For Questions That Don't Merit Their Own Thread

[p1t1o]

45 minutes ago, Spaceception said:

Hey guys, I think I need help double checking my numbers.

I'm designing a ringworld (New writing project, in development ), and I'm trying to find the surface area compared to Earth.

It orbits Lalande 21185 (not important, just context), at 0.15 AU, it has a 1.41 x 10^11 circumference, a 4,023,360 m width (2500 miles wide, about ~300 miles wider than the moon), and from my numbers, it has an internal surface area of 3,693,284,000,000,000,000 meters.

When I tried seeing the land area in relation to the Earth, the numbers were huge, way more than what's probably realistic, so I dropped the '^2' on both sides, and got 95.2623x the land area of Earth, but that doesn't sound right, which is why I'm asking for the actual number, and where I messed up. Or if it is correct, and it's just a lot lower than I expected.

Thanks

Did you get "Lalande" from the Night's Dawn trilogy by any chance?

Yup, Rimworlds have stupendous surface areas.

[Spaceception]

1 minute ago, p1t1o said:

Did you get "Lalande" from the Night's Dawn trilogy by any chance?

Yup, Rimworlds have stupendous surface areas.

No, never read that, or heard of it I just think it's an interesting nearby star, it's size is about as high as you can get with red dwarfs, which is cool.

Yeah, but it's smaller than Niven's, and the numbers I got seemed to be a lot higher than it.

[p1t1o]

6 minutes ago, Spaceception said:

No, never read that, or heard of it I just think it's an interesting nearby star, it's size is about as high as you can get with red dwarfs, which is cool.

Yeah, but it's smaller than Niven's, and the numbers I got seemed to be a lot higher than it.

Had to remind myself by having a gander at the wiki, but Niven's Ringworld had an area of approx 3million Earths.

Are you going by Earth's dry-land area or total surface area?

[Spaceception]

3 minutes ago, p1t1o said:

Had to remind myself by having a gander at the wiki, but Niven's Ringworld had an area of approx 3million Earths.

Are you going by Earth's dry-land area or total surface area?

Hmm, I was going for the total area, but dry is probably better.

[Green Baron]

36 minutes ago, Spaceception said:

Hmm, I was going for the total area, but dry is probably better.

Ok, i think the adjustment is trivial ...

:-)

[Spaceception]

Just now, Green Baron said:

Ok, i think the adjustment is trivial ...

:-)

True

[p1t1o]

1 hour ago, Spaceception said:

Hmm, I was going for the total area, but dry is probably better.

 

45 minutes ago, Green Baron said:

Ok, i think the adjustment is trivial ...

:-)

 

lol I really should have seperated those two points, I didnt mean to suggest a causal link XD

[NSEP]

If you have a space tower going up towards Geostationary orbital height, would it mean you are in geostationary orbit and there are no G-forces? Or would gravity still be there?

[Steel]

58 minutes ago, NSEP said:

If you have a space tower going up towards Geostationary orbital height, would it mean you are in geostationary orbit and there are no G-forces? Or would gravity still be there?

Being stood on top of a space tower at geostationary height would feel exactly the same as being on your own in geostationary orbit at the same place

[StrandedonEarth]

Gravity is always there, but in orbit it is balanced by the engineering phantom commonly known as centrifugal force. So at the GEO level, you would be weightless. Below that on the tower, you would be below orbital velocity, and would therefore experience gravity.   Above that, you would be above orbital velocity for that altitude, and would tend to want to ‘fall’ outwards. So if you were standing  in a glass room above GSO in this tower, Earth would be above your head and you’d see stars under your feet. 

Edited February 9, 2018 by StrandedonEarth

[kerbiloid]

1.

 

Almost any sci-fi movie, book, or project describing a lunar/martian ground base. Like Martian, Last Days On Mars, etc.

As we know there are two main types of spacesuits: working and rescue ones.
The working suits are to spend in vacuum several hours or maybe almost a day. They have a better protection against everything.
The rescue suits are to spend in vacuum an hour or so. They are lightweight, cheaper, fast-to-put-on, fast-to-take-off, so on.

