Hi!
I am looking at this article that says the Deep Space Network antenna was damaged… because it "over rotated": https://spacenews.com/damaged-dsn-antenna-out-of-service-until-may/
I have a strong background in engineering, so it makes me wonder… I understand acts of nature, for instance a major hurricane etc. that is a rare event and would damage an antenna like this.
But over-rotating, how is it possible that there are no fail-safes or limit switches to prevent this from happening?
Are our space operations relying on such, uh, badly designed (if I may) hardware? How come we can't have an interlock for something as basic as this? Did someone bypass fail checks because they stopped working long ago? Any insights?
Thanks!
How can this happen? DSN antenna "over rotated"
byu/uski inspace
13 Comments
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I’m also an engineer, and this story baffles me as much as you. I find it incredibly unlikely that this happened without several concurrent failures in procedure and detection.
All hardware can fail, including limit switches.
They haven’t disclosed what happened yet. The investigation/report was set back by the government shutdown, and hasn’t concluded yet.
> The DSS-14 antenna, a 70-meter dish at the DSN complex in Goldstone, California, was damaged Sept. 16 when it over-rotated, stressing cabling and piping. The incident also damaged hoses in the antenna’s fire control system, causing flooding.
Consider the weight that the neck muscles have to deal with when looking down (e.g. at a phone). https://bodyworksedinburgh.com/impact-of-mobile-phones-on-our-necks/
> As the head flexes forward the weight applied to your muscles changes from 10-12 lbs at a neutral position to 60 lbs at 60 degrees (Hansraj 2014).
The neck is (if I remember my physics right) a third class lever – and that’s where the additional weight comes from.
Likewise, the motors on the antenna are designed for particular strain. If they’re tipped beyond that point, then they’re experiencing more and can rip from their framework. Also cables and pipes running to the antenna through the joint are designed for particular directions of force. Having it at 90° from what is expected, the fasteners for them could be under excess strain and break.
As to the “badly designed” – they’re *old*.
https://science.nasa.gov/learn/basics-of-space-flight/chapter18-2/
> The three 70 m DSSs were originally built as 64 m diameter antennas. The first, GDSCC’s DSS-14, also known as the Mars Station for its support of Mariner-4, began operation in 1966. All three were expanded to 70 m diameter from 1982 to 1988 to increase their sensitivity to support Voyager 2’s encounter with Neptune.
https://www.findarticles.com/nasa-clears-artemis-ii-without-goldstone-antenna/
> **NASA’s Inspector General has repeatedly cautioned that maintenance and modernization must keep pace. A recent audit on Artemis II readiness concluded that communications disruptions are increasingly likely without sustained investments.** In response, NASA is expanding the network under the DSN Aperture Enhancement Program, adding six new dishes, including a 34-meter antenna at Goldstone slated to join operations soon.
https://oig.nasa.gov/news/revitalizing-the-deep-space-network-to-support-nasas-growing-space-exploration-program/
> Artemis II’s uncrewed predecessor, Artemis I, required more than 900 hours of DSN support over 25 days when it launched back in 2022. It experienced a temporary loss of in-flight communications, highlighting several issues with the DSN caused by maintenance deferrals and hardware deterioration.
https://oig.nasa.gov/office-of-inspector-general-oig/ig-23-016/ has a link to the 2023 audit report in which it says:
> DSN antennas are currently operating at capacity and are oversubscribed—meaning more time is requested by missions than the network’s current capacity can provide—with demand exceeding supply by about 40 percent at times. The Agency’s upcoming crewed Artemis missions to the Moon will require increasingly higher amounts of bandwidth and further constrict the network’s ability to meet growing mission demands. **Moreover, DSN’s infrastructure, some of which was built in the 1960s, is outdated and characterized by extensive deferred maintenance that is becoming increasingly difficult and costly to maintain.**
yeah, more details are needed, and we can only speculate.
But really, just a simple failure could have caused this, if the antenna thought it was at a certain position but that was wrong (for some hardware failure or software failure) then it could have moved into an overrated position without know it did.
That’s just one supposition, there are hundreds of ways something like that can fail. We’d need more info to say for sure.
Hardware fails sometimes, repairs aren’t done correctly sometimes. The DSN has functioned for decades with out significant failure, writing it off as ‘poorly designed’ is wildly presumptuous based on a single incident and no in depth knolege of the system.
My understanding is that there are actually multiple fail-safes and interlocks that should have prevented this. It’s why NASA has an ongoing investigation into how it happened anyway.
That this is so out of the ordinary, despite how many antennas NASA operates, shows that the existing systems tend to work to protect the hardware.
My money is on either an elevation brake failure, or a hiccup in the antenna control system.
Big, heavy antennas don’t like gravity 😂
The Azimuth rotation on most antennas is limited by a cam plate that is connected to the main drive gear with a gear train and has push spring switches for the limit signal. If the switch gets sticky they can not actuate properly and the antenna will over travel.
Typically however there is also a software limit in the controller to stop the antenna before it gets to the hardware limit. You do occasionally perform maintenance that requires disabling the software limit temporarily.
So there would have to be two failures in this case, one is for the hardware limit. The other would be a maintenance operator not watching ccarefully. This one is probably less likely.
The other case could be a runaway condition. As far as I can tell DSS-14 uses hydraulic motors for their positioning drives. So a jammed open valve, a shorted control signal and maybe a failure of a safety protection devices would cause the antenna to over travel.
It’s not necessarily maintenance oversight that cause something like this. It is an option but you also get unfortunate coincidences where a single unforseen design issue causes a cascade of failures if specific conditions are met.
Fail safes fail, end stops don’t, limit switches fail to. Things break and not always in expected or predictable ways.
Old stuff breaks. And NEVER discount good ol’ sabotage. Every control in the world cannot account for the human element in any system…
“I’ve got a strong background in engineering”
That says enough, to much time in the office and not enough in the shop.
Fail-safes fail, it happens, these are real life situations.