Congressional Candidate Brianna Wu Claims Moon-Colonizing Companies Could Destroy Cities By Dropping Rocks (washingtontimes.com)

Applehu Akbar quotes a report from Washington Times: A transgender-issues activist and Democratic candidate for Congress says the advent of the space tourism industry could give private corporations a "frightening amount of power" to destroy the Earth with rocks because of the Moon's military importance. Brianna Wu, a prominent "social justice warrior" in the "Gamergate" controversy who now is running for the House seat in Massachusetts' 8th District, suggested in a since-deleted tweet that companies could drop rocks from the Moon. "The moon is probably the most tactically valuable military ground for earth," the tweet said. "Rocks dropped from there have power of 100s of nuclear bombs." After users on social media questioned her scientific literacy, the congressional candidate clarified that the tweet was "talking about dropping [rocks] into our gravity well." Small space rocks can indeed do nuclear-weapons-scale damage if hitting the Earth at orbital speeds. But launching one from the moon, even setting aside issues of aiming, would still require escaping the satellite's gravitational field, a task that requires the power and thrust contained in a huge rocket.

Comments

Eh?

[hideki.adam]

The lunar module got off the moon with not much thrust at all, look at the size of it compared to the whacking great rocket that got them there...

Doesn't take all that much to escape the moon actually, you don't need a rocket the size of one required to get off earth...

Aiming, fair enough though.

Re:If he's transgender...

[drinkypoo]

Rocket power? Science fiction has typically suggested that you would use magnetic accelerators to send rocks from the moon to the earth, probably with solar power. It's not trivial, but it's theoretically possible to launch stuff from here to there using these means, let alone from there to here.

I'm not suggesting that it's trivial, far from it. You have to build the track and then you have to build the projectile. But if you're going there to build heavy industry, then yes, you absolutely could throw masses at the planet relatively cheaply.

A huge rocket?

[RobinH]

"But launching one from the moon, even setting aside issues of aiming, would still require escaping the satellite's gravitational field, a task that requires the power and thrust contained in a huge rocket."

Now you're just trolling. The Apollo moon landers managed to take off from the moon with a very small rocket. Yes, you'd need a comparatively larger one to launch a large rock, but the summary is misleading. It certainly wouldn't be a huge rocket. Now, you'd want to launch it retrograde from the moon's orbit so it would be moving slower than the moon's orbit around the Earth. That would make it take on an elliptical orbit around the Earth that picked up speed as it approached the Earth. The moon is going about 3.68 km/s in orbit and the escape velocity is 2.38 km/s so you'd only be going 1.3 km/s relative to Earth. You'd have to kill enough velocity that it would actually hit the Earth, but you're already 2/3 of the way there by escaping the Moon's gravity so it's not a "huge rocket" at all. In comparison, the delta-v required to actually get to the moon is somewhere around 15 km/s. This is basically straight from the plot of "The Moon is a Harsh Mistress." If your goal was to hit Earth with a big rock, you'd probably find it easier to do an asteroid redirect mission and nudge a large near Earth asteroid onto an impact course. Getting to the moon in the first place is about 15 km/s delta-v but getting to a near-Earth asteroid is more like 13.5 km/s, and then you can use something like a small ion thruster or solar sail to nudge it around and hit the Earth 3 passes later.