Satellite guided to assisted crash in Atlantic in world first | Hacker News Reader

Satellite guided to assisted crash in Atlantic in world first

theguardian.com

46 pointsnickserv47 comments

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Way better source:

https://www.esa.int/Applications/Observing_the_Earth/FutureE...

Along with a video of how it was performed:

https://dlmultimedia.esa.int/download/public/videos/2023/07/...

I'm not really getting what makes this a world first?

Controlled deorbits have been a thing for a while, and if we're talking about deorbits designed to minimize risk of debris impact, IIRC Starlink satellites were designed to maximize the amount of the satellite that is vaporized by reentry.

Edit: Ah, the "world's first" is that they were able to choose where any parts that aren't vaporized would crash. The esa article is clearer on that.

I guess if I were to be unnecessarily pedantic, most crewed capsules and reusable ISS resupply vehicles have also technically done that.

I think the other "first" was that the system wasn't designed for controlled re-entry. They just used re-purposed the orbit maintenance propulsion system.

I’m fairly confident this is not a first. It’s just good behavior if you have a defunct but controlable satellite in low earth orbit. A best-effort burn to deplete fuel and aim for an ocean is an obvious choice. While it’s interesting, it is not novel and I think the reporter over-sensationalized here.

A British-built weather monitoring spacecraft has been deliberately guided into the Atlantic Ocean, the first time a defunct satellite has been maneuvered to perform an assisted crash on Earth.

Aeolus, a satellite that has provided data to weather centers across Europe since 2018, was successfully helped to its final resting place by mission controllers at the European Space Agency.

Thanks ChatGPT for the summary!

It's actually just first two paragraphs from the article, I don't know why this was posted.

When I posted the story there was a "text" field, thought it was to provide a summary of the article, but it actually creates a first post.

I’ve done this before too. HN is broken in this way that if you post a link, the text field is ignored, or the site doesn’t support a link with original text.

I wonder how British-built Aeolus turned out to be, the initial prime contractor in 2003 was to a UK company, but by the time it was actually launched in 2018 it was Airbus that was the prime...

It was built by Airbus, in the UK, per the article.

I can't imagine how it must feel for the engineers who put their talent into this wonderful machine to have to contribute to its demise. I remember watching a video from the Cash For Clunkers program back in 2009 [0], where they replaced an engine's oil with sodium silicate and then ran it until the engine was destroyed [1]. Rationale of the program aside, it was so sad seeing a car being deliberately killed.

[0] https://en.wikipedia.org/wiki/Car_Allowance_Rebate_System

[1] https://www.youtube.com/watch?v=X0IcIxhd8ks

Human emotions are weird. People get super attached to things for strange reasons.

> it was so sad seeing a car being deliberately killed.

like this

Finding normal human emotions to be weird seems even weirder. Are you not also a human? I guess we can't actually take this for granted these days.

Beep boop.

Maybe it would be time to have a global agreement that all satellites must implement the means of "disposal re-entry" so they can be taken out of the space scrapyard and safely (as much as possible anyway) crashed to earth.

The amount of debris in space is going to be a problem that's going to be both costly to solve and very detrimental to future space systems if we continue to not do enough about it.

Not likely. The re entry tech is a critical component of ICBMs. Satellites are relatively easy in comparison, they are just a orbiting computer with a sophisticated radio/signaling processing stack. Most countries can build satellites, but the countries that can put them into orbit are all significant powers. I doubt major powers would be willing to transfer smaller players the technology for controlling re-entry.

Would it be possible that whoever launches the satellite (in a major power) somehow adds to it a re-entry module, so the knowledge and sensible devices stay out of the reach of lesser powers?

It would take a lot of trust. You can basically stick a bug in there and siphon the radio data (yes there is encryption etc. but you probably don't want another actor's hardware being permanently attached to your satellite, opens up all sorts of vulnerabilities. It's close enough for nearfield attacks like EMP or explosives or even wrong sensor data).

