How long can a ZPM last?

[BethDoodle]

We know from S.1,E.15 "Before I Sleep" that Weir babysat the city's 3 ZPM's for ten-thousand years and managed to get them to just barely last long enough. The ZPM's may not have all been fully powered, but for the sake of argument, let's say they were all full. That would mean that each ZPM lasted for 1/3 of that time, or ~3,333 years.

But, that was with only the shields being powered full-time because Weir had "set the city to slumber".

What I'd like to know is how long the 3 ZPM's would have lasted if the city were still submerged and fully populated. Keeping the city powered 24/7 with all those people would have to have eaten up a lot more power than while slumbering.

And, how long would the ZPM's have held out if, on top of all that, the Wraith kept up their siege? Keeping the city submerged attenuated the force of the Wraith beams, but they would still have taken a toll on the ZPM's, I would think.

And, while I'm at it - any guesses as to what the population of Atlantis might be, fully populated?

[garhkal]

I would say fully populated, around 1-2k years.
If the wraith kept up their bombardment, as we saw with just the 1 fully charged ZPM in the Siege.. less than a week!

[epg20]

fully populated, I would say 500-1000 years.

if the wraith kept up the bombardment with all three going, I would say 6 months to a year.

what I wonder is where did they make the z.p.ms' and why didn't they just make more, unless the factory was on a now occupied planet, and the wraith didn't know about it, it should have ben a simple matter to make new ones.

[garhkal]

what I wonder is where did they make the z.p.ms' and why didn't they just make more, unless the factory was on a now occupied planet, and the wraith didn't know about it, it should have ben a simple matter to make new ones.

That question has been asked many a time. The simple answer is since we don't even know HOW they are made, let alone low long it takes/where they were made at, its safe to assume that once they were down to atlantis they couldn't make any more.

[epg20]

I've ben working on that, and I don't have the full story fleshed out, but I do have an answer to that and one or two more questions that, more than likely, have ben asked.

[thekillman]

We know from S.1,E.15 "Before I Sleep" that Weir babysat the city's 3 ZPM's for ten-thousand years and managed to get them to just barely last long enough. The ZPM's may not have all been fully powered, but for the sake of argument, let's say they were all full. That would mean that each ZPM lasted for 1/3 of that time, or ~3,333 years.

But, that was with only the shields being powered full-time because Weir had "set the city to slumber".

What I'd like to know is how long the 3 ZPM's would have lasted if the city were still submerged and fully populated. Keeping the city powered 24/7 with all those people would have to have eaten up a lot more power than while slumbering.

And, how long would the ZPM's have held out if, on top of all that, the Wraith kept up their siege? Keeping the city submerged attenuated the force of the Wraith beams, but they would still have taken a toll on the ZPM's, I would think.

And, while I'm at it - any guesses as to what the population of Atlantis might be, fully populated?

I think all of this has been asked and answered before.

Per ZPM:
Submerged and populated: Close to 3000 years. Powering the city for a normal population actually doesn't nearly cost as much as keeping the shield up.

Submerged, populated and besieged: It's not clear how much energy dissipated, but judging from First Strike it probably wasn't more than an order of magnitude. Since the load on the shield from a siege is much higher than that of the ocean (Otherwise the strategy would be pointless), this would likely cut down the lifetime hard, probably to not much more than decades to a century.

Without submerging a ZPM was depleted in a week or so. So i don't believe that submerging would stretch this all that far. Oh and if we used realistic numbers, Atlantis could not be below the ocean as it would've been boiled away.


Lastly, population estimates are hard. However, it seems that the hundred or so people from the expedition could comfortably bunk up in the main tower. Judging from the amount and relative sizes of the towers, 10 000 or so should be doable.

[BethDoodle]

Thanks everyone for your input!

I think I can now come up with an estimate, but let's get your feedback on it too.

I was thinking that maybe a submerged, fully populated, besieged Atlantis with a full complement of 3 ZPM's might be able to last 100-200 years - if the Wraith bombardment weren't constant but only intermittent.

How does that sound?

[garhkal]

Even submerged, i am not sure if 100 years is doable with 3.. 50 i might see.

[thekillman]

Thanks everyone for your input!

I think I can now come up with an estimate, but let's get your feedback on it too.

