Wednesday, August 29, 2018

Looking for loft with all the comforts of home

I ran across this post over at the systemic blog about ballooning in the upper atmosphere of Venus and Jupiter. Presumably, there are sweet spots in their atmospheres where the temperature and pressure are close enough to STP at Earth's surface that a human could go ballooning in these locales with little more than breathing apparatus and attire suitable for surviving the climate (an acid-resistant full-body bathing suit for Venus, or a heavy parka for Jupiter).

In the case of Jupiter, however, the post leaves out one important detail: gravity. On Venus, the gravity is comparable to that on Earth. However, if one were to go ballooning among the cloud tops of Jupiter, one would likely spend a lot of time pinned to the floor of the gondola by about 2.5 g's (2.5 times the Earth's gravity).

The article reminded me of a little exercise in orbital mechanics that I had once worked out. I was looking for places in the solar system where one could experience about 9.8 m/s2 of gravitational acceleration and a 24 hour day. In addition to the Earth's surface, I thought that a space station orbiting a gas giant could possibly provide the proper environment. Simply place the center of gravity of the station in a 24 hour orbit around the planet, and extend a pair of tethers up and down from there such that a full 1G would be felt at either end. At the lower end, the force of the planet's gravity exceeds the centripetal force due to the orbit by exactly 1G, and at the upper end the reverse is true.

Let R denote radial distance from the center of the planet, and H be the height above the commonly accepted "surface" of each body. The numbers given below are for each planet around which this theoretical orbiting station could exist.

For Jupiter:
R[lower] = 110385 km
R[orbit] = 288208 km
R[upper] = 1861246 km
H[lower] = 39015 km

For Saturn:
R[lower] = 61187 km
R[orbit] = 192841 km
R[upper] = 1856417 km
H[lower] = 787 km

For Uranus:
R[lower] = 24196 km
R[orbit] = 103222 km
R[upper] = 1854656 km
H[lower] = 666 km

For Neptune:
R[lower] = 26324 km
R[orbit] = 109229 km
R[upper] = 1854715 km
H[lower] = 4024 km

If this same process is applied to the Earth, we get the recipe for a space elevator.

For Earth:
R[lower] = 6363 km
R[orbit] = 42233 km
R[upper] = 1854357 km
H[lower] = 0 km

Curiously, we see that no matter what planet we are orbiting, the upper end of the tether is always at approximately the same radial distance. As I look back at my equations now, I see that there is a weak dependence on M, however the coefficient is exceedingly small. The first two terms of the series expansion are:

R[upper] = 1854336 + M*3.6695e-16 + ...

where R is in km and M is in kg. I'm sure this is probably a well established conclusion in orbital mechanics or general relativity, but it's the first time I've encountered it.

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ISS-Alpha

I had a thought recently concerning public engagement with NASA's human spaceflight program. I was puzzling how the Hubble telescope, and the Mars rovers could get such good exposure with the public, and yet the ISS and Space Shuttle, let alone the astronauts themselves are barely acknowledged. I had also been reading a number of articles which described NASA's PR problem as essentially not being able to tell a good story. (We'll assume for the moment that they actually have a compelling story to tell.)

Then it slowly dawned on me. To understand the public's engagement with certain aspects of the space program, just look at how they refer to Hubble, Spirit, and Opportunity. This as opposed to The International Space Station, or the Space Shuttle Atlantis. Or even, The Crew of Expedition 20 to the ISS. Do you see the difference?

The Hubble Space Telescope, and the Mars Exploration Rovers have been successfully anthropomorphized. They have been transformed from mere pieces of hardware into entities unto themselves. We care about whether Hubble is revived and rejuvenated or left to burn up in the atmosphere. We've started rooting for those plucky little probes that just keep on going and going, exploring the places that we fancy ourselves going someday. People tend to imagine that these probes have grit and determination, even if they realize deep down that they are just remotely controlled devices.

