The Pod Bay

12:16 AM

@PearsonArtPhoto My favorite question so far :)

Although given an actual implementation is literally enough for a conference paper, I wimped out and tried giving an explanation of the underlying concepts.

PearsonArtPhoto

1:20 AM

@Chris Yeah, it's a bit tricky. I was playing around with the task today for the fun of it, and realized it would make a good question for this site.

Basically, I assumed a Gaussian distribution from the parameters provided, and took an estimate of what distance would a hit be.

It worked for a quick and dirty approach, but I'd like to come up with something better.

Chris

1:53 AM

@PearsonArtPhoto That's a very common assumption... the validity is a little questionable. Alfano has one of the simplest approaches... he assumes linearized dynamics near the time of closest approach and looks at the distance in the plane normal to the relative velocity vector, if that helps. His paper on it is easy-ish to follow.

PearsonArtPhoto

Interesting. I'm going to have to grab the papers our flight dynamics expert was pointing me to... Hmmm.

Chris

If you have the resources, you could do a full monte carlo simulation too... easier to understand, but the logistics are a little more complicated.

It's a very interesting problem

PearsonArtPhoto

Maybe I'll do something like that, but with a filter on the front end so it only happens for the close cases.

Hmmm... The possibilities...

Essentially, what I did was do a 100,000 random draw from the guassian. Almost as good, and much easier than digging up my text books to remember the math. Plus it only too 3 seconds...

Chris

if you start filtering out points, it affects the statistics, so be careful

PearsonArtPhoto

Not points, just scenarios.

Chris

2:01 AM

oh you mean you have multiple close approaches?

PearsonArtPhoto

Well, we deal with them on a regular basis.

Chris

gotcha

PearsonArtPhoto

I'd like to build something to automate a lot of the processing, but I'll get there eventually.

Chris

fun task

PearsonArtPhoto

Yeah. The boss isn't in this week, so sometimes I get to do fun things (If we don't have any crisis going on...)

Stuff that will help out, of course.

JohnB

2:14 AM

Do meta posts count for commitment?

I guess they must since I'm counted as fulfilled on A51 with only 7 non-meta posts

I'm reluctant to put my name down for Astronomy with the big "Ask your questions on Physics.SE" banner at the top =\

RhysW

9:09 AM

@JohnB im pretty sure they do, yeah

ManishEarth

9:59 AM

@JohnB Nope

I should know, usually I have more meta posts than main for betas :P

JohnB

@ManishEarth Oh. So then what are the reqs for fulfillment?

I thought it was 10 posts

ManishEarth

Q+A=10

actually meta may be counted

TildalWave

11:37 AM

@ManishEarth dunno, I have 5xA + 1xQ + 4xA' which is 10 and it says I still have commitment problems :)

ManishEarth

lol

PearsonArtPhoto

11:58 AM

The script to see if you've fulfilled commitments only runs once a day.

TildalWave

12:53 PM

@PearsonArtPhoto Yeah I figured that, but I have same stats for 2 days now LOL... I think they made the query with > instead if >= :))

I'll try to answer some questions later today, if I'll find the time :(

RhysW

1:05 PM

@TildalWave or just ask some more :P

PearsonArtPhoto

1:19 PM

I have in mind a question that could be really interesting, but it has a huge potential to turn in to a rats nest...

RhysW

@PearsonArtPhoto im too curious not to ask about it now, though i assume that was your intention? :P

PearsonArtPhoto

Basically, the question amounts to how would space travel be different if we lived on Mars, or Venus, or on a more massive planet than Earth.

TildalWave

@PearsonArtPhoto that's IMO again one of those whole areas of research and too broad, you might do better splitting it into 10 different questions

PearsonArtPhoto

Yeah, I know.

It's not quite formed that well, but it could be interesting still. Hmmm...

If I was going to ask the question, I would probably vary only one parameter, maybe a 10% reduction in gravity.

TildalWave

@PearsonArtPhoto I know you know I'm just wasting this 1 minute I had to waste and dragging you into it so I'm not such a lonely person :P

Rory Alsop

1:24 PM

And me!

RhysW

@PearsonArtPhoto other than reduced fuel to counter the pull of gravity, why wouldnt it be the same?

PearsonArtPhoto

I was reading nasa.gov/mission_pages/station/expeditions/expedition30/… which got me thinking.

If we had less gravity, spaceflight would be much easier. That would probably change the equation quite a bit.

TildalWave

@RoryAlsop collateral damage... or "added bonus" depends where you stand :))

RhysW

@PearsonArtPhoto surely the equation is the same, but the inputs are different

PearsonArtPhoto

@RhysW That's why it's probably not a very good question. Too much speculation. But a fun topic for chat!

