For Questions That Don't Merit Their Own Thread

[kerbiloid]

http://www.astronautix.com/g/groettrup.html

http://www.astronautix.com/g/g-2.html

 

[Spacescifi]

 

In scifi, space war often features high casualties, and I tend to think that is unrealistic.  Here is why:

 

Space war favors machines and robots over crews.... any day of the week. Why? They weigh less overall and can pack far more weaponry and better engines.

If you take for example a battle between two nuke pusher plate Orions, the only difference being one has a crew and the other has no crew and traded all life support for extra weapons payload, then the crewed vessel will be at a serious disadvantage.

 

No matter how advanced scifi tech becomes, crewed space warships with large numbers does not seem reasonable when noncrewed vessels fight better anyway.

I can see a small command vessel with a tiny crew sure, protected by a fleet of heavy noncrewed warships yes.

So the casualties of space war should be few if any.

 

Orbital bombardment is another story...

Edited January 1, 2020 by Spacescifi

[magnemoe]

2 hours ago, Spacescifi said:

 

In scifi, space war often features high casualties, and I tend to think that is unrealistic.  Here is why:

 

Space war favors machines and robots over crews.... any day of the week. Why? They weigh less overall and can pack far more weaponry and better engines.

If you take for example a battle between two nuke pusher plate Orions, the only difference being one has a crew and the other has no crew and traded all life support for extra weapons payload, then the crewed vessel will be at a serious disadvantage.

 

No matter how advanced scifi tech becomes, crewed space warships with large numbers does not seem reasonable when noncrewed vessels fight better anyway.

I can see a small command vessel with a tiny crew sure, protected by a fleet of heavy noncrewed warships yes.

So the casualties of space war should be few if any.

 

Orbital bombardment is another story...

Agree, history also point to this, Naval or air combat are technical branches, most deadly naval engagement in 20th century was the Battle of Leyte Gulf with 15.500 dead. However this was multiple engagements, Jutland was 8.500 dead. 
Compare this to ground battles. Space will be way more automated.
Now you probably have heavy armored orbital bases with lots of crew, doing stuff like repair and refit of warships and launching missile swarms and having some serious energy weapons but they would not have much more personnel than an super carrier. and would be armored with some hundred meter of regolith. 
The smallest combat crafts would be more like an missile torpedo boat, mostly because space combat takes a lot of time so you will spend months on an mission. 
 

[kerbiloid]

I believe, in a space war with asteroid bases and high-velocity crafts, the main form of combat will be an exchange with waves of single-use uncrewed missile carriers, launching a swarm of single-use gamma/xray-laser bombs.

Every wave is a fleet of one hit.
They will be building a fleet after a fleet and send them towards the enemy location.

This means that only ability of fleet building will decide who wins, and the primary objective is to disable the enemy's constructions sites.
The most important part of it is a power station. The most vulnerable and unlikely protected its part is a coolling system. It should be on surface even if the base itself is under a kilometer of rock (the regolith is a thin layer of milled rock on top).

So, the space war will look like an exchange with 1-2 waves of uncrewed carriers of gamma/xray lasers hitting the the enemy shipyard radiators.
The carrier itself after releasing all laserbombs will just ram the area itself, also polluting it with isotopes to prevent its fast repair.

[Spacescifi]

Yeah I have thought similarly.

 

Space war is a numbers game, and beyond having superior firepower there is no way to beat an opponent thay can crank out more spacecraft and weapons than you can.

Clever tactics won't even save you, unless your opponent is very incompetent, which is highly unlikely.

And suicidal ramming is very much a viable tactic when no crew are involved. Especially since it is considerably harder to make a spacecraft go boom when it is not even pressurized.

Edited January 2, 2020 by Spacescifi

[ARS]

Is there any expiration date for unused nuclear fuel rod? Assuming the fuel rod is still brand new, how long can it be stored while still could be used in nuclear reactor?

[kerbiloid]

Probably widely varies depending on the fuel composition (U & Pu). Probably from years to millions.
A well-known expiration of a just produced Pu-nuke is ~10 years (due to its pollution with short-living isotopes of Pu), then it must be recasted. Probably, for the Pu rods/pellets it's something similar.

But unlikely somebody manufactures it in advance without a solid contract and proper date.

Edited January 4, 2020 by kerbiloid

[magnemoe]

1 hour ago, kerbiloid said:

Probably widely varies depending on the fuel composition (U & Pu). Probably from years to millions.
A well-known expiration of a just produced Pu-nuke is ~10 years (due to its pollution with short-living isotopes of Pu), then it must be recasted. Probably, for the Pu rods/pellets it's something similar.

But unlikely somebody manufactures it in advance without a solid contract and proper date.

Nuclear bombs are more fine tuned than nuclear reactors. Imagining they just make the fisjon part of the warhead large enough to get fusion and its pure Pu. 
For the fuel rod, if its just reactor enriched uranium it would last for millions of years as you say, chemical breakdown is more of an issue. 

