Scroll down to read this post.

 

Please consider supporting my work here at Behind the Black. I keep the website clean from pop-ups and annoying demands. Instead, I depend entirely on my readers to support me. Though this means I am sacrificing some income, it also means that I remain entirely independent from outside pressure. By depending solely on donations and subscriptions from my readers, no one can threaten me with censorship. You don't like what I write, you can simply go elsewhere.

 

You can support me either by giving a one-time contribution or a regular subscription. There are five ways of doing so:

 

1. Zelle: This is the only internet method that charges no fees. All you have to do is use the Zelle link at your internet bank and give my name and email address (zimmerman at nasw dot org). What you donate is what I get.

 

2. Patreon: Go to my website there and pick one of five monthly subscription amounts, or by making a one-time donation.
 

3. A Paypal Donation:

4. A Paypal subscription:


5. Donate by check, payable to Robert Zimmerman and mailed to
 
Behind The Black
c/o Robert Zimmerman
P.O.Box 1262
Cortaro, AZ 85652

 

You can also support me by buying one of my books, as noted in the boxes interspersed throughout the webpage or shown in the menu above. And if you buy the books through the ebookit links, I get a larger cut and I get it sooner.


Why things break in space

Updated and bumped: I will be discussing this story on the the John Batchelor Show tonight, February 17, Friday, 12:50 am (Eastern), and then re-aired on Sunday, February 19, 12:50 am (Eastern).
———————————————————————-
Someday, humans will be traveling far from Earth in large interplanetary spaceships not very different than the International Space Station (ISS). Isolated and dependent on these ships for survival, these travelers will have no choice but to know how to maintain and repair their vessels whenever something on them should break.

And things will break. Entropy rules, and with time all things deteriorate and fail.

Each failure, however, is also a precious opportunity to learn something about the environment of space. Why did an item break? What caused it to fail? Can we do something to prevent the failure in the future? Finding answers to these questions will make it possible to build better and more reliable interplanetary spaceships.

ISS is presently our only testbed for studying these kinds of engineering questions. And in 2007, a spectacular failure, combined with an epic spacewalk, gave engineers at the Johnson Space Center a marvelous opportunity to study these very issues.

In November 2007, astronauts were preparing the station to receive its last of four solar panel arrays. To install the last array, however, required moving an array from the one end of the station’s truss where it had been deployed for seven years to its permanent home on truss’s port side. To do this, the array was retracted, folding up accordion-like as designed. Astronauts then moved it to its new home, where it was then to be reopened.

Parazynski at the end of the robot arm

As the panel was unfolding, however, the array began to tear in two places. For some reason a guide wire had snagged on a grommet, pulling the paneling apart and causing two tears one and three feet in diameter respectively. The deployment was halted, and an emergency spacewalk was then improvised in which astronaut Scott Parazynski — hanging on the end of the shuttle’s inspection boom that was attached to the station’s robot arm and thus out there farther than any astronaut had ever hung — cut the guide wire and then used cufflink-like attachments and straps to sew the tears back together.

After this spacewalk the panel was unfolded as planned, so that the station’s construction could go forward.

While everyone enthused about Parazynski’s surgical repair that saved the station, engineers had a more mundane but equally important question. What caused the guide wire to come free and snag the array?

When Parazynski cut the wire, he stored it so that it could be returned to Earth. Engineers at the Johnson Space Center in Houston then inspected the wire’s frayed ends using scanning electron microscopes. You can read their paper here [pdf].

The results were quite unexpected: The guide wire had broken because it had been hit by a tiny piece of space junk, melting and splitting the wire but damaging nothing else.

This conclusion was supported by two pieces of evidence. First, the frayed ends of three wires in the guide wire bundle showed clear evidence of melting. As the engineers noted in their report,

melted guide wire ends

Micrometeoroid and orbital debris (MMOD) particles typically impact at high speed and release a large amount of energy, resulting in the displacement of target material with a mass 10 to 100 times the projectile mass due to melting and plastic flow local to the impact site. The presence of melt is a clear indication that the damage to these three wires was caused by MMOD impact. Other wires in the bundle appear to have been broken by mechanical action.

