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calapine
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Reply #910 on: October 07, 2017, 12:50:50 PM

A little more about the ISS. The station maintains an (almost) circular orbit around Earth at a height of ~400 km.


Yet if one consults a map to find it's position, the result looks something like this:


(The projected track of 5 orbits)

The answer to "Why?" should, but might not be, obvious. Especially if you are like me and spatial understanding of 3D spaces isn't your forte.


I found this visualisation helpful:




The "Sinus-curve-orbit" is resulting from the fact that a maps are just 2D projections of a globe.

The "track drift" to the West is due the earth rotating below the station. (If someone can phrase this better PM me and I will edit gladly!)

And that's that!  smiley
« Last Edit: October 07, 2017, 12:54:01 PM by calapine »

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Strazos
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Reply #911 on: October 09, 2017, 02:19:38 AM

So why the roughly-45% orbit? I'd have thought it would be more parallel to the equator or something.

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Reply #912 on: October 09, 2017, 03:15:45 AM

So why the roughly-45% orbit? I'd have thought it would be more parallel to the equator or something.

Look at the picture above the animation. They basically get to be over every part of the planet within just a few orbits. Also, is parallel to the equator even possible outside geostationary orbits? I think it pretty much has to be right on the equator or any rotation of it (like that ISS orbit).

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calapine
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Reply #913 on: October 09, 2017, 10:23:31 AM

I have a cold from hell (including puking), so I have to do this in parts because it's actually quite challenge to verbalise an answer without resorting to an "Just BECAUSE, Timmy! Now please be quiet and let my mommy drive!!" answer. And just sitting at the desk makes nausea worse.

Also, is parallel to the equator even possible outside geostationary orbits?

Sure can do! It's actually almost the opposite: Any equatorial orbit that isn't at 35,786 kilometres wont be a geostationary orbit.


Centripetal force equation:



If you hop into the role of a spaceship captain and want to achieve a stable, circular orbit your goal to equate everything right of the "=" to the Centripetal Force "F" which is provided by gravity.

In essence Orbit Radius "R" and Velocity "V". For a geostationary orbit (= You appear motionless to ground observers) angular velocity is determined by the need follow the rotation of the Earth. Leaving Radius "R" as the only adjustable variable, which for earth works out at 35,786 km.

I hope that makes sense.



Look at the picture above the animation. They basically get to be over every part of the planet within just a few orbits.

That is reason a) yes. Reason b) is orbital mechanics.

For b) the quick "Shut up, Timmy!" answer is: Because you can't (directly!) launch into an orbit with an inclination (=angle between the orbit and the equator as reference plane. See image below. 0° inclination is an equatorial Orbit, what Strazos asked.) lower than latitude of your launch site. Cape Canaveral is at 28.5°, Baikonur at 45.6°, ISS inclination (the title Strazos guessed pretty close at 45°) is 51.6 degree, so it works out. Now you can do a plane change, but this is like, super expensive. Which brings up to the next WHY? which i'll do later.


« Last Edit: October 09, 2017, 10:59:23 AM by calapine »

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Reply #914 on: October 09, 2017, 10:51:54 AM

Urgh. I just noticed something:

So why the roughly-45% orbit? I'd have thought it would be more parallel to the equator or something.

If I misunderstood your question (language barrier and so) and you meant something like I pictured below:



Than the answer is: that's not possible. The plane of a natural orbit must always go through the center of mass. (Unless you constantly maintain thrust...)

off to bed again

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Reply #915 on: October 09, 2017, 02:27:02 PM

So basically, it has to cross the equator at some point. Is it possible to orbit along the equator, though not necessarily with a geostat orbit? ie - path along the equator, but at a speed faster than earth's orbit?


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Reply #916 on: October 09, 2017, 02:33:03 PM

It takes more fuel to get it over the equator cause the US and Russia don't have any launch sites there. Also it won't traverse as much of the earth if it's orbiting around the equator longitudinally.

https://www.quora.com/How-does-the-ISS-orbit-the-earth
calapine
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Reply #917 on: October 09, 2017, 02:48:45 PM

So basically, it has to cross the equator at some point. Is it possible to orbit along the equator, though not necessarily with a geostat orbit? ie - path along the equator, but at a speed faster than earth's orbit?

Yes to all points.

Edit: If someone who can explain the concepts better than me follows this thread please post. :)

Edit2: The link Trippy posted is perfect, really. Recommended reading.
« Last Edit: October 09, 2017, 03:30:55 PM by calapine »

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Reply #918 on: October 09, 2017, 05:00:45 PM

So basically, it has to cross the equator at some point. Is it possible to orbit along the equator, though not necessarily with a geostat orbit? ie - path along the equator, but at a speed faster than earth's orbit?



