Thrust KSC Land Speed Challenge

[Michaelo90]

Any thoughts on making a separate bracket for people playing with FAR? I suspect one group gets an advantage over the other, I'm just not sure which one. With FAR, you need to use aerodynamic parts and a more linear layout, which increases the mass, slowing acceleration. But it also increases the top speed, as I think the terminal velocity is higher with FAR at ground level.

I agree, i think FAR makes it easier. At least it should make it very different so it should have it's own category.

[Koolkei]

I agree, i think FAR makes it easier. At least it should make it very different so it should have it's own category.

well. FAR makes the atmosphere thinner so it is kinda easier to fight the drag, but ever thought that thinner atmosphere means less stability??

also FAR also deviates the physics a bit so it's slightly more realistic, and in some parts, more drag?

all that, still i agree to make it a separate Bracket race

anyway here's my try (Dragor 2(because Dragor 1 only managed around 250m/s)

(used FAR and KW rocketry)

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i need a lot of tricks just to get it to run stable enough....

like for one, i cant start at 100% throttle, i need to start at 50% and increase it to 100% while accelerating

after 4 hours of tinkering around i forgot the most important thing......

THE KERBAL!!!!!

D**** it

be right be with the new tweak later today, or tommorow

Edited February 18, 2014 by Koolkei

[Koolkei]

my second try.....

my god this thing is ridicolously hard to stabilize

the success run rate of this thing is like 10-20%, i need to retry around 10-15 times just to get it to NOT crash

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sorry i forgot to put the name here

i still named it the 'Dragor 2'

435m/s but made it to the start.... extra 100 points right?

there's no rule you cant reverse to the start with solid booster right?

besides, it's not i like i meant to make the boosters have extra fuel, the extra fuel initially used for offsetting the weight slightly to the front, i didn't planned to use the booster to make it back

Edited February 18, 2014 by Koolkei

[ihtoit]

haha... nice run, but no, you have to turn around and make it back at at least 75% of your outbound run speed for it to count for the bonus.

[ihtoit]

refer to OP for my argument against making another board for FAR.

[ihtoit]

Any thoughts on making a separate bracket for people playing with FAR? I suspect one group gets an advantage over the other, I'm just not sure which one. With FAR, you need to use aerodynamic parts and a more linear layout, which increases the mass, slowing acceleration. But it also increases the top speed, as I think the terminal velocity is higher with FAR at ground level.

show me consistent results with and without, on the same design, and I might consider it.

[Soda Popinski]

show me consistent results with and without, on the same design, and I might consider it.

I'll see what I can come up with. I'm not sure that's really the best test, as if I wasn't running FAR, I wouldn't bother with a nose cone, the size adapter, or the tail fin to put the center of drag behind. I also may have more luck with wheels, as stability is a real issue with FAR. In other words, the design may be completely different.

Anways, here's my latest entry:

467 m/s

Running FAR, DRE and a bunch of not relevant mods (see my Jool mission for a complete list in my sig).

Explanations of the changes I made are in my video description.

Edit: D'oh, I forgot, I'm using RealChutes for the radial drogue chutes. I honestly don't know if they're better than the stock chutes for this (are there radial drogue chutes in stock?). I just use them out of habit, since I play with DRE, and hard braking will kill my kerbals via G forces. I'm also running KJR (goes hand in hand with FAR, due to the need to build more vertical). This may be helping to keep my craft from not disintegrating, but I don't think it works on radial mounts, which is my main stress point (I'll test it later without KJR).

Edited February 18, 2014 by Soda Popinski

[Soda Popinski]

I've got some data on FAR versus no FAR using the same rocket.

This was my 467 m/s rocket as above, but unmanned and with no fuel tweaks.

This is the run without FAR in triplicate.

This is the run with FAR in triplicate.

[ihtoit]

yeah both come up "unavailable". Was it a control issue? Seems to me like with the aero tweaks in FAR, comes the inherent instability that comes with loss of control authority... so it becomes a real test of skill just to keep the thing on the tarmac. Rules is rules, if it goes off, it ain't an entry

^^strike that lot, the vids are up now... ok, it looks like you're actually hitting maximum speed at the same point (just past the hangar) whether you're using FAR or not, and when you run out of LF is the point you should be hitting the retro gear, FAR is handing you greater braking distance. In fact I'm not even sure you can wait that long with that setup and FAR...

Edited February 18, 2014 by ihtoit

[MiniMatt]

Yeah I think I might bow out at this stage. The inconsistencies between mods begin to make comparisons unviable. Looking above I can see RealChutes, and without testing I'd very much assume that the braking force afforded by them is far greater than that which can be achieved via a similar mass and drag of retro solid boosters.

Re FAR versus stock I'd note only that in the conceptually similar fastest air breathing jet under 1000m altitude challenge the fastest FAR run is currently 1,529m/s, the fastest non-FAR run is 381m/s.