A likely scenario that explains the observed damage to the guide wire is that [an] impact damaged and broke a few of the wires, which allowed the guide wire to snag in a … grommet during deployment. Subsequently, as the process of deployment continued with a snagged guide wire, additional wires in the guide wire were sheared as they were pulled against the grommet.

The next question: What was it that hit the wire? Spectroscopy of the melt points showed no evidence of micrometeroid materials. Instead, the engineers found evidence of bismuth metal as well as alloys of gold-copper-sulfur, gold-silver-copper, lanthanum-cerium, antimony-sulfur, and tungsten-sulfur. None of these materials are found in asteroids, and none in the wire itself. Instead, these kinds of materials would be expected from a piece of engineered material once part of a satellite and now space junk.

The odds of such a collision seemed unlikely if impossible. The wire is tiny. Orbital debris is generally made of larger pieces that would have caused greater damage. Instead, what happened was a very small piece of space junk hit the wire — and only the wire — at high speed, breaking it.

What can be done to prevent this from happening again? Well, in Earth orbit the best solution is to reduce the amount of space junk. In this sense, the proposal by a Swiss company to launch an orbital “street sweeper” makes sense.

For interplanetary travel the problem is less worrisome, though small micrometeorites do exist. Though engineering work continues [pdf] to develop better shielding to protect the skin of spaceships, you can’t cover solar panels with shielding.

A more practical solution is to design the spacecraft so that the occupants can reasonably access all of its parts, and provide them the tools to make repairs, as Parazynski did during his space walk. In this sense, having several different robot arms, spacesuits, repair tools, spare parts, and training to do this sort of work seems essential for any spacefarers traveling beyond Earth orbit to another planet.

Like the sailors of old, space travelers will need to able to repair and even rebuild their spaceships, wherever they are. Any interplanetary spaceship design has got to factor this reality into its design.

Genesis cover

On Christmas Eve 1968 three Americans became the first humans to visit another world. What they did to celebrate was unexpected and profound, and will be remembered throughout all human history. Genesis: the Story of Apollo 8, Robert Zimmerman's classic history of humanity's first journey to another world, tells that story, and it is now available as both an ebook and an audiobook, both with a foreword by Valerie Anders and a new introduction by Robert Zimmerman.

 
The ebook is available everywhere for $5.99 (before discount) at amazon, or direct from my ebook publisher, ebookit. If you buy it from ebookit you don't support the big tech companies and the author gets a bigger cut much sooner.


The audiobook is also available at all these vendors, and is also free with a 30-day trial membership to Audible.
 

"Not simply about one mission, [Genesis] is also the history of America's quest for the moon... Zimmerman has done a masterful job of tying disparate events together into a solid account of one of America's greatest human triumphs."--San Antonio Express-News

3 comments

  • Joe2

    Excellent article.

    But, it does raise an interesting question for the people that propose to pursue BEO operations by launching numerous small payloads and having them assembled on site autonomously (no human supervision provided for – in case of malfunction).

  • James Fincannon

    Good article.

    “Instead, what happened was a very small piece of space junk hit the wire — and only the wire — at high speed, breaking it.”

    We don’t know for sure if only the wire was hit. Perhaps other separate particles passed through the solar array. The solar array is designed to still function (provide power) with minor impacts and even some cracked solar cells. The power/voltage might be degraded somewhat.

    Since the impact on the wire was near the base of the solar array, there is a chance (depending on the angle) the debris object(s) proceeded to the pressurized module(s) and truss structure below it. Fortunately, they have shielding.

  • totally fascinating story! Thanks Bob! – I also listened to the show it is great.

Readers: the rules for commenting!

 

No registration is required. I welcome all opinions, even those that strongly criticize my commentary.

 

However, name-calling and obscenities will not be tolerated. First time offenders who are new to the site will be warned. Second time offenders or first time offenders who have been here awhile will be suspended for a week. After that, I will ban you. Period.

 

Note also that first time commenters as well as any comment with more than one link will be placed in moderation for my approval. Be patient, I will get to it.

Leave a Reply to Walter Walkie

Your email address will not be published. Required fields are marked *