Space Power!

On Earth we can deploy a 164-ton wind turbine to generate 1.5 megawatts of electricity, but in the also energy-hungry environment of space travel, far more efficient energy-per-mass systems are a must. The choices for such systems are not unlimited in the vacuum of space!

OK…this is a rather obscure topic, but as I discussed in my previous blog, in order to create space propulsion systems that can get us to Mars in a few days, or Pluto in a week, we need some major improvements in how we generate power in space.

I am going to focus my attention on ion propulsion, because it is far less controversial than any of the more efficient nuclear rocket designs. Although nuclear rocket technology is pretty well worked out theoretically and in engineering designs since the 1960s,   there is simply no political will to deploy this technology in the next 50 years due to enormous public concerns. The concerns are not entirely unfounded. The highest-efficiency and least massive fission power plants would use near-weapons grade uranium or plutonium fuel, making them look like atomic bombs to some skeptics!

Both fission and fusion propulsion have a lot in common with ordinary chemical propulsion. They heat a propellant up to very high temperatures and direct the exhaust flow, mechanically, out the back of the engine using tapered  ‘combustion chambers’ that resemble chemical rockets. The high temperatures insure that the isotropic speeds of the particles are many km/sec, but the flow has to be shaped by the engine nozzle design to leave the ship in one direction. The melting temperature of a fission reactor is about 4,500 K so the maximum speed of the ejected thermal gas (hydrogen) passing through its core is about 10 km/sec.

Ion engines are dramatically different. They guide ionized particles out the back of the engine using one or more acceleration grids. The particles are electrostatically guided and accelerated literally one at a time, so that instead of flowing all over the place in the rocket chamber, they start out life already ‘collimated’ to flow in only one direction at super-thermal speeds. For instance, the Dawn spacecraft ejected Zenon particles at a speed of 25 km/sec. If you had a high-temperature xenon gas with particles at that same speed, the temperature of this gas would be 4 million Celsius! Well above the melting point of the ion engine!

We are well into the design of high-thrust ion engines, and have already deployed several of these. The Dawn spacecraft launched in 2007 has visited asteroid Vesta (2011) and dwarf planet Ceres (2015) using a 10 kilowatt ion engine system with 937 pounds of xenon propellant, and achieved a record-breaking speed change of 10 kilometers/sec. It delivered about 0.09 Newtons of thrust over 2,000 days of continuous operation. Compare this with the millions of Newtons of thrust delivered by the Saturn V in a few minutes.

Under laboratory conditions, newer ion engine designs are constantly being developed and tested. The NASA NEXT program in 2010 demonstrated over 5.5 years of continuous operation for a 7 kilowatt ion engine. It used 862 kg of xenon and produced a thrust of 3.5 Newtons, some 30 times better than the Dawn technology.

Theoretically, an extensive research study on the design of megawatt ion engines by David Fearn presented at the Space Power Symposium of the 56th International Astronautical Congress in 2005 gave some typical characteristics for engines at this power level. The conclusion was that these kinds of ion engines pose no particular design challenges and can achieve exhaust speeds that exceed 100 km/sec. As a specific example, an array of nine thrusters using xenon propellant would deliver a thrust of 120 Newtons and consume 7.4 megawatts. A relatively small array of thrusters can also achieve exhaust speeds of 1,500 km/sec using lower-mass hydrogen propellants.

Ion propulsion requires megawatts of energy in order to produce enough continuous thrust to get us to the high speeds and thrusts we need for truly fast interplanetary travel.

The bottom line for ion propulsion is the total electrical power that is available to accelerate the propellant ions. Very high efficiency solar panels that convert more than 75% of the sunlight into electricity work very well near Earth orbit (300 watts/kg), but produce only 10 watts/kg near Jupiter, and 0.3 watts/kg near Pluto. That means the future of fast space travel via ion propulsion spanning our solar system requires some kind of non-solar-electric, fission reactor system (500 watts/kg) to produce the electricity. The history of using reactors in space though trivial from an engineering standpoint, is a politically complex one because of the prevailing fear that a launch mishap will result in a dirty bomb or even a Hiroshima-like event in the minds of the general public and Congress.

