For Questions That Don't Merit Their Own Thread

[Gargamel]

I know I drove this bus off the cliff, so with a smile I’ll say let’s not get too far off topic (wait, this thread has a topic? That can’t be right), and take this line of jokes too far before Snark rolls in with a scythe and a GWOT (patented Giant Wall Of Text) and explains to us why politics is not allowed on here.   
 

Carry on.  

[Hyperspace Industries]

If you had an electric engine (for example a tungsten resistojet (yes, I just found it on atomic rockets)) with good thrust and in this case double the chemical engine isp, but which is incredibly power hungry, could you power it with a power plant that works like this?:

Essentially, you have a bunch of water, which you slowly electrolyze into hydrogen and oxygen by using power from solar panels, and when you need to do a burn, you use the hydrogen and oxygen you made in a fuel cell to release electricity, this in turn makes water which you could then slowly electrolyze over a long time, for use in your next burn.

This would be a method of powering power hungry engines that have high thrust, and therefore only need a load of electricity over a short time. 

Could this work?

[kerbiloid]

Imho it's the only viable way to launch the Martian ships.

Just the reactor should be placed not on the ship but on a self-propelled shipyard (like the Nucleon/Zues, but ~100 MW electric).

Then it can assemble the ship rom modules, receive and dock water tanks, ionically move (uncrewed) to the outer rim of the Earth sphere of Hill, electrolyze all water into hidrolox and store it in the actively cooled (by same reactor) shipyard cryostats (not in the ship fuel tanks), receive the crew on something Orion-like, pump the hyfrolox from the cryostats into the booster tanks, and let it start away.

Then the shipyard ionically moves to the Moon, drops the empty water tanks to let them land in a crater where the lunar base can take and utilize them as metal scrap, and return to LEO for the next Martian assembly.

[Shpaget]

Any metalworking machinists here? @Gargamel perhaps?

I'm nervously expecting the delivery of my desktop CNC mill (half a step above router) and while waiting through all the delays, I've been ordering tools. I'm hoping to make some aluminum chips and figured it might be a good idea to have some single flute carbide end mills, so I ordered 8 sizes from Aliexpress, three pcs per size. Now that all 24 of them have arrived, I'm filling the tool table and I noticed something unexpected. They all are downcut.  Checking the Ali listing, yep, it says so in the title, so my fault entirely although, their listing titles are usually not quite exact, so I might have disregarded that or didn't even notice it, in any case, I don't think it would be worth the money and hassle to return them so my question is: are single flute downcut carbide endmills of dubious pedigree any good at cutting aluminum? Other than them being the wrong way around, they look ok.

The machine has 2,2 kW 24000 RPM spindle and flood coolant, but it's not high pressure jets, more like decent pour from the single blue segmented hose thing (y'all know what I mean?) Endmills are between 1,5 and 3 mm in diameter.

[Gargamel]

@ShpagetI'm more a lathe guy than a mill guy, and 99% steel, so I really can't answer your question.    But I will say this, buy good tools, and set them up to last.     Cheap tools aren't usually made well, and will have imperfections, affecting your cut quality and the length of the tool's life, forcing you to buy more.   You can quickly see how long it will take to save money by buying the good stuff early on.  Although, while you're learning to setup your machine, having a decent stock of 'expendable' tools, cause you're going to crash some, as you really don't want to shatter that shiny ISCAR endmill.   But once you got it setup, run the good tools.   And don't push the setup, there's no reason to save 45-60 seconds on a 15 minute cycle time running the tools at the top end of their speed range, especially since I doubt you're doing large production runs.    Keep em smooth and keep them cool.  

[JoeSchmuckatelli]

6 hours ago, Shpaget said:

carbide endmills of dubious pedigree any good

 

1 hour ago, Gargamel said:

run the good tools.  

Absolutely concur that buying good tools is actually cheaper in the long run.  Beyond that, it is easier to do good work with good tools! 

I don't know much about metalworking, but it is an absolute truth in carpentry 

[Shpaget]

Thanks anyway. That's exactly the plan. Play around with cheap stuff, learn and break some and gradually try to get better ones. These are $3 end mills, so definitely the bottom shelf stuff. Maybe they'll even live long enough to pay for themselves, if not, no major harm in breaking them. You are correct, I don't expect production runs, it's just a hobby thing. I do plan on getting some decent tools, but you know how much good carbide costs, and I'm the type that will easily fill up the virtual shopping cart to the brim with all the various variations of the same tool (standard end mill for alu, sure, but a longer version would also be good to have, now what about different coatings, I could use some for steel, and some for stainless...). For now, I have a decent collection of cheap stuff and as I go through them I'll try to replace them with brand name.

