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Readers!

 

My July fund-raising campaign to celebrate the fifteenth anniversary since I began Behind the Black is now over. I want to thank all those who so generously donated or subscribed, especially those who have become regular supporters. I can't do this without your help. I also find it increasingly hard to express how much your support means to me. God bless you all!

 

The donations during this year's campaign were sadly less than previous years, but for this I blame myself. I am tired of begging for money, and so I put up the campaign announcement at the start of the month but had no desire to update it weekly to encourage more donations, as I have done in past years. This lack of begging likely contributed to the drop in donations.

 

No matter. I am here, and here I intend to stay. If you like what I do and have not yet donated or subscribed, please consider supporting my work here at Behind the Black. You can support me either by giving a one-time contribution or a regular subscription. There are four 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 or subscription:

 

4. Donate by check, payable to Robert Zimmerman and mailed to
 
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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.


European engineers develop a tumbling rover design moved by the Martian wind

Tumbleweed being tested on sandy ground
Tumbleweed being tested on sandy ground. Click for video.

European engineers at Aarhus University in Denmark have now developed and tested a tumbling rover design that is propelled solely by the Martian wind. You can read their most recent paper here.

Not surprisingly, they call it “Tumbleweed.” The screen capture to the right comes from a video of a wind tunnel test proving the Martian atmosphere could move a prototype on sandy ground. The engineers also did similar tests successfully on rocky and coarse ground.

In July 2025, Team Tumbleweed conducted a week-long experimental campaign, supported by Europlanet, at Aarhus University’s Planetary Environment Facility. Using scaled prototypes with 30-, 40- and 50-centimetre diameters, the team carried out static and dynamic tests in a wind tunnel with a variety of wind speeds and ground surfaces under a low atmospheric pressure of 17 millibars.

Results showed that wind speeds of 9-10 metres per second were sufficient to set the rover in motion over a range of Mars-like terrains including smooth and rough surfaces, sand, pebbles and boulder fields. Onboard instruments successfully recorded data during tumbling and the rover’s behaviour matched fluid-dynamics modelling, validating simulations. The scale-model prototypes were able to climb up a slope of 11.5 degrees in the chamber – equivalent to approximately 30 degrees on Mars – demonstrating that the rover could traverse even unfavourable slopes.

Their concept is to send a swarm of Tumbleweeds to Mars, where they could cheaply document prevailing wind and speeds globally. More sophisticated versions could act as full weather stations, as well as provide in situ data about the landscapes they traverse.

The concept is still in its development stage. The next stage of testing will see if Tumbleweed will work with some science sensors attached.

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 print edition can be purchased at Amazon or from any other book seller. If you want an autographed copy the price is $60 for the hardback and $45 for the paperback, plus $8 shipping for each. Go here for purchasing details. 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

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