Solar Limbo: How Low can you Go?

[LordCorwin]

While experimenting, I found that heat shields radiate everything. I went to 10Mm by Hyperedit; temperatures behind the heatshield reached an equilibrium around 500K. Getting even lower was tricky: it takes only two or three seconds to rotate the vessel, yet that's enough to explode many parts. The ones that survive that long, however, start to shed heat as soon as they're behind the shield.

Solar panels work a treat: rotate the craft so that the panels are exposed, briefly, and you'll harvest thousands of units in a split-second.

There's only one problem: the heatshield has to face the sun at all times. Timewarp is out of the question.

Yeah, I was thinking to do something with heat shields and ion engines on one side, but I'm not sure how the balance will act.

[MarvinKitFox]

Ok, that's it. Apogee = 589,873,831m.

[

Great Job LordCorwin!

This is the first design that actually puts some thought into heat dissipation, not just resistance.

And the improvement in performance speaks for itself.

[LordCorwin]

Also, it is important how to approach to the Sun (always retrograde), and how you place your solar panels and temp sensor. I placed solar panels in line to the Sun, and the Thermometer sensor normal (90º, ie, not facing the Sun).

[Lhathron the Elf]

* The word "easy" is used in this context to mean "quite hard, but doable"

Is this a reference to A Series of Unfortunate Events?

About the challenge though, sounds awesome. What I might do is have a payload made out of mk2 cargo bays and fuselages to protect my stuff. I don't exactly know what kind of heat resistance they have, but from my experiences I have noticed that they survive fairly well in heated situations. (Pun intended but failed) :/

[cryogen]

Quick question -- anyone have a link to a description of KSP's thermal model? I'm curious how it works and what its limits are.

Can you make a multi-layer heat shield in KSP?

update: I guess not..

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Ok this is confusing...

Edited June 16, 2015 by cryogen

[MarvinKitFox]

Can you make a multi-layer heat shield in KSP?

Um. Yes but mostly no.

The frontmost plate will catch all the heat just fine, but with a tolerance of only 2000 kelvin, it will blow rather soon unless you have a *big* conductive heat drain from it.

Note that only exterior sources are considered for radiant heat. One hot panel of the ship will *not* cause another part in line of sight to heat, unless there is a conductive path to it.

[0111narwhalz]

I have a payload, viable to 110 Mm. No way to get it there yet, but...

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https://drive.google.com/open?id=0B4z16gRI-C__RVc4M2J4d0xTbEU&authuser=0

[John FX]

So I figured that this challenge is sort of a `how much Dv can you get a craft to expend` combined with `how much heat can you radiate` challenge as just getting a low Ap around the sun is a challenge in itself and so is dealing with the heat.

I made a refillable high Dv craft with an even higher Dv payload which should stand a fair bit of heat. It has taken a bit of time to do the burns though and also the burns of the craft that refuelled it (which is also designed to withstand heat although not optimised as much as the sundiver as it will not need to go as low and needs to be lighter).

I set off at dusk and headed straight up (it was probably the least aerodynamic thing I have launched so I didn`t even risk a turn) and continued to burn in a straight line (solar retrograde) until I ran out of fuel in my chemical stage. This got me a solar elliptical orbit with a respectably low Pe inside the orbit of Moho. I then rendezvoused with my craft to refuel it and circularised in a low solar orbit (closer than Moho).

Obviously I am using Mechjeb to keep my craft facing the sun to keep the sensitive bits in the shade...

I`ve taken a leaf from the book that mountain climbers use so I`ve set up some base stations along the way so my xenon refuel craft just needs to get into LKO then it can refuel to get to Moho where it can refuel again then I`ve made another fuel depot around the sun at 1000Mm for it to refuel again which is where things start to get warm. Using these depots I managed to move my `start point` for the refuel craft to the last fuel depot at an orbit of 1000Mm. This allowed me to refuel the sundiver at 650Mm and have some Dv left over to reduce my Pe with a relatively high TWR (compared to IONs)

I managed to get the Sundiver to an Ap of about 620Mm and a Pe of 350Mm using the refuel stations. The burn to drop the Pe to 350Mm had to be done in four sections and inbetween I had to face the sun and cool down. The refuel craft are of no further use as it would take too much Dv to reach the sundiver at this point and they would probably explode anyway..

This last burn took a LONG TIME as warping this close to the sun tends to explode your craft whatever the design.

Obviously I am using Mechjeb to keep my craft facing the sun to keep the sensitive bits in the shade.

Currently my Ap is 412,165.8Km although I have 7000Dv left. I have to get on a flight to spain now otherwise I would spend another day reducing my Ap to around 350Mm then shaving it until explosion...

TL;DR used a refuelled chemical tug to get my payload to about 650Mm then went full ION and spent AGES to get my Ap to 412Mm or so.

