What you suggest is possible, but the solution is a major problem, for larger reasons.

We have sent probes to crash into Jupiter. It is physically possible to send waste into a gas giant. Just as it is theoretically possible to send waste now into the Sun.

However, the primary issues encountered commonly with waste is economic and logistical. Waste is not a desirable commodity, unlike other products it has negative value. Therefore people will often settle for spending the bare minimum to 'get it out of sight', in contrast to spending a lot to 'get it where it needs to be'.

Many people don't realise that waste produced in cities often go into landfill close by - waste companies simply do not want to spend millions transporting waste long distances. 'Out of sight, out of mind' is the primary rule here, no one will support the enormous fuel costs of sending waste to another planet or into the sun, unless it is actually cheaper to do this than to dump it in a hole nearby.

The other contradictory dichotomy is that waste is valuable. Not in the fact that it holds value, but in that it represents the 'cradle to grave' aspect of society, ie lost economic, social and labour investment in redundant items. In other words, it should be more efficient to re-use, recycle, reduce waste than to dispose of it because that investment is re-invested, otherwise the society will bleed this value. This is difficult to resolve, and requires pre-emptive planning, but some are attempting to tackle it.

So rockets to dispose of waste is possible in a physical sense, but not possible / preferable economically or societally.

The problem is energy

Since you're on the moon orbiting the gas giant, both you and the trash are moving at the moon's orbital speed around that gas giant. And it takes a lot of energy/fuel to slow the trash down and get it out of the planet's orbit, allowing it to fall into the atmosphere. As long as you have cheap and plentiful energy resources and disposable engines, this shouldn't be a problem. In fact, the trash will be incinerated as it enters the atmosphere.

Yes, but for a different reason.

This is basically what happened with the Cassini probe, which was sent to crash into Saturn in 2017. However, the reason the probe was successfully disposed of wasn't because Saturn's a gas giant; it's because the spacecraft burned up upon entering Saturn's atmosphere. The same things happen with meteors, and would happen with spacecraft returning from Earth if they didn't have heat shields. They'd be burnt to a crisp.

Now, the waste might not burn up completely. Skylab didn't, in the 1970s; some pieces of debris hit Australia. Fortunately, Saturn's interior is hot (at the center, it's twice as hot as the surface of the Sun) and under a lot of pressure, and anything that survives entering the atmosphere will not survive for a whole lot longer.

That said, as folks have pointed out, this might not be phenomenally appealing. There are reasons for and against sending your rubbish to a gas giant.

Reasons against doing it:

• It takes time and energy and money and labor, and those are all in short supply in space.


• Who wants to waste rockets?


• Can't you just dump it elsewhere?


• Some of it can be reused.

Reasons for doing it:

• Let's try to not contaminate the moon we might be trying to study.


• Nobody wants nuclear waste in their backyard space colony.

The solution you are looking for is a mass driver. In essence, they are a giant electromagnetic gun that would accelerate a mass past escape velocity and send it to space. They were proposed decades ago as a cheaper method of sending cargo to space. The main benefit against rockets is that, as most of the energy is provided by the mass driver, the ship won't require as much fuel. The main drawbacks would be:

• Friction against the atmosphere. However, the only moon on the Solar System to have a significant atmospherical pressure is Titan at 147 kPa (1.45 atm, denser than Earth!). Triton has a pressure of about 2 Pa, most other moons are on the order of micropascals.


• The escape velocity. But even the biggest moon in the Solar System, Ganymede, has a relatively low escape velocity of 2,741 m/s, which is easily attainable with current technology.


• Related to that, if you want to reach the escape velocity in a short distance, you need a huge acceleration. For example, to reach 2,741 m/s on a 1 km long track you would need an acceleration of 3,755 m/s2 over a time of 0.73 s, or 383 g. Again attainable with current technology, even if you have to spend an enormous amount of energy, but such an acceleration would destroy any delicate machine, and would reduce a living being to a bloody paste. But not a problem for waste that you want to get rid of.

So all in all, I would say that a mass driver is your solution. Also, if you can make it several kilometres long and keep the acceleration low enough, you could use it to launch both manned an unmanned ships.

