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Gather Grand Slam seismometer data from Eve


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Posted (edited)

This one is actually a stock contract that seems nigh impossible.

Just gather Grand Slam data from Eve. Suggested this is Reddit too:

https://www.reddit.com/r/KerbalSpaceProgram/comments/oe2ya7/challenge_gather_grand_slam_seismometer_data_from/

The thing is, impact doesn't seem to calculate right with full physics, giving negligible science. While you can go around this on non-atmo worlds by just letting the impact happen on-rails, obviously that won't work on Eve. On top of this, there's the "legit" challenge of actually hitting Eve with any reasonable speed and not melting in atmo before impact.

Edited by teelaurila
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Disable drag and friction heating and that's easy :sticktongue:

But to do it legitimately will be almost impossible, and certainly very expensive! You could try mining a whole lotta ore out of Gilly, sticking it in a really dense stack with heat shields on the bottom (the normal kind, not the inflatable version) and then throwing that at Eve, or unleash your inner Marco Inaros and throw asteroids at it instead. Or maybe you could use a Breaking Ground KAL controller to crank the firework launch speed up to stupid velocities and fire those down at the ground while flying?

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Posted (edited)

Dropping anything will almost certainly not get anywhere. It will either burn up and explode, or slow down to ~200 m/s.  If it is something that does not slow down to ~200 m/s at sea level, it will come in way too hot and just explode around 30 km or so (>3500 K easily). Theoretically one could use engines to slow it down to survive re-entry, while it is still dense enough to hit the ground at ~1000 m/s? Probably easier to use the engines to boost up at the very end, though.

I tried the asteroid route, though only once. It blew up at ~40km height when dropped from ~Gilly orbit to ground. Now one presumably could find the optimal "stone throw" that still survives (pretty sure from low orbit it survives since rocks tend to be like huge heat shields). Fairly conviced it would amount to practically zero science because KSP rocks are not that dense. But would be interesting to see just how big a rock yields what.

Edited by teelaurila
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I think you won't get much science points for that anyway, because the impact speed influences the amount of science you get for it (if I remember correctly, feel free to correct me if I'm wrong) and impact speeds are usually quite slow in such a dense atmosphere.

But maybe I'll try it, I think I still have a Grand Slam Seismometer on Eve from my manned Eve mission.

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Solar retrograde.

Throw a probe (or better, an asteroid) up to a really high apoapsis above the sun, burn until the orbit reverses, get an Eve intercept when it’s heading straight for it and hope that you don’t hit the ocean… With a sufficiently high speed, you’ll bomb through Eve’s atmosphere in a few seconds which might be fast enough to prevent everything exploding.

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Posted (edited)
1 hour ago, jimmymcgoochie said:

Solar retrograde.

Throw a probe (or better, an asteroid) up to a really high apoapsis above the sun, burn until the orbit reverses, get an Eve intercept when it’s heading straight for it and hope that you don’t hit the ocean… With a sufficiently high speed, you’ll bomb through Eve’s atmosphere in a few seconds which might be fast enough to prevent everything exploding.

Would be extremely interesting to see this! I have my doubts, given that at >1000 m/s at low Eve atmo my impact rocket isn't just facing the heat, it's actually aero forces tearing it apart. But might be due to the control surfaces, so who knows, this might be doable with a heat-shielded blop  of a craft- or an asteroid.

Edited by teelaurila
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1 hour ago, teelaurila said:

Would be extremely interesting to see this! I have my doubts, given that at >1000 m/s at low Eve atmo my impact rocket isn't just facing the heat, it's actually aero forces tearing it apart. But might be due to the control surfaces, so who knows, this might be doable with a heat-shielded blop  of a craft- or an asteroid.

I tried it with a small (30t) asteroid, hit the atmosphere at almost 30km/s and- it exploded before it got to 75km up. I was expecting it to last a lot longer than that.

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11 hours ago, jimmymcgoochie said:

I tried it with a small (30t) asteroid, hit the atmosphere at almost 30km/s and- it exploded before it got to 75km up. I was expecting it to last a lot longer than that.

This would be the first expectation, as time in atmosphere is proportional to 1/v, whereas drag and heating is v^2 (or higher power)

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On 7/5/2021 at 4:08 PM, teelaurila said:

I did make a low-drag craft (see the links to reddit), and it didn't work.

You've gotta go even lower drag than that probably.

On 7/5/2021 at 4:08 PM, teelaurila said:

This one appears so easy when you just think about it, but let's see you do it

Alright, let's go. It's 9:05 PM for me right now, and I'll try to speedrun this.

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Posted (edited)

Had to get up and do something else in the middle. Took about 40 minutes, but probably closer to 25 minutes of actual playing KSP.

