass fraction considering the structural elements).
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herbal space program

herbal space program

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Posted (edited)
[quote name='Gaarst']The Vector gives 1000kN of thrust against 18kN for the Separatron. It is easier to put one inline Vector than dozens of Separatrons. Also, due to the weak thrust of the Separatron you need a lot to reach a high enough TWR, while 1 Vector is usually enough (think dry mass fraction considering the structural elements).[/QUOTE]

[COLOR=windowtext][FONT=Arial][FONT=Arial][SIZE=3]I dunno, the Octo2 probe core, a small battery, the smallest reaction wheel unit, four wheels, and a bunch of octagonal struts really does not weigh very much. The leaders here basically festooned their Vectors with hundreds of Sepratrons to improve performance. I say get rid of the Vector entirely! Finally, a use for the little thing![FONT=Times New Roman] ... [/FONT][COLOR=windowtext][FONT=Arial]Of course, I think the record here stems mostly from the frantic gimballing of the Vector near the ground creating Kraken forces, as I believe doing the math tells you that that you shouldn’t end up going that fast even in a vacuum. That consideration probably trumps the legitimate physics.[/FONT][/COLOR]
[FONT=Times New Roman] [/FONT][/SIZE][/FONT][/FONT][/COLOR] Edited by herbal space program
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RCgothic

RCgothic

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I couldn't beat ElMenduko, but you guys have the right of it. I managed a new personal best:

[URL=http://smg.photobucket.com/user/rcgothic/media/2015-11-17_00001_zpsqcskhr0w.jpg.html][IMG]http://img.photobucket.com/albums/v723/rcgothic/2015-11-17_00001_zpsqcskhr0w.jpg[/IMG][/URL]

[B]1092.4m/s
[/B]
The Vector does all right on starting TWR. It plus a full tank for the runway is 6.25t and gives you 1000kN thrust.

6.25t gets you 90 Sepratrons though. That's 1250kN of thrust ASL. Which considering you need to bring along extra support for them and they cause additional drag is not much difference.

Until you burn through all that fuel. The Vector dry still weighs 4.25t. The Sepratrons weigh just 0.9t.

Dump the Vector, it's not contributing.

I couldn't make a craft with 90 functioning Sepratrons on it. I couldn't keep it stable, undetonated, and pointing in the right direction. But I bet whoever does manage it will get a new high score. Edited by RCgothic
Wrong screenshot.
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herbal space program

herbal space program

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[quote name='RCgothic']I couldn't beat ElMenduko, but you guys have the right of it. I managed a new personal best:

[URL]http://img.photobucket.com/albums/v723/rcgothic/2015-11-17_00001_zpsqcskhr0w.jpg[/URL]

[B]1092.4m/s
[/B]
The Vector does all right on starting TWR. It plus a full tank for the runway is 6.25t and gives you 1000kN thrust.

6.25t gets you 90 Sepratrons though. That's 1250kN of thrust ASL. Which considering you need to bring along extra support for them and they cause additional drag is not much difference.

Until you burn through all that fuel. The Vector dry still weighs 4.25t. The Sepratrons weigh just 0.9t.

Dump the Vector, it's not contributing.

I couldn't make a craft with 90 functioning Sepratrons on it. I couldn't keep it stable, undetonated, and pointing in the right direction. But I bet whoever does manage it will get a new high score.[/QUOTE]

[FONT=Times New Roman][SIZE=3][COLOR=#000000] [/COLOR][/SIZE][/FONT][COLOR=windowtext][FONT=Arial][FONT=Arial][SIZE=3]Last night I managed to hit almost 900m/s with a rig consisting of a Flea, Octo2, small battery, 2 small reaction wheels, 4 small gear, nosecone, 3 of the smallest winglet, and a scaffold of octagonal struts covered with Sepratrons. I did not post it because I was not on the ground when I crossed the finish line, but that can be tweaked. Anyway, I will try tonight without the Flea. I don’t know how much drag those octagonal struts have in the current aero model, but they weigh next to nothing. I think the hard part as you said is going to be keeping the whole thing stable. [/SIZE][/FONT][/FONT][/COLOR]
[FONT=Times New Roman][SIZE=3][COLOR=#000000] [/COLOR][/SIZE][/FONT]
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ElMenduko