What you've described is the most expensive way possible to rid a world of waste, but yes, it can be done.

However, human nature (with regrettably rare exception) is to use the simplest, cheapest solution possible. So unless your story includes an explanation of either...

• Why it's cheaper and more efficient to ship waste to Saturn over, say, dumping it down an incredibly deep pit with flowing magma at the bottom, or




• Why the particular waste is of a nature that it's an absolute requirement to get it off the planet no matter what the cost,

...it might not be particularly believable.

There have been mentions of railguns/electromagnetic mass drivers, but while these would be more efficient than rockets, they have their own problems:

• A small railgun has to be operated constantly to get rid of waste. That requires a lot of valuable ferrous metal (for each slug cartridge) and a lot of energy (since the gun is being fired constantly).


• A big railgun only needs to fire once a day/week/month, but then it has a much larger volume of waste to get rid of, which requires a lot of metal (larger surface area and thicker cartridge) and a lot of energy (to accelerate the much larger mass).

A much simpler and more efficient solution, in my opinion, is essentially a catapult system that functions much like the US Navy's EMALS carrier aircraft launch catapult, except you replace the aircraft with a disposable container holding the waste you need to get rid of. There is no requirement for the container to be ferrous, or even regularly-shaped.

In fact, you can go one further: build an L-shaped "cart" that is attached to the accelerating part of the catapult, where the vertical part of the L is the "back" of the cart (i.e. opposite the direction of travel). You load up the cart with waste and accelerate it to escape velocity; when the cart reaches the end of its track, it stops, while the waste's momentum propels it out of the gravity well and into the gas giant.

A hybrid solution:

1. Put up a space elevator for planet-to-space transit. Elevators are intended to solve the expense of getting stuff off-planet, whether trash or treasure.(https://en.wikipedia.org/wiki/Space_elevator#Economics) Send the waste up the elevator as needed, and you've dodged the cost of overcoming escape velocity with rockets/mass drivers.


2. The terminus platform could have a (relatively) small mass driver to nudge the waste in the right direction toward the gas giant. Just slap a hazard beacon on the payload so system-local traffic can avoid it. :)

Would it not be true that the only necessary energy would be that which would lower the velocity of the trash to just below orbital velocity?

Then, it would eventually decay into the planet. The problem of almost infinitely orbiting trash would only be a problem, if there were some reason for valuable cargo to transit the space that the trash is orbiting in (towards it's inevitable doom).

No. It is far too expensive to reach escape velocity for really useful stuff already. Have any idea of how much it costs to send 1 kg of very sophisticated electronics out of earth's gravity grip? Then you say you want to pay those amounts of money for many many kilos of waste?

Better solution is to not produce any waste at all. Make the products recyclable instead of having them turn to waste.

As others have noted, the first big problem to solve is getting the payload to escape velocity of whatever moon you're on, but that is only the first problem. Escape velocity of Ganymede is roughly 2.7km/s, but that's nothing compared to the problem of getting out of Ganymede-height orbit and on a collision course with the planet. Ganymede orbits at about 11km/s, so you've still got over 8km/s to lose, and that's without considering gravity losses from the launch from Ganymede.

I have not worked out the math, but a likely good technique is to burn Ganymede-retrograde to get an encounter with Europa and get a gravity assist from it that lowers your Jupiter periapsis into the atmosphere. Remember, you'll want to pass in front of Europa in its orbit such that your projectile's course is altered in the Europa-retrograde direction. Try it out in your favourite orbital mechanics simulator and see what you can come up with.

If you have the tech to ferry waste to a Gas Giant, then you have more than enough tech to turn waste into useful material.

The concept of actually throwing all sorts of valuable mass away is so type-zero civilization, whereas ability to ferry it to a nearby gasgiant is at least tech-1

Make use of it instead.

The amount of true waste that a closed system colony like that produces is going to be truly miniscule. In the process of figuring out how to establish colonies that far out, we're also going to have to figure out how to economically reuse everything that we normally think of as waste. Face it, every gram of stuff that we send up the gravity well to a colony is horribly expensive to transport. There's going to be some way to reuse it--even running it through acid baths to break it out into constituent elements is going to be cheaper than firing something new up from Earth.