Humor Random Comments Thread
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martins
Orbiter Founder
Hmm ...
mass of electron m_e ~ 1e-30kg
540 billion trillion = 540*1e9*1e12 (assuming short scale)
=> 540 billion trillion electrons ~ 5.4e-7kg = 5.4e-4g
Am I missing something?
If you use long scale defintions for billion (1e12) and trillion (1e18) it overshoots in the other direction.
mass of electron m_e ~ 1e-30kg
540 billion trillion = 540*1e9*1e12 (assuming short scale)
=> 540 billion trillion electrons ~ 5.4e-7kg = 5.4e-4g
Am I missing something?
If you use long scale defintions for billion (1e12) and trillion (1e18) it overshoots in the other direction.
Yup. I've confirmed that. 5.4e-4g
Note for future: calculate before mindless reposting. :blush:
martins
Orbiter Founder
Ah well, don't worry. It's still a picture of a pretty strawberry
The more interesting question is: where did they get the number of 5.4e23 electrons for the "storage of the internet" from? What does that number mean (if anything) and how can it be verified?
Linguofreak
Well-known member
"Billion trillion" is ill-formed in short scale. If it were short scale, it would be "sextillion". Then again, it's also ill-formed in long scale (which I don't think ever goes above "thousand -illion" before going to the next "-illion"), but the construction would be more natural to someone raised on the long scale than the short.
You can reduce the error to a factor of ten (10^28 vs 10^27) if you make a "billion" 10^12 (like the long scale), but make a trillion a thousand million (like the short scale).
My thought is that someone who grew up on long scale but has been using short scale more recently got the two mixed up.
Urwumpe
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Can't test it this week. But the numbers seem to be in a good range. 20000 / 9000 means a mass flow of about 2.2 kg/s which seems to be a little low for keeping a large reactor cool. maybe you are below the possible there and need more mass flow.
If you could get the same pressure and temperature as in the SSME in an NTR with LH 2 as fuel, ISP would be 3 * 4550 = 13650 s with the same nozzle performance. Your engine has a exhaust power of 180 MW.
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Linguofreak
Well-known member
Ah well, don't worry. It's still a picture of a pretty strawberry
The more interesting question is: where did they get the number of 5.4e23 electrons for the "storage of the internet" from? What does that number mean (if anything) and how can it be verified?
Actually, they're calculating how many electrons the internet moves every second. They mention 40 GW as the total electrical power consumed by the internet, and 3 V as the average voltage inside a logic gate. This gives us 1.3 * 10^10 amperes. Divide by 1 second and we get as many coulombs. Divide by the charge of an electron and we get 8.3 * 10^28 electrons, multiply by the mass of an electron and we get 75 grams, which is about 50% off from the quoted 50 grams. Increase the voltage to 4 or 5 volts and/or throw errors from rounding during the calculation, and you get pretty close to 50 grams.
Artlav
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They do?
Astronut25
New member
I couldn't agree more. Most people are scared of the radiation that could be released from an accident, but heres some food for thought.
Sources:Wikipedia said:
http://www.ornl.gov/info/ornlreview/rev26-34/text/colmain.html
http://www.physics.ohio-state.edu/~aubrecht/coalvsnucMarcon.pdf#page=8
BruceJohnJennerLawso
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No problem, all I really need you to do is just look at it... I just need a hand-wavey guess as to what the engine performance is going to be like, and what things the design will require built-in (I hope a decent sheet of lead between the engine compartment & the hab tunnel should prevent the crew from growing in the dark?)
:hmm:
Couple things there, and one thing just dawned on me that Ill need to change...
What would be a reasonable propellant flow for the NTR? Im glad to see that the original estimate missed low, but would optimal be about 7, 8, 9 kg/s? (as a side note I always did wonder why the Orbiter API had calls for flow rate. Why would that be needed if one can just adjust the throttle?
Im not quite sure I follow your point with regards to the SSME comparison. What does your 3*4550 calculation show?
Im not sure whether LH2 makes the most sense as a propellant, due to that irritating disappearing act it likes to play, but it did dawn on me that what the ShuttleD will be really good at is in acting as the interplanetary ejection stage which rendezvouses with the main stack in orbit once assembly is complete, so propellant storage may not matter anyways.
Err two final things, first, are NTR engines limited in # of starts? I thought I read that they can be slowed in terms of fission rate and power production, but I wasnt sure. Secondly, is there a good resource that I could use to figure out how to model the electrical systems (ie buses & their dependent systems)?
Sorry to get so far off track, but it is the Random Comments Thread :lol:
Urwumpe
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Simply said, hydrogen is the optimal propellant for NTR and similar thermal rocket engines. Hydrogen has 9 times less molecular weight than steam which results in [math]\sqrt{9}=3[/math] higher specific impulse. Of course such temperatures are higher than what modern materials can take, without film cooling so only gas core engines can theoretically reach them. If they exist. Fuel flow depends on the thermal power of the reactor. If the mass flow is too low the engine overheads at a set power level. the smallest space reactor had 50 kW thermal if I remember correctly, but was using a different power cycle than a modern NTR. 180 MW might be realistic, but I am not sure. Would need to check this.
You can restart them easily. But the maximum power level drops with reaction rate over time. NASA has some good articles on the NTRS.
You can restart them easily. But the maximum power level drops with reaction rate over time. NASA has some good articles on the NTRS.
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PhantomCruiser
Wanderer
I'm more of a "The reactor vessel is twice larger than necessary" kind of guy.
Quick_Nick
Passed the Turing Test
---------- Post added 10-23-12 at 01:11 PM ---------- Previous post was 10-22-12 at 04:46 PM ----------
I remain amazed at the stupidity induced by human emotions...
EDIT: That wasn't related to the upper post. :lol:
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Izack
Non sequitur
I'm amazed at the number of people who dismiss human emotions as a software bug. :shrug:
