Kerbal Dynamics: Exploding Sun

[ihtoit]

I just watched this gem of a miniseries from 2013, and thought to myself: what a moderately interesting challenge profile!

So here it is:

The sun is going nuts! Some bright spark sent a new propulsion system barrelling into it by mistake and now it's amplifying "bad things" into "worse things" causing all sorts of havoc on Kerbin. Your mission is to deliver a bomb into the Sun and return to Kerbin to pick up your troubled relationship where you left off (although big deal is made of it, this has absolutely nothing to do with the mission at hand except to give you incentive to return safely - or not).

Complete the mission profile given below. Success or failure depends on precisely TWO things, both of which must be fulfilled for the mission to be considered a success - being, the deployment of a payload into the Sun and the safe return of the vehicle to KSC.

MISSION PROFILE:

- Vehicle is a runway-launched, two-seater SSTO spaceplane or shuttle-type vehicle (I like slick looking spaceplanes). No parts may be jettisoned, refueling is not an option.

- While in atmosphere (for the sake of argument and in keeping with the movie's profile, "in atmosphere" is anything below 47km), you may use airbreathing jets only. Above that altitude and within Kerbin SOI you may use nuclear engines only - no rockets below 47km, period. You may use Alcubierre drive (from KSPInterstellar) to 0.1c (Warp 0.1) only while OUTSIDE of Kerbin's SOI (84,159km altitude).

- RCS is not an option for this mission.

- Payload is a Probodobodyne OKTO probe core with two OX-STAT solar panels and a short-range radio antenna with range enough to maintain communication through deployment (I figure around 2000km). This represents your "bomb". You must release this payload at an altitude of no more than 500km from the Kerbolar surface, its trajectory being terminal. You must maintain radio contact with this probe all the way in to ensure its successful detonation.

- Vehicle must make a safe runway landing at KSC.

Kasuha shows us how it's done using flybys and very little fuel!

Edited May 25, 2014 by ihtoit

[xrayfishx]

- While in atmosphere (for the sake of argument and in keeping with the movie's profile, "in atmosphere" is anything below 47km)

I haven't seen the movie, but did you ever stop to consider that Kerbin's atmosphere is not as thick as Earth's? What you are asking of us is basically circularizing in atmo and then after that being able to coast to 47k, that's AT LEAST 10k vertical of coasting. Yeah, I could build that, sure. But then that thing (with its dozen jet engines) has to be able to slow down enough to crash into the sun, then correct at the last minute and then after all that circularize again and then reenter.

Did you try this challenge yourself?

[zarakon]

I agree, the feasibility of this challenge is questionable. A sun dive requires an awful lot of delta-v.

The 47km atmosphere requirement seems awkward, and would probably necessitate a lot of intake spam.

Edited May 22, 2014 by zarakon

[dbmorpher]

Challenges are required to be feasible, read the FAQ

[ihtoit]

taking a jet to 47k without "spamming" intakes is entirely possible, I've taken bomber-sized jets with a 1:1 intake:engine ratio to pe>90km (with rolling cutoffs from 24km and flameouts at 30-35km). Very recently, in fact.

A sun dive only requires 13km/s *from a vertical launch* and change. I've done that, too. Double that for return. Doable in a thirty ton aircraft, I'm sure.

[Capt. Hunt]

Why no RCS? What do you have against Reaction Control Systems?

[ihtoit]

no RCS in the movie, so none here. I hardly ever use RCS anymore anyway, except for when I'm docking. Gyro attitude control should be enough for anybody for this mission.

[Captain Sierra]

taking a jet to 47k without "spamming" intakes is entirely possible, I've taken bomber-sized jets with a 1:1 intake:engine ratio to pe>90km (with rolling cutoffs from 24km and flameouts at 30-35km). Very recently, in fact.

A sun dive only requires 13km/s *from a vertical launch* and change. I've done that, too. Double that for return. Doable in a thirty ton aircraft, I'm sure.

I'm not sure, because I know VERY few people that can do that with an SSTO. I think dropping the atmosphere limit down to a more reasonable 26-34km would be a lot more feasible. So,basically what I'm asking is are you trying to make a sundive challenge or an SSTO challenge? because asking for both is pushing the limits of what a lot of players can do.

[Whovian]

This would probably be quite doable (but difficult,) if it weren't for the restriction on release altitude. With this restriction, you need to be able to get onto a collision course, release it <500km above the solar surface, and then (here's the hard part) not crash into Kerbol. The delta-v required to make this course correction so low is probably somewhere at least 3 km/s and could be anywhere from 3 to 20 km/s (I have a little experience with sundive speeds cos I tried and failed to get to Ablate from PlanetFactory once.) Getting enough delta-v to sundive, make that course correction, and get a Kerbin intercept in a single stage without ion engines is probably just very very hard, but then getting a high enough thrust-to-weight ratio to perform that course correction before you hit the overheat line while maintaining enough delta-v to perform your maneuvers is, I am willing to say with absolute certainty, completely impossible in stock without resorting to Kraken drives or similar bugs.

