7) Icarus

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Flight 9 – Icarus

How close can you get to the sun before you burn up?

I have absolutely no idea, but I did find out how close you can get to Kerbol.

The ship:

Icarus sets off
Icarus sets off

A small rocket was all that was needed to take the small payload into orbit. I included a second stage of small oscar B fuel tanks with a little rockomax 48-7S engine. I originally wanted to make the entire rocket out of ‘tiny’ sized parts. This proved a bit awkward, as the oscar B’s have a lot of weight in them that isn’t fuel, so they weigh the craft down even when emptied. I was however impressed with the 48-7S which put out quite a lot of power when the rocket is so little! Anyway, the tiny parts were enough to get the probe out of Kerbin’s SoI and begin the de-orbit around Kerbol (once the ‘small’ sized parts lifted the rocket into Kerbin orbit). I do want to do something more in the future with tiny parts, maybe an SSTO rocket or a Mun landing but that’s for another time.

The teeny tiny 48-7S packs quite a punch when combined with other tiny parts
The teeny tiny 48-7S packs quite a punch when combined with other tiny parts

 

 

Annnnnyway back to the Icarus mission. The idea is to see what it it’s like to get damn close to Kerbol and see how far it’s atmosphere extends and at what point a ship will blow up (I’ve read that they DO blow up, you can’t land but I don’t know at what point that happens). No Kerbals were to be risked for this mission so all I really needed was a way to get any probe body close enough. I decided to use the most efficient engine in the game – the PB-ION electric propulsion system. This engine uses xenon as fuel and can make use of tiny amounts to push along the ship. The problem is that it produces barely any thrust. Since I only need to shove a tiny probe body around, that shouldn’t be a problem. I stuck on plenty of solar panels (six of the smaller panels ended up weighing quite a bit less than the two gigantor arrays I would need for balance) and a little battery and it was good to go. The whole thing weighed 1.47 tons, 1.05 of which was solar panels!

 

* After I did this mission someone pointed out that I could have gotten with just using one gigantor array if I put it on the very top of the probe, that would way much less and would get around the need to balance it. Doh!

The ion engine ROARS into life in an orgy of fire and destruction!! Or not.
The ion engine ROARS into life in an orgy of fire and destruction!! Or not.

The little blue glow from the silent ion engine told me it was on and the orbit speed around kerbol started to slowly go down. Even with such an insanely light payload, this wasn’t going to be a fast mission. The burn for my first taget (500million metres) was going to take 17 minutes. Nothing much exciting was going to happen in that time so I got some housework done, made some tea and waited for my little burn to be done.

For reference, Kerbin has an apoapsis of 13 billion metres and an orbital speed around Kerbol of around 9200m/s.

The trajectory after the first burn, this took over 6000m/s of delta V!
The trajectory after the first and largest burn, this took over 6000m/s of delta V!

So what does the sun look like from 500 million metres away?

This.

500Mm periapsis, 3000m/s orbital speed at apoapsis, 300/700 xenon remaining
500Mm periapsis, 3000m/s orbital speed at apoapsis, 300/700 xenon remaining

Fine so far, but it still doesn’t really feel like I’m close to the sun. Time for another burn then! This time to bring me to within 100 million metres of Kerbol.

100Mn periapsis, 2100m/s orbital speed at apoapsis, 200/700 fuel remaining
100Mn periapsis, 2100m/s orbital speed at apoapsis, 200/700 xenon remaining

Getting pretty close! Certainly looks a bit more impressive than 500Mmetres. But we can do better! MOAR xenon burn!

25Mm periapsis, 1900m/s orbital speed at apoapsis, 180 xenon remaining
25Mm periapsis, 1900m/s orbital speed at apoapsis, 180 xenon remaining

Gah! Now the sun takes up nearly the entire screen! Lets get another point of view…

Starting to get a feel for the size of Kerbol now, the probe feels very small!
Starting to get a feel for the size of Kerbol now, the probe feels very small!

Still no burning up though, the paint the Kerbals put on those solar panels must be pretty epic. This close to Kerbol, the speed at periapsis was a whopping 80000m/s!

But enough of these fly-by’s. I set out to see how close I could get before blowing up and there’s only one real way to do that.

No more periapsis!
No more periapsis!

The Icarus was never meant to be recovered and it got it’s name for a reason. Down it goes!

5Mm above Kerbol
5Mm above Kerbol

Thankfully, the corona-like glare disappears around this point, otherwise I think it might burn out my computer screen! I assume the cameras on my little probe have adaptive filters or somesuch.

1Mn above Kerbol
3Mn above Kerbol

Shortly before this picture was taken I lost the ability to timewarp (except for forcing physical warp). However, I figured this wasnt a problem as I was goint the insane speed of 84000m/s! Soon my main problem was  to be missing screenshot milestones! I assumed this might mean I was inside the ‘atmosphere’ of Kerbol. However, usually that would slow the craft down, at the very least decreasing my apoapsis. However, the ship wasn’t slowing and a check of the apoapsis actually showed it to be slowly increasing which was weird…. does that happen on other orbital bodies near periapsis? If so I’ve never noticed it.

1 Million metres above the surface
1 Million metres above the surface
500000m above the surface
500000m above the surface
250000m above the surface
250000m above the surface

It’s hard to get  a sense of scale in still pictures but that’s not the only problem. Things didn’t actually look very different in the last few hundred thousand miles ingame.

100000m above the surface
100000m above the surface

Having said that…. you can now see what look like indentations in the surface. I assume these are sunspots and I didn’t really expect to find details like that on Kerbol so I’m suitably impressed!

10000m above the surface
10000m above the surface

Now remember, although this would still be quite high on a planet, I’m still going well over 85000m/s here so I was getting pretty trigger happy with the F2 key (for screenshots).

1200m above the surface
1379m above the surface

But even so I almost missed it! Poof! At exactly 1379m the probe just disintegrates without warning. Well…. unless you count the rapidly decreasing altimeter and the fact that it was pointed straight at a star as warning. Also the fact that it was called icarus which was never going to end well for the poor probe.

Note that that does NOT look like I’m actually 1300m or so from the surface. The graphic for Kerbol seems to stop quite some way below what the altimeter counts as the surface, which would explain some of the lack of perspective changes below a million metres.

 

So there you have it! How close can you get to Kerbol?

1379m

 

Somehow I doubt NASA has enough aerogel to get that close to our star.

KSP 1 Reality 0

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