Tuesday, March 25, 2008

Spin Me to the Moon

Let's see. You're 82 years old, you're the father of the geostationary communications satellite, and you've won medals and honors and prizes all over the world presented by presidents and kings and other ne'er-do-wells. What to do now? Retire? Take up golf? Smell the roses?

The answer, if you're
 Harold Rosen, is none of the above. You look for a new challenge, one that you can solve in a unique way -- more cleverly and at a lower cost than anyone else. Since his so-called retirement some years ago from Hughes Aircraft Company's Space Systems Division (now part of Boeing), Harold barely left his office. He simply changed his title from vice president to consultant, and continues to work on novel satellite systems while waiting for big new challenges to emerge. [Full disclosure -- Harold is my brother.]

Six months ago, it happened. A really big challenge materialized -- the
 Google Lunar X Prize. This international competition is designed to land a robot on the surface of the moon, travel 500 meters over the lunar surface, and send images and data back to Earth. The first team to land on the moon and complete the mission objectives will be awarded $20 million.

As soon as the prize was announced, Harold began putting a team together and devising an elegant solution to the mission. The
Southern California Selene Group (SCSG) has attracted an all-star team of space scientists and engineers, one of whom is Deborah Castleman, a former deputy assistant secretary of defense for communications command and control, and also, by the way, the wife of Harold Rosen.

One of the main objectives of the Lunar X competition is to do privately and inexpensively what the government has been doing for decades for many hundreds of millions of dollars (and tens of billions for manned missions).

The competition has attracted a large number of applicants from around the world. Ten of them were accepted in February by the prize committee, including Harold's SCSG.

So how do you win this Mission Impossible, competing against a worldwide team of talented engineers, and do it at a low cost? The answer lies in history. To get an appreciation of why the Rosen team has a good chance, and maybe even an unfair advantage, we have to go back 50 years to the beginning of the space age.

After Sputnik was launched by the Soviet Union October 4, 1957, many people in the U.S. started thinking about not only how to compete with the Soviets, but what could be done productively in space. About a year later, and inspired by Arthur C. Clarke, Harold came up with the idea of creating a geostationary communications satellite. Clarke was, among other things, a science fiction writer, perhaps best known for writing the screenplay for Stanley Kubrick's movie, "2001."

But Clarke was also a visionary. In a May 1945 article in Wireless World, Clarke proposed a system of the three satellites orbiting at 22,300 miles above the Earth, an altitude that would put their period of revolution around the Earth at 24 hours -- the same period, of course, as the Earth's rotation. As a result, these geosynchronous satellites, if orbiting around the equator, would appear stationary to an observer on earth. This all-important feature would then permit antennas on earth to be fixed and inexpensive, rather than tracking and expensive.

Vision is one thing, but execution is another. Clarke had the vision; Harold set out to realize the vision. There were significant challenges to implementing a geosynchronous satellite. It would have to reach an altitude almost a hundred times higher than Sputnik. And its orbit would have to be, and to stay, precise. So a system had to be developed to keep the satellites from drifting out of their orbit; drift is caused by the earth's non-spherical shape, by solar pressure, and other perturbations. And all important, the signals from the antennas on the satellite had to point continuously to the fixed antennas on earth.

At the time, the conventional way of controlling a satellite's position and orientation was to use a three-axis stabilization system. But the problem with that approach is that it was complex, bulky and expensive for the technology of the 1960s. To solve the problem in an economical and practicable way, Harold conjured up a novel solution, one inspired by the way a quarterback throws a football.

Ever since he was an undergraduate student, Harold was intrigued with the physics of a football pass, and the spin that the quarterback put on the ball. Only when thrown with a spiral was the ball stable in flight. This led to his thinking that if we spin a satellite in orbit, it too would remain stable in its orientation in space. Indeed, this became the hallmark of the first synchronous satellite design. The spinning motion provided the stability needed, while clever spacecraft antenna design kept the signal pointed to the antennas on Earth. When implemented, three geostationary satellites 120 degrees apart could link the entire Earth.