EDIT: It just occurred to me that you could do it instead by getting into a 500 km circular orbit around Kerbol, making a small course correction to make your orbit a collision course, release the OKTO, and then get back into your circular orbit, and thus bypass the thrust-to-weight ratio problems. But getting enough delta-v (almost certainly around 40 km/s) in a single stage to do this is way more impossible.

EDIT 2: This is possible. I repeat, this is possible. It just requires a ton of precision. This is because of the bit about the Alcubierre Drive. Someone uploaded a tutorial on youtube about transferring anywhere using those and expending 0 delta-v; the basic idea is to warp into various strategic orbits and let gravity do all the delta-v for you. Once you're in solar orbit, this is probably most quickly doable by warping to ~500 km above the surface of the sun, releasing (due to the velocity preservation you'll be on a collision course,) and warping the **** out of there. The only problem is that the most precision I can seem to get with the Alcubierre Drives is about 80 megameters, so you'll need to use some nuclear engines anyway. The first scheme I proposed is probably the easiest; you'll have to do a warp instead of doing thrusting to get out of your collision course. I might try to do this once I'm done with Jool-5ing to my heart's content.

Edited May 22, 2014 by Whovian

[ihtoit]

see my sig panel for a mission I undertook to recover Kerbalnauts from a terminal sundive using another ship placed in a parallel terminal orbit which I managed to place in a low-pe kerbolar orbit then intercept with yet another ship (it was all practice, really). I won't post a challenge that's impossible, that's the domain of others. It takes planning, that's all.

[Kasuha]

Okay, enumerating possible approaches I'd like to ask for confirmation that there are no time limits or restrictions on other planet flybys.

I would also like to ask for relief on the two-seat rule since there is serious lack of two-seat cockpits in stock game. Alternately, is it ok if I send one of my Kerbals in command seat?

(reason is that I would like to do this with my already existing plane but it's just one-seater)

[ihtoit]

Okay, enumerating possible approaches I'd like to ask for confirmation that there are no time limits or restrictions on other planet flybys.

None at all. Use whatever flybys, slingshots, long-orbit swan dive configurations you want

I would also like to ask for relief on the two-seat rule since there is serious lack of two-seat cockpits in stock game. Alternately, is it ok if I send one of my Kerbals in command seat?

(reason is that I would like to do this with my already existing plane but it's just one-seater)

That (EDIT: the command chair) is acceptable. Although, there are three stock pods with two or more seats, only one is really suited to spaceplane configuration (the Mk. 3), you could even stack two Mk. 2 cockpits or a Mk. 1 and a Mk. 2. I think Bob'd end up hating you if you stuck him on a deckchair strapped to the back of your plane and flew him into the sun...

Edited May 23, 2014 by ihtoit

[Kasuha]

That is acceptable. Although, there are three stock pods with two or more seats, only one is really suited to spaceplane configuration (the Mk. 3), you could even stack two Mk. 2 cockpits or a Mk. 1 and a Mk. 2. I think Bob'd end up hating you if you stuck him on a deckchair strapped to the back of your plane and flew him into the sun...

Okay, it's not clear to me which option do you mean as acceptable so I'll be assuming command chair is ok. Somebody will have to keep his eyes on the bomb all through the mission. Adding one more command pod would make the plane too heavy and would require too substantial redesign.

[Kadrian]

Interesting challenge. It should be possible with some creative maneuvering. Will try some designs this evening.

Does the "bomb" have to be completely passive or can I strap some engines onto it?

[ihtoit]

Does the "bomb" have to be completely passive or can I strap some engines onto it?

Only if all you want to do is add weight to it, it's an almost completely passive device. Apart from the radio. And the uber-explosive thingumabub part. Hence the riding it almost all the way in part (else you could just like go into almost-Kerbin-escape and fire it on a dawn-retrograde escape until the bomb runs out of fuel, where's the challenge in that??)

[Kadrian]

Only if all you want to do is add weight to it

Noted.

How is the radio contact requirement checked? I'm playing all stock, so to my knowledge you don't need line of sight or big antennas to transmit science back to Kerbin (yet). And blowing things up sounds most scientific to me.

Cheers

Adrian

[Kasuha]

- Payload is a Probodobodyne OKTO probe core with two OX-STAT solar panels and a short-range radio antenna with range enough to maintain communication through deployment (I figure around 2000km). This represents your "bomb".

There's no such thing like maintaining communication in stock game. Is this "bomb" (on docking port Jr) ok?