Why does the personnel of a planetary base always wear the only of them?
Whether they are repairing an external equipment, running away by an excursion rover, walking around the base watching what to steal repair, just getting out from the base for fifteen minutes with a newspaper into bushes.

Why not have leisure rescue suits for local activities?
Fast and lightweight ones.

2.
About those fancy modern suits with a docking port from the back, which do not require an airlock aka suitports.

Spoiler

Their advantages are clear.

But what if the suit side docking port is deformed a little?
Temperature variations, mechanical damage, sticked grains of sand. So the port cannot close.
How then should the victim get into a base module without an airlock?

What if a spaceman is badly injured?
In a normal suit they can just carry him inside an airlock, pressurize the chamber, and then undress.
How should they scrape him out of the docked suit if he has broken bones, bleeding stopped with tourniqette, or so, and the door is 80x40 cm  in a meter above the floor?

(Should it be equipped with cyanide for both of these cases?)

Edited February 13, 2018 by kerbiloid

[p1t1o]

33 minutes ago, kerbiloid said:

But what if the suit side docking port is deformed a little?
Temperature variations, mechanical damage, sticked grains of sand. So the port cannot close.
How then should the victim get into a base module without an airlock?

What if you have a normal spacesuit but the airlock door is deformed or damaged? Same issue.

35 minutes ago, kerbiloid said:

What if a spaceman is badly injured?
In a normal suit they can just carry him inside an airlock, pressurize the chamber, and then undress.
How should they scrape him out of the docked suit if he has broken bones or so, and the door is 80x40 cm  in a meter above the floor?

What if you are in a normal spacesuit and now you have to extract him from that? It wont be like removing a pullover, if it was there'd be no need for fancy suit-locks. Same issue.

36 minutes ago, kerbiloid said:

1.
Almost any sci-fi movie, book, or project describing a lunar/martian ground base. Like Martian, Last Days On Mars, etc.

In pretty much every example, one can assume that they are advanced models beyond what we have now and possibly fulfil all the requirements you state.

****

In most of the sci-fi I read, the trend is for suits to be nano-technological - you walk through a membrane-wall and it leaves a gel-like coating all over your body which acts as a suit. Re-entry reverses the process. Or its a ball of gel that spreads over you on application/activation.

[kerbiloid]

21 minutes ago, p1t1o said:

What if you have a normal spacesuit but the airlock door is deformed or damaged? Same issue.

Then I just get into the door of another airlock.
If a spacesuit docking port is damaged, no door can help.

21 minutes ago, p1t1o said:

What if you are in a normal spacesuit and now you have to extract him from that? It wont be like removing a pullover

I/we will carefully carry him into an airlock on a stretcher or just on hands, put on the floor, close the door, make the air, cut the spacesuit in parts, carefully lift him and put on a bed.

21 minutes ago, p1t1o said:

In pretty much every example, one can assume that they are advanced models beyond what we have now and possibly fulfil all the requirements you state.

If so, why do they have no well-protected working suits, in all their inattractiveness?

Spoiler

P.S.
Why do they never breeze the airlocks with the Martian atmospheric CO2 to dust off not spending air?
Almost always: somebody gets into a chamber and immediately runs air.
In my opinion they must have a cylinder airlock chamber with air intake from above and air suckout below the underfeet lattice.

Edited February 13, 2018 by kerbiloid

[p1t1o]

1 minute ago, kerbiloid said:

Then I just get into the door of another airlock.
If a spacesuit docking port is damaged, no door can help.

Why does an airlock get a whole other spare door but the suit lock is the only way in and out of the station? It makes sense to have a backup airlock as well as suit doors - what if you want to take equipment outside or bring a sample in?

3 minutes ago, kerbiloid said:

I/we will carefully carry him into an airlock on a stretcher or just on hands, put on the floor, close the door, make the air, cut the spacesuit in parts, carefully lift him and put on a bed.

Why is that safer than extracting through a suitlock? Just because you typed "carefully"?