The Soviet Union has been launching nuclear reactors into space for decades in its Kosmos series of satellites. Early in 1992, the idea of purchasing a Russian-designed and fabricated space reactor power system and integrating it with a US designed satellite went from fiction to reality with the purchase of the first two Topaz II reactors by the Strategic Defense Initiative Organization (now the Ballistic Missile Defense Organization (BMDO). SDIO also requested that the Applied Physics Laboratory in Laurel, MD propose a mission and design a satellite in which the Topaz II could be used as the power source. Even so, the Topaz II reactor had a mass of 1,000 kg and produced 10 kilowatts for an efficiency of 10 watts/kg. Due to funding reduction within the SDIO, the Topaz II flight program was postponed indefinitely at the end of Fiscal Year 1993.

Similarly, cancellation was the eventual fate of the US SP-100 reactor program. This program was started in 1983 by NASA, the US Department of Energy and other agencies. It developed a 4000 kg, 100 kilowatt reactor ( efficiency = 25 watts/kg) with heat pipes transporting the heat to thermionic converters.

Proposed SP-100 reactor ca 1980  (Image credit: NASA/DoE/DARPA)

Believe it or not, small nuclear fission reactors are becoming very popular as portable ‘batteries’ for running remote communities of up to 70,000 people. The Hyperion Hydride Reactor is not much larger than a hot tub, is totally sealed and self-operating, has no moving parts and, beyond refueling, requires no maintenance of any sort.

Hyperion, Uranium Hydride Reactor (Credit:Hyperion, Inc)

According to the Hyperion Energy Company the Gen4 reactor has a mass of about 100-tons and is designed to deliver 25 megawatts electricity for a 10-year lifetime, without refueling. The efficiency for such a system is 250 watts/kg! Of course you cannot just slap one of  these Bad Boys onto a rocket ship to provide the electricity for the ion engines, but this technology already proves that fission reactors can be made very small and deliver quite the electrical wallop, and do so in places where solar panels are not practical.

Some of the advanced photo-electric system being developed by NASA and NASA contractors are based on the solar energy technology used in the NASA Deep Space 1 mission and the Naval Research Laboratory’s TacSat 4 reconnaissance satellite, and are based on ‘stretched lens array’ lens concentrators for sunlight that amplify the sunlight by up to 8 times (called eight-sun systems). The solar arrays are also flexible and can be rolled out like a curtain. The technology promises to reach efficiency levels of 1000 watts/kg, and less than $50/watt, compared to the 100 w/kg and $400/watt of current ‘one sun’ systems that do not use lens concentrators. A 350 kW solar-electric ion engine system is a suggested propulsion for a 70 ton crewed mission to Mars. With the most efficient stretched lens array solar arrays currently under design, a 350 kW system would have a mass of only 350 kg and cost about $18 million. The very cool thing about this is that improvements in solar panel technology not only directly benefit space power systems for inner solar system travel, but lead to immediate consumer applications in Green Energy!  Imagine covering your roof with a 1-square-meter high efficiency panel rather than your entire roof with an unsightly  lower-efficiency system!

So to really zip around the solar system and avoid the medical problems of prolonged voyages, we really need more work on compact power plant design that is politically realistic. Once we solve THAT problem, even Pluto will be a week’s journey away!

Check back here on Monday, April 24 for my next topic!

That was then, this is now!

Back in the 1960s when I began my interest in astronomy, the best pictures we had of the nine planets were out of focus black and white photos. I am astonished how far we have come since then and decided to devote this blog to a gallery of the best pictures I could find of our solar system neighbors! First, let’s have look at the older photos.

First we have Mercury, which is never very far from pour sun and a very challenging telescopic object.

Above is what mars looked like! Then we have Jupiter and Saturn shown below.

Among the hardest and most mysterious objects were Uranus shown here. I will not show a nearly identical telescopic view of Uranus.

Finally we come to Pluto, which has always been a star-like object for most of the 20th century.

These blurry but intriguing images were the best we could do for most of the 20th century, yet they were enough to encourage generations of children to become astronomers and passionately explore space. The features of mercury were mere blotches of differing shaded of gray. Uranus, Neptune were slightly resolvable to reveal faint details, and distant Pluto remained completely star-like and unresolved, yet we knew it was its own world many thousands of kilometers across. Mars continued to reveal its tantalizing blotchy features that came and went with the seasons along with the ebb and flow of its two polar ice caps. Jupiter was a banded world with its Great Red Spot, but the details of these atmospheric bands was completely hidden in the optical smearing of our own atmosphere. Saturn possessed some large bands, and its majestic ring system could be seen in rough detail but never resolved into its many components. As for the various moons of these distant worlds, they were blurry disks or star-like spots and never revealed their details.