Orbits are counterintuitive.  If you want to circle the earth faster, you have to slow down your orbital speed.  As you lose speed, your orbital altitude will decrease and you circle the earth quicker.  Such an orbit is unstable; eventually gravity will pull you down unless you accelerate periodically to maintain your altitude.

If you accelerate, you'll orbit at a higher altitude, and actually take longer to complete the circle.  Accelerate too much, you achieve escape velocity and stop orbiting.
« Last Edit: October 09, 2017, 07:09:42 PM by Polysorbate80 »
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Reply #919 on: October 10, 2017, 12:31:37 AM

also interesting is the French launch site is closer to the equator than either the US' or Russia's, which not only makes equatorial orbits (like the geosynchronous so popular for so many things) a little bit cheaper/less fuel because they can start out with less inclination to compensate for, but also double plus bonus they get a little more boost from the angular momentum of the earth's spinning itself, being fastest at the equator.

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Reply #920 on: October 10, 2017, 05:56:09 AM

In places like the US or Russia, I'm always surprised more stuff isn't damaged in transit between these sensitive production facilities and being loaded onto the rockets.

Doubly so for launches out of French Guyana - that's either a long set of flights, or a perilous boat ride.

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calapine
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Reply #921 on: October 10, 2017, 07:35:00 AM

In places like the US or Russia, I'm always surprised more stuff isn't damaged in transit between these sensitive production facilities and being loaded onto the rockets.

Doubly so for launches out of French Guyana - that's either a long set of flights, or a perilous boat ride.

It occurs, but rarely.

The worst recent accident happend still during the manufacturing phase:





 swamp poop ACK! Oh ho ho ho. Reallllly?

As for transport: Sats to Baikonour and French Guyana come per plane, for the Cape road or plane, AFAIK. All special airtight containers.

Example:





Transporting of the rocket is another issue, every manufacturer coming up with different solutions.

That Falcon 9 looks a flying asparagus is because the diameter was choose to be just-about road transportable. I have read the 3.6 meters are the maximum to still pass below interstate underpasses and such on the way from California to Florida.




Proton: Again form follows function



What looks like boosters on the first stage are actually strap-on tanks. The center tank (which carries the oxidiser, not the fuel) has a diameter of 4.1m, the maximum allowed by Soviet/Russian rail. The fuel tanks are attached once the launcher reaches Baikonur.



Ariane 5: With a diameter of 5.4 meters nly ship transport is really practicable.


« Last Edit: October 10, 2017, 07:38:40 AM by calapine »

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Reply #922 on: October 10, 2017, 07:49:46 AM

Reminds me that NASA were advertising earlier this year for an "earth protection officer". Basically someone whose job it is to work internationally ensure that no contamination gets onto any probes going to space and especially Mars or wherever. If Earth born bacteria got onto Mars no-one knows what could happen. Also her responsibilities would be to ensure no space pathogen got onto earth from something coming down from space.

IN actuality ist sthe same woman for the last 20 years, but they had to advertise with the change in the administration.

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Reply #923 on: October 10, 2017, 02:55:31 PM

Came across this today, and maybe of interest to some.



Echoes in space - Trailer

It's listed as a 5 week, 3 hours/week course. And free of course. https://eo-college.org/
« Last Edit: October 10, 2017, 02:59:24 PM by calapine »

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Reply #924 on: October 12, 2017, 05:16:43 AM

Last night's SpaceX lift off from the Cape provided some really stunning visuals visuals. At least the first 30 seconds are must watch, imho:



Watch me!
« Last Edit: October 12, 2017, 05:22:22 AM by calapine »

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Reply #925 on: October 14, 2017, 05:39:41 AM

Weekend guessing game. Looks like Paranormal Green Slime, but what is this actually?




« Last Edit: October 14, 2017, 05:48:29 AM by calapine »

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Reply #926 on: October 14, 2017, 08:38:45 PM

Elon Musk just did an AMA over on reddit (where else?).

Nicely technical round of question and answers this time, IMHO. And as an example oh how fast and fluid Elon's plans are, the BFS described at the most recent IAC barely a month ago now has three landing engines planned, changed from two. Not really for safety -- it gives the opportunity to land with a heavier cargo load.
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Reply #927 on: October 14, 2017, 11:45:29 PM

4 legs, changed from 3. wink

I live tweeted the AMA (sans the fluff talk), see here.

The talk was solely focused on BFR and Mars, and imho, won't convince any sceptics.

Elon was his usual optimistic self. 
Q: How does BFR radiation shielding look like?
A: Radiation damage is not significant for our transit times. Buzz Aldrin is 87.

Yeah well, Buzz spent 12 days, 1 hour in space.