Also, backup airlock door also solves problem.

4 minutes ago, kerbiloid said:

If so, why do they have no well-protected working suits, in all their inattractiveness?

Because its sci-fi, the well-protected suits look very similar to what we might term "light" suits. Or at least that is one plausible explanation. Also much less protection required if there is an atmosphere (ie: on Mars) and pressure-related issues much simpler too.

[kerbiloid]

37 minutes ago, p1t1o said:

Why does an airlock get a whole other spare door

A ground base should have at least two airlocks, like a civil defense vault. Otherwise it's a trap.

37 minutes ago, p1t1o said:

but the suit lock is the only way in and out of the station?

If the base doesn't have airlocks, just suitport ... doors, then if the suitport's own port is damaged it couldn't connect to any of thousand doors.
If the base has an airlock, why bother with the suitports.

37 minutes ago, p1t1o said:

what if you want to take equipment outside or bring a sample in?

In the Martian ship design published here there was a special baby-box for samples. Theproject used suitports, no airlocks.

37 minutes ago, p1t1o said:

Why is that safer than extracting through a suitlock? Just because you typed "carefully"?

Because if he has this

Spoiler

or this

Spoiler

then how can they get him into the base module through a suitport door without taking this off?

So, while they will be pulling him inside he will either bleed to death or his crashed bone(s) will be moving inside making injuries.

With an airlock you just carry him inside, then cut the spacesuit off around the wounded part of body.
Then you just give him medical assistance in usual way.

37 minutes ago, p1t1o said:

Also, backup airlock door also solves problem.

Yes. And makes the suitports unnecessary.

37 minutes ago, p1t1o said:

Also much less protection required if there is an atmosphere (ie: on Mars) and pressure-related issues much simpler too.

Mars is in vacuum. 0.001..0.01 atm is an atmosphere only by name.
Temperature is -100..+30, like on Moon.
Radiation is a bit lesser, but still you would better use a lead belt and codpiece. Also the more numerous are the narrow places - the harder to vent the body.
So, real spacesuits look antiheroically bawdy.

Edited February 13, 2018 by kerbiloid

[p1t1o]

8 minutes ago, kerbiloid said:

If the base has an airlock, why bother with the suitports.

Right, so why dont we just flush the idea of suitports entirely?

You mentioned they had clear advantages and now seem convinced they are dangerous?

Honestly the only place I've ever seen them is on mockups of that mars rover.

 

[kerbiloid]

4 minutes ago, p1t1o said:

Right, so why dont we just flush the idea of suitports entirely?

That's what I mean. Imho, suitports are heresy, but they from time to time are shown in animations, powerpoints, pdfs.
Iirc Constellation ones also mentioned them. And that ESA Martian ship project, too, I'm reading it these weeks.

4 minutes ago, p1t1o said:

You mentioned they had clear advantages and now seem convinced they are dangerous?

They have advantages while everything is going OK.

Edited February 13, 2018 by kerbiloid

[p1t1o]

48 minutes ago, kerbiloid said:

That's what I mean. Imho, suitports are heresy, but they from time to time are shown in animations, powerpoints, pdfs.
Iirc Constellation ones also mentioned them. And that ESA Martian ship project, too, I'm reading it these weeks.

They have advantages while everything is going OK.

Ohhhh ok, we're probably in agreement then.

I think the suitports are quite cool, but best for things like rovers, or minor excursions. A handy nice-to-have, but not a replacement for more robust solutions.

Injured astronauts are going to be tricky no matter which way you cut it, for sure.

[magnemoe]

On 13.2.2018 at 5:22 PM, p1t1o said:

Ohhhh ok, we're probably in agreement then.

I think the suitports are quite cool, but best for things like rovers, or minor excursions. A handy nice-to-have, but not a replacement for more robust solutions.

Injured astronauts are going to be tricky no matter which way you cut it, for sure.

On stuff like an rover you will not have an air lock, if you can not use the suit port you have to depressurize and enter like on the Apollo moon lander. this is also how you will handle an damaged suit lock in this setting. 