ElMenduko

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[quote name='herbal space program'][COLOR=windowtext][FONT=Arial][FONT=Arial][SIZE=3]I’m wondering why folks are even bothering with the Vector engines. It seems like all Sepratrons, with a mean TWR of 31 vs. the Vector’s 21 with even a T100 tank, would be the way to go. [/SIZE][/FONT][/FONT][/COLOR]

[/QUOTE]

[SIZE=2]I tested with serpatrons only, but I couldn't do any better (tried with octagonal struts, and putting them inside structural fuselages for better aerodynamics)

One of the main reasons is the vector's gimbal. At these speeds aerodynamics sometimes become a little crazy (body lift). Also, the center of thrust is misaligned (because of the wheels), and the wheels generate a little bit of friction: the end result is that anything without gimbals either took off, or outright crashed into the concrete.

I tried more methods for compensating, but not even a crazy number of small reaction wheels could prevent the thing from going crazy. I also tried spoilers (lifting surfaces used to create downforce) and elevons, but it didn't work either. I even tried downwards-facing serpatrons (with a little bit of success, but still not worth it)

Also, the vector has a much better TWR than the serpatron (not counting fuel), and it is easy to put one of them inline. In fact, you could reach 900-920m/s with one vector and no serpatrons.

In the end, serpatrons are just boosters, they boost the Vector. I had to adjust their thrust limiter carefully, because using a lot of them generates a lot of drag, and if they run out of fuel before the finish line they might even slow you down 50m/s according to some tests.


[COLOR=#0D0E00][FONT=Arial][QUOTE] I dunno, the Octo2 probe core, a small battery, the smallest reaction wheel unit, four wheels, and a bunch of octagonal struts really does not weigh very much. The leaders here basically festooned their Vectors with hundreds of Sepratrons to improve performance. I say get rid of the Vector entirely! Finally, a use for the little thing![/QUOTE][/FONT][/COLOR][QUOTE][COLOR=#0D0E00][FONT=Times New Roman] ... [/FONT][/COLOR][COLOR=#0D0E00][FONT=Arial]Of course, I think the record here stems mostly from the frantic gimballing of the Vector near the ground creating Kraken forces, as I believe doing the math tells you that that you shouldn’t end up going that fast even in a vacuum. That consideration probably trumps the legitimate physics.

[/FONT][/COLOR][/QUOTE]

I think octagonal struts have high drag compared to the other parts I used, not even counting the sheer amount of serpatrons.

Yes, I basically added lots of boosters to my original vector design. "Add more boosters!". I tried lots of other possibilities before that, even one involving mk3 parts and cargo bays, one involving 260 surface attached vectors on big tanks, and none worked better than the first one.

I already recognized I detected some Kraken forces that gave me +/- 140m/s between tests. I blame the serpatrons for that, not the vector. Actually, the vector was the only thing that could stabilize my rolling fireball (but it still crashed 90% of the time due to the Kraken, and the speed was very inconsistent)

Kerbal engineer told me that I could've reached a way higher speed in a vaccuum. When going faster than mach 2 ASL, with lots of radially attached draggy things, that's what slows you down the most. Actually, the Kraken forces were not THAT great (but I haven't been able to come near my own record in subsequent tests, nor I have been able to make a Kraken drive out of it... yet...)

-------------------------------------------------------------------------------------------------------------------------------------------------------------------
[B]TL;DR[/B]:

* The vector's gimball greatly helped stabilize the thing (to prevent it from taking off or crashing)
* I saved up weight by not using a reaction wheel
* Struts might have been draggy (and they can't fit liquid fuel inside them)
* A (not draggy) structural fuselage full of serpatrons was extremely unstable, and it couldn't beat the original design
* A Mk3 cargo bay full of vectors and/or serpatrons wasn't any better
* Surface-attaching lots of vectors wasn't better
* Empty serpatrons at mach 2+ generate A LOT of drag[/SIZE] Edited by ElMenduko
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rocx

rocx

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Here is my attempt to make a craft with 90 sepratrons. Well, 56 of them, in three rings around a very lightweight core. There is no room for luxuries such as attitude control, gimballing or RCS, so going in a straight line is not a guaranteed outcome.
[IMGUR]BLxT6[/IMGUR]
I claim 900 m/s. I might improve this a bit later.

