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Challenge: Drag race to 100KM altitude

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Fool

Fool

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Seeing as we've got a new version I'd like to say congratulations and round one to Foamyeaque.

I'd been able to take a second or two off my best time, but anything I tried to build that would have gone faster got destroyed by the end of burn acceleration spike after 24-25 seconds. (any tips anyone might have on how to tame that when using 200+ SRBs at once will be gratefully received)

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foamyesque

foamyesque

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Seeing as we've got a new version I'd like to say congratulations and round one to Foamyeaque.

I'd been able to take a second or two off my best time, but anything I tried to build that would have gone faster got destroyed by the end of burn acceleration spike after 24-25 seconds. (any tips anyone might have on how to tame that when using 200+ SRBs at once will be gratefully received)

My first stage was 229 SFBs. I used struts. LOTS of struts.

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zarakon

zarakon

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I promised myself not to get mad as much, but how can you POSSIBLY not notice the date of the post you\'re quoting? The date is RIGHT there!

Why are there so many necrobumpers lately?

why does it matter?

it\'s not like this is some political discussion that\'s lost its relevance

A really, really big first stage. =)

I should try it in .13, see if it flies any better.

3 stages of SRBs, where each stage dwarfs the one above it?

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foamyesque

foamyesque

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3 stages of SRBs, where each stage dwarfs the one above it?

Yep. If you scroll up a few posts, you\'ll see that I said I have 229 SFBs in my first stage... and of course in the screenshot, you can see I only have three in my last one. =)

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foamyesque

foamyesque

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Don\'t use LFEs is the big one. They\'re amazing for doing SSTO or space manouvering because of the insane dV you get with the stock LFE/LFT interactions, but their TWR is terrible compared to SFBs and for this challenge TWR is king. You need to get going as fast as possible as early as possible in the atmosphere.

I\'ve found out that apparently I can\'t use my .12 and earlier designs in .13, which means I\'ve got to rebuild the ship. Blargh. =/

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foamyesque

foamyesque

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Another thing: winglets create a huge amount of drag. Try to use as few as possible. Struts have a similar problem, but with weight rather than drag.

Struts, however, are essential for heat radiation and structure integrity in mass SFB designs.

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UmbralRaptor

UmbralRaptor

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Well, here\'s a 1:29 2-stage design.

Dragracer13_time_1_29.png

I think it needs a smaller upper stage or a bigger lower stage. Also, I need to work out a more organized/expandable strut pattern.

Dragracer13_pad0.png

edit: Going from 19 to 7 boosters in the upper stage does help.

1:24

Dragracer13b_time_1_24.png

Dragracer13b_pad0.png

edit again: I think to optimize the lower stage, I should push it up to 100+ boosters? o_O

edit 3: I\'m thinking that I\'ve been overbuilding upper stages. At least compared with the largest lower stages my P4 can reasonably handle. (Running TWR and mass ratio numbers suggests that an upper stage with 3 boosters gives you most of what a 7 or even 19 booster upper stage does)

1:21

Dracracer13c_time_1_21.png

7 booster upper stage, 61 booster lower stage.

Dragracer13c_pad0.png

edit 4: Maybe not? 1:24 with the upper stage reduced to 3 SRBs.

edit 5 (and last for the night):

1:18

Dragracer13d_time_1_18.png

98 SRBs (91 in the lower stage, 7 in the upper stage), 108 struts.

Dragracer13d_pad1.png

I don\'t think I\'m at the limits of what KSP can handle, but my P4 is getting abysmal framerates. I\'ll post a .craft if there\'s interest.

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UmbralRaptor

UmbralRaptor

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Yes, I\'m replying to myself. But I\'d like to think I\'ve earned it.

Lessons learned:

1) Adding even 6 additional boosters to the upper stage requires an additional set of struts to keep the stack decoupler from snapping.

2) The lower stage is *still* not big enough to make a larger (13 or 19 booster) upper stage useful.

3) Watch your positioning and winglet placement better, and you can fix a lot of tower clipping.

4) Sometimes all you need is another ring of boosters on the first stage (91 -> 127)

Dragracer13e_time_1_16.png

I\'m tempted to add another ring of boosters (127 -> 169), but this is getting silly.

edit: 1 more ring, 1 more second shaved off. It\'s developing aerodynamic stability issues just before first stage burnout, though.

Dragracer13f_time_1_15.png

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