Ablation Challenge

[Diche Bach]

I have been fiddling with trying to get Kerbin launched vehicles in orbit to impact as close to a specific site as possible and an idea for a "challenge" occurred to me.

I cannot say what the specifics should be, but maybe someone can help out but . . . the general idea is: launch a ship within certain parameters, and ablate the main heat shield to lower than 25% of its value, and then recover the vehicle (from surface) successfully.

No idea if this would be way too easy, way too hard, or is just a lame idea, just an idea . . .

 

[zolotiyeruki]

Maybe you could word it like this:

"build a craft with a heat shield full of ablator.  Get it into space, and then re-enter.  Burn off as much ablator as possible without burning *all* of it, and land safely.  Your score is the percent of ablator used up."

And you can add various tweaks to make it more interesting, like:
--once on a re-entry profile, do not touch the controls until re-entry is complete, i.e. ablator is no longer being consumed
--extra leaderboard:  largest ratio of burned-ablator-mass to total craft mass (i.e. 100kg or ablator used on a 1T craft = 10%)

[Diche Bach]

Right! That is exactly the sort of thing I had in mind!

Two key issues:

1. It seems that "surviving" re-entry has a "narrow" margin of error, but once you are "inside" that margin of error (in terms of a. heat-shield CHECK; b. reasonable trajectory CHECK.; c. not unreasonable velocity CHECK; d. parachutes or other velocity mitigating devices for final descent CHECK): it is "quite difficult to screw it up."

Another way to put this: I don't think I've EVER seen my ablator burn to less than 90% of its original value. I HAVE however, burnt up and/or crashed because my velocity was just too high, even since the time that I first learned how to deal with the "deadly reentry" characteristics in the newer versions of the game (I started 3 years ago when deadly reentry was only  a mod if memory serves, and didn't play until recently).

2. The whole topic of how you get a "non-spaceplane" to land on a specific target is interesting (as is the topic of aerobraking) and this challenge sort of relates to those topics.

The basic idea here is: burn up as much of your ablator as possible, without catastrophic failure.

3. Probably/Maybe necessary to impose certain other limits on the challenge (in order to keep it challenging, e.g., using a space plane [an art form I have yet to master] might well make this challenge far easier), but I do not know for certain.

4. Probably there could also be additional "levels" to the challenge such as: burn off a certain threshold of your ablator in each of the celestial bodies with an atsmophere (from a Kerbin launch) and then land back on Kerbin!

[Spricigo]

50 minutes ago, zolotiyeruki said:

Maybe you could word it like this:

"build a craft with a heat shield full of ablator.  Get it into space, and then re-enter.  Burn off as much ablator as possible without burning *all* of it, and land safely.  Your score is the percent of ablator used up."

 

Pretty much this.   Other possible rules:

-pics or it didn't happened. 

-mods prohibited/allowed/required (my suggestion it's only stock parts,  no autopilot and no mods that change the physics (if enough people get interested in using,  say deadly reentry,  make it a different category) 

-no retro burn,  craft must slow down by atmosphere (body drag,  aerobrakes, parachutes.)

-extra leadboard: same rules on Eve,  Duna,  maybe Earth,  Kerbin x6, 4... 

50 minutes ago, zolotiyeruki said:

--extra leaderboard:  largest ratio of burned-ablator-mass to total craft mass (i.e. 100kg or ablator used on a 1T craft = 10%)

 

Perhaps [score]  =( [craft mass at reentry]  + [craft of mass after landing] ) /[units of ablator left]  

This is to account for fuel burnt while in atmosphere if allowed by the rules. 

[Diche Bach]

Ah good, my work here is done! The whacky seed of an idea has been planted

I'd personally prefer to allow mods, as long as they do not make reentering "too much easier." Obviously letting MechJeb or some other autopilot control it for you would be missing the whole point, but I have like 60 or 70 mods installed and most of my ships make use of at least half-dozen (mostly KW Rocketry, Kerbal Engineer, DMagic, that sort of thing) and I'm not sure any of that sort of thing should be excluded.

[zolotiyeruki]

8 hours ago, Diche Bach said:

Ah good, my work here is done! The whacky seed of an idea has been planted

I'd personally prefer to allow mods, as long as they do not make reentering "too much easier." Obviously letting MechJeb or some other autopilot control it for you would be missing the whole point, but I have like 60 or 70 mods installed and most of my ships make use of at least half-dozen (mostly KW Rocketry, Kerbal Engineer, DMagic, that sort of thing) and I'm not sure any of that sort of thing should be excluded.

No, I don't think your work is done.  You've received some help on how to refine the challenge into something interesting.  it's still up to you to form the ideas into a workable (and fun!) challenge.

[Diche Bach]

Hmmm, well let me think on this a bit more. I'm just getting a grip on landing within 3000^2 km of a particular lat/long coordinate and the whole dynamics of setting the re-entry burn in such a way as to account for planetary rotation, etc.

The main thing with this challenge is: it should require a high level of understanding and mastery of the "re-entry" dynamics and the measure of success: how much of your ablator can your burn off and still survive will reflect this.

The initial idea came from the observation that:

Wow, if my re-entry doesn't screw completely and cause total catastrophe, then it seems quite difficult to burn up much more than about 10% of the ablator. This made me wonder: "how much ablator could one burn off? how would one go about that?"