It would make more sense to ensure that any sensitive technology on board is in a demisable subunit that will melt during reentry, so nobody has a chance to snag it after it reenters.

This is also a safety consideration in satellite design - see, for instance: https://spectrum.ieee.org/spacex-claims-to-have-redesigned-i...

If the whole thing comes apart into tiny pieces, you have no chance that anyone/anything on the ground will be injured/damaged by falling debris..

Lots of satellites have thrusters to stabilize and adjust their orbits. Especially those at lower orbits since they do have to counter the effects of atmospheric drag.

All that's really needed is a convention for those satellites than can, to use the last remaining propellant to perform a de-orbit maneuver.

My understanding is most of ICBMs don't go to orbit anyways, mostly because it'd just delay the strike. Why would anything from a suborbital launch be needed to control re-entry?

FOBSs go to orbit.

The reentry tech in ICBMs has nothing to do with satellite disposal, and, in fact, would make satellite disposal more hazardous (because it would mean the satellite would reenter in one piece rather than breaking up into smaller pieces that are more likely to burn up/melt in the atmosphere).

An ICBM warhead reaches space but at suborbital speeds. It never reaches orbital velocity and will reenter no matter what; it has a heat shield so that the warhead remains intact when descending through the atmosphere.

For satellite disposal, the satellite starts off at orbital velocity and needs to be decelerated above the atmosphere to drop the low point in the orbit far enough that the atmosphere will decelerate it below orbital velocity.

https://what-if.xkcd.com/58/ has a good overview of the difference between suborbital and orbital velocity.

I think tech for gradual reentries (stuff like electromagnetic tethers) is not useful for ICBMS

Relevant: https://www.esa.int/Enabling_Support/Preparing_for_the_Futur...

This is already (effectively) the case. All satellites launched from the US need to have a plan to safely deorbit within 25 years after they’re no longer in use. I believe this was recently lowered to 5 years. For many satellites this just means natural decay and burn up on reentry. Satellite owners need to submit an orbital debris analysis as well to prove they won’t hit anything. Other countries and the EU have similar (often more strict) regulations.

Do these satellites typically have such a seemingly short life?

That's what struck me most from this article too! 3 years?! That's a huge capital investment for very little service life.

I had naively expected at least something like 10 years, even in LEO.

Sort of, Aeolus was a technology demonstrator and it had a intended lifetime of three years, which it surpassed. Other Earth Explorer missions have had similar lifetimes, but many have had much longer... I think since these are all very experimental things getting the up and working to prove the technology is the main thing, how long they make it past that is sort of random.

The satellite orbited at 320 km. At that altitude the atmosphere drag is non-negligible, so it had to burn fuel to stay there. So the life was limited by how much fuel it had and that is limited by launch vehicle capabilities. If the launch cost get lower, I imagine refueling might become option, but we are not there yet (except for ISS, but that is different case).

The laser technology for space-based winds measurement is very difficult to make work in space. The requirements on materials, optics, and power dissipation are daunting. This was a technology demonstrator to show that it had a chance of working and it succeeded.

If the area above the earth is many orders of magnitude larger than the earth’s oceans, and the oceans are vast in the extreme, what really are the chances of a collision given the relatively small amount of debris in orbit? One can easily find a debris map online. Compared to say “ships in the ocean” the number of “satellites in orbit” must be tiny. And the ships exist on a 2D surface, so are that much more likely to collide. With 3D to move in and such a vast area, what is the actual risk? To be clear I’m not saying there is no risk and I know about cascading debris collapse. I just doubt the whole thing, I’d really like to know if anyone has done the math here.

Orbits degrade over time. A defunct satellite out of propellant has no guarantees to “stay in its lane”. Space debris are already an issue and we’ve only been putting things in space ~66 years.

Imagine if every ship to ever sail was still afloat and never sank. We’d have thousands of unmanned, uncontrollable vessels ping-ponging around the ocean.

