“The uncontrolled disposal of the pallet, however, was not part of the original plan. It was made necessary by a disrupted spacewalking schedule following the failed launch of a Soyuz rocket in 2018, which forced NASA astronaut Nick Hague and Roscosmos cosmonaut Alexey Ovchinin to make an emergency landing in the Kazakh steppe. This event led to a backlog in the disposal of such equipment. Normally, old batteries would be placed inside an HTV and jettisoned from the ISS to burn up on re-entry.”
The current tragedy has the batteries just minutes away from hitting London or Berlin. A controlled reentry would be much further from large population centres.
That's what I get for typing on a phone with autocorrect. The word should have been "trajectory" though I concede that I may have spelled that incorrectly enough for the autocorrect to mistake the word.
Is it not possible (yet) to return them to the surface in a controlled manner via a SpaceX capsule of some kind? (Or just not seen as worth the expense?)
The Space Shuttle was weird and unusual in that it was the only spacecraft ever capable of bringing significant payload back down to Earth. It cost a whole lot of payload up mass to get that capability (every flight had to carry the reentry protection for that huge payload bay, even if you didn't actually need it) and it was used on several occasions- things like Palapa and Westar (STS-51A), Solar Max, and all the SpaceLab missions- but on many other flights the payload bay came home ~empty and all that protection weight could have had better uses.
All that comes home in current spacecraft (Dragon, CST, Soyuz, Shenzhou) is the small compartment with the people in it, and each of them even leaves the "orbital module"- all the fuel etc. behind to be burned up in the atmosphere. (Progress cargo flights burn up, but Cargo Dragon is actually recovered so some amount of cargo can be returned fully to Earth, but its mostly scientific stuff that is coming back in there right now as I understand it.)
That's because the Space Shuttle was designed to be a spy-agency space cargo van (with parts from nearly every congressional district to guarantee it would sail through congressional approval despite being hideously expensive and impractical.)
Make everyone go "ooo, lookie at the science teacher doing experiments to see how [plant/animal] acts in space, everybody!" so they pay no attention to the spy satellite in the cargo bay (or the different spy satellite, or other equipment, being brought back.)
The only such capsules available are already being used to return astronauts. There isn't enough spare capacity for returning much else -- and certainly not 2.6 metric tons of batteries.
It's basically free to let the orbit decay. It is hundreds of millions or billions of dollars to return it to earth. It doesn't make sense to spend a billion dollars on literal trash.
I would imagine that breaking them up instead of dropping as a single unit could be beneficial - higher surface to volume ratio, leading to more thorough burn up in the atmosphere.
> prohibitively expensive to just boost them into the sun or elsewhere, while in low orbit?
It’s easier to exit the Solar System than it is to boost mass into the Sun from any Earth orbit [1][2]. The atmosphere providing braking for “free” is a huge propellant saver.
The Earth's orbital velocity around the Sun is ~30km/s. You need to cancel almost all of that out in order to shift to a trajectory that intersects the Sun, and that trajectory still has you impacting the Sun at quite some speed.
The Moon's orbital velocity around the Earth is ~1km/s. A slingshot manoeuvre around the Moon isn't going to help nearly enough here.
One of the most efficient ways to get to the Sun is to leave Earth in the same direction it is going (and yes you can use a Moon slingshot to help here if you want) which will result in your rocket going further away from the Sun than the Earth. Once you're out in the region of the outer planets, you'll be travelling a lot slower and won't need to cancel out nearly as much velocity. Neptune's orbital velocity is ~5.5km/s, and if your rocket has an apohelion around there and a perihelion around Earth then you'll be travelling slower than that. However, it still takes a huge amount of delta-v to get out to the region of Neptune and then cancel out your velocity relative to the Sun.
Compare that to the amount of delta-v required to de-orbit an object from low Earth orbit. The object's velocity around the Earth is going to be about 7.9km/s, but it only requires a delta-v of around 100m/s to put it into a nice predictable atmospheric entry. That's comparatively nothing.
How does delta-v prevent you from aiming in a direction that intersects with the sun? That's all that's required for trash disposal. You aerobrake in the solar atmosphere, if your want to think of it that way
To reach the sun, you need to shed a lot of kinetic energy - and given that you’re in a vacuum on most of the way there, the only way to do that is through a lot of deceleration, which is really the same thing as retrograde acceleration, and maybe some gravitational slingshots, but these aren’t free either (you need delta-v to execute them) and therefore have limited gains.