In any case, I'll keep you guys posted and report back when the machine arrives and I try these things.

[Gargamel]

I’ve been planning on doing a little essay/thesis on metrology in the home shop, perhaps knowing we have some hobby machinists here will spur me to Finish it. 

[Shpaget]

That would be great! I don't think we have many professional or hobby machinists here, but we do have a few tinkerers and 3D printers, and I'm sure some of the lessons would translate to those fields as well.

 

[Gargamel]

1 minute ago, Shpaget said:

That would be great! I don't think we have many professional or hobby machinists here, but we do have a few tinkerers and 3D printers, and I'm sure some of the lessons would translate to those fields as well.

 

That was exactly my thought too. 

[Hyperspace Industries]

How much algae, the tiny microorganism kind, not seaweed, specifically an edible species, would you need to have in order to make one kilogram of algae a day, assuming a regular earth day night cycle, and that you remove the new kilogram once it has been made?

[lrd.Helmet]

1 hour ago, Hyperspace Industries said:

How much algae, the tiny microorganism kind, not seaweed, specifically an edible species, would you need to have in order to make one kilogram of algae a day, assuming a regular earth day night cycle, and that you remove the new kilogram once it has been made?

According to http://allaboutalgae.com/faq/ 
Some species of micro-algae can double in size in 24hrs. So I would assume you'd need 1kg of the stuff.

Edited February 21, 2022 by lrd.Helmet

[ARS]

On 2/21/2022 at 6:25 PM, lrd.Helmet said:

According to http://allaboutalgae.com/faq/ 
Some species of micro-algae can double in size in 24hrs. So I would assume you'd need 1kg of the stuff.

Double that number just in case the yield is less than 1kg

[kerbiloid]

The next question is: can you consume them?
The default answer is no. It causes metabolic dis  des  dec illnesses (the limbs swell, the mood hits mud, etc).
It was  tested in 1960s..1970s.

The best way you can use them is either a nutrition addition for cattle, or a fertilizer/edible substrate for more edible species.

So, actually you can't radically decrease the total amount of organics, rotating in your life support system.

(And it's about, iirc, 15 t per human on the Earth, including the soil humus.)

So, anyway you need a tonne or so of organics per everyone.

As you need same amount of dry food for a 3 year long trip (and anyway can't survive longer in zero-g), this makes the onboard farming useless.

P.S.
Except bonsai. They are funny.

Edited February 22, 2022 by kerbiloid

[JoeSchmuckatelli]

Don't try this at home, kids:

https://www.cnn.com/2022/02/21/us/byu-rocket-fuel-fire-trnd/index.html

 

[TheSaint]

14 minutes ago, JoeSchmuckatelli said:

Don't try this at home, kids:

https://www.cnn.com/2022/02/21/us/byu-rocket-fuel-fire-trnd/index.html

And whatever you do, don't try corning your own black powder. It's really hard to get it proportioned and mixed properly, so it doesn't cake up right, and when you try to light it it just fizzles. And then when Dad finds out he gets super mad, because it's apparently really dangerous or something.

Or, so I hear....

[JoeSchmuckatelli]

My dad's famous 'home chemistry' story is when he and his friends (in the Philippines) left their HS chem class and devised a really stable explosive.  They did not follow a formula; instead they applied the concepts and used stuff they'd cribbed from the lab.  On paper it should have been fantastic... but it was really stable.

So stable they couldn't light it.  Figuring they'd gooned up somehow, they gave up and tossed it into the incinerator.

Some time later they heard a boom.

(The story of my grandfather's response is stuff of legends!)

30 minutes ago, TheSaint said:

corning your own black powder

Oh - and specific to this: "Urine of a wine drinking man" is apparently a traditional corning media.

Strange Tales: Gunpowder and ‘the urine of a wine drinking man’ - The Drinks Business

 

Also, since we are talking about urine and stuff that burns:

Technique to recover phosphorus from urine (phys.org)

 

 

Edited February 22, 2022 by JoeSchmuckatelli

[kerbiloid]

27 minutes ago, JoeSchmuckatelli said:

https://www.cnn.com/2022/02/21/us/byu-rocket-fuel-fire-trnd/index.html

Quote

22 students displaced

Trying to sort and fix the student parts placement?

 

12 minutes ago, TheSaint said:

It's really hard to get it proportioned and mixed properly, so it doesn't cake up right, and when you try to light it it just fizzles. And then when Dad finds out he gets super mad, because it's apparently really dangerous or something.

That's why we should dump any info about someone's medieval rockets.