The advent of the Space Program in the 1960s, and the steady investment in spacecraft to ‘fly by’ these planets led to progressively higher and higher resolution images starting with Mariner 4 in 1965 and its historic encounter with Mars, revealing a cratered, moonlike landscape. The Pioneer spacecraft in the early 1970s gave us stunning images of Jupiter, followed by the Voyager spacecraft encounters with the outer planets and their moons. Magellan orbited Venus and with its radar system mapped the surface to show a dynamic and volcanic surface that is permanently hidden beneath impenetrable clouds. Finally in 2015, the New Horizons spacecraft gave us the first clear images of distant Pluto. Meanwhile, many return trips to our own moon have mapped its surface to 2-meter resolution, while the MESSSENGER spacecraft imaged the surface of Mercury and mapped its many extreme geological features. Even water ice has been detected on mercury and the moon to slacken the thirst of future explorers.

For many of the planets, we have extreme close up images too!
Jupiter’s south pole from the Juno spacecraft shows a bewildering field of tremendous hurricanes each almost as large as Earth, swirling about aimlessly in a nearly motionless atmosphere.

Pluto details a few hundred meters across. Can you come up with at least ten questions you would like answers for about what you are seeing?

Here is one of thousands of typical views from the Martian surface. Check out the rocks strewn across the field. Some are dark and pumice-like while others are white and granite-looking. ‘Cats and dogs living together’. What’s going on here?

The Venera 13 image shown below from the surface of Venus is unique and extremely puzzling from a surface that is supposed to be hotter than molten lead.

We also have images from a multitude of moons, asteroids and comets!
The Lunar Reconnaissance Orbiter gave us 2-meter resolution images of the entire lunar surface allowing us to revisit the Apollo landing sites once more:

The dramatic canyons and rubble fields of a comet were brought into extreme focus by the Rosetta mission

Even Saturn’s moon Titan has been explored to reveal its extensive liquid nitrogen tributaries

This bewildering avalanche of detail has utterly transformed how we view these worlds and the kinds of questions we can now explore. If you compare what we knew about Pluto before 2015 when it was little more than a peculiar ‘star in the sky’, to the full-color detailed orb we now see, you can imagine how science progresses by leaps and bounds through the simple technique of merely seeing the object more clearly. It used to be fashionable to speculate about Pluto when all we knew was its size, mass and density and they it had a thin atmosphere. But now we are delightfully challenged to understand this world as the dynamic place that it is with mountains of ice, continent-sized glaciers, and nitrogen snow. And of course, the mere application of improved resolution now lets us explore the entire surface of our moon with the same clarity as an astronaut hovering over its surface from a height of a few dozen feet!

We Old-Timers have had a wonderful run in understanding our solar system as we transitioned from murky details to crystal clarity. All of the easy low-hanging fruit of theory building and testing over the last century has been accomplished for the most-part. Now the ever more challenging work of getting the details straight begins, and will last for another century at least. When you can tele-robotically explore planetary and asteroidal surfaces, or perform on-the-spot microscopic assays of minerals, what incredible new questions will emerge? Is there life below the surface of Europa? Why does Mars belch forth methane gas in the summer? Can the water deposits on the moon be mined? Is Pluto’s moon Charon responsible for the tidal heating of an otherwise inert Pluto?
One can only wonder!

Check back here on Tuesday, April 18 for my next topic!

Things we agree on…

Although many survey questions you hear about show close to a 50/50 split in public opinion, there are still many questions that offer nearly unanimous agreement and probably help to define who we are as a Nation in terms of core values and beliefs. I have always wondered what these key issues are, so I gathered up as many of these “over-80 percent” responses as I could easily locate back in 2014. They come in two kinds of statistical samples: biased and un-biased.

