The thread for space cadets!

[Thorgalaeg]

This is too Kerbal to resist. KSP.exe ignition in 3,2,1...

 

[GreatLordofPie]

This is too Kerbal to resist. KSP.exe ignition in 3,2,1...

Fly safe, and don't forget to check yo staging!

 

[uppi]

Cameras are lightweight and small but they still add a ton of complexity to your electronics design. They also pose a serious bandwidth challenge when comes to sending more images back to Earth from distant locations. As I said above, I'm somewhat confident that these camera's main function was to take pretty pictures rather than to serve as a useful diagnostic tool. There are enough telemetry channels (sensors/data points) on the landing system that it's doubtful they'd need a video feed to reverse-engineer the source of any problems. NASA designs like that - they instrument the heck out of everything.

I will say that if a private company had built this rover, it's far more likely that they would use a few cheap cameras and a lot less of the expensive sensors that NASA uses to monitor and diagnose problems. The approach I'd say is a lot less robust than NASA's but far cheaper to implement. As you say, taking a picture of the lander can be helpful in figuring out what happens, with the caveat that they're only especially useful if you do not already have a bunch of other, better instruments taking data.

Sensors are good at giving data about everything, which you know is interesting in advance, and when everything goes as expected. Cameras are often good if something unexpected happens for which you do not have sensors. So your sensors might tell you that some part has broken off, but a camera might be the only chance to locate it and tell whether it is gone for good or might be somewhere where it could cause problems. So even if everything is covered in sensors, a few cameras could help a lot.

And, obviously, how are you going to present your results without some pretty pictures?

 

[hobbsyoyo]

And, obviously, how are you going to present your results without some pretty pictures?

Scientist and engineers have this odd habit of thinking that everyone else is as enthused and taken away by pretty line graphs as they are.

 

[hobbsyoyo]

A defunct NOAA satellite blew up in orbit, and its just the latest in a long string of such failures. There's a whole series of Lockheed Martin produced spacecraft which tend to detonate after retirement due to a faulty battery design - and some, like this one, are still in critical orbital slots.

 

[Cutlass]

And they didn't send it down why? Pretty soon it will be unsafe for anything in orbit.

 

[GreatLordofPie]

A defunct NOAA satellite blew up in orbit, and its just the latest in a long string of such failures. There's a whole series of Lockheed Martin produced spacecraft which tend to detonate after retirement due to a faulty battery design - and some, like this one, are still in critical orbital slots.

And they didn't send it down why? Pretty soon it will be unsafe for anything in orbit.

Kessler Syndrome is definitely something we need to address before it becomes a real issue (i.e. industrializing LEO and cislunar space). It's too bad that bad faith actors will label debris sweepers as anti-satellite technology to justify more militarization.

 

[hobbsyoyo]

And they didn't send it down why? Pretty soon it will be unsafe for anything in orbit.

The government only got serious about debris mitigation in the last decade and even then, most of that seriousness has been limits they've placed on private companies, not on themselves. This satellite likely did not have enough fuel to de-orbit itself or move to a graveyard orbit and that's because the satellite was kept alive and on-mission for a decade beyond its original use-by date.

Satellite operators in geostationary orbit are pretty good about moving their satellites into graveyard orbits at their end of life but that's because of how insanely valuable those orbital slots are. In polar orbit (where the NOAA bird flew), it's mostly scientific, intelligence and weather satellites that fly and if their government operators do not require themselves to de-orbit then it isn't done. They're getting better about it now but we're seeing lots of problems like this that were caused by decisions made in the 80's, 90's and 2000's.

 

[Cutlass]

Is there a way to build a system to force everything out of orbit?

 

[hobbsyoyo]

Is there a way to build a system to force everything out of orbit?

There are several different ways of de-orbiting and a few companies are trying to commercialize various ideas.

The classic way to de-orbit is to just let it happen. For lightweight satellites with relatively high surface area in low orbits, you can expect to naturally decay within 25 years which is the current US rule for de-orbit (and you can often come down much faster). The vast majority of CubeSats fit this bill, for example. Some satellites can also speed up this process by increasing their aspect ratio - at the end of life they can tilt the spacecraft so that its solar panels are facing normal to the direction of travel and this acts like a drag sail that pushes against the rarefied air and pulls them in faster.

