Story Monday March 26 2018

[Don Edwards 548]

4 hours ago, Drasvin said:

The principals of rocket science are fairly easy to explain: Fuel and oxidizer mix in a controlled fashion to provide thrust out the rocket nozzle.

Actually, what comes out the nozzle is a generally-undesirable but (according to current knowledge and theory) unavoidable side effect. The thrust occurs because there is no part of the rocket blocking the nozzle, so the pressure being applied in that direction does not affect the rocket as a whole, while the pressure in the opposite direction is pressing against the wall of the reaction chamber and trying to push the rocket away from the center of the reaction.

1 hour ago, CritterKeeper said:

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

"Then I looked, and behold, four wheels beside the cherubim, one wheel beside each cherub; and the appearance of the wheels was like the gleam of a Tarshish stone. As for their appearance, all four of them had the same likeness, as if one wheel were within another wheel. When they moved, they went in any of their four directions without turning as they went; but they followed in the direction which they faced, without turning as they went.…" - Ezekiel 10:9-10

[Drasvin 123]

2 hours ago, Don Edwards said:

6 hours ago, Drasvin said:

The principals of rocket science are fairly easy to explain: Fuel and oxidizer mix in a controlled fashion to provide thrust out the rocket nozzle.

Actually, what comes out the nozzle is a generally-undesirable but (according to current knowledge and theory) unavoidable side effect. The thrust occurs because there is no part of the rocket blocking the nozzle, so the pressure being applied in that direction does not affect the rocket as a whole, while the pressure in the opposite direction is pressing against the wall of the reaction chamber and trying to push the rocket away from the center of the reaction.

The stuff coming out of the nozzle is very important, due to the fact that rockets primarily operate on Newton's 3rd Law (For every action, there is an equal and opposite reaction). If they didn't expel reaction mass, then they wouldn't work in space. As an action-reaction system, the amount thrust generated by the rocket is dependent on the mass and the exhaust velocity of the reaction mass. In orbit, this can even be achieved with non-combusted gasses and materials, as is often done with maneuvering thrusters, though such systems don't generate as much thrust per unit of mass expelled, as it's much more difficult to accelerate the reaction mass to the same velocities as a combustion-based engine, which is why they're not used as main engines, at least in atmosphere.

The nozzle itself is responsible for expanding and accelerating the combustion gases. The gases are initially moving at subsonic speed as they enter the nozzle system, which then constricts down to the throat. As it constricts, the hot gases are forced to accelerate until the velocity becomes sonic(Mach 1.0). The nozzle then expands, causing the gases to accelerate further to supersonic velocities. By the time the gases exit the nozzle, they should ideally be the same pressure as the ambient atmosphere in order to maximize thrust and ensure a consistent flow of reaction mass.

[hkmaly 490]

17 hours ago, ijuin said:

On 3/28/2018 at 0:32 AM, The Old Hack said:

Hrm. I do not really see what you mean but that may be due to me being very tired. At any rate I am glad we came to some level of understanding.

640K ought to be enough for anybody.

          -- Bill Gates (1981)

Well 640k would definitely have been enough for anybody who was using any desktop machine that was on the market in 1981. By the PC-AT era (286-based), it was definitely limiting.

... you mean, year later?

80286 appeared in February 1982.

9 hours ago, Drasvin said:

The hard part about rocket science is detail work. If you want the rocket to do more than go up, you need to calculate a lot of numbers to figure out how to get it exactly where you want it (or at least close enough for whatever work you're doing). Even simply achieving orbit require calculating what velocity you need to achieve the desired orbit, and then calculating when burns need to be made to reach the needed velocity. If a person wants a rocket to reach another planet or moon or such, then even more calculations have to be made along with proper timing of the rocket's launch(Something I still have trouble with in Kerbal Space Program). Even if a person just wants the rocket to go up and then come down, calculations have to be made in order to get the rocket to come down at the right spot. 

There is also quote lot of work related to fact that most materials don't work for space rocket. You need materials capable of withstanding extreme temperatures - both high AND low. And the rocket needs to be airtight WITHOUT using rubber, as rubber is not elastic in vacuum.

9 hours ago, Drasvin said:

The principals of rocket science are fairly easy to explain

... but, yes, even the proverbial rocket science is not THAT hard if you focus just on basic principles.

[Vorlonagent 442]

2 hours ago, hkmaly said:

... you mean, year later?

80286 appeared in February 1982.

Nobody had any love for the 80186...

