What is the mass of the Death Stars?

[Lucky]

There is a tread here where someone calculated the mass of the Bre'el moon by the effects it had and would have on the planet. Is it possible to do the same with the Death Star1 and the larger Death Star2?

[Mike DiCenso]

No, mostly because there are no described gravitational effects caused by the Death Stars to work off from. And since anti-gravity and repulsor lifts and other exotic technologies are involved, it kind of makes the whole idea moot anyway. The best we can do is pick a known material, and try to use that coupled with volumetrics and a rough guess of how much material occupies the enclosed space.
-Mike

[Lucky]

No, mostly because there are no described gravitational effects caused by the Death Stars to work off from. And since anti-gravity and repulsor lifts and other exotic technologies are involved, it kind of makes the whole idea moot anyway. The best we can do is pick a known material, and try to use that coupled with volumetrics and a rough guess of how much material occupies the enclosed space.
-Mike

The second Death Star would not have had those anti-gravity devices working as that would have given away the fact it was fully operational, and when it blew up none of those would be working anyways.

Where are we told the first Death Star had anti-gravity drives? It sounds familiar. Do you have the quote?

Repulsor lifts don't remove gravity. They push off the ground, and we see them fall off cliffs.

[mojo]

the fact that the second death star was not known to be fully operational doesn't mean that the antigrav stuff wouldn't be functional. there were clearly people all over the thing. why would we assume specific equipment to be offline?

[KSW]

the fact that the second death star was not known to be fully operational doesn't mean that the antigrav stuff wouldn't be functional. there were clearly people all over the thing. why would we assume specific equipment to be offline?

The antigrav would have to work, because the DS was way too close to Endor to be in geosynch.

[KSW]

No, mostly because there are no described gravitational effects caused by the Death Stars to work off from. And since anti-gravity and repulsor lifts and other exotic technologies are involved, it kind of makes the whole idea moot anyway. The best we can do is pick a known material, and try to use that coupled with volumetrics and a rough guess of how much material occupies the enclosed space.
-Mike

The second Death Star would not have had those anti-gravity devices working as that would have given away the fact it was fully operational, and when it blew up none of those would be working anyways.

Where are we told the first Death Star had anti-gravity drives? It sounds familiar. Do you have the quote?

From the ANH Novelization:


Antigrav could operate only when there was a sufficient gravity well to push against-like that of a planet-whereas supralight travel could only take place when a ship was clear of that same gravity. Hence the necessity for the dual-drive system on any extrasystem craft.
----
A voice announced over a hidden speaker that they had approached within antigrav range of Alderaan-approximately six planetary diameters.
--


Nothing about "repulsor lifts," those sound the same as antigrav.

Obviously the DS2 would have to have working antigrav to hold it up; it was far too near Endor for it to be in geosynch, unless the planet rotated every 20 minutes.
And the shield-generator certainly wasn't keeping it up there.

[Mike DiCenso]

If the DS2's construction follows along similar patterns to the first one, the first thing constructed for it will be the reactor and north-south running power core, then a structural framework built off that as seen in RoTS. But in that core one might assume there is plenty of room for anti-grav and other propulsion related machinary. Until then, temporary units for the core's components can be attacged or a field projected up from Endor along with the shield. As the battlestation construction progresses, it becomes more self-sufficent.
-Mike

[General Donner]

No, mostly because there are no described gravitational effects caused by the Death Stars to work off from. And since anti-gravity and repulsor lifts and other exotic technologies are involved, it kind of makes the whole idea moot anyway. The best we can do is pick a known material, and try to use that coupled with volumetrics and a rough guess of how much material occupies the enclosed space.
-Mike

That's the method I'd use if I went about it. The closest thing to what the OP appears to be looking for I could find in the EU is this:

The Death Star II is not parked in a naturally synchronous orbit above the Forest Moon, so remaining over one point on the moon's surface requires a considerable uplift force against Endor's gravity. Initially, the station was supported by a repulsorlift field projected from the same ground facility that would eventually supply the station with its defensive shield. Tales told by Ewok shamans relate that the extra weight on the moon's crust had dramatic side-effects, including massive groundquakes, land that shifted and buckled, and lakes that spilled out of their natural basins.

Though I for sure don't have the science background to be able to reverse engineer any hard figures from that, if such a thing is possible.

The snippet does clarify some of the related issues currently under debate, though. They did use repulsors, initially based on the planet (or well, moon) until they could activate the ones aboard the Death Star itself.

[Lucky]

the fact that the second death star was not known to be fully operational doesn't mean that the antigrav stuff wouldn't be functional. there were clearly people all over the thing. why would we assume specific equipment to be offline?

There is no reason to think that the shield generator only generated a shield around the second Death Star.

[Lucky]

No, mostly because there are no described gravitational effects caused by the Death Stars to work off from. And since anti-gravity and repulsor lifts and other exotic technologies are involved, it kind of makes the whole idea moot anyway. The best we can do is pick a known material, and try to use that coupled with volumetrics and a rough guess of how much material occupies the enclosed space.
-Mike

The second Death Star would not have had those anti-gravity devices working as that would have given away the fact it was fully operational, and when it blew up none of those would be working anyways.

Where are we told the first Death Star had anti-gravity drives? It sounds familiar. Do you have the quote?

From the ANH Novelization:


Antigrav could operate only when there was a sufficient gravity well to push against-like that of a planet-whereas supralight travel could only take place when a ship was clear of that same gravity. Hence the necessity for the dual-drive system on any extrasystem craft.
----
A voice announced over a hidden speaker that they had approached within antigrav range of Alderaan-approximately six planetary diameters.
--


Nothing about "repulsor lifts," those sound the same as antigrav.