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Reply #928 on: October 14, 2017, 11:56:43 PM

4 legs, changed from 3. wink

I live tweeted the AMA (sans the fluff talk), see here.

The talk was solely focused on BFR and Mars, and imho, won't convince any sceptics.

Elon was his usual optimistic self. 
Q: How does BFR radiation shielding look like?
A: Radiation damage is not significant for our transit times. Buzz Aldrin is 87.

Yeah well, Buzz spent 12 days, 1 hour in space.
Unless he has a working large scale microwave cavity drive squirreled away, or some other constant thrust solution, radiation is absolutely something he needs to plan for.

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Reply #929 on: October 15, 2017, 11:09:53 AM

4 legs, changed from 3. wink

I live tweeted the AMA (sans the fluff talk), see here.

The talk was solely focused on BFR and Mars, and imho, won't convince any sceptics.

Elon was his usual optimistic self. 
Q: How does BFR radiation shielding look like?
A: Radiation damage is not significant for our transit times. Buzz Aldrin is 87.

Yeah well, Buzz spent 12 days, 1 hour in space.
Unless he has a working large scale microwave cavity drive squirreled away, or some other constant thrust solution, radiation is absolutely something he needs to plan for.

--Dave

Calapine left out mention of the storm shelter and the fact that fast transit times are means of planning for radiation hazards. The fact is that a few months of interplanetary radiation (barring solar storms) are still within NASA approved lifetime radiation counts. It's hazardous, but certainly less so than, say, a lifetime of smoking, and we've had generation on generation happily subject themselves (and others) to that potential cancer risk, for far less gain.

It *does* mean that there probably won't be any veteran Mars transit crews. Pilots and crews will likely be limited to one or two round trips to keep exposure down.
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Reply #930 on: October 20, 2017, 01:52:38 PM

You probably already heard about this, but anyway: Japan's lunar orbiter "Selene" found something....VERY interesting on the Moon:

http://www.dailymail.co.uk/sciencetech/article-4996024/Huge-cave-moon-house-astronauts-Japan-scientists.html

You know, now that we're also entering an era of private exploration, a manned mission that actually goes there and take a look around doesn't seem so far-fetched.

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Reply #931 on: October 25, 2017, 06:25:55 PM

This forum is a bit gun-ho withe ALIENS!!! (see KIC 8462852 --> It's probably dust) but this time we have reasonable chance.

Comet C/2017 U1, which recently passed relatlvy close to earth, seems to have a strongly hyperbolic trajectory, ie. not bound to to sun.

Unless there have been errors in the tracking, which is still quite possible at this point (Edit: There are already voices that claim one of the observations is faulty), this indicates it's coming from outside the solar system. Ie. the first interstellar comet we found!



« Last Edit: October 25, 2017, 06:49:46 PM by calapine »

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Reply #932 on: October 25, 2017, 08:11:03 PM

So if it comes from outside the solar system, what's the mechanic on that? What expels a comet from its solar system of origin, and with sufficient energy that it could intersect another solar system and be drawn in to what must be in interstellar terms a relatively weak gravitational attractor? Because the scenario of something at the outer-outer edge of its solar system of origin's Kuiper Belt being so weakly held by its sun of origin that it just sort of drifts slowly into interstellar space sounds kind of plausible--but then what? Just drifting and drifting and being not attracted to anything until? our solar system intersects it and it gets yanked into a gravitational relationship with our Sun? Why wouldn't it just be another outer Kuiper Belt object with no particular momentum? If on the other hand it was on its own trajectory and then intersected our solar system, that means a pretty strong ejection from somewhere else, doesn't it?
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Reply #933 on: October 26, 2017, 05:59:50 AM

Watched the gif and thought to myself of that comet : 'Leeeroooooy Jenkins'

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Reply #934 on: October 26, 2017, 06:46:21 AM

So if it comes from outside the solar system, what's the mechanic on that? What expels a comet from its solar system of origin, and with sufficient energy that it could intersect another solar system and be drawn in to what must be in interstellar terms a relatively weak gravitational attractor? Because the scenario of something at the outer-outer edge of its solar system of origin's Kuiper Belt being so weakly held by its sun of origin that it just sort of drifts slowly into interstellar space sounds kind of plausible--but then what? Just drifting and drifting and being not attracted to anything until? our solar system intersects it and it gets yanked into a gravitational relationship with our Sun? Why wouldn't it just be another outer Kuiper Belt object with no particular momentum? If on the other hand it was on its own trajectory and then intersected our solar system, that means a pretty strong ejection from somewhere else, doesn't it?


RNGesus.

Something explodes -> comet is expelled -> “impacts” a solar system by virtue of traveling through relatively “dense” space.

