My goal here is to figure out how far, how much energy and how long a ship can tug another body in hyperspace, and what are the other parameters to consider.
There are two main episodes to look at, one which involves Goa'uld technology, Failsafe, the other related to the Asgard's, Unnatural Selection, but I'd lack to focus on the Goa'uld more.
Unnatural Selection may be used to get a very rough estimate of how asgard hyperdrives are hampered, get a factor from something, and just see how it would work when applied to Goa'uld hyperdrives.
But let's directly work on the first episode.
SG-1
Failsafe (5.17)
To go straight to the point, in this episode, a tel'tak opens an hyperspace window close to an asteroid previously tugged by one of Anubis' ships, and thus tugs it away, beyond the other side of Earth... by literally flying through Earth.
Besides the fact that this episode established beyond any doubt that hyperdrives in Stargate could go through densely packed matter, it also revealed that the size of the object, and maybe its mass, determine the amount of energy the hyperdrive will require.
We also know that hyperdrives tax energy increasingly in proportion to the mass of objects the hyperspace brushes against. We may check Memento (season 6) and New Order (season 8) for that later on.
For the moment, we know that ships create subspace bubbles around them to go into hyperspace. This was made clear in the episode Grace (season 7).
It could be that the larger the size of the bubble, the more energy it will tap into the power core.
However, it could also be a question of mass.
My plan is to get a ratio either from "tugged object's size / trip duration", "subspace bubble size / trip duration", or "tugged object's mass / trip duration", for a same hyperdrive.
But before that, let's get a couple of quotes.
That's for the size.CARTER: This image was generated based on satellite observations made over the last few hours. The asteroid has an irregular shape but we've calculated its length from end to end to be approximately 137 km.
Time before impact. Or eventually, fail safe point. We'll see that later.CARTER: I hope you're right. Otherwise in 11 days and 16 hours, all life on Earth will be wiped out.
Shows that the ship's hyperdrive was pushed beyond recommended maximum. We've seen this happen in Tangent, and things go bad when this happens.O'NEILL: I say we nuke it ourselves.
CARTER: We have sufficiently high yield warheads to deflect it. We don't have a multi-stage delivery system capable of reaching the asteroid in time.
DANIEL: Wait a minute, what about the cargo ship that Jacob and I crashed on Revanna during the Goa'uld attack. That must still be there.
O'NEILL: In how many pieces?
CARTER: Our understanding of Goa'uld technology has improved quite a bit. We might be able to fix it.
HAMMOND: How much time?
CARTER: Given the right team, maybe a couple of days.
HAMMOND: I'll assign anyone you need, Major.
DANIEL: Assuming we can fix it, how long will it take to fly back to Earth?
CARTER: Revanna's not exactly next door. Even pushing the engines past 100%, it would take eight, nine days.
TEAL'C: Leaving little margin for error.
So we started at 11 days and 16 hours. Now, they're 3.5 hours from the fail safe checkpoint. There's 39 minutes of travel between the fail safe position and impact point.CARTER: All right. 39 minutes before impact the asteroid will reach the fail safe position. Once it's past that point it will be too close to earth for the explosion to deflect it. That leaves us three and a half hours.
If the former time was relative to ground zero, we'll have to remove 39 minutes from it.
There's also the part about how they passed through the Leonids sooner than Carter expected, so it's possible there's something else to consider.
CARTER: Something's not right. The asteroid's gravitational field is way stronger than we thought.
DANIEL: So?
CARTER: Gravity is determined by mass and mass is determined by size and composition.
DANIEL: So?
CARTER: So the core of the asteroid must be made up of something a lot heavier than nickel and iron.
That's for potential mass cals, but I'm not sure it will be necessary.CARTER: Sir, the asteroid's core is composed almost entirely of naqahdah.
O'NEILL: Of course it is.
CARTER: It makes up about 45% of the total mass.
DANIEL: Of course it does.
See:
It should confirm that the key factor here is the size of the hyperspace bubble.O'NEILL: We get communications back yet?
CARTER: Sorry Sir, we tried. The only way would be to pull the components we used to fix the hyperdrive. It would take hours.
O'NEILL: What then?
DANIEL: Well we have a couple of options. Number one, we give up. Use what's left of power and life support to make it to the nearest unoccupied Gate world. Small chance we'd make it. From there we head to the Alpha site.
O'NEILL: Number two?
DANIEL: We take off and hope that our radio signal can be picked up by the Asgard in time to inform them that this was a Goa'uld attack disguised as a natural disaster.
CARTER: There not enough time for that.
DANIEL: I know.
O'NEILL: Is there a number three?
CARTER: There's no three.
DANIEL: Well maybe there is. Teal'c, you said naqahdah wasn't native to our solar system. Which means that the Goa'uld must have towed it through hyperspace by ship.
TEAL'C: A mothership.
CARTER: Daniel, that's it.
O'NEILL: What's it?