The other standard way is for a satellite to use propulsion to de-orbit itself or move into a relatively safe orbit. Large satellites and satellites in high orbits have to do this because drag won't pull them in within centuries or millennia. Satellites that choose to de-orbit don't have to come down in one big burn, they can instead just lower the orbit so that it is low enough that the satellite will decay quickly even if it is large. This, however, is only an option for satellites that orbit up to say 1,000 km or so. Above that and the amount of propellant you need to do this de-orbit burn has historically been prohibitive. This is why so many NOAA and other birds in the 700-1000 km range were not de-orbited; also, the fact that budgets are tight and satellites are kept on orbit for years past their expected mission end date means they often have no fuel left at the end of their life.

The above is beginning to change a bit as SpaceX's Starlink constellation has high-efficiency electric propulsion which they use to aggressively de-orbit their satellites, and OneWeb will do something similar. However, for satellites in geostationary orbit at ~36,000 km, you would need a rocket similar in size to the spacecraft itself to do a de-orbit, so these birds instead hop into a ring of dead satellites (the 'graveyard') above the geostationary altitude before deactivation. Operators here are actually really good at complying with this and will even choose to graveyard a satellite that is experiencing technical difficulties rather than try and stick it out to protect the integrity of the Clark orbit.

A new thing happening now is that Northrup has begun docking with geostationary satellites that are nearly out of fuel but otherwise fine, in order to extend their life. This is an image from the first such docking (taken from the perspective of the active satellite servicer) and a second docking is going to happen in the coming weeks.

Another new thing is that one company is making a magnetic drag tape that is basically a thin metal wire that gets deployed off of a spacecraft at the end of life. This magnetized wire interacts with Earth's magnetic field totally passively and creates magnetic drag which will pull the satellite in over time. This only works for small satellites at the moment and will only work up to around a few thousand kilometers at most but an interesting feature is that you can buy a completely self-contained drag tape which will detect when the satellite has suddenly died and deploy itself automatically as a failsafe to de-orbit. It's being tested in orbit right now - two identical satellites in identical orbits have been deployed, one with and one without the tape, and they will be monitored to measure how fast the tape-equipped satellite returns to earth.

Finally, there are a couple of start ups that are trying to prove they can launch a small satellite into space that can maneuver to a defunct satellite, grapple it, then pull it down using propulsion. This last thing really depends on government mandates and subsidies to happen, or otherwise for launch prices to drop by a couple of orders of magnitude, because it is by far the most expensive and complicated de-orbit scheme there is. The reason why it is attractive at all then is because a system that can do this can theoretically deal with any space junk and is not restricted to specific orbits or altitudes or whatever. There are some demonstration missions launching right now or within a couple of years from Japan and Europe.

 

[hobbsyoyo]

Note that none of the above is that helpful in dealing with dead satellites that explode before they come down. Once that happens, you now have a ton of small debris that acts like shrapnel in and around the orbit of the satellite that blew up. There are some concepts to deploy catcher satellites with nets to grab this kind of debris or to use ground lasers to ablate the debris and make it de-orbit but none of them are very mature or likely to work.

It's going to be hard (or even impossible) to develop nets which stow small enough to fit on a spacecraft but deploy large enough to be useful, while also being rugged enough to survive being hit by high-speed shrapnel. And the space-laser idea basically has all the same problems as Reagan's Star Wars SDI program but it isn't being backed and researched by any national government like Star Wars was.

 

[Thorgalaeg]

It should be mandatory for any satellite to have a reserve of fuel for deorbiting.

 

[EnglishEdward]

Space debris removal demonstration launches

Space debris removal demonstration launches - BBC News

A Soyuz rocket has launched from the Baikonur cosmodrome in Kazakhstan to put 38 different satellites in orbit.

Among the payloads was a 500kg Earth imager developed by the South Korean space agency; and a pair of spacecraft from
the Tokyo-headquartered Astroscale company which will give a demonstration of how to clean up orbital debris.

 

[red_elk]

Looks cool, but expensive. I wonder how it supposed to clean debris - does it just "swallows" pieces and then deorbits with them, or can kick them down?

 

[Samson]

Looks cool, but expensive. I wonder how it supposed to clean debris - does it just "swallows" pieces and then deorbits with them, or can kick them down?

