Scroll down to read this post.


I am now in the third week of my annual February birthday fund-raising drive. The first two weeks were good, but not record-setting.


There are still two weeks left in this campaign however. If you have been a regular reader and a fan of my work and have not yet donated or subscribed, please consider doing so. I take no ads, I keep the website clean from pop-ups and annoying demands (most of the time). Thus, 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

BepiColumbo about to do third Mercury flyby

In its long journey to get into orbit around Mercury, BepiColumbo needs to do nine different flybys of the inner planets, with third fly-by of Mercury coming up on June 19, 2023.

The mission launched into space on an Ariane 5 from Europe’s Spaceport in Kourou in October 2018 and is making use of nine planetary flybys: one at Earth, two at Venus, and six at Mercury, to help steer into Mercury orbit.

After this flyby, the mission will enter a very challenging part of its journey to Mercury, gradually increasing the use of solar electric propulsion through additional propulsion periods called ‘thrust arcs’ to continually brake against the enormous gravitational pull of the Sun. These thrust arcs can last from a few days up to two months, with the longer arcs interrupted periodically for navigation and manoeuvre optimisation.

The spacecraft will zip past Mercury at a height of 147 miles. If all goes well, this dual orbiter mission, carrying both a European and a Japanese orbiter will arrive in 2025, beginning a planned three year mission in different complementary orbits.

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


  • John hare

    To me, all these precision fly by maneuvers over many years is a symptom of undersized launchers. Given the time value of money and the man hours involved over the years it seems that an equivalent mission from a Falcon heavy could have producing results years ago instead of still waiting for the main event.

  • Star Bird

    They Mercury on Mercury is just too High

  • Edward

    John hare,
    The problem is that the delta-v for getting into Mercury’s orbit is almost as high as launching into low Earth orbit. The flybys are an attempt to use planetary gravity (various planets) to slow down rather than send a booster-sized rocket to slow the orbiter into orbit. Since it is unmanned, and since our probes are fairly reliable, taking this much time to get somewhere interesting has become routine practice.

    See this delta-v chart as an example of what it takes to get around the Solar System (please note that these are approximations based upon transfer orbits being the Hohmann transfer orbit, which (despite Hohmann’s intention) is not necessarily the lowest delta-v way to get around the Solar System*):

    The orbital mechanics who designed this route used what they had at the time. If Starship becomes operational, then we should expect either a larger payload or a more brute force route for the next Mercury probe.

    The Hohmann maneuver often uses the lowest possible amount of impulse (which consumes a proportional amount of delta-v, and hence propellant) to accomplish the transfer, but requires a relatively longer travel time than higher-impulse transfers. In some cases where one orbit is much larger than the other, a bi-elliptic transfer can use even less impulse, at the cost of even greater travel time.

  • john hare

    I am well aware of the reasons and methods of gravity assists. I am also well aware of the time value of information and the costs of keeping a team functional for extended periods of time. Without running the hard numbers, It is not obvious that all the meandering around saved money compared to buying a larger launcher, or using orbital refueling.. And it certainly reduced the effective duration of the mission. (time on station)

  • Edward

    John hare,
    The launcher large enough to lift the propellant needed to avoid these maneuvers does not yet exist. Orbital refueling is still a goal for the future. The time on station may not be limited by the stationkeeping propellant, it may be limited by the willingness for ESA and JAXA to continue funding the mission after it reaches the point of diminishing returns.

    Missions have a limited duration. Without these limits we would still have the Lewis and Clark mission in progress, as happens with all too many government programs (government missions). Despite all of rural America having been electrified many decades ago, the Rural Electrification Act continues to fund Rural Development in the Department of Agriculture.

    So I stand corrected. Some missions become their own empires that never die their natural death but plague us forever with unnecessary costs to We the American Taxpayer.


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

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