NASA rocket transporter: in slow motion to the launch pad

NASA crawlers Hans and Franz
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The second largest land vehicles on the planet (in first place are the S bucket-wheel excavators from the open pit ) weigh each 2,857 tons, as much as 1,000 pickup trucks. Hans and Franz, or as they were technically correct called 'CT-1' and 'CT-2' (Crawler Transporter), were developed and built to move the nearly 3,000 ton Apollo Saturn V moon rocket from its production hall in the Kennedy Space Center to 76 kilometers away from launch pad 39B. They can currently transport loads of up to 10,000 tons. And that with today's laser-based accuracy of up to 6.35 millimeters. Their first day of work was in August 1967 (unmanned Apollo 4 mission).

During their decades of work, the crawlers transported seven different types of rockets, including the Saturn V and all five space shuttles. Every Apollo moon mission began with a crawler ride to the launch pad, just like every shuttle mission. That means: No moon landing without a crawler.

Two moving baseball fields

The crawlers are real load donkeys.

The 39.9 meter long and 34.5 meter wide mobile monsters have a 752 square meter transport area - practically the same size as a baseball infield, the so-called diamond (exactly 752.51 square meters). That should be a coincidence even with the sport-crazy Americans. For Europeans: Either a handball game (800 square meters) or 4.5 volleyball matches could be held on a crawler at the same time. However, it becomes problematic at the edge of the field: it is up to 7.9 meters high. But the ball games could also be played while drivingtake place, because the top speed is a comforting 3.22 kilometers per hour. This is made possible by a gear ratio of 168: 1.

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Anyone who thinks that a humane fuel consumption can be expected at such a snail's pace is very wrong. At a fuel price of 1.50 euros per liter, 58,215 euros would be due after 100 kilometers. The colossuses consume 38,810 liters per 100 kilometers or 388.1 liters per kilometer. In view of the fuel tank volume of 18,927 liters, it quickly becomes clear that such distances are not on the plan. At the petrol station, the sentence “Complete please” would also be answered with a 28,391 euro bill.

39-page manual on the subject of “Starting”

Around ten The 6.76 kilometer journey takes hours. Here the space shuttle Discovery arrives at launch pad 39A.

To pick up the rocket, the crawlers drive under the launch platform including the rocket, connect using the 16 JEL (Jacking, Equalizing, Leveling) hydraulic cylinders at four points with it and then sneak 5.47 kilometers to launch pad 39A or 6.76 kilometers to launch pad 39B. 'The two crawlers have already covered over 5,400 kilometers (CT-1 1,915 km, CT-2 3,600),' enthuses NASA Shuttle Processing Director Michael Wetmore on the NASA website. “This is not because we have an 8,000 kilometer or 50 year guarantee, but because of the ambition of the men who keep these machines running,” he explains. Alone the manual for the start-up processCrawlers consists of 39 pages.

Four different systems develop the power to drive the four trucks at each of the four corners of the crawler and for its hydraulic system. Two 2,788 hp 16 cylinder locomotive diesel engines and four 1,000 kilowatt generators generate direct current. The alternating current is provided by two further 16-cylinder diesel engines, each with 2,220 hp and two 1,500 kilowatt generators. In 2012, the CT-2 diesel engines were replaced by two 2,040 hp diesel engines. In order to enable the start of the SLS 1 /EM-1 and all other Mars test and final Mars missions planned for December 2019, the engineers increased the maximum load capacity of the CT-2 from 5,443 tons to almost 10,000 tons ( or 20 fully loaded Boing 777 aircraft).

The largest shoes in the world

Bob Myers, a crawler systems engineer, stands in one of the cockpits of a NASA crawler.

456 links of the total of eight drive chains are significantly involved in driving the crawlers (there are two chains on each of the four corners). A chain link, known by crawlers as a “shoe”, is 2.3 meters long, 46 centimeters wide and weighs 998 kilograms. By 2004 the 'shoes' came from the Marion Power Shovel Company. The current 1,060 shoes in total come from ME Global Manufacturing in Duluth, Minnesota.

Minimalism reigns in the cockpit of a crawler: a small, red steering wheel in go-kart format is in the center. The speedometer can be found directly behind it. It ranges from 0 to 3.22 kilometers per hour (0 to 2 miles per hour). The speed itself is controlled by a button on the left side. Displays on the right reflect the height, steering angle and status of the laser docking system. The driver's seats have three settings: sit, lean, stand.

This is how a legendary giant drives

The big question is, of course, how does such a monster actually drive? Sylvan “Skip” Montagna, one of the few, has the answer(We are talking about a handful) Driver of the crawler: 'When we drove the Apollo missiles out of the huge production hall the 6.76 kilometers to the launch pad, we needed a total of over ten hours and around 30 engineers, including three drivers, including me. We drivers rotated every three hours.

20 Boing 777 aircraft (stacked) could be transported on the platform of the crawler.

Driving these vehicles was very monotonous. The problem is, it's so slow. The engineers told us we could go 1 mile per hour (1.6 km /h), but only if it was absolutely necessary. So we drove at around 1.2 kilometers per hour. To travel so slowly over such a distance and to keep the vehicle straight on the road is extremely boring - but at the same time very demanding! Because such a crawler loves to drift away. So you have to constantly use the controls in order to work against this inclination all the time.

In addition, if you sneak up the five percent incline to the launch pad, you have to orientate yourself on something. Nowadays the crawlers have a computer-controlled guidance system that navigates them exactly there. We had a yellow rope. That was on the edge and we had to drive right along this yellow rope. We were like dinosaurs. At the same time, such an hour-long drive is incredibly annoying because it is very loud and you are shaken the whole time. 'Bob Myers, also a former crawler driver, adds:' However, if you have over 8,000 tons on the roof, come you see the 1.5 km /h damn fast. '

The beginnings of the crawlers

In July 1964 the first crawler tests took place. Left to right: Richard L. Drollinger, Director of Engineering, Marion Power Shovel Co .; Theodor A. Poppel and Donald D. Buchanan, both from the Kennedy Space Center; S. J. Fruin, Executive Vice President and Philip Koehring, Project Engineer, both from Marion; and Kurt H. Debus, Center Director at Kennedy.

It is May 25, 1961, as US President John F. Kennedy Steps in front of the microphones and announces, “It is time for this nation to take a clear leadership role in space.” Why did he do this? Very simple: six weeks earlier, on April 12, 1961, the 1.57-meter-tall Russian cosmonaut Yuri Gagarin completed an orbit around the earth in 108 minutes and then landed unscathed in the Volga region. Reason enough for the Americans to invest huge sums in the Gemini project led by Wernher von Braun. On July 21, 1969 at 3:51 a.m. German time, the time had come: Neil Armstrong was the first person to step on the moon in front of over 500 million TV viewers and his President Richard Nixon. Without the crawlers, this chapter of human history could never have been written.

Because developing and producing a 110 meter high rocket with 33,737.5 kilonewtons of thrust is one thing. Transporting them from their place of birth to the launch pad is another. This is exactly where Philip Koehring enters the history stage. Because when the Marion Power Shovel Company was entrusted with the task of developing the crawlers in the early 1960s, the project manager switched from the competitor Bucyrus-Erie to the crawler developers in Ohio. A company that has so far been involved with the largest land vehicles in the world: bucket wheel excavators. His job: to convert the huge caterpillar vehicles into rocket taxis. The results of this task have been going back and forth in the Sunshine State for over half a century.


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