For Questions That Don't Merit Their Own Thread

[StrandedonEarth]

26 minutes ago, JoeSchmuckatelli said:

why not put it in L4 or 5 for the stability? 

IIRC, a lot of dust has collected at those points, because of the stability there

[kerbiloid]

38 minutes ago, JoeSchmuckatelli said:

while at L1 and L2 a coorbiting body should only be stable for a few months.  Is this purely through the 3-body problem, or is it because of the moon?

Afaik, it's because of absolutely any type of perturbation.
A 3rd party gravitation, the orbit non-circularity, solar wind, etc.

44 minutes ago, JoeSchmuckatelli said:

station keeping ability - thus a finite fuel source. I've not seen anything on this, but does JWST have some kind of engine for this? 

https://space.stackexchange.com/questions/7820/what-kind-of-thrusters-will-the-james-webb-space-telescope-use-for-station-keepi

Spoiler

 

[Gargamel]

I have found a new hobby.   Speed scrolling through this thread and stopping at random times, reading random bits.  

It must be what walking through a Trek convention would sound like.   "Well the Raptor has guns... But the Other one has lasers! .... No the treadmill is going the wrong way!.... No hear me out.... what if we put a dinosaur on the moon?".  

 

[kerbiloid]

2 hours ago, Gargamel said:

I have found a new hobby.   Speed scrolling through this thread and stopping at random times, reading random bits.  

It must be what walking through a Trek convention would sound like.   "Well the Raptor has guns... But the Other one has lasers! .... No the treadmill is going the wrong way!.... No hear me out.... what if we put a dinosaur on the moon?".  

 

How else, do you think, shall the Almighty Global AI learn everything to rule the world?

[Cavscout74]

So I had a random thought today - I wonder if newspaper subscriptions have increased during the pandemic?  Emergency toilet paper, delivered to your door every day.   A single person could probably get by with just the Sunday paper.

[kerbiloid]

And preferrably plain blank, without text and pictures.

[JoeSchmuckatelli]

On 6/14/2020 at 5:52 AM, Gargamel said:

I have found a new hobby.   Speed scrolling through this thread and stopping at random times, reading random bits.  

... 

S-s-such pastimes call forth the evil Necro-Threads! 

Woe! 

 

Doom! 

 

Gloom! 

 

 

... 

 

(I know this, because a couple of weeks ago  I almost answered a post from 2014!) 

[magnemoe]

14 hours ago, Cavscout74 said:

So I had a random thought today - I wonder if newspaper subscriptions have increased during the pandemic?  Emergency toilet paper, delivered to your door every day.   A single person could probably get by with just the Sunday paper.

Don't throw that in the toilet good chance you clog it, even kitchen wipe paper has this risk even if I have used it as an backup. But once I used a lot because a leak and dumped in the toilet and totally clogged the system.
I thought they was the same just that the kitchen one had other motifs and was double length. 
Back then outhouses was common some publication like the farmer almanac came with an hole in the corner so you could reuse previous year version it in the outhouse

 

[kerbiloid]

2 hours ago, JoeSchmuckatelli said:

(I know this, because a couple of weeks ago  I almost answered a post from 2014!) 

Just six year old.
Feel talking to Barnard Star.

[DDE]

3 hours ago, JoeSchmuckatelli said:

(I know this, because a couple of weeks ago  I almost answered a post from 2014!) 

[ARS]

If we colonize other celestial bodies on solar system, realistically speaking, assuming we can easily send stuff and personnel to earth orbit, does the number of colonist sent to farther celestial body should increase or decrease? (Up to a minimum number required for developing population) Assuming if we aim to make a sustainable population in a self-sufficient colony in a single trip (assume stuff such as prefabricated bases, supplies and resources are non-issue)

Also unrelated, but assuming if you can sneak into space shuttle cargo bay as it launched (Don't ask how), could you survive all the way into space with nothing but pressurized G-suit and oxygen supply, and not strapped on any seat like on the cockpit (just holding on railings inside cargo bay). Assuming you have been to space before

[Nightside]

37 minutes ago, ARS said:

does the number of colonist sent to farther celestial body should increase or decrease? 

