Landing in the radar dish: The weird science of personal parachutes and altitude.

[Klapaucius]

This may be old news for many, but this was new to me, so I thought I would share:

Yesterday I was flying over some mountains, and since I was running low on fuel, decided to parachute out, figuring I would land in one of the valleys.  I was quite surprised to see my chute open well above 5000 meters.  I planted my flag on my first peak!

 

Later on, I tried to do the same on the peak with radar dish near the southern pole, after spotting the dish on a flyby. However, I was unsuccessful. So, this morning I went into the handy Mission Builder and did some experimenting. I discovered that how high a parachute will open is contingent on the altitude of the terrain you are flying over.

 

If I was right over it, it opened above 7000 meters:

But if I was some distance away, the chute deployed, but did not fill until a far lower altitude. 

 

This shot was taken just after the chute filled:

 

I can't figure out what the exact math is.  It is not as simple as adding the surface altitude to your deployment height.

But the coolest thing by far, I managed to land at the dish:

And later, IN the dish:

The dish was moving, so Bill slid all over the place. Whenever he slid over one of those bands you see in the picture, the "press f to climb" notice would pop up, but I never managed to grab onto anything or even get him standing. He wound up hung up on the edge of the dish, and I was unable to move him until he slid off on his own accord, and alas, died.

I'm not sure what skill he was supposed to have that would have changed the outcome here...

Edited May 12, 2018 by Klapaucius

[KerikBalm]

20 hours ago, Klapaucius said:

I can't figure out what the exact math is.  It is not as simple as adding the surface altitude to your deployment height.

...

And later, IN the dish ... The dish was moving, so Bill slid all over the place. 

So I knew that it opened at AGL level, not ASL. I thought it was as simple as deployment height setting + altitude of the surface... that is assuming that the chute is in its pre-deploy state (its out but not filled). The pre-deploy state is determined by air pressure (it won't pre-deploy on Mun, regardless of altitude above terrain, for example). By default, chutes are set at 0.04 atmospheres, although you can lower that to 0.01.

Anyway 0.04 corresponds to some altitude between 15 and 20k,  Kerbin's highest peak is around 6.7km, so this shouldn't be an issue. Are you sure its not that simple? minimum deployment pressure is really only an issue on Duna.

As for the dish, shortly after they came out, I saw a video of a guy making a VTOL craft, and landing a plane on the dish, and then deploy a rover to "surf" the dish/use it as a skate park.

[wumpus]

Reality Note: while wifi issues and other "RF issues" are clearly bunk, high power RF is dangerous at levels used for such long distance power such as deep space communications.  You might want to put this in a link for "crimes against kerbality" as well.

- PS: the other danger is when you are closer than the wavelength being transmitted, in which case the danger changes from "being cooked like a microwave oven" to "being charged like a wireless charger" and the power transfer becomes efficient and ugly fast.  The reason that you *know* phones* and wifi aren't dangerous is that [A] that range of RF isn't ionizing and your phone would overheat before it could have problems "charging" you brain, and various glasses of water around the house would raise a few degrees (and burn out the wifi) if wifi could hurt you.

* "EMI issues" only.  Blunt trauma involving cars is another story.
** EMI isn't completely safe.  Use proper care when being exposed to huge EMI emitters that emit in a broad range including UV and other dangerous ranges.  As in wearing sunscreen whenever you go out into the big blue room and deal with our alleged Kerbol equivalent.  This is the only real RF danger most humans will ever meet, but KSP players are an odd lot and might need to know about the weird effects in places like deep space networks...

Edited May 14, 2018 by wumpus
debolded autobolded text.

[Corona688]

On 5/12/2018 at 2:44 PM, Klapaucius said:

I discovered that how high a parachute will open is contingent on the altitude of the terrain you are flying over.

This is true of all parachutes.  They used to not do that - real parachutes won't ask your RADAR what altitude to open, and KSP parachutes require no power to operate anyway - but this caused significant rage from capsules hitting mountains and was changed.

Quote

I can't figure out what the exact math is.  It is not as simple as adding the surface altitude to your deployment height.

If it's anything like the rest of in-game parachutes, there is a

• Maximum altitude (above surface)
• Minimum air pressure
• Maximum amount of strain

I say strain, not velocity, as the velocity capsule parachutes will open is dependent on mass.  A heavy craft will need to slow down a lot more before chutes open than a light one.

Weight here is constant, so it's probably an equation of velocity versus altitude below the maximums it will open at all.

Edited May 17, 2018 by Corona688