Re skids rather than wheels, this one I'm a little more tolerant of. It's rather difficult to retrofit with skids a craft designed for wheels and vice versa, but in the knockups I've got successfully running I've seen a roughly 10% top speed advantage given to wheels and a roughly 250 metre braking advantage given to skids. At current records I'd suggest the overall advantage lies with skids but I note that the friction inherent in skid designs appears to put limits on the total amount of thrust which can be applied before craft disintegration. This limits the logical progression of "MOAR MAINSAILS" which can take place with wheeled designs and I'd assume the theoretical max speed attainable would come from wheels. But while mods are only classified as "controlled versus non-controlled" I'd suspect that simply adding a super strength strut mod would allow skid designs to blitz all competition.

[ihtoit]

MiniMatt: the difference between the jet one and this is that in the jet one you're looking to minimise drag and for that matter lift as well (can't have a supersonic Kitty Hawk, too much lift!). For this challenge it's all about downforce - keeping the sled on the ground. As the brake tests confirm, FAR is a handicap in stopping

[MiniMatt]

If you say so but I fear it begins to make comparisons unviable.

As an example I've just downloaded RealChute and had a quick play whilst I should be working Take my 12 mainsailed Land Speed 8 for which the craft file was provided a few pages back - max speed attainable was 423m/s - and that 423 is 100% repeatable as that's the maximum speed it attains before running out of fuel. The only way to reach a higher speed in the acceleration phase would be reduce drag, reduce mass or add thrust.

So I removed the four RT-10 solid boosters which were hindering the acceleration phase, adding significant unwanted drag and mass and simply added three radial drag chutes from Real Chutes. That's it, no other redesign other than changing action groups to fire front brakes separately from back brakes and deploying the chutes. Max speed now attainable from the Land Speed 8 has now increased from 423m/s to 441m/s.

Neither the chute braked or booster braked variant is better than the other, they're both simply playing by different rules.

EDIT: Perhaps worth clarifying that I - and I don't believe anybody - thinks use of FAR makes the challenge easier as such, or indeed that use of any particular mod is cheating. None of these mods detract from the skill of the designer, all they do is change the course. Formula 1 engineers have a different set of parts, rules, and challenges to play with than Rally engineers and their courses are different. The Formula 1 car may be able to accelerate and brake harder than the rally car but nobody is suggesting the F1 engineers have devised a better design, only that their design fits their course.

Edited February 18, 2014 by MiniMatt

[MiniMatt]

Ok, very quick test and still not ironed out all the kinks as amply demonstrated below but taking the Land Speed 8, installing FAR and Real Chutes, capping the fuel cans with aerodynamic nose cones, take away two of the four RT-10 solid boosters and add five radial drag chutes:

Yes it's a failure but it was surprisingly close to success. Overall braking force seems nearly sufficient, failure came right at the very end of braking as an engine dipped and clipped the runway. The chassis and Bill survived intact at the end of the runway. Fixing those final stability issues will likely dampen the final max speed achieved but this failure achieved 566m/s. With exactly the same chassis, the exact same number of engines, the exact same quantity of fuel - only changes were installing FAR & Real Chutes, swapping two of the four retro boosters for five radial chutes, and capping fuel cans with nose cones - that achieved a raise from 423m/s to (ultimately nevertheless a failure at) 566m/s.

I'll again restate: FAR or any other mods do not make the challenge easier. FAR or any other mods certainly don't "cheat" the challenge. They make the challenge different.

EDIT: As a suggestion, I'd simply create three tables: Stock, Controlled Mods (allowing eg. only B9, Far, and Real Chutes), and Open (wherein everything else is allowed & competitors are on their honour to list what they use and keep potential OP mods in check). Like I say, no mods really make the challenge easier, they just change the course. A stock craft won't be optimal for a FAR course, and a FAR craft won't be optimal for a stock course - they cease to be comparable but that is not to diminish the design ingenuity required to make either craft work. Giving them their own category makes such designs comparable once again to other craft driving the same course.

Edited February 18, 2014 by MiniMatt

[Soda Popinski]

Funny, I put up the FAR vs. Non-FAR to show that FAR increased the top speed from 391 m/s or so to 474 m/s. The braking distance isn't a fair comparison, as the speed is much, much higher with FAR.

I also edited my last post and added Real Chutes. I use them out of habit, as my Kerbals die with harder braking of the stock chutes. I didn't think to use the stock drogue chutes, but I don't recall if they have a radial version.

Thanks for giving it a cool name. I actually called it the "Yoyodyne Cluster F mk 17," due to the...engine cluster.

And thanks for setting up this challenge. It's been a lot of fun (my first challenge I've tried for).

Edited February 18, 2014 by Soda Popinski

[MiniMatt]

I didn't think to use the stock drogue chutes, but I don't recall if they have a radial version.

Yeah, stock chutes of any variety don't open if you're on the ground making their use impossible in this challenge - arguably this is something of a design oversight on the stock parts. I am really liking the Real Chutes mod as it does add a great deal more to think about, some new solutions and some new challenges.

[Koolkei]

Funny, I put up the FAR vs. Non-FAR to show that FAR increased the top speed from 391 m/s or so to 474 m/s. The braking distance isn't a fair comparison, as the speed is much, much higher with FAR.