Alternately the “low momentum” answer also works. Remember that everything is relative so an object that is dropped by a weak gravitational attractor will only have to have enough velocity relative to that attractor to escape. That system will have its own relative velocity at ejection to our system (the sum of which would be the objects relative velocity to us). That value could be anything really and then in it comes(or in we come, same difference)

Additionally worth noting that it’s now classified as an asteroid and so the aliens possibility is increased as it is ever so slightly more likely space bugs shot it as Beunos Aires and missed.
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Reply #935 on: October 26, 2017, 08:59:44 PM

Terminal guidance package hasn't activated yet.

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calapine
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Reply #936 on: October 27, 2017, 12:32:50 PM

Really would like to know the chances of this encounter.

I mean, just look at that track:

« Last Edit: October 27, 2017, 12:34:40 PM by calapine »

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Reply #937 on: October 27, 2017, 01:03:44 PM

And other image.

The JWST sunshield fully deployed for the first time:


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Reply #938 on: October 27, 2017, 02:48:18 PM

That is the biggest jiffy pop package in history...  why so serious?

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calapine
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Reply #939 on: October 27, 2017, 04:16:33 PM

I was seeing a trampoline.  Oh ho ho ho. Reallllly?

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Reply #940 on: October 28, 2017, 08:09:06 AM

Ok, Space Story time. Get some Cocoa!


A Long Time Ago, On This Day in 1972...

the Space Age began for Britain: A Black Arrow rocket brought the first the first British satellite, callled Prospero, into orbit.



As consequence the British Government took the only sensible next step: Cancelling all further Black Arrow flights and ending Britain's independent launcher programme for good.  headache

How did we get here? The main takeaway, which applies for all British launcher programmes, is lack of political will.
The UK Gov wanted to demonstrate that Britain was capable to develop it's own satellite launcher, but it was not willing to supply the required funds. But let's start at the beginning, with a project called:


Blue Streak

The British ballistic nuclear missile. The Blue Streak shared with other contemporary first-generation missiles, such as the US Atlas and Soviet R-7 (Soyuz)), the main drawback of using the non-storable fuel combination RP-1 with Liquid Oxygen.
Thus they were susceptible to a first strike, as preparation for launch would have taken a couple of minutes.



This reason and as well as the ballooning costs lead the UK Gov to give up on the programme in 1960 and instead tag along with an American made missile (Polaris).

In order to not lose all the invested resources the idea was brought up to repurpose parts of the Blue Streak as a satellite launcher. Which lead to:


Black Prince

The idea was emplyoing Blue Streak as 1st rocket stage and topping it of with a 2nd stage based on the Black Knight, an small research rocket. Together they would be the Black Prince.

Again the UK Gov was not willing to shoulder costs of the project, so the plan was to turn the Prince into a Commonwealth programme. As it turned out that neither Canada, Australia or New Zealand was able to contribute major funds it was time for Plan C: Work with the smelly Europeans.

Enter stage left:


Europa

A multi-national Frankenstein launcher made of a British Blue Streak 1st stage, a French Corallie 2nd stage and a German Astris 3rd stage.



Europa failed (More about this another time) Exit stage Europe.


<INTERMISSION>


Black Knight was cancelled in 1960. The next 4 years not much happend, until.....the French Diamant launch was about to turn France 3rd space faring power. This national disgrace gave renewed impetus to the UK plans, the new goal now being:
"Be the 4th nation in space, but with a total programme cost of below 9 Million Pound, including the satellite, tests flights, ground equipment & development costs."


This last attempt at Space Glory was dubbed:


Black Arrow

[ Stay tuned for more ]
« Last Edit: October 28, 2017, 03:17:51 PM by calapine »

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Reply #941 on: October 30, 2017, 05:45:50 PM

Until I get around to part 2 (I hope someone reads this stuff)...today SpaceX had another photogenic launch and a somewhat toasty landing:






Bonus content:
Aurora over Canada, photraphed 2016 by British ESA Astronaut Tim Peake


Link to high-res version
« Last Edit: October 30, 2017, 06:00:09 PM by calapine »

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Reply #942 on: October 30, 2017, 07:43:21 PM

I'm still reading this stuff!   Heart

Why don't you try our other games?
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WWW
Reply #943 on: October 31, 2017, 12:00:02 PM

I'm still reading this stuff!   Heart

 Heart Heart

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Reply #944 on: October 31, 2017, 11:17:14 PM

this is my favorite thread on the whole site!

and yeah, toasty landing which I heard they quickly put out the fire, but how? barge is unmanned I thought, so robots or remote operated fire extinguisher or what?

Yes, I know I'm paranoid, but am I paranoid enough?
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