If is designed to be totally self sufficient from the beginning then the number is arbitrary, based on whatever your starteR system would support.

you would certainly need lots of redundancy in specialists. And a certain number for long term genetic diversity, but some clever gene editing could help circumvent that.

42 minutes ago, ARS said:

Also unrelated, but assuming if you can sneak into space shuttle cargo bay as it launched

Just watched Brad Pitt do this in a particularly cringe Worthy scene in  AdAstra. 

[ARS]

2 hours ago, Nightside said:

Just watched Brad Pitt do this in a particularly cringe Worthy scene in  AdAstra. 

By the "cringe-worthy", does it means ridiculously stupid that it's just plain impossible, or crazy awesome that it's actually possible but no one has attempted it?

[Nightside]

26 minutes ago, ARS said:

By the "cringe-worthy", does it means ridiculously stupid that it's just plain impossible, or crazy awesome that it's actually possible but no one has attempted it?

They made a great effort with interesting, realistic ships (with radiators! take that Kubrick!), and the setting is realistic. (The movie is basically Heart of Darkness in space, where the hero, on his way to confront the monster, becomes a monster himself.) 
So amid all that, there was a strange sequence where he has like 5 minutes to swim through an underground lake in a spacesuit, on Mars and somehow board a rocket in its final countdown and struggle in while it takes off. I mean, I guess you can lift off from Mars at <1g, so maybe, but the lake really bothered me.

[SOXBLOX]

For colonizing anything further than Earth orbit, you'll probably want nuclear power, so you'll need lots of specialists, but overall, a self-sufficient colony on Sedna shouldn't require many more colonists than one on Duna Mars.

As for liftoff in a shuttle bay, you'd want to lie down or sit. IDK if there's a suitable spot on that aft bulkhead. Anyone care to look? I'm too lazy...

Here's my own question: Is it possible to truly colonize a world with less than Earth gravity? Are humans up to it? I know the standard stuff, loss of bone density in 0g, etc. but I wanted to see what else there is on the topic. What alterations would occur to human proportions, growth, lifespan (not due to time dilation in a gravitational field, I mean because of potential health effects), muscle strength, etc?

Also, I haven't watched or read the Expanse, but I know that "Earth gravity wreaks havoc on the Martian physique". So do Martian ships accelerate at 1/3 g for cruise, or is there another solution to this (e.g. training, a drug of some sort)? How does the show address this issue? It seems that this gravity factor would give Terrans an advantage over Martians in high-g scenarios.

[p1t1o]

On 6/8/2020 at 3:52 AM, ARS said:

On stealth aircraft that's difficult to detect with radar (such as stealth bombers), assuming that it's detected visually by conventional aircraft, and they open fire using onboard machine guns instead of attempting missile lock at such close range engagement, will the damage from machine gun fire that riddled stealth aircraft's outer skin with bullets make it more visible to radar (compromising it's stealth)?

Also, I've seen this clip: in a scene involving a dogfight between 2 fighter aircrafts, A is behind B and launched a semi active radar homing missile (clearly because the pilot of A said Fox 1), but then the pilot of B used flares to deflect said missile (clearly because pilot B said Flares!). Can SARH missile be deflected that way? Or is it possible to mix chaff in flare dischargers to confuse the radar homing of said missile? Because AFAIK, modern SARH missile can differentiate between actual aircraft and chaffs since chaffs usually slows down dramatically once it's released (for info, aircraft A is Su-30, while aircraft B is Su-27)

 

On 6/8/2020 at 8:46 AM, DDE said:

Given that the "machine guns" of modern aircraft tend to cause enormous holes? Yeah.

It's not just possible. To my knowledge, it's how it's always done.

From what I understand, chaff is more about obscuration than a true decoy. However, there'd be a complex interplay between chaff and Su-27's own, albeit rudimentary, radar jammers.

The new hotness is "Jaff". Jammed-Chaff. Modern ECM suites use phased array anntennae which give excellent control over where the signal beam goes.

You point a tight (as tight as these things go, you know, physics) beam in a favourable direction (ie: behind you, where your chaff is going) and eject chaff into it. Naturally, care is taken not to point this beam directly at a known enemy sensor (unless of course you want to jam it conventionally.)