[ihtoit]

There's no such thing like maintaining communication in stock game. Is this "bomb" (on docking port Jr) ok?

yep, that's fine (though I think you got the wrong OKTO core on there, not that it matters *that* much since there's next to no difference in mass, I picked the OKTO because its sides cover the width of the solar panels nicely).

If you're not running Remote Tech mod (which adds radio functionality but also adds a handicap in that a relay network is required for deep space/robotic probes), I'll just trust that you're running a deployed Communotron or equivalent antenna on the bomb and an equivalent receiving antenna on the spaceplane.

[Kasuha]

yep, that's fine (though I think you got the wrong OKTO core on there, not that it matters *that* much since there's next to no difference in mass, I picked the OKTO because its sides cover the width of the solar panels nicely).

If you're not running Remote Tech mod (which adds radio functionality but also adds a handicap in that a relay network is required for deep space/robotic probes), I'll just trust that you're running a deployed Communotron or equivalent antenna on the bomb and an equivalent receiving antenna on the spaceplane.

Well, duh. I'm only reading it after I finished the mission. Sorry for mismatch in probe core, that's completely my fault. Wherever I read OKTO I see OKTO2. On the other hand, I believe the plane did return with sufficient leftover fuel to be able to run the mission with 0.06 t of extra mass.

I also don't play with remote tech or any other mods so I don't need to put any antennas on my ships to "maintain communication". I deployed the antenna on the "bomb" but only after I detached it from the plane. I don't feel that was completely my fault, though.

I'm sorry for missing some guidelines but Bill and Bob are completely convinced they did great and saved the Kerbalkind. It's up to you to decide whether their effort counts or not.

To anybody who wants to run the mission, be warned the following album may contain spoilers:

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[ihtoit]

...and that is how we do that! I must learn how to do those slingshots, they must save a LOT of fuel...

[Kadrian]

So here is my attempt.

Let's see if the imgur embed works:

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It's a Shuttle very similar to Kasuha's. The two engines pointing in opposite directions on the same tank are a nice touch and solve a lot of problems that appear when using more than one Turbojet at high altitudes (if one of them flames out, the shuttle gets pulled to the side by the non-central thrust - impossible to fly...).

The mission itself uses a Jool Slingshot to get a very high elliptical orbit around the sun. On the apoapsis breaking to a terminal course uses only 700 m/s delta-v, which means that the 4000 m/s I started with in low Kerbin Orbit are quite enough (basically the budget just consists a Jool transit, the breaking maneuver, the burn at Kerbol periapsis to avoid the crash and some minor course corrections. Way less than retrograde burns outside of Kerbin and speeding up again to get back home, which I estimate at about 20,000 m/s). Only downside is that this high orbit takes quite some time to run through, so the whole mission took about 90 years.

At 500,000 m above Kerbol, the bomb goes away and I fire radial to get a safe periapsis and retrograde to reduce the orbit to about 3 years. After that, it's just some minor corrections to get back to Kerbin, although aerobreaking from 12.000 m/s has the nice effect of bouncing me off the atmosphere and pushing me back into a medium orbit. That turns out to be a good thing, because the landing strip is on the other side of the planet and I have to wait a few days for the position to synchronize.

After that it's smooth gliding.

I also watched the movie (what a turd), should have done that before because I could have killed one of my Kerbals for authenticity (and weight loss...). A reference to another movie this reminds me of: The pictures don't show it, but the mission was called "Dark Star" and the bomb had the name "Bomb 20".

[Kasuha]

Good job, nice mission!

I have recently found a way around problems with asymmetric flameout, the devil is in order in which intakes and engines are placed. You need exactly the same intakes for each engine (types and numbers), then you place intakes for first engine, then the engine, then intakes for the second engine and then the second engine. Without symmetry. That will allow you to fly at full throttle until both engines flame out and only need to reduce throttle to keep them up after that. As a proof, here's image of my ship with eleven engines, all active and producing equal thrust at 38 km at full throttle.

Edited May 31, 2014 by Kasuha

[SSSPutnik]

Can I just create a colony for myself on Duna or Laythe and let her fry?

[Kadrian]

Good job, nice mission!

I have recently found a way around problems with asymmetric flameout, the devil is in order in which intakes and engines are placed. You need exactly the same intakes for each engine (types and numbers), then you place intakes for first engine, then the engine, then intakes for the second engine and then the second engine. Without symmetry. That will allow you to fly at full throttle until both engines flame out and only need to reduce throttle to keep them up after that. As a proof, here's image of my ship with eleven engines, all active and producing equal thrust at 38 km at full throttle.

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

Wow.

I was going to make a remark about someone being a megalomaniac, then I took a look at my current 5 kiloton Eve and Back ship. I had noticed the internal routing of intake air based on build order, but I didn't finish the thought. Thaks for the tip!

Edited May 31, 2014 by Kadrian
typos