[kerbiloid]

35 minutes ago, magnemoe said:

Nuclear bombs are more fine tuned than nuclear reactors. Imagining they just make the fisjon part of the warhead large enough to get fusion and its pure Pu. 

Tuning doesn't matter. You can't make pure Pu from scratch. A new-born Pu is polluted with other, short-living, isotopes of Pu. They decay and decrease the nuke's possible yield.
It's like wine, it needs to be exposed for several years.
So, a decade after making the nuke you have to melt it, sort out the decay products, and get an older, more tasty Pu, more storable.

As this is unsignificant for fuel pellets (you don't store them for decades ready to use), this probably means that any produced Pu fuel pellet should be melted after a decade-like period.
And as you make them on contract, this means it doesn't matter can it be stored for ten years or for a hundred.

[Spacescifi]

 

Say I give everyone in the USA a laptop size device that provides infinite amounts of electricity. You can run how ever much power you want from the device, the only limits are thermal ones based on where the power goes to, like the cord taking the power and where the power is going. The device itself will nevet overheat, but the electricity it is pumping out can overheat stuff if the power is too high.

 

What can we improve techwise and what is still beyond our reach?

 

Can we do SSTO's with 40 ton payload finally?

[ARS]

What I'm gonna do? Since there's around 330 million people in US alone, just gather all of the infinite batteries, connect all of them into a a network of cold temperature superconductive power line, which then connects into a field of high-energy supercapacitors to power a mass driver for sending things to space in one shot (idk the power requirements for that, someone please double check it with laptop battery power output x US population before putting the result into railgun formula of lorentz force that provides propulsion for the payload (assume 1 ton), and ignore the rails getting disintegrated during use, we do it for the lolz)

[Arco123]

19 minutes ago, ARS said:

What I'm gonna do? Since there's around 330 million people in US alone, just gather all of the infinite batteries, connect all of them into a a network of cold temperature superconductive power line, which then connects into a field of high-energy supercapacitors to power a mass driver for sending things to space in one shot (idk the power requirements for that, someone please double check it with laptop battery power output x US population before putting the result into railgun formula of lorentz force that provides propulsion for the payload (assume 1 ton), and ignore the rails getting disintegrated during use, we do it for the lolz)

You cant go to orbit in on shot. We tested this with our battleship cannon pointed upwards experiment.

[Spacescifi]

21 minutes ago, Arco123 said:

You cant go to orbit in on shot. We tested this with our battleship cannon pointed upwards experiment.

 

Yeah I was curious... since the irony is that even with scifi stuff we do not have, there are hard limits on what we cam actually do.

Infinite electrical power won't make us all powerful.

What it will do is kill our dependence on gas power and make recycling and powering machines an easy thing.

What it won't do is get rid of your electric bill, since the state will enforce device registration and charge by power usage.

So not much changes after all... so long government gets involved... and they would.

[kerbiloid]

2 hours ago, ARS said:

What I'm gonna do? Since there's around 330 million people in US alone, just gather all of the infinite batteries, connect all of them into a a network

Spoiler

 

[ARS]

What is the connection between the ambient air temperature with it's relative humidity? If the temperature drops, does it means the relative humidity rises? And also, if the temperature rises, does the relative humidity drops? Is it possible to have 0% or 100% relative humidity?

[kerbiloid]

https://en.wikipedia.org/wiki/Heat_index

[Terwin]

15 hours ago, ARS said:

What is the connection between the ambient air temperature with it's relative humidity? If the temperature drops, does it means the relative humidity rises? And also, if the temperature rises, does the relative humidity drops? Is it possible to have 0% or 100% relative humidity?

Relative humidity is the amount of water in the air compared to the maximum amount that can be held at the current temperature.

Clouds, Fog and Dew are formed because the air cools off too much for the water currently in the air(> 100% humidity) and so it condenses.

Generally speaking, if it is raining, then the humidity is at 100%.

If the temperature rises and there is no source of moisture, then relative humidity goes down.

While 0% relative humidity is theoretically possible, it is only ever achieved in controlled circumstances(air-tight chamber with pure nitrogen atmosphere for example).

[Exploro]

I was wondering if my understanding of an analog Absolute Magnetic Encoder is sound.

In a project this last semester we used such a sensor for a wind vane. The signal output range was between 0 volts and 5 volts. As the encoder rotated through 360 degrees the voltage would increase to the maximum output and then reset to zero. While that was easy to understand the relationship between voltage and position, the data sheet never made clear as to how the sensor was generating the signal. But the project also had us working with Hall Effect sensors, which had me thinking.

The magnitude of Hall Voltage, Vh, is directly proportional to the magnetic flux acting on the conductor of the sensor. Thus is is safe to assume that it is the magnetic flux that is changing as encoder rotates, and in turn, causes the change in the voltage signal of the encoder?

Edited January 6, 2020 by Exploro

[Wjolcz]

Is there any way to check if there are any satellites operating at around 4462.3 MHz?

[ARS]

If we want to create a self-sustaining and developing population on a colony in another planet, how many colonists (minimum amount in a single colony ship) that must be sent there? Assuming that the infrastructure, resources and logistics to go there is available. Also, what's the qualifications that must be passed in order to become colonist?