The number of satellites is less than the number of oceangoing ships, but satellites are on track to be ahead in the next decade or so.

Then if you start counting every single piece of debris a satellite can run into, you're looking at millions of objects. Unlike ships, the debris (and even many satellites) doesn't have anyone "on watch" and there's no way to steer out of the way at the last minute. Because of how orbits work you can't really organize traffic into "shipping lanes".

If you want to do the math yourself, NORAD publishes satellite orbital parameters, which can be used to look for potential conjunctions. You can also sign up for an account at https://www.space-track.org to see the Space Force's data, or CelesTrak for something similar that isn't login-walled (https://celestrak.org/SOCRATES/). The tl;dr is that it's not rare for 2 satellites (or a satellite+debris) to have a 1 in 10,000 chance of crashing into each other. As more and more satellites go up and more and more "1 in 10,000" events happen on a daily basis, more conjunctions will occur. Each conjunction can create thousands of pieces of debris, which exacerbates the problem- nowadays I think ~30% of all debris in LEO comes from China's 2007 ASAT test.

This might be a good time to enjoy the ESA film on the necessity of cleaning up space junk, A Journey to Earth:

https://www.youtube.com/watch?v=zT7typHkpVg

didn't Galileo do this quite a while back: https://solarsystem.nasa.gov/missions/galileo-probe/in-depth.... ?

Per the text, no, it was not guided to a controlled crash on earth (or in this case a planet/ moon)

The article states the on-launch weight of it was 1,360kg, but what would have been interesting to know is the expected weight of debris that would reach the surface.

The satellite was built with only a 3 year operational lifetime? Is that common??

nevermind the fact that boats are in the Atlantic and could be struck

That is why we have Navigation Warnings:

NAVAREA VII 229 OF 2023: (24 JUL 23) 1. INDIAN OCEAN – SW SECTOR – AND SOUTH ATLANTIC OCEN – SE SECTOR 2. CHART SAN 1 3. AREAS TEMPORARILY DANGEROUS TO NAVIGATION DUE TO ROCKET CARRIER ELEMENTS ATMOSPHERIC RE-ENTRY FROM 0009 – 0712 UTC 27 JUL TO 02 AUG 2023 DAILY. A. 08 - 52S 092 - 27E B. 07 - 45S 089 - 27E C. 30 - 12S 061 - 09E D. 40 - 45S 002 - 20w E. 42 - 56S 002 - 23w F. 32 - 15S 063 - 10E 4. ALL VESSELS REQUESTED TO KEEP CLEAR POTENTIAL DANGER SHOULD VESSELS ENTER RANGE 5. CANCEL THIS MESSAGE 020730 UTC AUG 2023

Did British and Germans and the rest of ESA members salvage it from the ocean or will it stay as trash in the ocean ? So much money so much power ... yet all we can to is burn it a little in the atmosphere and let the rest fall into the ocean. Ocean is full of life... lets not forget that. Anyway the solution could be a repairable satellite or removable by some device like space shuttle... ESA has the money, scientists... so on. Space agencies should join in the effort and solve such things together if money is a problem or lack of technology.

the total volume of all oceans is roughly 1.335 bn km^3. the volums of this sattelite is ~6.612m^3, which is about 4.952*10^-16 % of the total ocean volume.

i think it will be fine.

The article seems to imply otherwise, but I suspect not much actually reached the surface. Re-entry is extreme and the majority of it would've vapourised in the atmosphere.

A shuttle launch to repair or retrieve an end-of-life satellite seems like it would prove rather worse for the environment with the thousand-plus tonnes of fuel, including solid fuel boosters and the 30 tonnes of burned-up fuel tank that also falls in the sea than dropping what remains of a compact car's (the Aeolus dry mass is 1200kg) worth of metal after an unshielded reentry.

Fish don't care about a ton or two of scrap metal. Whole ships sink all the time and fish love it.

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