Curiosity fake...?

[Peter B]

A candidate for the new queen of woo.  Sharing "valuable 'inside' information of which the public and even most researchers are
not familiar with."

I see from her website that she's associated with a group called BUFO. It occurs to me, probably completely unfairly, that bufo is Latin for "toad".

[ka9q]

With lower surface density but larger scale height, there is an altitude where the density would be the same. For Earth and Mars it's 101 km.

Good point! So the Karman line is more general than we realized...

I help mentor a high school group that flies balloons. We typically make it to 30 km or so (about 100,000') before the balloon bursts. I like to tell them that at that altitude earth's atmospheric pressure and temperature (if not composition) are roughly the same as on the surface of Mars. So in that sense they're building a payload to go to Mars.

[Chew]

Mary didn't write the OP quote. "Shadow" did.

[Chew]

Good point! So the Karman line is more general than we realized...

Actually, the Karman line on Mars is at 71 km. Remember you have to account for gravity vs lift and compare lift to orbital speed.

[ka9q]

Oh, right...it's not just atmospheric density, but the altitude at which the lift of an aircraft wing at orbital velocity would be insufficient.

[ka9q]

It would be interesting to work out the Karman line for all the planets with atmospheres (and Titan).

[Chew]

It would be interesting to work out the Karman line for all the planets with atmospheres (and Titan).

Venus   266 km
Mars       71 km
Jupiter   415 km
Saturn   810 km
                         Titan 152 km
Uranus   366 km
Neptune 270 km

 

Couldn't find the atmo info I needed for Titan.

[ka9q]

Titan's atmosphere is nearly all N₂, with a surface pressure of 1.5 bar (146.7 kPa), surface gravity of 1.352 N/kg (less than our moon), and surface temperature of 93.7 K.

[Chew]

Titan 152 km

[ka9q]

What are the reference altitudes for the gas planets? I think the usual convention for their "surfaces" is the 1-bar (100 kPa) pressure level.

[ka9q]

Interesting that they're all higher (in some cases much higher) than Earth with the sole exception of Mars. OTOH, the planets and moons with surface-bounded exospheres have Karman lines at 0 km.

Speaking of planetary comparisons, I've always found it interesting that their surface gravities tend to fall into just a few bins. Mars and Mercury are about 1/3 g. Venus, Earth, Saturn, Uranus and Neptune are all around 1 g. Jupiter, at about 2.5 g, is in a class by itself.

[Chew]

What are the reference altitudes for the gas planets? I think the usual convention for their "surfaces" is the 1-bar (100 kPa) pressure level.

Yeah, 1 bar.

[Captain Swoop]

Why are these web sites always so terrible to look at?

[cjameshuff]

Titan 152 km

You sure about that? Orbital velocity at that altitude would be ~1800 m/s, and Titan's atmosphere at that altitude ought to be about equivalent to Earth's at 10 km...about 4x as dense at the surface and in 1/7.25 as strong a gravity field.

[Chew]

What scale height did you use? I calculated a scale height of 20.58 km.