I also edited my last post and added Real Chutes. I use them out of habit, as my Kerbals die with harder braking of the stock chutes. I didn't think to use the stock drogue chutes, but I don't recall if they have a radial version.

Thanks for giving it a cool name. I actually called it the "Yoyodyne Cluster F mk 17," due to the...engine cluster.

And thanks for setting up this challenge. It's been a lot of fun (my first challenge I've tried for).

last page, i did say FAR do some kind of tweaks to the atmosphere, it makes it thinner, yet it makes any moving parts on an airplane have a lot more drag.

so in this case a dragster with no actual aero parts would benefit, but it also add to the instability, not all craft are stable both in non-FAR and FAR.

[Michaelo90]

I still think there should be a separate category for mods, but i will try using FAR and Real chutes to beat you all again

Also, why isn't my v6 on the leaderboard? It's on page 5.

[Soda Popinski]

I agree, there should be a mod and stock leader board (controlled or not I don't have an opinion).

It's way too complicated to do a FAR, and a FAR + DRE, and a FAR + DRE + RealChutes.

I have to say, this challenge really got me thinking outside the box. When I put in my original entry, I was the only guy crazy enough to use a Main Sail. As competition tightened up, it looks like everyone has found what seems to work, and all of our builds are getting conceptually closer (cubic struts + 48-7S + skids). So things may be looking less interesting, but I'd love to be surprised. I've really enjoyed watching people's entries evolve over the course of the challenge.

I do think FAR's inherent instability is the main reason I can't use wheels very well (trust me, I tried with a whole series of "Yoyodyne Banzai" rocket cars that will never see the light of day). Wheels inherently want to move in the direction they are facing. So if you have any yaw occurring, you'll get a sideways vector. For me, this usually ends up rolling my rocket car as the sideways force vector from the wheels is obviously below my center of mass. Skids on the other hand, have no "preference" for which way to "roll." So yawing isn't such a problem.

BTW: Anybody getting the "Yoyodyne" reference? Or am i showing my age again.

Edited February 18, 2014 by Soda Popinski

[MiniMatt]

Okies, either a multiple entries or an illustration as to need for mod categories.

FAR + Real Chute = 503m/s

Real Chute = 433m/s

Completely stock = 425m/s

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The only change between the stock model and the FAR & Real Chute runs were that the drag chute was replaced with a nose cone and the retro rocket filled with 20% fuel rather 10% to make up for the loss of braking force - this added to mass accounting for the drop from 433 to 425 seen in the chute versus stock run. Will make craft file available in a bit.

[Soda Popinski]

Okies, either a multiple entries or an illustration as to need for mod categories.

FAR + Real Chute = 503m/s

Real Chute = 433m/s

Completely stock = 425m/s

http://imgur.com/a/besBX

The only change between the stock model and the FAR & Real Chute runs were that the drag chute was replaced with a nose cone and the retro rocket filled with 20% fuel rather 10% to make up for the loss of braking force - this added to mass accounting for the drop from 433 to 425 seen in the chute versus stock run. Will make craft file available in a bit.

I am pleasantly surprised. Nicely done. How in the name of the Kraken do you manage to keep that thing stable using wheels?

At least I was first for a little while. I've got some ideas, but I'm been neglecting my Jool Mission...and real life.

[MiniMatt]

How in the name of the Kraken do you manage to keep that thing stable using wheels?

By luck alone! Numerous FAR attempts have been horrendous (although the 116 ton Land Speed 8 also doesn't do too badly under FAR... until one tries to stop it).

Anyway, craft file for above entry is here so you're more than welcome to see if there's some magic trick I've accidentally stumbled across. It's got the Real Chute drag chute at the back so I'm not sure how it'll load without that installed.

EDIT: Oh, action group 1 deploys the chute, fires the booster and engages front brakes. Back brakes can be safely engaged when it's decelerated down to 200m/s or so.

Edited February 18, 2014 by MiniMatt

[Michaelo90]

Is anyone else having problems with realchutes not deploying at the same time?

[MiniMatt]

Is anyone else having problems with realchutes not deploying at the same time?

Yep, though suspected it might have something to do with high part count resulting in sluggish performance and chutes missing a turn between update cycles as a result. Partial solution for part heavy craft was to stage central chute first to take the bulk of the initial forces and fire side chutes a second or two after once initial forces had settled down. Or design light enough such that one central chute is sufficient.

[Michaelo90]

Yep, though suspected it might have something to do with high part count resulting in sluggish performance and chutes missing a turn between update cycles as a result. Partial solution for part heavy craft was to stage central chute first to take the bulk of the initial forces and fire side chutes a second or two after once initial forces had settled down. Or design light enough such that one central chute is sufficient.

It's not because of high part count, I tested a craft of about 10 parts and they still didn't deploy at the same time

[ihtoit]

OK, due to people threatening to "come see me" ( ), I've split the scores into FAR and non-FAR. If I put you on the wrong table, please let me know, also if I missed you during the shuffle, let me know