# Why's it so hard to fire something into the sun? **URL:** \ **Category:** Factual Questions\ **Created:** [May 24, 2014, 8:38pm UTC](https://boards.straightdope.com/t/whys-it-so-hard-to-fire-something-into-the-sun/689208 "2014-05-24T20:38:16Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![cmyk](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cmyk/32/3353_2.png) [@cmyk](https://boards.straightdope.com/u/cmyk)\ **Post date:** [May 24, 2014, 8:38pm UTC](https://boards.straightdope.com/t/whys-it-so-hard-to-fire-something-into-the-sun/689208/1 "2014-05-24T20:38:16Z")
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. Is that the gist or am I missing some detail(s)? ---
**Author:** ![Terr](https://avatars.discourse-cdn.com/v4/letter/t/839c29/32.png) [@Terr](https://boards.straightdope.com/u/Terr)\ **Post date:** [May 24, 2014, 8:42pm UTC](https://boards.straightdope.com/t/whys-it-so-hard-to-fire-something-into-the-sun/689208/2 "2014-05-24T20:42:53Z")
> [@cmyk](#): > > 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. > > Is that the gist or am I missing some detail(s)? 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. ---
**Author:** ![cmyk](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cmyk/32/3353_2.png) [@cmyk](https://boards.straightdope.com/u/cmyk)\ **Post date:** [May 24, 2014, 8:44pm UTC](https://boards.straightdope.com/t/whys-it-so-hard-to-fire-something-into-the-sun/689208/3 "2014-05-24T20:44:40Z")
:smack: That’s what I was overlooking… A subtle but critical detail. ---
**Author:** ![Knorf](https://avatars.discourse-cdn.com/v4/letter/k/58956e/32.png) [@Knorf](https://boards.straightdope.com/u/Knorf)\ **Post date:** [May 24, 2014, 9:01pm UTC](https://boards.straightdope.com/t/whys-it-so-hard-to-fire-something-into-the-sun/689208/4 "2014-05-24T21:01:12Z")
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. ---
**Author:** ![cmyk](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cmyk/32/3353_2.png) [@cmyk](https://boards.straightdope.com/u/cmyk)\ **Post date:** [May 24, 2014, 9:04pm UTC](https://boards.straightdope.com/t/whys-it-so-hard-to-fire-something-into-the-sun/689208/5 "2014-05-24T21:04:23Z")
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? ---
**Author:** ![Knorf](https://avatars.discourse-cdn.com/v4/letter/k/58956e/32.png) [@Knorf](https://boards.straightdope.com/u/Knorf)\ **Post date:** [May 24, 2014, 9:08pm UTC](https://boards.straightdope.com/t/whys-it-so-hard-to-fire-something-into-the-sun/689208/6 "2014-05-24T21:08:51Z")
> [@cmyk](#): > > 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](https://kerbalspaceprogram.com/) 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! ---
**Author:** ![cmyk](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cmyk/32/3353_2.png) [@cmyk](https://boards.straightdope.com/u/cmyk)\ **Post date:** [May 24, 2014, 9:10pm UTC](https://boards.straightdope.com/t/whys-it-so-hard-to-fire-something-into-the-sun/689208/7 "2014-05-24T21:10:56Z")
I think I see what you mean: Basically, to get the the sun faster, you have to slow it down, otherwise it’ll circle the sun for god knows how long. ---
**Author:** ![Knorf](https://avatars.discourse-cdn.com/v4/letter/k/58956e/32.png) [@Knorf](https://boards.straightdope.com/u/Knorf)\ **Post date:** [May 24, 2014, 9:14pm UTC](https://boards.straightdope.com/t/whys-it-so-hard-to-fire-something-into-the-sun/689208/8 "2014-05-24T21:14:39Z")
> [@cmyk](#): > > I think I see what you mean: > > Basically, to get the the sun faster, you have to slow it down, otherwise it’ll circle the sun for god knows how long. Yep. ---
**Author:** ![Senegoid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/senegoid/32/6606_2.png) [@Senegoid](https://boards.straightdope.com/u/Senegoid)\ **Post date:** [May 24, 2014, 9:15pm UTC](https://boards.straightdope.com/t/whys-it-so-hard-to-fire-something-into-the-sun/689208/9 "2014-05-24T21:15:21Z")
> [@Knorf](#): > > 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. Too bad we can’t use regenerative braking to “slow it down” and somehow beam all that recovered energy back down. ---
**Author:** ![Knorf](https://avatars.discourse-cdn.com/v4/letter/k/58956e/32.png) [@Knorf](https://boards.straightdope.com/u/Knorf)\ **Post date:** [May 24, 2014, 9:19pm UTC](https://boards.straightdope.com/t/whys-it-so-hard-to-fire-something-into-the-sun/689208/10 "2014-05-24T21:19:23Z")
> [@Senegoid](#): > > Too bad we can’t use regenerative braking to “slow it down” and somehow beam all that recovered energy back down. If the æther were real, this might have been possible… ETA: er, wait, even then it wouldn’t work. The æther wasn’t supposed to affect matter or energy, only electromagnetic waves. Never mind. ---