Now the ECM broadcast is not coming from your exact location, helping (nothing is absolute in this game of arms-races) to spoof Home-on-Jam-capable weapons and your chaff is shining like a star, increasing its conventional effectiveness. It also serves to somewhat offset the rapid deceleration of the chaff (since its reflected ECM can obscure its velocity/range to a sensor.)

Much of this has been enabled quite recently (last couple of decades) due to advances in processing power, beam agility and shaping.

A simplistic explanation but that is where the tactics are going.

****

During last-ditch encounters, chaff and flares are often ejected together because you never really know what has been fired at you (there are some surprising long-ranged IR guided missiles today and medium-long-range radar guided missiles are handy even in a short range scrap as they have a TON of kinetic energy for manoeuvre and are FAST). Launches at longer ranges are more problematic as it is rarely possible to even detect the launch. There are such things as Missile Launch Warning Systems but they are not perfect, in fact quite limited and can be prone to false-positives. But you might, say, employ a "camoflage" scheme if flying within range of known sensors, ie: when in such and such an area, ejecting a chaff every 10 seconds or so, just to screw thigs up and make it harder to resolve you and elongate engagement times, as a precaution. There are exception to all this and the avionics can help by automating a lot, but really, if you are down to using chaff or flares to save your aircraft or having to actually *dodge*, you are in deep doo-doo already. Clean pair of pants at a minimum. Modern aircraft are geared towards avoiding being there in that situation first place, in BVR or a dogfight, by using energy management and large and small scale manouvre and tactics, as their primary defence, everything else is a thin film of prayer.

I mean, we are talking about a type of combat which is *exceedingly rare* these days, and it has *never* occurred between any pair of cutting edge (say jets designed post-1990) modern jets outside of training. Much of this is theoretical.

[ARS]

Is there a formula to calculate the distance to the point of origin from impact site of an object traveling at parabolic trajectory (assuming we ignore air resistance and the object does not go suborbital) if the known values are the object's mass (5 kg), impact velocity (150 m/s) and angle of impact (15° angle from flat ground)

[p1t1o]

2 hours ago, ARS said:

Is there a formula to calculate the distance to the point of origin from impact site of an object traveling at parabolic trajectory (assuming we ignore air resistance and the object does not go suborbital) if the known values are the object's mass (5 kg), impact velocity (150 m/s) and angle of impact (15° angle from flat ground)

 

Yup.

If ignoring air resistance it is very simple, you dont even need Newtons laws of motion. Dont need the mass either.

Angle and speed of impact will be the exact inverse of angle and speed of launch. Adn without air resistance, the only force acting on the projectile is gravity.

First seperate the trajectory into horizontal and vertical components.

So at 15deg from horizontal and 150m/s, the vertical component is (150*Sin15)=approx 38.8m/s and the horizontal component is (150*Cos15)=approx 144.9m/s

Somebody should check that math, my trigonometry is VERY hazy. But we can use the numbers as examples anyway and sanity-check them along the way.

 

 

The vertical component figure gives you time of flight - how long until 1g deceleration brings the vertical velocity to zero - which would be at max altitude reached. Double that (to include the fall back to earth) to get the ToF. 

So lets just set 1g to 10m/s2 just for ease.

ToF is therefore (38.8/10)*2= 7.76s       (sounds about right)

 

The the horizontal distance travelled is simply the horizontal velocity component multiplied by ToF.

144.9 * 7.76 = 1124.4m

 

Which seems like a pretty sane answer, so I reckon my trig was right  I hope....

Without air resistance, simple 2-body trajectories are quite trivial once you're familiar (and if you can get a handle on trigonometry lol)

 

Naturally, this is an ideal scenario. There are obviously many complications for real-world examples. Like if the projectile goes high enough that the force of gravity felt by the projectile changes. Or if you want to take into account curvature of the earth (this example assumes an infinite flat plain, which give very accurate answers for most human-scale questions).And if you do include air resistance, the complexity rises very dramatically. Etc.