[mlooney 3,417]

19 minutes ago, Vorlonagent said:

Nobody had any love for the 80186...

It was used a lot by people making embedded systems.  If Wikipedia is to be believed that was it's primary market. The Dialogic voice / telephone boards that I spent about 10 years working with used an '186 as it's on board chip.

[ijuin 572]

The science behind Rocket Science is easy. It's the engineering that is hard. You have to build something that can withstand extreme heat, pressure, radiation, and vacuum, while also being as lightweight as possible. Too heavy, and your fuel efficiency is shot to hell. Too light, and you'll end up with structural failure during ascent.

[The Old Hack 2,448]

8 hours ago, ijuin said:

The science behind Rocket Science is easy.

I suspect the mathematicians that spent decades working out the necessary formulae for actually getting your payload to where you want it to go while navigating a system with several bodies moving at different speeds and in different directions while gravitationally affecting one another might slightly disagree with that.

[Vorlonagent 442]

16 hours ago, mlooney said:

It was used a lot by people making embedded systems.  If Wikipedia is to be believed that was it's primary market. The Dialogic voice / telephone boards that I spent about 10 years working with used an '186 as it's on board chip.

My first job out of college was doing assembly programming on a 186.  Burning my code onto an EEPROM and plugging it into a chip socket on an industrial computer.  Debugging that code was awful.

[hkmaly 490]

7 hours ago, The Old Hack said:

15 hours ago, ijuin said:

The science behind Rocket Science is easy.

I suspect the mathematicians that spent decades working out the necessary formulae for actually getting your payload to where you want it to go while navigating a system with several bodies moving at different speeds and in different directions while gravitationally affecting one another might slightly disagree with that.

You don't need much of THAT if you want just to the orbit and don't care what orbit would that be. Of course, if you want to hit some specific target, like moon ... well, you might think that moon is big, but it's not THAT big. And of course, if you plan to almost hit five different planets ... or single comet ...

2 hours ago, Vorlonagent said:

19 hours ago, mlooney said:

It was used a lot by people making embedded systems.  If Wikipedia is to be believed that was it's primary market. The Dialogic voice / telephone boards that I spent about 10 years working with used an '186 as it's on board chip.

My first job out of college was doing assembly programming on a 186.  Burning my code onto an EEPROM and plugging it into a chip socket on an industrial computer.  Debugging that code was awful.

Could be worse. At least it had socket. Imagine soldering it on, finding typo, unsoldering ...

(Not that I had any experience with that. Anything I was programming was capable to being reprogrammed over wire.)

[The Old Hack 2,448]

4 hours ago, hkmaly said:

You don't need much of THAT if you want just to the orbit and don't care what orbit would that be.

This is true. But call me old-fashioned, when I am part of a manned expedition headed into space, I would like the calculations to be just a little more exact than that. Especially that bit at the end where you probably want to head back to the Earth without either burning to a cinder or becoming a huge impact crater somewhere. (Admittedly the odds are against that -- a huge splash is more likely by far. But even though the odds of the crater outcome are low, I am sure that those who potentially might live where the crater-to-be is about to form would appreciate more exact calculations, too.)

[hkmaly 490]

17 hours ago, The Old Hack said:

22 hours ago, hkmaly said:

You don't need much of THAT if you want just to the orbit and don't care what orbit would that be.

This is true. But call me old-fashioned, when I am part of a manned expedition headed into space, I would like the calculations to be just a little more exact than that. Especially that bit at the end where you probably want to head back to the Earth without either burning to a cinder or becoming a huge impact crater somewhere. (Admittedly the odds are against that -- a huge splash is more likely by far. But even though the odds of the crater outcome are low, I am sure that those who potentially might live where the crater-to-be is about to form would appreciate more exact calculations, too.)

Sure. I was thinking unmanned expedition. Or expedition manned by some politicians which would be offtopic to name.

[The Old Hack 2,448]

4 minutes ago, hkmaly said:

Or expedition manned by some politicians which would be offtopic to name.

Sadly, if there is one skill such creatures possess in abundance, it is sending others into harm's way while never themselves risking as much as a bruise.

[hkmaly 490]

16 minutes ago, The Old Hack said:

22 minutes ago, hkmaly said:

Or expedition manned by some politicians which would be offtopic to name.

Sadly, if there is one skill such creatures possess in abundance, it is sending others into harm's way while never themselves risking as much as a bruise.

Yes. Unfortunately, they learnt that very well in last two thousand years.

I suspect only reason they are even thinking about stuff like paperless office is they are afraid of papercuts.