Edit: well, there's an improvement. Eight more engines, wheels locked and on all sides.
[IMGUR]yaiD3[/IMGUR]
New best: 980 m/s. Edited by rocx
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herbal space program

herbal space program

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Posted
[quote name='tewpie']Pure sepratron design

1208.6 m/s, Mach 3.3

[URL]http://imgur.com/a/a1cR9[/URL]

850% of terminal velocity :sticktongue:[/QUOTE]


[FONT=Times New Roman][SIZE=3][COLOR=#000000] [/COLOR][/SIZE][/FONT][FONT="Arial"][COLOR=#000000]Well done! Based on El Menduko’s post, I was about to conclude that the drag issue would doom the all-Sepratron approach, but apparently not. The only way I could see making it go faster would be to figure out a way to get an extra kick from the Launch Escape System, but based on my early attempts I think getting that to work would be a massive PITA.[/COLOR][/FONT]
[FONT=Times New Roman][SIZE=3][COLOR=#000000] [/COLOR][/SIZE][/FONT]
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Friethjoph

Friethjoph

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Posted
hmmm... What if... We take a Mk2 cockpit, Mk2 comouter core, then an empty Mk2 cargo bay, prop on wheels and fill the cargo bay with seperatrons?That would reduce drag (for they are not in the airtream) but add weight... with enough seperatrons it might work out though, and if the rear wheels are a bit higher than the front onse, it could stabilize the machine to stay on the track via downward lift.
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tewpie

tewpie

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Posted
[quote name='Friethjoph']hmmm... What if... We take a Mk2 cockpit, Mk2 comouter core, then an empty Mk2 cargo bay, prop on wheels and fill the cargo bay with seperatrons?That would reduce drag (for they are not in the airtream) but add weight... with enough seperatrons it might work out though, and if the rear wheels are a bit higher than the front onse, it could stabilize the machine to stay on the track via downward lift.[/QUOTE]

That was actually exactly what I did for my original all-sepratron design (well, I used a mk2->mk1 long adapter and a tailcone), but I found using a mk1 fuselage (which is now hollow in 1.0.5) has the same effect as using a mk2 cargobay. I think the fastest I got with a mk2 design as around 1150m/s.

In any case the limiting factor is the physics engine which seems to generate huge resonant vibrations once the number of sepratons becomes large (>200).
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ElMenduko

ElMenduko

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I just realized... OP, is Kerbal Joint Reinforcement allowed? I didn't use it because the rules said "no mods", and that's why most of my designs crashed... a lot...

But if it is allowed I could do better (and have less wheels go totally crazy)


[quote name='herbal space program'][FONT=Arial][COLOR=#000000]Well done! Based on El Menduko’s post, I was about to conclude that the drag issue would doom the all-Sepratron approach, but apparently not. The only way I could see making it go faster would be to figure out a way to get an extra kick from the Launch Escape System, but based on my early attempts I think getting that to work would be a massive PITA.[/COLOR][/FONT]
[/QUOTE]

The thing with the drag is, once the serpatrons ran out of fuel they acted as parachutes, and they slowed you down a lot. However, tewpie managed to get them burning till the end.

The Launch Escape System creates sideways thrust too, and WILL take anything it is connected to out of the way. It's designed to do that after all. In the runway this has terrible consequences.

[quote name='Friethjoph']hmmm... What if... We take a Mk2 cockpit, Mk2 comouter core, then an empty Mk2 cargo bay, prop on wheels and fill the cargo bay with seperatrons?That would reduce drag (for they are not in the airtream) but add weight... with enough seperatrons it might work out though, and if the rear wheels are a bit higher than the front onse, it could stabilize the machine to stay on the track via downward lift.[/QUOTE]

I tried going bigger bit-by-bit too, and I concluded that smaller was better (using 1.25m parts). Maybe 0.625m parts COULD do better if we used tweakscale, but that's not allowed here.

Regarding downforce, if you create a bit too much the front wheels freak out and the thing crashes.

[quote name='tewpie']Pure sepratron design

1208.6 m/s, Mach 3.3

[URL]http://imgur.com/a/a1cR9[/URL]

850% of terminal velocity :sticktongue:[/QUOTE]

Well done, gentleman! I see you managed to keep them burning till the end, how much did you have to tweak thrust limiter?
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