 

Related reading: https://en.wikipedia.org/wiki/Equations_of_motion

 

 

Edited June 18, 2020 by p1t1o

[K^2]

3 hours ago, ARS said:

Is there a formula to calculate the distance to the point of origin from impact site of an object traveling at parabolic trajectory (assuming we ignore air resistance and the object does not go suborbital) if the known values are the object's mass (5 kg), impact velocity (150 m/s) and angle of impact (15° angle from flat ground)

What @p1t1o gave as steps is perfectly valid, but there's actually a well known range formula in physics exactly for this: d = v² sin(2a) / g, where v is velocity of impact, a is the angle it makes with horizontal, and g is gravity. Mass isn't necessary. Plugging your numbers in, we get something very close to p1t1o's result.

[p1t1o]

1 minute ago, K^2 said:

What @p1t1o gave as steps is perfectly valid, but there's actually a well known range formula in physics exactly for this: d = v² sin(2a) / g, where v is velocity of impact, a is the angle it makes with horizontal, and g is gravity. Mass isn't necessary. Plugging your numbers in, we get something very close to p1t1o's result.

Yeah I probably learned that at some point. Its what you get if you just collapse down everything I typed. Man I had a hard time remembering the trig thou, I had to get a pen+paper and draw diagrams again lol! (I am a bit starved of science in my job you might be able to tell)

[K^2]

1 hour ago, p1t1o said:

Man I had a hard time remembering the trig thou, I had to get a pen+paper and draw diagrams again lol! (I am a bit starved of science in my job you might be able to tell)

We're always hiring in game dev. 

[SOXBLOX]

You're a game dev, K^2? Cool! If so, which studio?

 

Also, let me bring this back down here; I think it got lost way up there.

On 6/16/2020 at 3:53 PM, SOXBLOX said:

 Is it possible to truly colonize a world with less than Earth gravity? Are humans up to it? I know the standard stuff, loss of bone density in 0g, etc. but I wanted to see what else there is on the topic. What alterations would occur to human proportions, growth, lifespan (not due to time dilation in a gravitational field, I mean because of potential health effects), muscle strength, etc?

Also, I haven't watched or read the Expanse, but I know that "Earth gravity wreaks havoc on the Martian physique". So do Martian ships accelerate at 1/3 g for cruise, or is there another solution to this (e.g. training, a drug of some sort)? How does the show address this issue? It seems that this gravity factor would give Terrans an advantage over Martians in high-g scenarios.

 

[ARS]

Thanks, @p1t1o, @K^2. I double check that values and the results are pretty close to each other

3 minutes ago, SOXBLOX said:

 Is it possible to truly colonize a world with less than Earth gravity? Are humans up to it? I know the standard stuff, loss of bone density in 0g, etc. but I wanted to see what else there is on the topic. What alterations would occur to human proportions, growth, lifespan (not due to time dilation in a gravitational field, I mean because of potential health effects), muscle strength, etc?

Possible, as long as we are willing to accept the permanent alteration towards the colonists in the long term (subsequent generations tend to adapt). Generally, compared to earth, those live in lower gravity would grow taller, but weaker (especially in zero g). Lifespan is not gonna change much as long as there's plenty of supplies and keeping the body healthy by daily exercise, unless some major thing happens on the colony such as loss of life support

[K^2]

1 hour ago, SOXBLOX said:

You're a game dev, K^2? Cool! If so, which studio?

I'd rather not share that publicly, because I kind of want to keep my opinions here well separated from anything that might be associated with the studio. If you are curious, feel free to ask me in a PM.

On 6/16/2020 at 1:53 PM, SOXBLOX said:

Also, I haven't watched or read the Expanse, but I know that "Earth gravity wreaks havoc on the Martian physique". So do Martian ships accelerate at 1/3 g for cruise, or is there another solution to this (e.g. training, a drug of some sort)? How does the show address this issue? It seems that this gravity factor would give Terrans an advantage over Martians in high-g scenarios.

In Expanse the TV series (haven't read the books), they have drugs and special chairs that let crew survive significantly higher acceleration for a brief time. In addition, Martian Marines and Navy routinely train in higher gravity to both be competitive in space combat and be prepared to do ground ops on Earth if necessary. There are a lot of liberties taken with science of it in the show, but they definitely tried to make it consistent at least within the narrative.

[SOXBLOX]

Great! Thx! Sorry if I offended you; not my intention to pry.