DANIEL: We don't have a mothership.
CARTER: The effect only has to last a few seconds.
O'NEILL: What.. only has to last a few seconds? What?
CARTER: Choice three, Sir. We expand the ship's hyperspace field to encompass the entire asteroid. We take it out of normal space long enough to avoid the collision with Earth.
O'NEILL: Is there a four?
CARTER: I know it sounds far-fetched Sir, and it is.
O'NEILL: You wanna ride an asteroid through Earth?
DANIEL: Yes.
CARTER: To the outside observer, it would disappear on one side and reappear on the other. The problem is, it would take every ounce of power we've got. The field would have to be expanded far beyond its usual envelope. It could cause the engines to explode.
O'NEILL: Explode?
CARTER: Even if we survived the engine overload sir, we wouldn't be able to take off again. We'd have a couple of hours of life support and that's it.
O'NEILL: But you think this is the best shot we have of stopping this rock?
CARTER: Yes Sir, I think so.
O'NEILL: Well that's the plan then.
The cargo ship is in a rift that goes down close to the core of the asteroid.
Eventually, this bit of transcript could provide info on how deep they were, based on speed and the size of the asteroid:
Now they're about to engage the hyperdrive:CARTER: Our scans show the asteroid is potmarked with impact craters and fissures. We fly the ship into the deepest crater we can find at a right angle to its current trajectory. The crater itself should help direct the explosive force of the bomb like a rocket nozzle. When we're a few metres above the surface we ring down the MALP with the bomb. And we land and two of us go EVA.
O'NEILL: That would be me and you.
CARTER: We walk the MALP down into one of the fissures at the bottom of the crater to focus as much as the blast as possible. We set the timer and then we get out of there.
O'NEILL: Piece of cake.
CARTER: There is one other thing. We're about to pass through the Leonids. It's a commentary trail that Earth passes through periodically. The shields should help protect the ship but anyone caught outside is gonna have to find cover, fast.
There's a strange noise.
O'NEILL: What was that?
TEAL'C: I am having difficulty with the sublight engines.
Another strange noise.
DANIEL: Yes, you are.
CARTER: Sir.
Sam gets up and walks into the back room, Jack follows her. She goes to a panel and pushes it, opening it. She checks the crystals.
O'NEILL: What is it?
CARTER: It's building up an overload in the control systems.
O'NEILL: Backups?
CARTER: We don't have any.
The crystals spark and Sam goes down. Jack goes to her.
Scene: SGC Control Room
WALTER: Sir. We just lost SG1's signal.
HAMMOND: SG1, this is Hammond. Do you read me? SG1, please respond.
Walter shakes his head.
Scene: Cargo Ship
Jack is propping Sam up.
O'NEILL: How's the head?
Sam looks confused. Teal'c walks in.
TEAL'C: The sublight engines have shut down.
DANIEL: Big asteroid problem here.
The cargo ship is approaching the asteroid too fast.
Sam, Jack and Teal'c walk to the front of the ship.
CARTER: Try using maneuvering thrusters to slow us down.
DANIEL: I am. It's not working.
Teal'c takes over flying the ship.
TEAL'C: Daniel Jackson is correct. Maneuvering thrusters appear to be insufficient.
CARTER: They're all we've got.
Scene: SGC Control Room
DAVIS: Sir. Deep space tracking still has a fix on the ship but we show them approaching the asteroid way too fast.
Scene: Cargo Ship
The ship is still approaching the asteroid.
O'NEILL: Any time now.
TEAL'C: Thrusters are at full reverse, O'Neill.
CARTER: We're coming in a lot faster than we should be.
DANIEL: Yes we are.
CARTER: Faster than we should with thrusters at maximum. Ninety metres per second. Eighty. This rate of deceleration isn't gonna cut it. We're gonna hit.
The ship plummets.
O'NEILL: What happened?
CARTER: We're inside a deep crater. Fifty metres per second. Forty. Thirty.
The ship plummets but seems to come to a stop a few metres above the ground.
CARTER: We stopped descending.
So by the time they activated the hyperdrive, they were within the last minute before impact.Scene: SGC Control Room
Hammond is watching the countdown go under a minute. He then turns and walks away.
Scene: Cargo Ship
CARTER: I really need more time to make the calculations.
O'NEILL: Well Carter, now might be a good time.
CARTER: Almost.
DANIEL: Now?
CARTER: If I engage too soon we'll reappear right inside the Earth.
Jack looks out of a window.
O'NEILL: Carter, I can see my house!
CARTER: Engaging hyperdrive now!
The asteroid goes into hyperspace and reappears on the other side of the Earth.
CARTER: We're there.
TEAL'C: The navigational computer confirms we have emerged from hyperspace on the other side of the planet.
O'NEILL: Yep, plan three. Works every time.
We see the asteroid continue on past the moon.
Any thoughts and comments are welcome. I'll add my own later on.