A gun shot is at least more or less linear at first hundred meters, but two similar rockets to have a ballistic flight predictable?
With ingredients of random composition and quality every time?

[JoeSchmuckatelli]

Unrelated - but also interesting: https://www.sciencenews.org/article/military-towns-integration-segregation-united-states

Plus, Room Temperature Superconductor: The first room-temperature superconductor has finally been found | Science News

Quote

Scientists have reported the discovery of the first room-temperature superconductor, after more than a century of waiting.

 

Edited February 22, 2022 by JoeSchmuckatelli

[TheSaint]

20 minutes ago, JoeSchmuckatelli said:

My dad's famous 'home chemistry' story is when he and his friends (in the Philippines) left their HS chem class and devised a really stable explosive.  They did not follow a formula; instead they applied the concepts and used stuff they'd cribbed from the lab.  On paper it should have been fantastic... but it was really stable.

So stable they couldn't light it.  Figuring they'd gooned up somehow, they gave up and tossed it into the incinerator.

Some time later they heard a boom.

(The story of my grandfather's response is stuff of legends!)

Oh - and specific to this: "Urine of a wine drinking man" is apparently a traditional corning media.

Strange Tales: Gunpowder and ‘the urine of a wine drinking man’ - The Drinks Business

 

Also, since we are talking about urine and stuff that burns:

Technique to recover phosphorus from urine (phys.org)

 

Nice. Yeah, my brother and I were, IIRC, about 12 and 10. We had no recipe either, we were just messing around with sulfur, charcoal, and saltpeter that we bought at Student Science Service in Glendale (God I loved that place). Dad came out to the shed to see what we were doing, and he ended up going off like we thought the gunpowder would.

The worst was when we lit the neighbor kid on fire though. We were making smoke pots: mix sulfur and zinc dust, wrap it into a aluminum foil ball, then wrap that in a paper towel like a little ghost. Lite the paper towel on fire and stand back. We were making these and setting them off in the front yard, kid down the block came and watched, then asked if he could buy one off us for a dollar. We're all $URE! So apparently he went back down the block, gathered up a bunch of his friends in his backyard, said, "Wanna see something cool?" Lit it on fire, THEN HELD IT IN HIS HAND IN FRONT OF HIS FACE! He dropped it pretty quick, but he still got a burn on his palm and lost his eyebrows. His mom called the cops. But, luckily for us, my dad knew more Glendale cops than his mom did. So it morphed from "Attack of the mad scientists," into, "Boys will be boys." But while we didn't face any legal consequences, the domestic consequences were swift and calamitous.

[JoeSchmuckatelli]

4 minutes ago, TheSaint said:

domestic consequences were swift and calamitous.

Sounds like my childhood.  Although, I usually only blew myself up... but I did get two white mice for a Science Fair project (the Maze thing)... which rapidly became 14 white mice.  After my cat ate two, I started selling the mice and garage sale habitrails to other kids at school.

Their parents were... I'm not sure 'thrilled' is the correct word.

[magnemoe]

19 minutes ago, kerbiloid said:

That's why we should dump any info about someone's medieval rockets.

A gun shot is at least more or less linear at first hundred meters, but two similar rockets to have a ballistic flight predictable?
With ingredients of random composition and quality every time?

Who is why rockets for bombardment went out off fashion. back in 1800 they made some sense for carpet bombing as you could put an explosive or incendiary warhead on it, this was very hard with cannon shots. 
However the civil war timed fused ball was not that complex.  An hollow cannon ball, I assume an plug on the front to fill it with gunpowder, at the rear you had an dish over an hole into the charge and the disc was pretty cool in that it was an spiral filled with powder and covered with an sheet metal plate, you punched an hole for the range you wanted. So exploding cannon balls was an thing in the civil war but not in the Napoleonic war. 
But that design should be possible much earlier if you simplify it. Make it more sturdy, fixed timing as this is only for ship to ship use because of cost, accuracy and making many of them is probably the main issue here.

[Admiral Fluffy]

Could Starship recover the HST?

[kerbiloid]

8 hours ago, magnemoe said:

1800 they made some sense for carpet bombing as you could put an explosive or incendiary warhead on it

What explosives in 1800? They hardly had chemistry.

Any rocketry units in Napoleon wars or later until 1930s?

[TheSaint]

1 hour ago, kerbiloid said:

What explosives in 1800? They hardly had chemistry.

Any rocketry units in Napoleon wars or later until 1930s?

Oh, come on now. The Star Spangled Banner, written in 1814 by Francis Scott Key. "...and the rockets' red glare!"