Progress 59 ISS Resupply ship malfunctions, docking postponed indefinitely | Hacker News Reader

Progress 59 ISS Resupply ship malfunctions, docking postponed indefinitely

arstechnica.com

41 pointsChuckMcM31 comments

If it is spinning how does the video feed work? Wouldn't the antenna be spinning wildly as well?

You can actually see the video feed blip out once per revolution. I assume it's because the transmitter is briefly pointing away from the receiver.

Yeah noticed, but I was suprised it wasn't actually completely black but with just quick flash of an image once in a while.

Yeah. The coverage area of the transmitter must be massive.

It's likely an omnidirectional antenna on the satellite and a (very directional) tens-of-meters ground station (or series of them) following the satellite's position.

Or the antenna is always mostly in the direction of earth, and the spin (from the point of view of the earth) just has the antenna describe a circle.

What's the bandwidth of the video and transmit rate of the antenna? How large is the video buffer?

We haven't had to rely on a 1:1 record->transmit system for about 50years now. If the antenna has more bandwidth than required then a few seconds of connectivity each revolution may be enough to give a perfectly smooth video signal.

Video feed appears to be analog. Telemetry hardcoded in the video signal, all looks very 1980s technology.

If it works, don't fix it.

Graceful degregation is very useful.

An omnidirectional antenna on the satellite, a high gain large dish on the ground tracking the satellite across the sky, and error correcting codes that spread errors over time.

Combine those things together and you get a pretty large section of the original signal intact.

Depends on which direction it's spinning. You can spin in a way that the antenna keeps pointing at the ground (but rotating, which would not affect it).

http://imgur.com/pp1xoJI Notice the massive drop in propellant on board during orbit 1 and 3.

From "The Guardian" live feed:

"JSpOC, located at Vandenberg air force base in California, also says there are 44 pieces of debris in the vicinity of the cargo vehicle and part of the rocket body."

I'm speculating then that it got nailed by something. With the large drop in propellant as you noted, maybe something nailed a pressurized tank? That could punch a hole in it, and maybe the resulting thrust from the tank is what drove it's spin.

Interesting video clip of it going around and around. As NASA points out these have been pretty reliable so the occasional failure isn't a big deal, but the the unstated issue is that these things are in an orbital plane to intercept the ISS, which one doesn't want to do if you don't have control given the MIR experience. Presumably they will be able to either permanently abort it through a de-orbit burn or find another way to keep it out of the way.

To achieve a deorbit burn they'd have to be able to stop the spinning, right? The thing that's worrying is, if they could exercise that kind of control they'd have probably done it by now.

My understanding is that it is going to burn up naturally unless they do something about it. Its orbit is low enough that it feels a fair amount of drag.

That's what I was reading as well from places like http://spaceflightnow.com/

Here's a question. IF it's in the ISS's orbital plane and it finished its burn, so it basically had enough oomph to reach ISS with a little boost in altitude... doesn't this imply that it's travelling in a longer ellipse, with higher altitude apogee than ISS?

I'm probably visualizing this wrong but it seems as though it might have the potential to pass by ISS every now and then.

> Here's a question. IF it's in the ISS's orbital plane and it finished its burn, so it basically had enough oomph to reach ISS with a little boost in altitude... doesn't this imply that it's travelling in a longer ellipse, with higher altitude apogee than ISS?

It won't have completely "finished its burn" until it's docked. But I don't think it would ever have a higher apogee than the ISS, because that's just a waste of fuel. If it's just short of docking then I'd expect it to be either in a same-shaped orbit slightly lower than the ISS (i.e. almost circular) ready for a Hohmann transfer, or in an ellipse whose apogee just touches the ISS' orbit ready for a circularization burn.

Even if the orbits do cross an accidental collision is extremely unlikely - the objects are very small compared to how fast they're travelling, their motion is predictable years ahead, and the Progress is at an altitude where its orbit will naturally decay in a few months if nothing is done.

Same orbit plane yes, but it sounds as if it is in a lower orbit which will be more exposed to atmospheric drag

What's MIR experience?

"Progress M-34 was a Russian unmanned cargo spacecraft which was launched in 1997 to resupply the Mir space station, and which subsequently collided with Mir during a docking attempt, resulting in significant damage to the space station."

https://en.wikipedia.org/wiki/Progress_M-34

Edit. Some more detail here: https://en.wikipedia.org/wiki/Mir#Shuttle.E2.80.93Mir and here: https://en.wikipedia.org/wiki/Mir#Accidents

> Progress 59 was carrying "more than three tons of food, fuel, and supplies for the space station crew, including 1,940 pounds of propellant, 110 pounds of oxygen, 926 pounds of water, and 3,128 pounds of spare parts, supplies and scientific experiment hardware,” NASA said.

(1940 + 110 + 926 + 3128) = 6104 lb = 2771 kg = 3.054 short tons.

If any U.S. agency is in desperate need of converting to the metric system, it's NASA. Remember the Mars Climate Orbiter? [1] As long as there is at least one person in the general vicinity of NASA who does not habitually use the metric system, that can happen again.

[1] https://en.wikipedia.org/wiki/Mars_Climate_Orbiter

NASA has used metric exclusively since 2007.[1] I bet an important motive was the loss of the said craft.

[1] http://www.space.com/3332-nasa-finally-metric.html

NASA spec'd a system that outputs values in metric, Lockheed provided one that output values in customary units. The problem was a failure of verifications/validation, not of units per se.

I'm 90% sure they intentionally use imperial units when speaking to the press and someone converted it for the purpose.

I'm having trouble figuring out the intent of your post. Are you confused about the conversion factor with pounds and tons (it's 2), or are you taking the opportunity to snark about something unrelated?

Edit: Wait did you seriously convert pounds to kilograms to short tons? That's like going from meters to feet to kilometers.

ars> "more than three tons of food, fuel, and supplies ..." NASA said

This is the first time in my reasonably long life I see "tons" used for something that is not 1000 kilos. The way it read was "3000+ kgs of payload", not "3000+ pounds" of it. Really quite confusing and worthy of a comment.

Isn't a ton = 1000 kg, if so, why is this 3.054 and not 2.771 tons?

A "short" ton == 2000lb

A metric ton (aka "tonne") == 1000kg

And in fact 6104 / 2000 = 3.052, so OP lost a few lbs in the conversion process as well.

Interesting - Wikipedia tells me that, "In the United Kingdom the ton is defined as 2,240 pounds (1,016 kg)" - so an imperial "ton" is almost 1000 kg there.

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