Space and Astronomy in general

Are we sure there wasn't a secret Ukrainian hospital up there?

Comet Nishimura peaking in Sept.

Only chance to see it for 400 years. But also it's going to be inside Mercury orbit at perihelion so there is a change it doesn't make it.

Yeah was just reading about it yesterday. Pretty cool mission finish coming up.

For those who didn't tune in last weekend - there were a few nerve-wracking moments but everything went well.

There will be a reveal of the contents at an event on October 11.

Next up: the Psyche launch was moved back from October 5 to October 12.

NASA is having a bit of a problem with the samples from Bennu.

NASA wrote:

The initial curation process for NASA’s OSIRIS-REx sample of asteroid Bennu is moving slower than anticipated, but for the best reason: the sample runneth over. The abundance of material found when the science canister lid was removed earlier this week has meant that the process of disassembling the TAGSAM (Touch-and-Go Sample Acquisition Mechanism) head – which holds the bulk of material from the asteroid – is off to a methodical start.

Is there a graph/formula that displays how fast you have to be moving at what altitude to feel weightlessness? (while maintaining that altitude..?) These may not be the right terms. Maybe what I am looking for is a range of the lowest reasonably attainable orbits?

You could technically orbit at an altitude of one foot, if you're going fast enough, with a source of propulsion to counteract drag.

Practically, you'd hit things before long, so for the purposes of "reasonableness", let's say 30,000 feet (Mount Everest peak is 29,029), and hope you miss all the commercial airplanes.

If you're talking about a ballistic orbit, then you need to be high enough that atmospheric drag approaches zero, otherwise you'll be deorbiting pretty quick. And that's roughly going to be above the Karman Line, where air pressure is assumed to be zero, at 100km / 330,000 feet.

In the real world tho, 450km is about as low as Low Earth Orbit gets.

fangblackbone wrote:

Maybe what I am looking for is a range of the lowest reasonably attainable orbits?

The ISS orbit is listed on Wikipedia as nearly circular, with a mean altitude that ranges from 370 km to 460 km above mean sea level. If they don't reboost on occasion the station will get dragged down as Jonman mentioned. The atmosphere can still cause drag at a surprisingly high altitude.

For other references, Yuri Gagarin's Vostok 1 orbital altitude was 181 km x 327 km. Likewise John Glenn's Mercury-Atlas 6 orbital altitude was only 150 km x 248 km but those were both pretty short flights so they weren't too worried about orbital decay due to atmosphere.

There is a pretty cool animation at the Wikipedia page for Geocentric Orbits, which illustrates the relationship between orbital altitudes, the orbital speed required to maintain each altitude, and the resulting orbital period.

IMAGE(https://upload.wikimedia.org/wikipedia/commons/b/b4/Comparison_satellite_navigation_orbits.svg)

The original version from the wiki page is cooler since it lets you hover your mouse over individual parts of the diagram.

Or you could go play Kerbal Space Program.

As an aside: I work on GPS satellites. The orbit for GPS was chosen to be one-half of a (sidereal) day. This makes it so each vehicle repeats the same track over the ground daily.

That is really cool. I wonder why so much space between the sub 500km orbits and the 20K-30K km orbits?

fangblackbone wrote:

That is really cool. I wonder why so much space between the sub 500km orbits and the 20K-30K km orbits?

The Van Allen radiation belts are in there (really between about 640 km to 58,000 km).

Also, it costs a little more in terms of launch vehicle performance to get to higher orbits.

Hmm. Too bad we can't capture some of that energy
But knowing us, we'd create a weapon first

Next XCOM game has to have space bears.

I assure you fellow humans I am also a human like you. Now pass me another salmon, winter is coming soon and I'm feeling like a long, totally human nap.

Looks more like a penguin to me

Hrdina wrote:

Psyche launch

With a name like that, they probably will keep pushing it back when it's almost time.

We've kinda all been psyche launched these last few years...

PSYCHE!

The moon is just a wee bit battle-scarred, isn't it?

Earth's shield.

A bit disappointed the music wasn't Thus Spoke Zarathustra.

IMAGE(https://i.imgur.com/6wwsLwM.jpeg)

Ah, the joys of the American educational system...

Robear wrote:

Ah, the joys of the American educational system...

the education system clearly failed you if you are not acquainted with KenM.

Spoiler:

kidding! But KenM is great

Clearly I am missing something. Is he a funny troll or something?

Essentially yeah. He got started when dumb internet comments seemed harmless and amusing. It seems harder to laugh at that type of trolling these days (and I wonder if it’s a copycat).

Osiris-Rex mission extended

Yeah that's right, it's got extra fuel and the instruments are working so they're sending it to another asteroid!