**Author:** ![MichaelEmouse](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/michaelemouse/32/101_2.png) [@MichaelEmouse](https://boards.straightdope.com/u/MichaelEmouse)\ **Post date:** [May 24, 2014, 9:35pm UTC](https://boards.straightdope.com/t/whys-it-so-hard-to-fire-something-into-the-sun/689208/11 "2014-05-24T21:35:05Z")
Play Kerbal Space Program. You will understand. ---
**Author:** ![Isilder](https://avatars.discourse-cdn.com/v4/letter/i/cc9497/32.png) [@Isilder](https://boards.straightdope.com/u/Isilder)\ **Post date:** [May 26, 2014, 5:04am UTC](https://boards.straightdope.com/t/whys-it-so-hard-to-fire-something-into-the-sun/689208/12 "2014-05-26T05:04:35Z")
> [@cmyk](#): > > Is that the gist or am I missing some detail(s)? 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. ---
**Author:** ![enipla](https://avatars.discourse-cdn.com/v4/letter/e/54ee81/32.png) [@enipla](https://boards.straightdope.com/u/enipla)\ **Post date:** [May 26, 2014, 1:02pm UTC](https://boards.straightdope.com/t/whys-it-so-hard-to-fire-something-into-the-sun/689208/13 "2014-05-26T13:02:44Z")
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? ---
**Author:** ![abel29a](https://avatars.discourse-cdn.com/v4/letter/a/ebca7d/32.png) [@abel29a](https://boards.straightdope.com/u/abel29a)\ **Post date:** [May 26, 2014, 2:18pm UTC](https://boards.straightdope.com/t/whys-it-so-hard-to-fire-something-into-the-sun/689208/14 "2014-05-26T14:18:56Z")
Unless I’ve missed something, [this](http://solarprobe.jhuapl.edu/) 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?` ---
**Author:** ![Knorf](https://avatars.discourse-cdn.com/v4/letter/k/58956e/32.png) [@Knorf](https://boards.straightdope.com/u/Knorf)\ **Post date:** [May 26, 2014, 4:13pm UTC](https://boards.straightdope.com/t/whys-it-so-hard-to-fire-something-into-the-sun/689208/15 "2014-05-26T16:13:56Z")
> [@enipla](#): > > 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? 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. ---
**Author:** ![Knorf](https://avatars.discourse-cdn.com/v4/letter/k/58956e/32.png) [@Knorf](https://boards.straightdope.com/u/Knorf)\ **Post date:** [May 26, 2014, 4:22pm UTC](https://boards.straightdope.com/t/whys-it-so-hard-to-fire-something-into-the-sun/689208/16 "2014-05-26T16:22:23Z")
> [@abel29a](#): > > Unless I’ve missed something, [this](http://solarprobe.jhuapl.edu/) 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?` 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! ---
**Author:** ![Rick](https://avatars.discourse-cdn.com/v4/letter/r/9f8e36/32.png) [@Rick](https://boards.straightdope.com/u/Rick)\ **Post date:** [May 26, 2014, 4:24pm UTC](https://boards.straightdope.com/t/whys-it-so-hard-to-fire-something-into-the-sun/689208/17 "2014-05-26T16:24:21Z")
> [@cmyk](#): > > :smack: That’s what I was overlooking… A subtle but critical detail. You also have to launch at night. ---
**Author:** ![Knorf](https://avatars.discourse-cdn.com/v4/letter/k/58956e/32.png) [@Knorf](https://boards.straightdope.com/u/Knorf)\ **Post date:** [May 26, 2014, 4:27pm UTC](https://boards.straightdope.com/t/whys-it-so-hard-to-fire-something-into-the-sun/689208/18 "2014-05-26T16:27:39Z")
Typos. :rolleyes: > [@Knorf](#): > > …Dodging the inner planets are their gravitational influences, of course… 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. > [@](#): > > Certainly, the equations for the Δv give smaller numbers if the craft is small. By small, of course I mean the salient issue is low mass, not size per se. ---
**Author:** ![Knorf](https://avatars.discourse-cdn.com/v4/letter/k/58956e/32.png) [@Knorf](https://boards.straightdope.com/u/Knorf)\ **Post date:** [May 26, 2014, 4:28pm UTC](https://boards.straightdope.com/t/whys-it-so-hard-to-fire-something-into-the-sun/689208/19 "2014-05-26T16:28:40Z")
> [@Rick](#): > > You also have to launch at night. Only if you don’t want the probe to spend time in a parking orbit. ---
**Author:** ![Rick](https://avatars.discourse-cdn.com/v4/letter/r/9f8e36/32.png) [@Rick](https://boards.straightdope.com/u/Rick)\ **Post date:** [May 26, 2014, 5:19pm UTC](https://boards.straightdope.com/t/whys-it-so-hard-to-fire-something-into-the-sun/689208/20 "2014-05-26T17:19:10Z")
> [@Knorf](#): > > Only if you don’t want the probe to spend time in a parking orbit. Whoosh! [Next page](https://boards.straightdope.com/t/whys-it-so-hard-to-fire-something-into-the-sun/689208.md?page=2)