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Give them an inch …

20/02/2012

… and the danger is that they won’t take precisely 2.54000507 centimetres.

We earthlings haven’t had a great deal of luck with Mars, because the little green men have occasionally tried very hard to inhibit our exploration of their little Red Planet. Oh yes, there have been notable successes such as NASA’s two Mars Rovers, Spirit and Opportunity, which engaged the popular imagination as they pootered across the planet’s surface and provided fascinating images of its silent desolation, to say nothing of the invaluable data that they have transmitted back to base. On the other hand, the Russians’ latest mission, Phobos-Grunt (Фобос-Грунт, literally Phobos-Ground but Phobos-Grunt has an irresistible euphony in English), which was also carrying a Chinese Mars probe, Yinghuo ( 萤火一号 or Firefly) never even got out of Earth orbit in November 2011. The whole lot burned up on re-entry on 15 January 2012.

After the still unexplained loss in 1993 of their Mars Observer mission, which simply went permanently out of contact 3 days before going into orbit around Mars, NASA tried again with the more successful Mars Global Surveyor of 1996. Then came Mars Climate Orbiter [MCO], which was launched at the end of 1998. The mission comprised the Orbiter itself and a landing probe. If you’re a cosmological train-spotter and want to know the detail, Wikipedia is your friend; that’s not we’re interested in here. No, we are concerned with the sometimes eye-watering cost of poor, sloppy or simply unfortunate flubs in proofreading or communication.

Nevertheless, everything went perfectly over MCO’s 416m mile trajectory until the final, (not very) triumphant moments of the journey. Just as the champagne was being eased out of the ice-buckets and the cigars (not Havanas, of course, thanks to JFK’s 50-year-old trade embargo and thus hardly worthy of the name) were having their ends clipped, the Orbiter went into Mars orbit far too steep and burned up in the atmosphere. As NASA’s post mortem report said:

“The MCO MIB has determined that the root cause for the loss of the MCO spacecraft was the failure to use metric units in the coding of a ground software file, “Small Forces,” used in trajectory models. Specifically, thruster performance data in English units instead of metric units was used in the software application code titled SM_FORCES (small forces). The output from the SM_FORCES application code as required by a MSOP Project Software Interface Specification (SIS) was to be in metric units of Newtonseconds (N-s). Instead, the data was reported in English units of pound-seconds (lbf-s). The Angular Momentum Desaturation (AMD) file contained the output data from the SM_FORCES software. The SIS, which was not followed, defines both the format and units of the AMD file generated by ground-based computers. Subsequent processing of the data from AMD file by the navigation software algorithm therefore, underestimated the effect on the spacecraft trajectory by a factor of 4.45, which is the required conversion factor from force in pounds to Newtons. An erroneous trajectory was computed using this incorrect data.”
[Mars Climate Orbiter Mishap Investigation Phase I Report]

In plain language, people were not using plain language. The engineers at Lockheed-Martin (the supplier) were using Imperial measures while NASA (the customer) was employing the industry standard and using Metric, and NASA had simply assumed that Lockheed-Martin had adjusted accordingly. The flight system software on the MCO had been written to calculate performance in Newtons (N), the metric unit, while the ground crew was entering course correction and thruster data with the Imperial measure of pound-force (lbf). As any fule kno (well, they do at St. Custard’s), a pound of force is equivalent to 4.448221615 Newtons (approximately!).

The total ‘torn up’ cost of NASA’s rash assumption was some $656m: broken down roughly as $328m for the 2 spacecraft themselves, $193m for spacecraft development, $92m for the launch and $43m for the operation of the mission. Ouch! Check everything. Check again.

Less than 3 months after MCO, NASA’s Mars Polar Lander crash-landed. That cost another $165m, the loss in that case being attributed to budget restraints and inexperience, blaming poor programming. “The software — intended to ignore touchdown indications prior to the enabling of the touchdown sensing logic — was not properly implemented, and the spurious touchdown indication was retained.” You know, pretty soon these millions start adding up towards serious money.

Taking any opportunity to expatiate upon cigars, JFK’s trade embargo on Cuba was signed on 3 February 1962. Late the previous afternoon, he had sent his Press Secretary, Pierre Salinger, out to buy as many Havanas as he could find. Salinger appeared the following morning with 1,200 Petit Upmanns, the President’s favourite stogie, and he immediately signed the decree. The Petit Upmann (now known as the Coronas Junior), is a fairly underwhelming machine-made smoke, in my view, but I expect that the President’s stash lasted until he took his fatal trip to Dallas in November 1963.

If you have the time for a couple of good yarns, here is Salinger telling the tale at a 1991 lunch in Wilton’s restaurant, Jermyn Street, London:

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