And it really is not that hard to do. I believe that humans are at least partially hard-wired to attribute familiar qualities to inanimate objects or even natural physical processes. Consider how the ancient Greeks anthropomorphized the Sun, Moon and planets, as well as wind, rain, seasons, etc. All of these were given the guise of deities, each with their own motivations desires, and emotions. It is this ability to project human qualities onto these inanimate objects that allow us to empathize with them. This empathy moves us to interact more fully with the object. This allows us to better understand it and possibly respond more effectively when its behavior suddenly changes.

What conclusions can we draw from this? Well, apparently it's not enough for a mission to be nominal, and its science output to be outstanding. To be truly successful in capturing the imagination of the public, there has to be some part of the mission which people can identify with. Whether it be an probe, a spaceship, an astronaut, or even the science itself, when the story is told there needs to be something that people can empathize or identify with.

Now, let's see if I can remember my creative writing lessons correctly: To tell a compelling story, you need to have a sympathetic character, the hero, who must obtain something of great value (either in general or personally). Then, there is the journey, wherein there are obstacles to be overcome and problems to be solved along the way. Then, there's the climax where the goal is within reach. And finally, the resolution; where the hero either gets what he is after and/or realizes something more profound after having made the journey.

Nearly all of our spaceflight endeavors have all of the elements of a good story. Unfortunately, we have not had very many good story tellers. Just off the top of my head, the ISS is an excellent story waiting to be told. It's more than just a place. The ISS is the realization of an epic quest to establish a foothold among the stars. It's very existence is a testament to the imagination, ingenuity and dedication of humanity. That what it wants more than anything is to be allowed to fulfill its potential as a research station, and a way point to the stars for humanity. It is a port of call (come on people, think Babylon 5).

ISS-alpha has been on a journey from concept to reality for thirty years. Her birth was tricky, and she has grown quickly throughout these first twelve years of life. Now, she is nearly fully grown and ready to start a useful and productive life. But wait, there is still trouble ahead. There are those who would see her fail, even now. Those who would starve her of the resources she needs to stay aloft and to care for her human crew. Those who do not recognize her true potential to do great things for humanity.

Will ISS-Alpha be allowed to continue on her quest? Will she be allowed to continue caring for her human crew? Or will the short-sighted bureaucrats deny her the opportunity to prove her worth? Will she be destroyed in a flaming death when she can no longer keep herself aloft? What lessons have we learned from ISS-Alpha while following her on her journey? What more is there that she can tell us by allowing her to continue?

People are not always rational. They make decisions based on what they feel is the right thing to do in any given circumstance. I've heard several times that we could have built and launched an improved version of Hubble for less money than we've spent in the various missions required to upgrade and repair it. Meh.. Maybe, maybe not. But if we were to do that, then they would be just another bunch of satellites, like a Chandra or Spitzer. They will continue to produce great science through out their useful service lives, but when they eventually fail, they will have no chance of redemption.

If we really want to reach out to people beyond our narrow circles of fellow space enthusiasts, we have to learn how to tell a compelling story about all of the great (and not-so-great) things that are happening. We have to tell the story in such a way that people actually start caring about what happens next. They need to be engaged to the point where they can't help themselves but to imagine what it must be like. If we tell the story right, then our audience should be able to come to their own conclusions and actually form their own opinions as to what they think we should be doing in space. Whether these opinions are good or bad, they will at least have them and will be prepared to make an issue out of it if it happens to come up in conversation in the future. This is the kind of engagement we need to get from the general public.

So, I will be rethinking how I relate to ongoing and future space missions. I want to engage them on a more personal level, but more importantly, I want others, who don't normally think about these things, to be inspired, or outraged, or something.. anything.. except apathetic. Because I've been apathetic. Not about space, but about enough other things to know that there is nothing more frustrating than feeling like there is nothing you can do that will make a difference, especially when we really need to start making a difference.

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