Moving a Moon
Let’s say some eccentric billionaire like Tony Stark decided that The Moon we have now isn’t just going to cut it. What would it take to move a moon from another celestial body in our Solar System into Earth’s orbit? First things first, let’s ignore a few of the major pressing matters here. We’re going to assume that it wouldn’t have an effect on Earth’s gravity and anything associated with it (Tides, etc.), even though it’d totally mess with everything. We’re also going to ignore how biological life relies on the Moon and stars to navigate (look it up). Really, we’re focusing only on the aesthetics of having a 2nd moon, or replacing our own Moon, with Europa, a moon a Jupiter.
Next, we need to find out the most powerful space rocket we have currently available to us. Yes, Space-X at the time of this post said they’re developing a bigger rocket, but it’s not built yet so we can’t count it. A simple Google search for the keywords “Most powerful space rocket” net me something I already knew but wanted to confirm, the Saturn V rocket as the most powerful space rocket we have. (Source)
- First Stage: 7.46 Million pounds-force thrust for 150 seconds maximum.
- Second Stage: 1 Million pounds-force thrust for 360 seconds maximum.
- Third/Final Stage: 225,000 pounds-force thrust for 500 seconds maximum (two individual burns, grouped).
With this data we can now average out the total force the rocket could push, and for how long, before it’s dead weight to us. The numbers work out to be 1,591,500,000 total pound-force over its 1010 second lifespan before all fuel is exhausted. Adding in the additional fuel for its payload wouldn’t change that that much, maybe add an extra 5 seconds or less, so we’re not going to factor that in as a usable source of additional fuel to increase the total forward thrust, rather we’re going to give that additional fuel as a reverse rocket to push the fuselage off the planet when spent. This is very unlikely, but it’s the most practical way to get rid of the additional mass on the planet and other unforeseen problems. Holy smokes that’s a lot of numbers.. time for a break..
- Mass: 4.7998 x 10^22 kg (aka: 47,998,000,000,000,000,000,000 kg)
Converting pound-force to kg-force is easy, so the rockets are now 721,892,257 kg-force. I’m well aware that kg-force isn’t an actual unit of measure. All I’m doing here is converting pounds to kg, the actual math still checks out here if you convert it back. I did this because I’m Canadian and most of the readers of this site use the Metric system.
The total thrust we would require to push the moon itself, assuming no other gravity gets involved (such as ripping it away from Jupiter, etc) is 6.6475294 x 10^13 rockets, or 664,752,940,000,000,000,000 rockets full of fuel, pushing it on one side, at the same time, expending all of their fuel instantly (instead of over the course of the 1010 second burn). We’d also have to assume that these rockets, since their footprint is now much larger than Earth itself, has some sort of structure to keep them all aligned applying force to the equator of Moon itself. We’re going to assume that it’s made of force fields from Star Trek and therefore, weigh nothing, because that’s an entirely other math problem to conquer.
Assuming no other interactions on the moon itself occurs, that’s what we would need to move Europa to Earth. We’ve still not factored in how to slow it down, and position it into a stationary orbit. I have a feeling that everyone’s brains are hurting after reading all of that, so go take a break, have a smoke if you need it, and come back after this break:
We’d need an additional 1,560,574,000,000,000 rockets to overcome the pull of Jupiter’s escape velocity, breaking it free and pushing it far enough away that another greater force now has attraction on it. Specifically, that thing is now The Sun. The above number also includes the additional rockets to counteract the gravity of the moon itself (inertia). We now require 664,754,500,000,000,000,000 rockets. With each rocket requiring 10 metres of space, we now need an apparatus 10 times larger than the amount of rockets, which is now 6,647,545,000,000,000,000,000 metres in a square shape.
That’s 1.658776 x 10^14 times larger than the circumference of Earth.
We still need to factor in slowing this mass down, and positioning it. We’ll need to save that for another day..