An air lock will be build far more sturdy and its unlikely the seal will fail but suits is build to be lightweight. 

More about suit locks http://freefall.purrsia.com/ff1000/fv00981.htm
Interesting suit Florence is wearing, no legs, probably an benefit for her not having human legs, a bit unpractical however since you can not anchor your feet who was common with shuttle missions, not sure if done on ISS: 

[cubinator]

Anyone know what happened to Iridium 911? I saw it rotating pretty fast the other day, like once every 3 or 4 seconds, and wanted to know how it got going like that.

Edited February 14, 2018 by cubinator

[p1t1o]

9 hours ago, cubinator said:

Anyone know what happened to Iridium 911? I saw it rotating pretty fast the other day, like once every 3 or 4 seconds, and wanted to know how it got going like that.

If its a defunct satellite, sunlight pressure could spin it up over a long time.

[NSEP]

If we got a closed container, with 1 litre of volume, where we put 1000grams of water inside, and heat it up untill it boils, to because the density of at 100C water vapor is 0.59 grams per litre does it mean that (1000/0.59=1654) the pressure inside is 1654 times higher then it was before, or does it turn into liquid because the pressure is too high?

[p1t1o]

4 hours ago, NSEP said:

If we got a closed container, with 1 litre of volume, where we put 1000grams of water inside, and heat it up untill it boils, to because the density of at 100C water vapor is 0.59 grams per litre does it mean that (1000/0.59=1654) the pressure inside is 1654 times higher then it was before, or does it turn into liquid because the pressure is too high?

The pressure will rise until it is at a point on the phase diagram where it is happy to be liquid at 100C.

Since water is happy to be liquid at 99C, the pressure rise will only be slight (see chart below, at 100kpa, 100C water is gas, at 101kpa its still liquid) but it will rise. As soon as the pressure rises a bit, the boiling point rises a bit, so thats why you dont get the full 1654atmospheres.

Since water is not 100.0% incompressible (there is always a tiny amount of leeway) there will be a tiny bubble or two maybe, this will account for the rise in pressure - as obviously if the volume doesnt change, the pressure cannot rise in a fixed-volume container.

 

 

[Slam_Jones]

Edit: Never mind, found the answer I was looking for!

Edited February 16, 2018 by Slam_Jones

[Steel]

53 minutes ago, Slam_Jones said:

So I have a question.  Someone posted this in another forum I visit, and I just wanted to see if the math checks out.  My gut instinct is that something is missing from the equation, but I'm not knowlegable enough to know what it is. In summary, the poster claims that an arrow launched vertically by this fictional character will reach 6159M/S before striking the ground (assuming the arrow is 100% heat-resistant).  Frankly this seems outrageously wrong, but maybe I'm the one that's wrong!

Here's the post (in spoiler):

  Hide contents

Physics of Hanzo:

First we need to find delta T, delta X, acceleration, initial velocity and final velocity.

When shooting scatter arrow upwards with no obstacles in the way, the speed for it to come back down is 8 seconds, so our delta T is 8 seconds.

The acceleration is 9.81M/S^2, but since we will be finding the final velocity we will be using this in a negative format.

The initial velocity is 0 because it is starting from a rest.

Now we know the acceleration, time, and initial velocity, so we can find delta X.

Delta X = 0(8S)+.5(-9.81M/S^2)(8S)^2 = -313.92 M.

Now that we have delta X we can find the final velocity.

VF^2=0^2+2(-9.81M/S^2)(-313.92M) = -6159.1104 M/S

If we were using a positive displacement and positive acceleration it would be +6159.1 M/S

Either way this has been completed; the final velocity, which is the speed of the arrow before it strikes the ground is 6,159.1104 M/S. which is 6159M/S^2.

I have a feeling that whoever did those calcs has a very poor grasp of the physics, seeing as they keep confusing acceleration and velocity.

 

Anyway, they've missed the fact that the equation they've used gives the velocity squared, not the velocity. So the the actual velocity is root(6159) which is about 78 m/s

Edited February 16, 2018 by Steel