Off the top of my head, it seems that: to burn up a large fraction of your ablator one needs to be:

A. going faster and

B. descending with as prolonged of trajectory as possible (one in which deceleration as a result of air resistance is strung out for as long as possible).

Sure, if you descend very steeply, you may well reach a high speed, but if your ship is as "non-aerodynamic" (probably a proper word for that eh?) as possible, you'll likely slow down from anything non-fatal enough that again . . . little more than 10% of ablator consumed.

So that is where I'm at with it right now. Basic rules

1. Mods are okay, unless they involve automation of reentry maneuvers or otherwise make reentry easier (I'd prefer if no one use a mod to help them into their initial orbit, but I don't suppose that would disqualify).

2. No space planes: the reentry vehicle can have no wings or aerodynamic control surfaces of any kind (other than the hull itself and the heatshield or other "blunt" instruments! )

3. The vehicle must be built in the VAB & launched from the Kerbin Launch pad (not the runway)

The specifications of the challenge:

A. Launch your vehicle from Kerbin Space Center Launchpad. Either manned or Unmanned is fine. Crew complement, vessel overall size, etc., all at your discretion (someone might figure out a way to use a giganti lumbering hulk that can barely crawl into orbit as a way to maximize ablation??)

B. No more than 8,000 dV allowed for the vehicle sitting on the launch pad. That is probably more than enough to allow for a variety of "techniques," possibly too much . . . but for starters we can  go with that large amount. Perhaps we can say that: left over fuel (not hydrazine) counts as "bonus points?"

C. If the main engines do not use hydrazine, no more than say 100kg of monopropellent? (maybe 500kg?), reason being: I think KER doesn't consider hydrazine into dV  so one could cheat on the dV limit by having one main engine that used a bipropellant and then final stage RCS with lots of hydrazine.

D. Vehicle must have at least one "heat shield" part (screen caps needed).

E. Achieve a parking orbit with periapsis of at least 100km (inclination, eccentricity no limits)

F. Without docking or otherwise adjusting the vehicle in orbit, reenter Kerbin's atmosphere in such a way as to ablate the maximum amount of your heat shield (obviously changing your orbit to do this is fine, as long as you _start_ the re-entry process from an orbit with a periapsis of 100km or more)

G. Land your vessel without any casualties and without destroying the main portion of the craft (the command module), post screen caps of your ablation proportion left.

Whoever gets the ablator to the lowest value wins!

-=-=-=-=-

I'm guessing that the way to "win" this is to basically "skirt" along the upper atmosphere for as long as possible without losing too much altitude. Possibly even some sort of eccentric orbit that results in many repeated "bounces" off the top portions of the atmosphere on the low side . . .

How is that for a functional challenge this is interesting and "sounds fun?"

Edited August 19, 2016 by Diche Bach
fix

[zolotiyeruki]

If you think it's ready for prime time, take what you've written, edit your first post in the thread, and then I'd suggest you update the title so that other forum-goers know that it's ready for people to play.

[Diche Bach]

@zolotiyeruki I think I need to fiddle with it in sandbox mode myself . . . too caught up in my career play at the moment and my KSP binge time allotment is rapidly dwindling into the negative side of the number line . . . (12 Java programs in 9 days is doable but I probably need to get back to work tomorrow . . .)

When I've done that I'll make some edits to the first post and see if that seems sufficient to meet the standards for a proper challenge. I did not realize that this "challenge" ritual was quite so "structured" (albeit informally and obviously in the spirit of good fun and comraderie).

I read Sal Vager's post on "how to make a good challenge," but one thing I'm not understanding: is there a single "leaderboard" somewhere for all challenges or is is simply the steward of the challenge who maintains a list in the first post?

Link to an example of an exceptionally well-conceived challenge that has proven to be popular and fun??

 

[DoctorDavinci]

12 minutes ago, Diche Bach said:

I read Sal Vager's post on "how to make a good challenge," but one thing I'm not understanding: is there a single "leaderboard" somewhere for all challenges or is is simply the steward of the challenge who maintains a list in the first post?

The issuer of the challenge (meaning yourself) keeps record of the leaderboard in the OP if you choose to have a leaderboard

Remember, the 'how to make a good challenge' thread is there to help you form your challenge and is not the definitive be all and end all of rules but more a guide to help forum users to conceive of a good challenge that the forum community would like to take part in

[zolotiyeruki]

4 hours ago, DoctorDavinci said:

The issuer of the challenge (meaning yourself) keeps record of the leaderboard in the OP if you choose to have a leaderboard

Remember, the 'how to make a good challenge' thread is there to help you form your challenge and is not the definitive be all and end all of rules but more a guide to help forum users to conceive of a good challenge that the forum community would like to take part in

Right--it's a guide that will make it more likely (though not guaranteed) that other users will participate.

[AlexanderB]

On 8/19/2016 at 11:33 PM, Diche Bach said:

Possibly even some sort of eccentric orbit that results in many repeated "bounces" off the top portions of the atmosphere on the low side . . .

Its really easy to completely run out of ablator that way, the trick might be to not go too high, and re-try a bunch of times until you have as little as possible left over on landing.