Un-Biased Surveys

The only correct way to survey people’s opinions is through a carefully designed randomized survey to eliminate biases that would skew the results. The answers you get from these surveys are probably the most reliable. After each question I give the response and its percentage, the number of people in the sample, the name of the surveyor, and the date. Many of these surveys are by land-line telephone, so a fair question is: Are people that answer their land-lines typical of the general population today?

Do you use your seatbelt? Yes=98 percent (1500, Washington state poll, Traffic Safety Commission 9/23/2010)

Do you believe that man-made climate change is real? Yes=97 percent (1372 scientists, National Academy of Science, 6/22/2010) Note. Pew Research survey in 2016 of 1019 US adults found that only 65% believed this was true.

There are now all too many examples of significant climate change..How many more do we need? (Credit: NATO Review)

Do you play video games? Yes = 97 percent (1102 children ages12-17, Pew Internet and American Life Project, 9/17/2008)

Do you broadcast your location on the Internet using location-based services? No = 96 percent (1500, Forrester Research, 8/30/2010)

Do you believe in a God? Yes = 95 percent (1500, Gallop Poll, 3/29/2001) Note Gallup Poll 2016 shows that 89% now believe in God. Related to this is the Pew Research poll in 2015 that showed 72% of people believed in an afterlife. A Roper Survey in 2011 found 40% of US adults believed in ghosts, but this belief has been declining since 2005 when it was 48%.

Do you want stronger protection for your Internet privacy? Yes=94 percent (2117, Pew Internet and American Life Project, 5/2000 ) Note: In April 2017, President Trump signed an executive order that now allows Internet Service Providers to sell your private information without telling you!

Are the Arts vital to providing a well-rounded education to children? Yes=93 percent (1000, Harris Poll, 6/13/2005)

Would you vote for a woman for President? Yes=92 percent (1229, CBS News/New York Times, 2/5/2006 ) In the 2016 presidential election, over 3 million more people voted for the female candidate than the male candidate.

Would you stop doing business with a company because of bad service? Yes = 87 percent (2000, Harris Interactive,10/8/2008)

Do you use the print version of the Yellow Pages phone book? Yes = 87 percent (9008, Knowledge Network/SRI Industry Usage Study, 2/26/2008)

Do you think that English should be the official language of the US? Yes= 87 percent (1000, Rassmussen Report, 5/11 /2010) Note, in 2016 a Pew Survey found that 90% of American adults thought that English should be the official language.

Do you think it is important for America to use and develop solar energy? Yes=92 percent (1000 online survey, SCHOTT Solar Barometer; Kelton Research, 10/8/2009)

Do you think the federal government is broken? Yes= 86 percent (1023, CNN/Opinion Research Poll, 2/22/2010). Note in 2015, 75% of Gallup Survey believed that widespread government corruption exists. President Trump was elected to shake up the government and ‘drain the swamp’, only to demonstrate that he was himself a major corrupting influence supported by intense Russian influence in the election.

Would you prefer to stop using paper and go Green? Yes=85 percent (1000, Harris Interactive/DocuSign Inc, 6/30/2010)

Should you have to prove you are a citizen before you receive healthcare in the U.S.? Yes=83 percent (1500, Rassmussen Report, 9/7/2009)

Do you shop ‘Green? Yes = 82 percent (1000, Opinion Research Corporation, 2/6/2009)

Do you favor legalizing marijuana for medical use? Yes=81 percent (1083, ABC/Washington Post, 1/18/2010)

Is a car a necessity? Yes=86 percent (2967, Pew Research, 4/2/2009)

Do you think the government will make progress on important issues? No=90 percent (1010, Pew Research, 9/23/2010)

In the future, will computers be able to talk to humans? Yes=81 percent (1546, Pew Research, 6/22/2010 )

Do you know what Twitter is? Yes= 85 percent (1007, Pew Research, 7/15/2010)

Is President Obama a Muslim? No = 82 percent (3003 adults; Pew Research 8/19/2010) Note by 2015 this had fallen to 79% (CNN/ORC Poll). This truly shows that nearly 30% of American adults are certifiably as dumb as dust. This belief among GOP voters is nearly 3 times higher than for democrats.

Has science had a positive effect on society? Yes = 84 percent (2001, Pew Research, 7/9/2009)

Is climate change a serious threat and are you willing to make sacrifices to combat it? Yes=80 percent (1000, Institution of Civil Engineers, 11/20/2009). President Trump’s official position is that climate change science is a Chinese hoax.