VCkZdJ3.png

Overengineered craft in VAB

I5N7QRr.png

On pad

GmhAUSG.png

Liftoff

NU7weRI.png

Booster jettison

I8wJEXb.png

Kerbin orbit

mlmrvNq.png

Eve transfer

DT4dAV3.png

Eve insertion

isdQiR8.png

Detaching the impactor

okaHUd5.png

Deorbiting

eY50DDI.png

Aerobraking using the transfer stage as a partial heat shield

b7mvb6z.png

The final stage wasn't even used

EQKQP0A.png

Chutes deployed

ofpbQHc.png

Instruments deployed. My Breaking Ground install's broken so this is the best I can get

Fd2TGp6.png

Deorbiting impactor

gqPob6D.png

Impactor entering atmosphere

jN6Hy78.png

Impactor about to crash

mfV56eu.png

Impactor crashed

mZ6s6cV.png

Proof of 100% reentry heat

(This is what I mean by a dragless craft.)

 

Edited by camacju
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Posted (edited)
4 hours ago, camacju said:

Had to get up and do something else in the middle. Took about 40 minutes, but probably closer to 25 minutes of actual playing KSP.

...

mfV56eu.png

Impactor crashed

(This is what I mean by a dragless craft.)

 

Thank you greatly! Impressive work, and seems to show simple wins. Could you run me through what is the impactor made of? It is just a 2.5m service module with a little bit of engines to deorbit (and some weight) in it?
As I understand your picture, you managed to impact at  almost 3500 m/s with that thing, using only gravity to "propel" you down? I am still baffled that it neither melted nor slowed down more. Looks like I was way off using mk2 pieces for their heat resistance, somehow drag seems leagues more?

There is one big question that remains, though: How much actual science that yields? Because I get like 0.1 or less science with 1000 m/s impact, assuming it is proportional to v^2, this impact would yield about 10 times more, or 1 science or so. Out of 100 or so. So only 99 such impacts to go? This seems to be due to a bugged out impact detection while the impactor is on full physics.

Edited by teelaurila
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6 hours ago, teelaurila said:

Could you run me through what is the impactor made of? It is just a 2.5m service module with a little bit of engines to deorbit (and some weight) in it?

It's two 1.25m service modules clipped into the same space, with some fuel and engines, probe core, etc

6 hours ago, teelaurila said:

As I understand your picture, you managed to impact at  almost 3500 m/s with that thing, using only gravity to "propel" you down? I am still baffled that it neither melted nor slowed down more. Looks like I was way off using mk2 pieces for their heat resistance, somehow drag seems leagues more?

Look at the AeroGUI when I'm about to crash - drag is exactly 0 newtons. Each service bay blocks the other service bay from receiving any heat or any drag force, and they both shield anything inside them. This is also the easiest way to do a Jool dive.

Mk2 parts have a huge amount of drag in general - I almost never use them. The corresponding Mk1 parts are lighter and have less drag.

7 hours ago, teelaurila said:

There is one big question that remains, though: How much actual science that yields? Because I get like 0.1 or less science with 1000 m/s impact, assuming it is proportional to v^2, this impact would yield about 10 times more, or 1 science or so. Out of 100 or so. So only 99 such impacts to go? This seems to be due to a bugged out impact detection while the impactor is on full physics.

My Breaking Ground install's slightly broken so the science instruments don't actually work. So I don't know exactly how the impact will translate to science.

However if it's a physics related problem you can always switch back to your science station while the impactor's still suborbital and wait for it to crash. It'll still crash but won't be loaded with physics.

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3 hours ago, camacju said:

Look at the AeroGUI when I'm about to crash - drag is exactly 0 newtons. Each service bay blocks the other service bay from receiving any heat or any drag force, and they both shield anything inside them. 

I see. Each to his own, but seems to me like this is abusing a bug on how service bays work to create a craft of artificially too low drag. 

Another, more straigthforward and probably less effective, way to use  clipping would be to create a massive-density craft by clipping 20t into a small bay. But since this craft would face "legit" drag of one bay, it probably wouldn't be able to impact with more than a few hundred m/s, or else it would melt

Or in other words, if one doesn't use clipping, the impact velocity that can be achieved by dropping alone is an order of magnitude less?

3 hours ago, camacju said:

However if it's a physics related problem you can always switch back to your science station while the impactor's still suborbital and wait for it to crash. It'll still crash but won't be loaded with physics.

I though on-rails physics wipes the craft in atmo when pressure becomes quite high. Can this be Kerbin only? Didn't even think of testing it before...

https://wiki.kerbalspaceprogram.com/wiki/Atmosphere :

 

Quote

 

A ship is "on rails" when it's no longer the primary focus of the simulation, which occurs when it's further than 2.25 km from the actively-controlled ship. If such a ship have its orbit passing through a planet's atmosphere, one of two things will happen based on atmospheric pressure at the ship's altitude:

  • below 0.01 atm: no atmospheric drag will occur — the ship will be completely unaffected
  • 0.01 atm or above: the ship will disappear

The following table gives the altitude of this 0.01 atm threshold for each celestial body with an atmosphere:

Body Altitude (m)
Eve 44 745
Kerbin 25 789
Duna 10 814
Jool 219 397
Laythe 32 755

 

 
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