RhysW

1:27 PM

i mean, X + 1 is always equal to 1 more than X regardless of what X is. So surely space exploration would be identical to it is now, potential differences being, escape velocity, the height of orbits, depending on the size and mass of the planet

@PearsonArtPhoto definately in intersting thought experiment

TildalWave

PearsonArtPhoto

" If our planet was 50% larger in diameter, we would not be able to venture into space, at least using rockets for transport. "

Rory Alsop

I loved that film @tildal

RhysW

@PearsonArtPhoto if the diameter is larger, is our mass the same as it is now, or also increased? e.g which do we maintain, density or mass, whilst increasing diameter?

PearsonArtPhoto

I guess it would have to assume the same surface gravity.

TildalWave

1:30 PM

how about... how big of an area of the Moon would we need to use it as a target for asteroids from the asteroid belt that we intentionally change trajectory for later mining on the Moon base... LOL that sounds quite funny, made more sense before I wrote it

RhysW

@TildalWave you want to fire asteroids onto the moon to make it easier to mine and want to know how big an area to designate as the 'holy hell dont stand here' zone? :P

PearsonArtPhoto

@TildalWave It's far more efficient to put them in the Earth-Moon L4 point.

TildalWave

@RoryAlsop watched it probably 10 times already because it's one of those SF movies that is agreeable with the missus :)

RhysW

@TildalWave what film is it?

TildalWave

@RhysW yup :))

@RhysW Moon

RhysW

1:32 PM

@TildalWave depends on the size of the asteroids and their velocity i guess :P

TildalWave

@RhysW imdb.com/title/tt1182345

PearsonArtPhoto

It got me thinking though, if we lived on a planet with more gravity, it would be really hard to get to orbit. That might make it less likely in turn to become interstellar.

Thus, interstellar aliens will likely be from a planet with less gravity than Earth, or at least, equivalent gravity.

TildalWave

@RhysW any velocity that would be economical to achieve, and then the Moon's gravity (no negative acceleration, passive drop only)

RhysW

@PearsonArtPhoto thats a depressing thought

more depressing is the thought that if we ever land on heavier planets, its pretty much a one way trip if you cant get off it again

TildalWave

@PearsonArtPhoto Or the atmosphere is so dense and thick you'd actually be achieving escape velocity easier?

PearsonArtPhoto

1:34 PM

If only we can attract the science fiction writers to build on that thought...

Rory Alsop

A plethora of writers have looked at the gas giant exploration issue

RhysW

@PearsonArtPhoto i wonder at what gravity it becomes too difficult to get back out of without nearly stripping the planet for fuel

PearsonArtPhoto

@TildalWave A thicker atmosphere would only help if you can use a plane to orbit somehow. You could get higher easier. But essentially, it would be a wash out at some point, and you have to get to a higher orbit to have a worthwhile orbit.

A thick atmosphere would make spaceflight more difficult, no matter how you cut it.

TildalWave

also, the atmosphere could already provide one or more of the components of the chemical rocket ... maybe liquid hydrogen... all you'd need is oxygen then... of course, we do this here, and the heavier oxygen is already provided, only not really enough of it for a heavy burn

RhysW

@PearsonArtPhoto isnt it on europa that the atmosphere is thick enough that we can fly by flapping our arms (ignoring need to breathe ect)

PearsonArtPhoto

1:36 PM

@RhysW Titan, but...

RhysW

@PearsonArtPhoto ah my mistake,

PearsonArtPhoto

@TildalWave That is true. A scramjet system could work. Hmmm...

RhysW

@PearsonArtPhoto i imagine trying to build the rocket would be hard enough, everything would be heavy as hell, though the native organisms would also then be beefier presumeably to survive, making liftoff even harder and heavier for them

TildalWave

@PearsonArtPhoto and you could decrease the atmospheric drag with a laser ;)

PearsonArtPhoto

Higher gravity would seem to imply smaller organisms for me.

RhysW

1:39 PM

@TildalWave so your solution is to get a hydrogen stealing plane that shoots lasers?

TildalWave

or even controlled forward explosions and use their wake to push against once the exploded area starts collapsing

RhysW

@PearsonArtPhoto true, smaller habitats and using everything in smaller quantities

@TildalWave if i could suggest one change it would be ditch the plane and have it as a hydrogen stealing shark that shoots laser beams, but im not sure if that helps with the whole, reaching escape velocity thing

PearsonArtPhoto

Higher gravity would force the inhabitants to built more efficient rockets sooner.

TildalWave

@RhysW it's actually a lot easier, but I like your proposal that I'm like the wild coyote from those roadrunner cartoons :)) Acme FTW!!!