It sounds like this is focused on the capturing of the debis:

Astroscale launched what it calls Elsa-D (End-of-Life Service by Astroscale demonstration). The demonstration mission consists of two spacecraft: a 175kg "servicer" and a 17kg "client".
On the Soyuz, the duo were connected, but in the coming weeks they will be commanded to separate to begin a repeating game of cat and mouse.
The servicer will use its sensors to find and chase down the client, latching on to it using a magnetic docking plate, before then releasing "the mouse" for another capture experiment.
The task will become increasingly complex, with the most difficult rendezvous requiring the servicer to grab the client as it's tumbling.
Ultimately, the pair will be commanded to come out of orbit to burn up in the atmosphere.​

I think the news that they may have found dark matter, or at least departure from the standard model, is exciting:

Hints of unexpected behaviour by a sub-atomic particle called the beauty quark could expose cracks in the foundations of the Standard Model (SM) .

The LHCb produces sub-atomic particles called "beauty quarks", which are not usually found in nature but are produced at the LHC. Sub-atomic particles undergo a process known as decay, where one particle transforms into several, less massive ones.
According to the Standard Model, beauty quarks should decay into equal numbers of electron and muon particles. Instead, the process yields more electrons than muons.
One possible explanation is that an as-yet undiscovered particle known as a leptoquark was involved in the decay process and made it easier to produce electrons.

In particle physics, the gold standard for a discovery is a level called five-sigma, in which there is a one in 3.5 million chance of the result being a fluke [no it does not].
The measurement from LHCb is three-sigma - meaning there is roughly a one in 1,000 chance that the measurement is a statistical coincidence. So people should not get carried away by these findings, according to team leader Prof Chris Parkes, from the University of Manchester.
​

 

[red_elk]

It sounds like this is focused on the capturing of the debis:

Astroscale launched what it calls Elsa-D (End-of-Life Service by Astroscale demonstration). The demonstration mission consists of two spacecraft: a 175kg "servicer" and a 17kg "client".
On the Soyuz, the duo were connected, but in the coming weeks they will be commanded to separate to begin a repeating game of cat and mouse.
The servicer will use its sensors to find and chase down the client, latching on to it using a magnetic docking plate, before then releasing "the mouse" for another capture experiment.
The task will become increasingly complex, with the most difficult rendezvous requiring the servicer to grab the client as it's tumbling.
Ultimately, the pair will be commanded to come out of orbit to burn up in the atmosphere.​

​

Yes, I got this part. Just thought that using some kind of catapult to shoot debris on lower orbit might be more efficient than collecting pieces. Capturing is necessary in any case.

 

[GreatLordofPie]

​

Yes, I got this part. Just thought that using some kind of catapult to shoot debris on lower orbit might be more efficient than collecting pieces. Capturing is necessary in any case.

Don't forget that orbital mechanics is really unintuitive; the most efficient way to change an orbit is to accelerate or decelerate parallel to the ground, and even then you'd need to change your velocity (aka have a delta-v) of at least 1km/s to move from a high orbit to a lower one where atmospheric drag has a chance of deorbiting whatever needs to be disposed of. It's a lot easier to spread the energy required to do that over a longer period of time, whether it be with a small harpoon or net satellite with ion thrusters, or a large bulk carrier like Starship going around and collecting a bunch of debris then dumping it in a safe orbit.

 

[Buster's Uncle]

...Why not a couple of great blobs of aerogel on a long tether? One's moving a little faster than the orbit, the other a bit slower, both gently sweeping out a lot of paint chips and smallish crap over time - maneuvering fuel needs minimized w/ magnetic breaking, which would tend to supply considerable power to any needed systems at the center...

 

[red_elk]

Don't forget that orbital mechanics is really unintuitive; the most efficient way to change an orbit is to accelerate or decelerate parallel to the ground

In opposite direction to the current velocity vector, to be precise. You don't have to assume I don't realize that.

and even then you'd need to change your velocity (aka have a delta-v) of at least 1km/s to move from a high orbit to a lower one where atmospheric drag has a chance of deorbiting whatever needs to be disposed of.

1 km/s seems rather arbitrary, but you are right that this task may be too difficult technologically.

 

[GreatLordofPie]

In opposite direction to the current velocity vector, to be precise. You don't have to assume I don't realize that.

You're right, dumb assumption to make for the space nerd thread especially as a newcomer