Do you live in a house with at least one cellphone? Yes = 90 percent (3001, Pew Research Center, 2/4/2011) Note in 2015 the Pew Research Center found that 64% of American adults owned a smartphone.

Will you be eating Thanksgiving meal with family? Yes= 89 percent (2691, USA Today, 11/30/2011)

Did you make a good investment getting your undergraduate degree? Yes= 89 percent (1500, American Council on Education Winston Group survey, 12/30/2010)

Biased but Interesting Surveys

Biased surveys a not regulated (a person can vote multiple times) and often ask you to vote online, or are conducted by institutions that have a point to make and could be suspected of selecting in advance the people they want to survey that are like-minded (e.g. Fox News). In the results below I have selected’s daily online voting results because they were easily available. CNN readers are in equal shares, Liberal, Moderate and Conservative. In addition 50 percent are Democrats and 16 percent are Republicans. Of course ,all have access to the internet and are not surveyed by land-line telephone so they probably represent a younger population.

Do you think Japan should become a permanent member of the United Nations Security Council? “ Yes = 94 percent (924,421, 4/12/2005 )

Do you know how you will vote in the mid-term elections? Yes=90 percent (30799, 10/21/2010 )

Is it time to break out of the two-party political system? Yes = 84 percent (26837, 10/26/2010)

Do political TV ads influence your vote? Yes = 83 percent(70588, 10/27/2010)

Did you brave the crowds and shop on Black Friday? No=84 percent (112322, 11/27/2010)

What do you think of a publisher’s decision to remove the N-word from Huckleberry Finn? Disapprove = 92 percent (44377, 1/7/2011)

Do you think there may be life on planets other than Earth? Yes = 88 percent (243250, 5/22/2011).

Is raising a child free of gender roles a good idea? No=85 percent (198329, 5/27/2011)

Do you approve of the performance of your congressional representatives? No=86 percent (123776, 8/3/2011) Note in 2017 the Rassmusen Survey found that 75% of adults gave Congress a poor rating. So we like the Congressperson we voted for, but dislike everyone else and what they do.

Have you lost confidence in the ability of world leaders to tackle economic problems? Yes=86 percent (187969, 9/16/2011)

Should states require welfare recipients to pass drug tests? Yes = 80 percent (170382, 10/26/2011)

Do you snack on grocery store food before you buy it?
No=89 percent (59894, 11/4/2011)

Are you ready to “boot out” your representative in Congress?
Yes=81 percent (89916, 12/10/2011)

Should racist remarks be subject to criminal prosecution?
No=86 percent (106918, 12/22/2011)

Should convicted murderers be eligible for full pardons?
No = 86 percent (86970, 1/12/2012)

Things we should agree on but don’t.

There are also many issues we should agree on but don’t. It doesn’t matter how much money we invest in ‘public education’. The general public simply doesn’t get it on many significant issues…and they vote accordingly. Here are some of my favorites, sad to say.

Does Ebola spread easily? No=27 percent (1025, Harvard School of Public Health, 8/13/2014). This is a case of fear overcoming reason and evidence.

Are childhood vaccines safe and effective? Yes=53 percent (1012, AP/GFK Poll, 3/24/2014). This is another case of fear overcoming evidence, but with potentially devastating results if too many people ‘opt out’.

Did the universe begin with a huge explosion? Yes= 38 percent (1500, National Science Board,2014 ). This is a case of personal belief and religious fundamentalism overcoming evidence and reasoned discussion. Even the Catholic Pope finds no contradiction with believing the scientific story!

Have humans and other living things evolved over time? Yes=60 percent ( 1983, Pew Research, 3/8/2013). Again, religious fundamentalism and pseudoscience have biased American public thinking.

Would you support a candidate who advocate carbon emission reduction? Yes=68 percent (2105, University of Texas, 9/4/2014). This is directly connected to the public’s lukewarm belief in climate change and the massive negative campaigning by the GOP and industrial lobbyists. In 2016 we elected a president who sides with industry and climate change deniers and is now dismantling both the EPA and canceling all research on climate change at many governmental institutions.

Check back here on Wednesday, April 12 for my next topic!