[LordCorwin]

That structure is simply... terrific, and the performance awesome.

Appart from the result being approved by MarvinKitFox, may I ask how did you put that in orbit?. I never thought it was possible. I'm quite interested for other projects.

For the Solar Limbo Challenge, I've beaten myself and already reached Apogee 570Mm. I have another probe on route that I think it will reach apogee 530Mm, with a Design quite similar to my Solar-Probe4 but using greater solar panels to check if it radiates better and reallocate stuff. Nothing compared to yours :-D

[Laie]

The frontmost plate will catch all the heat just fine, but with a tolerance of only 2000 kelvin, it will blow rather soon unless you have a *big* conductive heat drain from it.

Note that only exterior sources are considered for radiant heat. One hot panel of the ship will *not* cause another part in line of sight to heat, unless there is a conductive path to it.

Huh? In my tests, a heat shield would radiate everything; I could hyperedit a vessel down to 1Mm (not 100 or 10, but 1) and provided I point the shield towards the sun fast enough, it would survive indefinitely.

Putting a 1.25m stack behind a 3.75m shield, I found that the shield only protects the stack. Any radially-attached parts would receive radiation even if visibly in the shadow of the shield. By building the stack mostly of pre-coolers and having only very few radial attachements, no part ran hotter than 600 degrees.

Trying to get any lower was difficult, as things would go poof within one second or two. When I finally had oriented my vessel, the surviving parts quickly shed heat and cooled down to way below 1000 degrees.

So, the problem is that you have to keep your shield pointed towards the sun at all times. No timewarp possible. Orbital period was still 11 hours... no way that I would gradually lower the orbit in real time, so I didn't even start to consider the delta-V problem.

[11of10]

Just give it enough Xenon, use SAS to put it on always retrograde, and let the ions use up that deltaV, maybe with added mechjeb for automating staging to discard some wasted xenon tanks or something. Then go for a walk/run/sleep/work/school/all of the above...

[John FX]

That structure is simply... terrific, and the performance awesome.

Appart from the result being approved by MarvinKitFox, may I ask how did you put that in orbit?. I never thought it was possible. I'm quite interested for other projects.

For the Solar Limbo Challenge, I've beaten myself and already reached Apogee 570Mm. I have another probe on route that I think it will reach apogee 530Mm, with a Design quite similar to my Solar-Probe4 but using greater solar panels to check if it radiates better and reallocate stuff. Nothing compared to yours :-D

it took a couple of times but then I learned to just not attempt any sort of turn inside the atmosphere. I just burnt straight up limited my acceleration to around 16m per second per second. if I tried to accelerate too hard it just flipped. I had the largest engine on it and some liquid boosters and a lot of fins. I refilled the massive stage a couple of times to get my solar orbit down to around 650Mm at which point the heat was getting too much so I dumped it once my periapsis was around 350Mm.

then it was just a case of get to the periapsis and use the ion engine to try and reduce my Ap as much as possible. I had enough Xenon on the craft to burn my engine for around 24 hours...

there was no way of getting around the fact I had to do a full Solar orbit using Physics warp which took a very very long time. the payload still has around 7000DV on it so once I am back from Spain I may hand in a better entry.

I found solar panels to be a little bit fragile and I am using small wing parts behind structural panels and a service pay as a heat sink. the strange thing I found was that cubic struts seem to not pay attention to shielding and suffer lots of radiative Flux.

I did contemplate another design with service bays at the front facing the sun no cubic struts and lots of wings behind to radiate heat...

[LordCorwin]

Thanks for your reply. 16m/s2... that's about 1.67G. I'll adjust TWR accordingly and try the vertical liftoff.

As said , I basically am using my former design with some improvements, but I'm not sure I'll bet the 500km.

PS: welcome to Spain! Heat flux here is high too :-D

[John FX]

Thanks for your reply. 16m/s2... that's about 1.67G. I'll adjust TWR accordingly and try the vertical liftoff.

As said , I basically am using my former design with some improvements, but I'm not sure I'll bet the 500km.

PS: welcome to Spain! Heat flux here is high too :-D

depending on how an aerodynamic it is there will be a different maximum speed you can go before it flips and as you get higher that speed will increase so it's a bit of a balancing act between drag and gimbal/fin control authority. I found going more than 100m/s at sea level made it flip and so did more than the speed of sound at 30km. I found mechjeb to not do a great job at keeping it upright. Stock SAS worked better for stability although mechjeb was better for limiting acceleration.

As your fuel depletes it wants to flip more as well. It really is trial and error to find the sweet spot.

[LordCorwin]

My new own record: Solar_Probe10, Apogee 454.724.371m. And I've depleted all my fuel.