[Arco123]

I don't know much but I do know that at least 600 people are needed. They also have to enforce strict stuff and make the population grow as much as possible. There should be a lot of diversity between colonists so there's no holes. Skilled people are needed to run or program the things and even people with less skill are needed to do things. Much of it relies on diversity though. 

[linuxgurugamer]

36 minutes ago, Arco123 said:

I don't know much but I do know that at least 600 people are needed. They also have to enforce strict stuff and make the population grow as much as possible. There should be a lot of diversity between colonists so there's no holes. Skilled people are needed to run or program the things and even people with less skill are needed to do things. Much of it relies on diversity though. 

Curious as to where you got the “600” from. 

[Okhin]

I would say it depends a lot of what you have as tutoring tech. Skills is mostly a matter of hour spent learning, and this can be done during travel for instance. Depends also on drones. If you have drones and robotic servants, you'll mostly need engineer and technicians to be able to monitor, repair and program them. Agricultural skills can be limited at first, running an hydroponic farm can probably be automated a lot.

So, your colony is mechanized now and just need supervision. This supervision can be tricky, because you need background understanding of the specific system yur monitoring (for instance, you need to know at least about nitrates for growing plants, even in hydroponics) and it can require that humans have to do the job once in a while, to supplement a failing drone. But then, that's mostly tutoring tech, so a huge databases of all the knowledge, in read/write mode (a bit kind of a wiki) is needed at some point. As well as information tech skilled people (again, probably to monitor digital agents and assets, and fix them when needed).

One thing you absolutely wanna do is have a high bus factor. The bus factor is defined as follow : How many people needs to be in the same bus when it have an accident and they all die for my organization to survive. When you look at company you would be surprised to note that it really often is one (for instance, the one guy who got the key to the office. If he dies in a bus accident, no one can enter the office, that's why you want more than one people with access to critical infrastructure … which then reduce the security of the access to said structure, extremely interesting topic, but then I digress).

Basically, your first batch of colonist must have basic training is as much field as needed. Training that can be acquired during travel, but you do not want to have high skilled specialists at first, you want people who can work their way around unexpected stuff (because you'll have), being able to fix, repair and improve the tech, to be able to fix, repair and improve people, and to be able to fix, repair and improve social structures. Once everything is on the rail, you can have people specializing, which will happen naturally because of personal interests and the fact that you cannot know everything (or at least, you can only work some specific amount of time per day, and you need to share works with fellow colonists).

To maintain and grow a population, you'll need to have some medical and genetic tech. The higher your tech level is, the less people are needed. For instance, if you have exowombs and a diverse enough gene bank (that can be different from the colonist you send), you can grow your population following the growth of your outpost, with most of the adult of the trip in charge of raising the children, and teaching them (again, tutoring tech will help).

The biggest issue is, I think, the social structure. We humans do not fare well alone or in cramped space with a limited number of people. That's one of the key recruitment issue for astronauts, you want people who can manage loneliness well, because their next email from his family is 2 light years away. Forget also about chatting with your relatives of planet, the communication lag makes it non practical (having to wait hours or month between sentences, makes conversation over long distance weird loveed up and inefficient). So your initial group should be big enough for colonists to find their social needs among the group.

What size is that group ? I think that going under ten is to low. Even ten is a low number. It's nice because a small group of people, means the strain on locally sourced resources is low, but your bus factor is low. And if the social structure is not strong enough, the colonists will eventually fights each other or be depressed and kills themselves, leading to a colony failure. One thousands seems like way too much and complex. Especially if you have one thousand people active on day one, that would requires a lot of planning and preparation before hand, remotely done without any live feed of what's happening there.

So, I'll guess anywhere between one to three hundred would be enough. Think nomadic tribes for instance, you want to stay in this kind of size. Your bus factor can be quite high, the initial planning can be low, especially if your space ship can be canibalised, their enough people for individual to satisfy their social needs, and it can take one or two severe catastrophic issues, leading to swath of colonists dying. Pack that with exowombs, a diverse gene banks, a good computer with  lot of tutor tech and entertainment, and you should be able to do something permanent.

I really think that going under the thirty people is not viable, if you want a hard limit.

[Arco123]

1 minute ago, linuxgurugamer said:

Curious as to where you got the “600” from. 

Somewhere in my mind. I got it from a video somewhere though. I'm thinking 600-6000 rn. 

[linuxgurugamer]

1 minute ago, Arco123 said:

Somewhere in my mind. I got it from a video somewhere though. I'm thinking 600-6000 rn. 

Well, there are two possible reasons for that number.  The first would be just needing enough hands to get the work done, and the second woulf be for genetic diversity.

The only places I’ve seen numbers is in fiction, and the numbers ranged from a low of 50 on up.  Ignore the labor part (no pun intended),  the best way to find out any realistic number would be to look ar real world examples of isolated populations.  Not something I’m going to do, but the data is there; there have been enough isolated populations that a reasonable answer could be found.  Doesn’t have to be people either.