They are what let speeders fly, and fall off cliffs.

That is the quote I was thinking of, and it makes no sense. It sounds like the author mixed up gravity and magnetism.

Obviously the DS2 would have to have working antigrav to hold it up; it was far too near Endor for it to be in geosynch, unless the planet rotated every 20 minutes.
And the shield-generator certainly wasn't keeping it up there.

There was a shield generator on the moon. There is no real reason to assume the Death Star even had a single reactor running until the emperor wanted to fire his superlaser since the moon base could just be beaming it power.

[Lucky]

The closest thing to what the OP appears to be looking for I could find in the EU is this:

The Death Star II is not parked in a naturally synchronous orbit above the Forest Moon, so remaining over one point on the moon's surface requires a considerable uplift force against Endor's gravity. Initially, the station was supported by a repulsorlift field projected from the same ground facility that would eventually supply the station with its defensive shield. Tales told by Ewok shamans relate that the extra weight on the moon's crust had dramatic side-effects, including massive groundquakes, land that shifted and buckled, and lakes that spilled out of their natural basins.

Though I for sure don't have the science background to be able to reverse engineer any hard figures from that, if such a thing is possible.

The snippet does clarify some of the related issues currently under debate, though. They did use repulsors, initially based on the planet (or well, moon) until they could activate the ones aboard the Death Star itself.

That is what I was looking for. It sounds similar to what was being caused by the Bre'el moon in Star Trek.

I just don't know how to use it.

[Praeothmin]

the fact that the second death star was not known to be fully operational doesn't mean that the antigrav stuff wouldn't be functional. there were clearly people all over the thing. why would we assume specific equipment to be offline?

There is no reason to think that the shield generator only generated a shield around the second Death Star.

Then why didn't the DS start "sinking" towards Endor as soon as the Shield Generator was blown to smithereens?
Why did the Rebels waste time and good ships attacking the DS once the shield was down, instead of simply letting it fall on Endor?

[Lucky]

the fact that the second death star was not known to be fully operational doesn't mean that the antigrav stuff wouldn't be functional. there were clearly people all over the thing. why would we assume specific equipment to be offline?

There is no reason to think that the shield generator only generated a shield around the second Death Star.

Then why didn't the DS start "sinking" towards Endor as soon as the Shield Generator was blown to smithereens?

Because the trap had been sprung, and the Death Star 2 was in fact fully operational.

The Emperor's entire plan hinged on the Death Star 2 appearing to not be operational while being fully operational. The only way to really do that is to not have the DS2's reactor operating

Why did the Rebels waste time and good ships attacking the DS once the shield was down, instead of simply letting it fall on Endor?

Aside from the fact at least some of the Rebel command are total idiots, this is like asking why Earth's Moon does not crash into the Earth. Earth's Moon is in fact getting farther from the Earth every year.
http://www.bbc.co.uk/news/science-environment-12311119

We see the Death Star 2 get farther and closer to Endor so the logical conclusion would be that the Death Star 2's orbit is set to fling it away from Endor for safety reasons, and to help it leave the system.

[Praeothmin]

The only way to really do that is to not have the DS2's reactor operating

Or, you know, JAM their sensors...

Lando: "What do you mean, you can't get a reading?
You should be getting a reading on that shield, up or down!"
Alien: "Brrrppleepdle ffpwefkf fdkwf"
Lando: "How can they be jamming us if they don't know we're..." Realizes the Empire knows they are there...

Sensors were being jammed, which is a great way to have a fully operational Battlestation seem non-operational...
After all, how dumb would the Rebels have to be to think:
"Gee, I'm getting huge power readings from that DS, but it can't be operational because I know the Shield Generator is also pushing on it and keeping it in orbit"...

Aside from the fact at least some of the Rebel command are total idiots, this is like asking why Earth's Moon does not crash into the Earth. Earth's Moon is in fact getting farther from the Earth every year.

Earth's moon is not as close to Earth as the DS II was to Endor.
You yourself said it was too close for Geo-syncronous orbit...
What, are we keeping the Moon at bay with some Earth-generated anti-grav now?

[Lucky]

Or, you know, JAM their sensors...

And jamming takes a lot of power, and tells you there is a trap. It means there is either a fleet there, or the Death Star is operational.

Sensors were being jammed, which is a great way to have a fully operational Battlestation seem non-operational...

That actually is as much of a give away that the Death Star is fully operational as readings the reactor would be. YOu would need a massive power source or sources to do such a thing.

After all, how dumb would the Rebels have to be to think:
"Gee, I'm getting huge power readings from that DS, but it can't be operational because I know the Shield Generator is also pushing on it and keeping it in orbit"...

They are idiots who got lucky. That is canon. They would of all died by crashing into the shield had Lando not been the only guy using his sensors.

Jamming that hides the reactor out put would require a massive power-source...

Earth's moon is not as close to Earth as the DS II was to Endor.

Earth's Moon was at one time far closer to the Earth then it is now.

You yourself said it was too close for Geo-syncronous orbit...

???Where did I say this???

What, are we keeping the Moon at bay with some Earth-generated anti-grav now?

The Moon gets farther from Earth each year, and has been doing that since the Moon was formed. The Moon in billions of years will go flying off into space barring something else happening to it and the Earth first.

You seem to not understand what I was saying. The Death Star 2 was likely being held in orbit by the shield. There needn't be anything keeping the Death Star 2 from falling on to Endor at least by the time of the Rebel attack.