Relatively speaking, I’ve seen it mentioned (here on this board, in fact) that if I want to launch, say, nuclear waste or my mother-in-law into the sun you’d need quite a bit of speed and energy to do so. Usually much more than worth doing (although with my MIL that’s debatable)
At first blush this seems counterintuitive since the sun has a huge gravity field. OTOH, I can imagine crawling out of the Earth’s gravity well might take far more work than it seems. I think of the Apollo missions, but then remember they only needed so much initial velocity until the moon pulled them in—The moon being only 250k miles away as opposed to the sun’s 93 million miles.
Anything you launch from Earth is orbiting the Sun at about the same orbit as Earth - at speed of around 67,000 mph. In comparison, Earth’s surface escape velocity is about 25,000 mph. In order to switch to “lower” orbit - closer to the Sun - you have to slow down. Drastically. That takes a lot of energy.
Newtonian physics, simple as it: an object in motion remains in motion unless a force acts upon it. It’s all about the Δv, change in velocity: slowing a vehicle down enough to plop it into the sun from Earth orbit takes a huge amount of it, given the velocity of an object in that orbit.
Despite its delta-v moving much faster than a much lower orbit around the sun, is there something preventing a single trajectory that simply intersects the sun itself? Or will its high velocity just cause it to go whisking around the sun and off into a highly eccentric orbit?
Δv is required for any change of trajectory. To alter the perihelion of an object in solar orbit so that it intersects the sun requires a change: in this case, a change retrograde (force against the direction of motion). I.e. “slowing it down.” However, a lower orbit around the sun is faster, paradoxically.
The odd, non-intuintive thing about orbital mechanics is you have to slow down to go faster, and vice versa.
ETA: I highly recommend playing Kerbal Space Program to get a real hands-on feel for how this works. I understood these concepts more-or-less from physics before playing the game, but not as well as I do now. You can’t get anywhere in that game without getting a solid grip on orbital mechanics, which, is turns out, is actually really fun!
The energy to escape from earths surface is a lot, but the energy to hit the sun is far more than that.
What the others said, even if you were talking trash from about satellites or moon bases, they take a lot of energy to aim into the sun , at least the energy is the same kinetic energy they have due to the speed of their present orbit. And then add more energy to get them going fast enough to ensure they hit the sun… (you don’t want Earth, Venus, Mercury coming along and interfering with the shot… )
The energy cost of shooting the trash from earth is a bit more expensive than that.
Side note, hope it’s not to much of a hijack but I think the OP has been answered.
Have we ever launched anything into the sun? Could it be done from the ISS? Could we launch/slow a small object down enough that it would fall into the sun?
Unless I’ve missed something, this will be our first attempt at launching something so close to the sun that it could be considered touching distance, and it will require a lot of Venus flybys, which I assume is to slow the probe down enough?`
Not that I know of (ETA, to answer the first question). For the second, sure, provided sufficient thrust. For the third, here’s a fuller explanation:
So the thing that has to happen first is for your craft to be blasted out of Earth orbit into a more or less purely solar orbit. That takes considerable Δv itself (depending on the craft’s mass), but obviously is quite doable. You launch your craft into space, and keep burning prograde, pushing the craft’s apogee until it escapes the Earth orbit. Once it is in solar orbit, you then have to burn retrograde to pull in the craft’s perihelion until it intersects the sun. Dodging the inner planets are their gravitational influences, of course. That takes an enormous about of Δv, by far the biggest step so far. Doable, I’m sure. The question is would it be worth the effort?
Certainly, the equations for the Δv give smaller numbers if the craft is small.
Talking about burning prograde and retrograde is probably easier to understand than “slowing down” and “speeding up.” Burn prograde at apogee (or aphelion) to raise perigee (or perihelion) and vice versa. Burn retrograde to lower same.
Essentially, yes. Doing it all with a burn would be a lot less efficient. Of course the solar probe has other issues, namely to be sufficiently heat resistant to avoid being fried or melted.
Interesting article! I wish it provided more detail about the probe’s trajectory.
To be launched in 2018. Le sigh. Sounds like an interesting mission!
That is, replace “are” with “and.” And dodge them unless you want to use their gravity to help pull your trajectory inward, as per the solar probe mission.
By small, of course I mean the salient issue is low mass, not size per se.