I was thinking that maybe a submerged, fully populated, besieged Atlantis with a full complement of 3 ZPM's might be able to last 100-200 years - if the Wraith bombardment weren't constant but only intermittent.

How does that sound?

It varies heavily based upon a number of assumptions. If i recall correctly, the submerged scenario ended up with a 10^28 or so joule estimate for the ZPM. Other estimates (Blowing up a planet) Puts that at 10^33 (that's 5 orders of magnitude higher!) while episodes like Trinity put it at 10^40-ish.

The biggest question is one of charge, or "how full is the ZPM when we found it?". Especially Rising is a very questionable case; The ZPM's were likely close to depletion when Atlantis was abandoned, as the Ancients did not think of any measures to resurface the city nor did they care to take the ZPM's with them. It's probable that under siege, the city would only have lasted a short while.

The question then becomes, "how much power does a standard ZPM hold?" which is very difficult to answer. Trinity is not a clear case because it's a comparison to a ZPM and not an actual one. Rising only involves having the shield up, no bombardment. The Siege involves a rare scenario where the Hiveships output far, far more power than in any other case, giving the hint that maybe something else is going on. Enemy At The Gate is a scenario which too is unclear.

However, in all cases the most reasonable case remains 10^33 joules, as the fear of blowing up planets is fairly equal among the ZPM blowing up cases.

How long a ZPM can last is variable, as it's clearly a device with a set amount of energy that it can drain however fast it likes. However, regarding how long Atlantis lasts is a question of how big a fleet is attacking.




Let's examine The Siege closer. Atlantis is only expected to last days against a 10-hive fleet. However, something is clearly wrong. Against a device that we assume holds 10^33 joules, that's a LOT of power. Yet the mode of failure is clearly stated to be ZPM draining. Every other case however shows that Hiveships do not output this much power. Mckay does state that the shield is under incredible strain. It's not clear what "a couple of days" means exactly, but judging from terminology i'd say 6 days max (else he would've said a week).

So 518400 seconds of bombardment (3600*24*6) for 10^33 joules is 1,9E27 watt. For 10^27 thats 10^21 watt. A kiloton is 4E12 joules, so we're talking Teratons at least. This is clearly not regular Wraith firepower, so it seems more logical to me that the shield was at breaking point. Remember that the Wraith sent 12, which probably means that Atlantis would likely have been destroyed in hours or seconds if the full fleet had been there. Also, in Enemy At The Gate the shield clearly has a shield integrity, Atlantis was just never stressed that far before.

In First Strike the beam is a sustained one, with the shields at max. This time it's 29 hours (at a full 10^33 joule ZPM, that's 9,6E27 watt) or about 5x more energy than our first (lowest number) case. This may indicate a number of things, including that the Siege ZPM had less energy (e.g. only 20% charge vs 100%) or that 6 days is too much.

Looking at the submerger solution in First Strike, the beam is attenuated about 30% (29 hours, buys 10 hours). Mckay comments that for the Wraith bombardment it was "far more". However, if we're gonna get to, say, a decade you'd need a LOT of attenuation. For instance, if we assume that the shield in The Siege would've lasted a week, then to last a year you'd need a 52x dissipation rate (or a beam weakened by a factor 1/52 or 98%)


So the conclusion is that if the Wraith attacked Atlantis, with 3 ZPM's, it would likely not last beyond a decade. If we assume Atlantis was only attacked near the end of the war (which lasted a century) then that makes sense: atlantis was abandoned when it's ZPM's were close to failure, and once not under strain it could still last 10 millenia.

[BethDoodle]

It varies heavily based upon a number of assumptions. If i recall correctly, the submerged scenario ended up with a 10^28 or so joule estimate for the ZPM. Other estimates (Blowing up a planet) Puts that at 10^33 (that's 5 orders of magnitude higher!) while episodes like Trinity put it at 10^40-ish.....................

OMG! If I were ever to go back to college for my third degree it would likely be for an engineering degree. If I do, can I hire you write all my papers?

Or at least to proof them all?

Delighted LOL!

What a well-thought-out, impressive response! One that is wasted on me seeing as my actually-earned degrees are in Computer Science and Anthropology.