AT&T, by contrast, was championing a more conventional approach -- hundreds of low-altitude satellites that communicated with tracking antennas on Earth. The cost? Astronomical. Each satellite would only be visible 20 minutes, requiring complex handoffs from one satellite and antenna to the next pair. Of course, low cost was not a motivation of AT&T in those days of rate-base regulation, where the higher your rate base, the higher your dollar return.

In 1962 successfully launched Hughes Syncom II to compete with AT&T's TelStar . Which would win the battle for communications supremacy -- the geosynchronous or the random orbit? As we now all know, the geosynchronous approach won. The newly created Communications Satellite Corp. selected a Hughes satellite, a follow-on to Syncom II dubbed Early Bird, to usher in the new world of satellite communications in 1963. David had beaten Goliath.

syncom - 1961
Thirty-five-year-old Harold Rosen (right) at an Eiffel Tower presentation in 1961 with a Syncom mock-up. One skeptical attendee said, "Dr. Rosen, this is as high as your satellite will ever go."

Now fast-forward 45 years to the Google Lunar X Prize. The mission is quite different from communication satellites, but the winning solution may have a striking similarity to Syncom.

Two of the most difficult problems to solve in this new competition are how to land the payload on the Moon (without crashing) and how to get it to roam on the Moon's surface. In the SCSG approach, the payload that lands on the Moon will be spinning, much as the quarterback spins his spiral pass. On separation from the launch vehicle, the payload spins itself up from the 6 rpm of the launch vehicle's spin to 50 rpm on landing. This spin gives it the stability to land reliably, simply and inexpensively without crashing.

Spinning has other benefits. It simplifies the attitude and orbit control systems, and it creates a more benign thermal environment for the delicate electronics inside the spacecraft.

Once we're on the Moon, how do we roam? The Moon's surface has very few paved roads. Indeed, it is replete with rocks, boulders, crevices, and other unwanted impediments to unfettered locomotion. The conventional approach, both historically and prospectively, has been to use a wheeled vehicle. This, however, can be complex and costly.

The Harold Rosen approach is as imaginative as it is different. The spinning payload, after landing on its spring-like legs on the Moon's surface, continues spinning (the body spins, the legs don't). When it's time to roam, instead of rolling on wheels, it
 hops; a small propellant thrusts it up off the surface; the spinning keeps it stable. Hopping has a big advantage. When approaching obstacles, it can, in the words of a legendary cartoon hero, leap over them in a single bound. SuperHopper!

southern_california_selene_group
Depiction of the Southern California Selene Group's payload landing on the moon. The body is spinning, the springy legs are not.

Last summer, when Harold and Deborah were visiting us in the country, he demonstrated the stability and hopping capability of his proposed system. To do it, he used one of the world's simplest and least expensive models: a skate wheel and two hairpins. I made a brief video of his demonstration, seen below:


Video showing advantages of spin stabilization

There is, by the way, one more non-trivial challenge. To develop the system and to pay for launch-vehicles services, a fair amount of money will have to be raised. Presumably, it will come from sponsors whose interests are not commercial but idealistic. The technical challenges may prove easier to solve.

Winning the Google Lunar X prize is not Harold's only improbable goal in life. He is in training to set the world record for the 100-meter dash -- for 100-year-olds. With 18 years to go, he feels he can easily beat the record set in 2004 by a South African centenarian, Philip "Flying Phil" Rabinowitz, who ran the 100 meters in a world record 30.86 seconds (a Jewish sprinter?).

Among his training techniques are Tarzan-like swinging from overhead rings at Muscle Beach in Santa Monica, and practicing a challenging form of yoga. Here's a shot of Harold performing with the yoga peacock. I photographed him doing the peacock last year when he was still a spry 81-year-old.

harold yoga 2
Harold Rosen performing a yoga peacock last year.

A final note. As brothers, we seem to be attracted to spinning objects. With Harold, it's spinning footballs, satellites, and lunar landers. With me, it's trays. While a member of the Fleming House Waiters Union as a Caltech undergrad in the early 50s, I became proficient at spinning trays on my finger. I'd like to think that Harold got his inspiration for spin-stabilized satellites from his brother rather than from a football, but he'll never admit to it.

Tray balance
Ben Rosen spinning a tray -- his version of the origin of spin-stabilized satellites and lunar landers.


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