PearsonArtPhoto

Thus, they would be more likely to explore further away from home, as they could easily do it with their more efficient rockets.

RhysW

1:41 PM

@PearsonArtPhoto but would they be more efficient?

PearsonArtPhoto

Lower gravity would allow the building of space stations easier.

RhysW

smaller yes,

but proportionally heavier

PearsonArtPhoto

@RhysW They would have to be, or you couldn't launch. Thinks like Nuclear Thermal Rockets.

TildalWave

@RhysW No stealing of anything... just pushing against. When you're fast enough gases start behaving exactly the same as liquids... what I'm saying is kinda like the waterjet

RhysW

@PearsonArtPhoto they would have to be more efficient before they could even start though, higher chance of giving up if the initial, inneficient tests fail

as their higher efficiency ones, would be the equivalent of ours now, pound for pound thrust wise

PearsonArtPhoto

1:42 PM

Or scramjets or such.

RhysW

would have to be twice as efficient in a 2x gravity just to be equal to us

PearsonArtPhoto

@RhysW Maybe. Hmmm, will have to think about things a bit more...

TildalWave

@PearsonArtPhoto yeah... well to be more exact, I don't think there's a name for "exactly" what I described yet... or maybe "the improbability drive"? :))

RhysW

@PearsonArtPhoto its definately interesting to think about

@TildalWave the tildalwave drive, youre more improbable with your suggestions than anything else i can think of :P

TildalWave

@RhysW LOL cheers! I'll take that as a compliment :P

RhysW

1:45 PM

@TildalWave :P hehe, either way, im off to read about hawking radiation, catch ya in a bit

PearsonArtPhoto

If we had less gravity, there could be all sorts of junk in space from when rockets were first build. Unlikely, but still possible. Hmmm...

TildalWave

seriously though... I'll try to assemble more comprehensive description of what I had in mind, and we'll see if it could work on planets with highly reactive atmospheric gases

RhysW

@PearsonArtPhoto but wouldnt we also have orbited closer to the planet, meaning that junk would still 'fall' like we plan for ours on earth?

PearsonArtPhoto

@RhysW Yeah, that's probably true.

RhysW

@PearsonArtPhoto we would probably be in a different orbit too, if the planet is lighter

PearsonArtPhoto

1:48 PM

@RhysW Not really.

RhysW

@PearsonArtPhoto no?

PearsonArtPhoto

Planetary mass doesn't have much to do with what orbit it's in.

I'm assuming you mean orbit around the star?

TildalWave

How much of a push does the magnetism of the Earth's magnetosphere have that we could harness in any way?

RhysW

@PearsonArtPhoto but the mass of both bodies is taken into consideration when calculating gravitational attraction

TildalWave

Radiation pressure

Radiation pressure is the pressure exerted upon any surface exposed to electromagnetic radiation. The term can also refer to pressures generated by other forms of wave motion, e.g. acoustic radiation pressure. According to special relativity, the momentum of a photon is equal to its energy divided by the speed of light, thus, if absorbed, the pressure is the power flux density divided by the speed of light. If the radiation is totally reflected, the radiation pressure is doubled. For example, the radiation of the Sun at the Earth has a power flux density of 1,368.8485 W/m2, so the rad...

this

RhysW

1:50 PM

so if we are being pulled less, wouldnt we need to orbit slower than earth to stay the same distance from the star?

PearsonArtPhoto

Venus and Mars are both lighter than Earth. It really wouldn't affect us much if Earth was lighter as far as our orbit to the Star.

The pull is less, yes, but so is the required pull.

RhysW

@PearsonArtPhoto ah true

less mass, less momentum,

TildalWave

OK... here's then an idea for a question: With Rosetta planned to orbit the 67P/Churyumov–Gerasimenko, what distance to the comet will it orbit and how will its trajectory be affected by its corona and tail

RhysW

i wonder what would be different if the volume of our liquid core was doubled, but the area it occupies is the same, so, higher pressure in the core

i think atleast the surface temperature would be hotter

volcanic eruptions would be more violent

PearsonArtPhoto

There are too many possibilities...

Anyways, got to go do some work.

RhysW

1:56 PM

@PearsonArtPhoto cya later

TildalWave

2:20 PM

@RhysW I think pressure on the core would remain much the same as the mass pushing against it wouldn't change (if only it's phase changes)... but the outer solid layers would be thinner, and also pushed against with higher force from the core, because of the compressibility of the liquid core storing more potential energy. And as you can compress the liquid core more, there'd probably be a bigger unstable pockets between it and the solid outer layer... I don't see many positives

RhysW

@TildalWave its not sounding good tbh :P

wouldnt we end up with bigger landmasses? Fissures from receeding tectonic plates would result in a higher volume of molten rock seeping to the surface wouldnt it?