But, it has helped me so that I think I'll be able to come to a reasonable conclusion concerning my particular need - which is to figure out the whole how-long-can-a-ZPM-last for a fanfic.

Thank you everyone for your help!

Much appreciated!

[garhkal]

Let's examine The Siege closer. Atlantis is only expected to last days against a 10-hive fleet. However, something is clearly wrong. Against a device that we assume holds 10^33 joules, that's a LOT of power. Yet the mode of failure is clearly stated to be ZPM draining. Every other case however shows that Hiveships do not output this much power. Mckay does state that the shield is under incredible strain. It's not clear what "a couple of days" means exactly, but judging from terminology i'd say 6 days max (else he would've said a week).

So 518400 seconds of bombardment (3600*24*6) for 10^33 joules is 1,9E27 watt. For 10^27 thats 10^21 watt. A kiloton is 4E12 joules, so we're talking Teratons at least. This is clearly not regular Wraith firepower, so it seems more logical to me that the shield was at breaking point. Remember that the Wraith sent 12, which probably means that Atlantis would likely have been destroyed in hours or seconds if the full fleet had been there. Also, in Enemy At The Gate the shield clearly has a shield integrity, Atlantis was just never stressed that far before.

You also need to take into account, that
A) they also suffered bombardment from all those darts going 'Balistic" into the shield just after it came on, and since Atlantis was already damaged maybe some power was 'bleeding off'
B) they also kicked in the cloak' which might have drained a lot MORE power.

[thekillman]

OMG! If I were ever to go back to college for my third degree it would likely be for an engineering degree. If I do, can I hire you write all my papers?

Ha ha, well you're talking to an engineer . no problem

You also need to take into account, that
A) they also suffered bombardment from all those darts going 'Balistic" into the shield just after it came on, and since Atlantis was already damaged maybe some power was 'bleeding off'
B) they also kicked in the cloak' which might have drained a lot MORE power.

A: the kinetic energy of darts is laughable compared to the power output of the bombardment
B: The cloak has absolutely nothing to do with the power of the shield during bombardment. Unless i'm missing your point.

[garhkal]

Ahh forgot the shield got kicked over to the cloak AFTER the bombardment stopped..
As to the darts though, didn't Mccay say EACH one was like a couple of hundred megatons worth of impact.??

[thekillman]

Ahh forgot the shield got kicked over to the cloak AFTER the bombardment stopped..
As to the darts though, didn't Mccay say EACH one was like a couple of hundred megatons worth of impact.??

nope.

At 10 000 km/h (what zelenka says: "their approach is ballistic, speeds in excess of ten thousand kilometers per hour") the kinetic energy of the velocity alone is 10^8 (m^2/s^2). So unless you're dealing with darts that each weigh about 100 tons a piece (since there clearly weren't 1000 darts) you wouldn't even reach a kiloton.

After all:

1kg dart @10 000 km/h : 10^8 Joule
10 ton dart: 10^12 joule (a quarter of a kiloton TNT eq)
10 000 ton dart: 10^15 joule (a quarter of a megaton).

The amount of dots, if memory serves, was only a couple of dozen.

Even if we double the speed: we get 4*10^8 joule for a 1kg dart (and so you can just use above table to extrapolate the numbers).

The new JSF weighs about 28 ton max, and it's fairly clear that darts aren't that big compared to modern fighters. Furthermore, they're supposed to be organic in nature which has a lower density than stuff like titanium and aluminium. (organic matter density is in the vicinity of water, after all).

To reach a kiloton you'd need to have a 30 ton Dart go about 11500 km/h.
To reach a megaton you'd either need a thousand dart or you need a single dart to go 32 times as fast. Either case, i think it's safe to say that the Dart Rain was peanuts. Unless i stretch the numbers REALLY thin, 10^27 joules per second isn't even remotely reached.

[BethDoodle]

I just found the answer to my question about what the population of Atlantis might be fully populated.

I recalled someone saying in an episode (don't recall which one) that searching Atlantis room-by-room would be the equivalent to searching Manhattan. I then checked on the Stargate Wiki and they have several mentions that Atlantis "has approximately the same internal space as found in Manhattan".

According to Wikipedia, Manhattan has "a Census-estimated 2014 population of 1,636,268".

Wow! Atlantis is bigger than I thought!