Leadership: the curious lasting appeal of the space lander superfluous fourth leg, and what to do about it

Leadership: the curious lasting appeal of the space lander superfluous fourth leg, and what to do about it

This article suggests testing three, or five, landing gear or legs for a lander rather than the ubiquitous four used since the 1960s when the Apollo 11 Eagle successfully landed on the Moon’s Sea of Tranquility. The scope is landers launching people and equipment into space, but don’t let that limit your own problem solving imagination.

You’ve seen and experienced the thrill of spacecraft landing here on Earth, the moon, and beyond. There it is, in historic black and white, or improving to 4K color; the craft extends four legs to stick the landing.?

Yet there is the common but untested logic, a lander doesn’t need four legs. Rather, three is the minimum required, making the rocket simpler and more cost-efficient, or at least five is needed for full safety and redundancy. Still, for more than 50 years we seem to be stuck with four. Four is a bore. It’s time for change.

You only need three legs

Check it out for yourself with a simple experiment or two. Cut one leg off of your favorite four-legged chair. What happens? Remove a wheel from your favorite four-wheeled car. What happens? Snatch a leg from a three-legged stool, make it a favorite if you have one. What happens? Rewatch several videos, or read the online article, of different spacecraft losing one of its four legs. Examples go back at least as far as the 1990s DC-X. Some of these vehicles have already flown into space and some are still experimental. What happened? If you didn’t try this at home, let me tell you that in all cases the object falls over when one of the four is lost. (Be sure to revisit all the amazing landings, too, still exciting even with that extra leg!)

There are definitely many examples with three points of contact, including airplanes. Recall Black Widow in her own iconic landing pose. Yep, just two legs and one arm for a total of three. Music drum sets only use three legs for cymbals and snares. Handheld cameras are steadied using a tripod.?

For rockets, three legs must be spread out across greater than all of them on the same 180 degrees of the vehicle, and all on the same side is the result when a four-legged lander unfortunately has one leg removed. Now, sure, in that situation there is the rather small chance that the center of gravity of the rocket is slightly on the same side as the remaining three legs, but not slightly enough to guarantee that an astronaut moving around wouldn’t change that, or that the descent ladder is also on the same side of the vehicle. Think of the car teetering on the edge of a cliff in a dramatic or comical movie. In summary, if the current rocket design loses a fourth leg, the vehicle and possibly the mission is lost. At best, all you really have is a false sense of security, reflecting our near universal usage of four-legged animals for transportation, chairs to sit in, and cars to ride on. We can do better.

Another interesting point to consider about three legs, is that they are more stable on an uneven surface, as four legs tend to wobble. For example, place a small rock under the leg of your now-favorite chair (since you ruined your previous favorite a little while ago), or put one leg over a shallow hole, and what happens? Next, do the same with a three-legged stool. Similarly, the moon is infamously notorious for having craters and boulders, making tilt a bigger risk with four legs rather than three. The same risk is experienced on other planets, moons, asteroids, and comets.

Three legs is simpler and less expensive

Going back even further in spacecraft history, we didn’t start with landers using four legs. Surveyor had three legs. Luna had three legs. Apparently for larger vehicles, we decided more is better. And certainly to increase safety, it would be better to have five legs for reducing risk if a leg is lost. This risk reduction is even more paramount with landers carrying human life.

And yet on the Apollo lunar lander, the initial requirement for five legs was tossed aside and the number reduced to four. So much for the safety of human life. Sure, they were also trying to reduce weight and fit the vehicle into the already too small volume of the launch craft. I’m not being critical here; the specs were done years before anyone had done anything like this; decisions were made within context constraints. I just think design solutions should be revisited today; it’s really pretty amazing back then what those space pioneers accomplished. My point is, even back then the lander could have been even lighter and taken less room with three legs, without any additional risk to mission or life. Today, with all of our technological advances, we definitely should reconsider past decisions.

Three legs can be designed for the load

Let’s say that a landing craft weighs 500, using an unnamed unit for illustrative purposes. Each leg on a four-legged craft must bear 125 (the result of 500 divided by 4). That number is the bare minimum design requirement. There might be additional load from unused rocket fuel, future updates to the lander, or extra force from too fast of a landing. So we would include in the design requirement a safety factor, which might bring the load bearing weight up to 150 or even 175.?

We would need to consider how much extra weight is added to each of these now stronger legs, as compared to bringing along a superfluous fourth leg. Some of you have already jumped ahead of me, done the math, and noticed that three legs only need to carry 167 each, which is already below the previously mentioned 175. Design each of the three legs for 175, consider the simplification and cost reductions throughout the vehicle, and you might be ready to do some initial testing.

Test three legs and improve

Of course, space is all much more complicated than my example above. So much so that we would really benefit from testing the three-legged approach. Then compare those results to all the development time, systems, electrical harnesses, computer code, testing, mission control, and other costs associated with using four legs.?

There is a predictable cost savings to remaining the same, not incorporating changes, and remaining in stasis. There is an even greater cost loss from not checking out new ideas or following continuous improvement. How awesome to test and verify that perhaps you do have the best solution, and how awesome to test and verify a different and improved better solution.

It seems to me, from my simple online search for publicly-available information, that a three-legged lander hasn’t been tested. Instead, we’ve just maintained and brought forward a decision from the 1960s. Those were different times and circumstances for space. I’ve also found online posts that suggest that four legs are needed, based on using an online simulator. While it’s an incredible simulator, simulations aren't real and can’t take into account all the design decisions a top engineer or team may come up with to simplify, reduce costs, and maintain safety. My response is similar to just using math to explain why we should use four legs rather than three.

Test, test, test, to verify and improve and move forward. Document your results with video. Document the why behind the what and how. Come up with another solution from what has been done before. Do something stupendous that is simpler and less expensive, which helps launch and then land equipment, vehicles, research, people, and ongoing missions to space.

Now it’s your turn

Some of you work on rocket legs, or landing legs, or whatever you specifically call them. Some of you are in positions impacted by using those four legs. Do some experiments. Do some calculations. Ask questions. Challenge past decisions. Involve and let others know what you are doing. Be the hero that helped bring simpler and less expensive into space by first testing and then using a three-legged lander.

Looking forward to seeing how you solve the three-legged lander to simplify, reduce cost, and maintain safety. Or use five legs rather than four, if it’s more likely that the lander will lose one. I’d be happy to help you succeed.

Thank you.

Tom Sehmel | Leader Development and Coach | https://www.dhirubhai.net/in/tomsehmel/

#Leadership #Space #STEM #Change #ContinuousImprovement #NewIdeas #Testing