TildalWave

@RhysW once in it's history Earth must have been exactly like that... probably no liquid water on the surface, tectonic plates moving a lot faster, violent electrical storms, lava flowing out of every crack in the thin crust, every other peak an active volcano, toxic atmosphere,... a proper picnic place ;)

RhysW

@TildalWave sounds picturesque :P

i would love to be able to have seen earth, form start to finish, would be interesting i bet

TildalWave

@RhysW there'd be no oceans to speak of, so ... yes? :))

RhysW

@TildalWave everything would be a landmass so xD

TildalWave

2:30 PM

@RhysW now I wonder, if it's possible for lightning to stretch from one planet to another, or a planet and it's sun... maybe in early stages of a new solar system and the space between proto-planets still filled by gaseous clouds?

RhysW

@TildalWave oh wow, that is an interesting thought

something in my gut says no,

let me see if i can figure out why

TildalWave

I'll leave you with it... I need to go ;)

RhysW

The lightning spark can occur between clouds,

weather quote

so perhaps, they could

as a 'ground' object isnt required

@TildalWave ah cya

JohnB

hello space people

RhysW

@JohnB sup

@CrazyBuddy i see you here too now, party time :P

JohnB

2:35 PM

not much! I missed the Project Morpheus live stream yesterday I see :(

I wish they would be more explicit when they do it

RhysW

aha! Lightning can occur in space! @TildalWave

"try imagining a single bolt of lightning 50 percent longer than the entire Milky Way galaxy."

it occured 2 billion light years away, caused by a black hole

JohnB

:S

TildalWave

> you can wrap a line in a quote onebox with > before it ;)

:P gotta go

RhysW

@JohnB impressive huh! I bet that contained more energy than the human race has ever used

speaking of awesome things, there is a star thats only 80 degreesF

bunch of brown dwarfs

> The star VY Canis Majoris. It's a red hypergiant roughly 1.7 billion miles in diameter, which means it's so big it takes eight hours for its own light to travel from one of its sides to the other

JohnB

neat

RhysW

2:43 PM

space has some amazing things in it

the scale of which we can barely concieve xD

e.g that red hypergiant is 60Au in diameter, thats 60 times the size of the gap between us and the sun

Crazy Buddy

3:36 PM

@RhysW Ugh.. Actually, there was a power shutdown... Then, laptop died temporarily..! R.I.P ;-)

RhysW

@CrazyBuddy that sucks xD welcome back

Crazy Buddy

@RhysW So, with that response, I can assure you that you won't stay in my hometown for an hour :P

RhysW

@CrazyBuddy i live an electronic life, so no :P

Crazy Buddy

Hah..! Me too ... But, quite intermittent :)

RhysW

@CrazyBuddy hehe, oops, almost spammed this chat with physics, im in the wrong one for that, your prescence threw me off :P

Crazy Buddy

3:46 PM

@RhysW What..? Space.SE has a deep relationship with Physics.SE, provided they still remember the 2 Phys.SE people who actually advertised around :P

RhysW

@CrazyBuddy who were they? :P

Crazy Buddy

@RhysW What? Space.SE screwed me... I shoulda thought this before..! o.O

RhysW

@CrazyBuddy we arent space.se :P were SEx.SE :P

Crazy Buddy

Nice title... You know that? (attracts more people) o.O :P — Crazy Buddy yesterday

RhysW

@CrazyBuddy ha, probably will

JohnB

3:58 PM

►

newspace.spacefrontier.org/agenda

Paul A. Clayton

4:44 PM

Concerning the effects on space exploration of originating on a different type of planet, the rotation rate of the planet would also seem significant (if only for the height of synchronous orbits). The presence of a significant-sized moon might also be significant as an easily understood, more achievable goal. Atmospheric density might also be significant (both for launch--a denser atmosphere might make balloons more useful--and descent).

Large bodies of water or climate variation would support areas with sparse population which could influence space programs. I suspect there are many other factors.

Donald.McLean

4:56 PM

Not to mention things like the type of atmosphere - something that is nearly opaque to starlight would change the way natives view the universe. The availability of metals - a metal poor world might never develop a civilization advanced enough to leave the planet.

Paul A. Clayton

5:16 PM

@Donald.McLean Yep.

Donald.McLean

5:28 PM

One of the things I liked about John Ringo's looking glass series is the discussions of comparative biochemistry.

Donald.McLean

5:50 PM

Anyone see the trailer to the movie "Gravity"?

JohnB

7:38 PM

@Donald.McLean I did, mixed feelings