Currently with my current design I think I can reduce 3km or 4km more, but that's all. Far from the 408Mm achieved by JohnFX

It's always the same: the part that gets hotter is the unmanned probe. I've selected the one that shows minimal cross section (the Probodobodyne OKTO2), placed in the middle protected by big solar pannels that (I think) radiates as much as possible, and with xenon tanks up & down that should help cooling too. Nevertheless, It's always the hottest part.

Edited June 21, 2015 by LordCorwin

[John FX]

My new own record: Solar_Probe10, Apogee 454.724.371m. And I've depleted all my fuel.

Currently with my current design I think I can reduce 3km or 4km more, but that's all. Far from the 408Mm achieved by JohnFX

It's always the same: the part that gets hotter is the unmanned probe. I've selected the one that shows minimal cross section (the Probodobodyne OKTO2), placed in the middle protected by big solar pannels that (I think) radiates as much as possible, and with xenon tanks up & down that should help cooling too. Nevertheless, It's always the hottest part.

http://i454.photobucket.com/albums/qq262/Lord_Corwin/Solar003.png

http://i454.photobucket.com/albums/qq262/Lord_Corwin/Solar004.png

Nicely done. Did you refuel yours on the way?

A couple of things I did was to shield stuff with a structural panel which had aerolons on the back face, I found they radiated more heat than solar panels as they weigh more so were better heat sinks. I also loaded it with about 5t of xenon to give around 12.5KDv although with only a single ION engine that would take around 24 hours to use up which meant muliple orbits to reduce the Ap. I still have around 7kDv left. My craft can stand to be as low as 350Mm so I may try for that in a couple of weeks when I return from holiday.

I do have ideas for another version which I think should be able to get even lower than 350Mm and now that I have set up the infrastructure for refueling it should be a much easier task...

[LordCorwin]

Nope, it was done with just a rocket with about 25KDv. The chemical fuel leaves the ion stuff in an orbit about 1000Mm perigee and 5000Mm apogee. Then 8 Ion engines reduces the orbit to 1000Mm perigee and apogee. The last step involved 3 ion engine.

My new Solar_Probe11 is now in its 800Km orbit, we'll see how far can it take. I have more solar panels so I had to reduce the number of ion engines to 2 in the last stage. Moreover, I will concentrate the remaining xenon fuels in the middle tanks and remove those at the beginning and at the end when depleted. We'll see if that allows me to cool the core probe for more time.

PS: as you approach the Sun, when viewing the probe the game crashes a lot. Anyone has the same problem?

Edited June 22, 2015 by LordCorwin
Postscript added

[LordCorwin]

Hello, my new record altitude with Solar_Probe11: Apogee 399,433,568

As told in my previous post, I've added more solar panels and placed all the remaining xenon in the tanks closest to the probe.

Lord

[John FX]

Hello, my new record altitude with Solar_Probe11: Apogee 399,433,568

http://i454.photobucket.com/albums/qq262/Lord_Corwin/Solar005.png

http://i454.photobucket.com/albums/qq262/Lord_Corwin/Solar006.png

http://i454.photobucket.com/albums/qq262/Lord_Corwin/Solar007.png

As told in my previous post, I've added more solar panels and placed all the remaining xenon in the tanks closest to the probe.

Lord

Nicely done. From the temps you have there you look like you could go lower too...

[LordCorwin]

Not at the moment, the central core was close to the maximum temp! May be Solar_Probe12 ;-)

[Teilnehmer]

Does this challenge reset with 1.0.3?

[2001kraft]

^ this guy has 69 posts.

I will try my best to see what I can do. My current idea is to take an octagon probe, surround it with those long i-beams, then put heat shields on the end of each beam, and also put double long i-beams on top and bottom and put 2 gigantor solar panels on each end. Propulsion is going to be ion. My idea is to take the probe as low as possible and see how low it can get, then when the transfer stage overheats, I will circularize with ions.

[Teilnehmer]

My current idea is to take an octagon probe, surround it with those long i-beams, then put heat shields on the end of each beam, and also put double long i-beams on top and bottom and put 2 gigantor solar panels on each end. Propulsion is going to be ion.

I used a similar thing but tetrahedron-shaped.

In 1.0.2, there is a bug: when at moderate time warp (50×, 100×) the heatshield temperature starts to fall down till 4 Kelvins for some reason.

Abusing this bug, I managed to enter the Solar atmosphere (below 600 km above the surface). Then the warp switched off but the heatshields remained cold while the other parts start getting hot. So I flied through the atmosphere lowering my apoapsis without any propulsion. I haven’t managed to lower it significantly though.

Edited June 23, 2015 by Teilnehmer

[John FX]

I'm beginning to wonder if this challenge has been forgotten by the original poster...

[Jodo42]

I wonder if anyone can get significantly lower with the new radiator systems in 1.0.3. It seems heat and not dV was the biggest problem for most people.