(Technically it’s cheaper by a factor of three to go to escape velocity out of the solar system and then plunge back into the sun, but at that point, why go through the trouble and come back if your concern is trash disposal?)
> To reach the sun, you need to shed a lot of kinetic energy - and given that you’re in a vacuum on most of the way there, the only way to do that is through a lot of deceleration, which is really the same thing as retrograde acceleration
If you can fenagle yourself into a highly elliptical solar orbit, then a relatively small retrograde burn at apoapsis could get you into the sun.
> aiming in a direction that intersects with the sun?
We are moving really fast relative to the sun. Perturb your orbit to seem to intersect with the Sun and you’ll tend to fly past it. (Loose analogy: swimming in a current and aiming for a point on shore.)
"Aiming in a direction that intersects with the sun" requires a huge momentum change when an object already has a large orbital velocity around the sun.
You don't need to just "get past Earth's orbit", you need to deorbit out of Earth's orbit around the sun if you want to reach the sun. This requires a much higher (at least double) delta-v than leaving Earth's gravity well alone.
Slingshots steal orbital momentum. When one slingshots around Jupiter, one is stealing Jupiter’s orbital momentum about the Sun. (It only works in one direction.)
Slingshotting about the moon to gain velocity relative to the Sun doesn’t work. That said, I’d love to see an orbital solution for cheap decay into a solar-impact trajectory. (Orbital mechanics are complex enough that nobody should feel comfortable entirely precluding subliminal sets of solutions.)
> Slingshotting about the moon to gain velocity relative to the Sun doesn’t work. (It only works in one direction.)
Most slingshot maneuvers do gain or lose momentum relative to the Sun! And they do work in both directions (gain and lose) – we've used them for quite a few probes, e.g. MESSENGER.
> Slingshotting about the moon to gain velocity relative to the Sun doesn’t work.
It does, as used by e.g. STEREO [2].
All that said, they're still not "free" in terms of delta-v by any definition. They provide an efficiency gain, but sending stuff to the sun is still prohibitively expensive for anything other than lightweight scientific probes.
> Why not? And you don't actually want to gain velocity, you'd want to change direction
If you fall towards an object and then fall away from it, there is no net force. You can’t bleed or gain delta-V simply by falling into an object and then falling away from it.
The reason planetary slingshots work is you’re “dragged” along with their orbital velocity about the Sun. You can be clever about using that to reduce the delta-V to the Sun. But it’s still more than system escape velocity.
This is analogous to trying to turn a plane by only yawing. Or travel in a current by turning your head.
This guy [1] is wrong. Delta-v comes from Tsiolkovsky’s rocket equation, which in turn derives from Newton’s second law and the conservation of linear momentum. It’s incredibly fundamental math that you can’t cheat by changing direction. (You’ll change orientation and keep going where the math says you will. Because you’re going sideways relative to the Sun at an incredible velocity, the inheritance of every atom in the Earth’s sphere of influence, including the Moon.)
No, the direction change is relative to the Moon, not your orbit around the Sun. The Moon, when retrograde, is still moving forward around the Sun. Your orbit will become more eccentric, but the periapsis won’t even make it past Venus’ orbit.
It's not about "gain velocity", but "change angle".
A very wide variety of angles are frequently used in slingshot maneuvers, simply by controlling how close you get to the Moon or more often the planet.
Yes. LEO is "halfway to anywhere" but only halfway, boosting up to a high earth orbit requires significant amounts of fuel, getting all the way out of earth's gravity well takes more, and to get to the sun would take even more than boosting all the way out of the solar system. If they put them in an orbit "next to" the ISS then atmospheric drag would eventually carry them down until they burned up (even the ISS itself needs to be regularly boosted or it would eventually fall down) but that way it's unpredictable and uncontrolled (and there's always the risk of them hitting a satellite or something), a planned re-entry burnup is generally thought to be safer.
I recently saw in person a non-flight part of a Vega satellite dispenser - rather solid looking 80+ kg aluminum ring like shape, that during a normal flight profile burns up about 100 minutes after lunch via controlled re-entry of the upper stage.
Apparently, very little of that is expected to come down, courtesy of the 8 km/s of kinetic energy it has turning into heat in a very short amount of time.
I image it will be the same for the battery pallet, aided with parts being thin skinned & pressurized.