I watched a 1969 film on YouTube about the inner workings of the Apollo Guidance Computer that helped put a man on the moon. The navigation details are fascinating. I had no idea that the astronauts used a sextant to shoot bearings to stars!
Integrated circuits vintage
The film shows logic gates that are packaged in TO cases. (TO cases are small diameter metal cans used to house transistors.) By 1967 these would have been obsolete. In 1967 we were already developing products with readily-available quad NAND gates (using TTL — transistor-transistor logic). These 7400-series parts were packaged in 14-pin plastic DIPs (Dual In-line Packages). The higher spec’d 5400 series were packaged in ceramic DIPs. I’d guess that the Apollo Guidance Computer (AGC) in the film was designed well before that — maybe 1964 or even earlier.
I’m a little confused. The Wikipedia description of the AGC states that it exclusively used Fairchild resistor-transistor logic (RTL) dual NOR gates in a flat-pack. Hmmmm. That’s not what the film shows.
In any case, both the single logic gate in a can and the dual RTL NOR gates in a flat pack would have been obsolete by 1969. I would have thought that NASA projects would have used the latest technologies, not 5 year old technologies. I guess that subsystems within large projects such as Apollo acquire momentum, and once they’ve been proven, the “If it ain’t broke, don’t fix it” motto applies.
Elon Musk’s SpaceX has been working on a system that will return the launch missile intact to its launch pad, ready for the next launch. This video clip was taken two days ago at their Texas launch facility. They moved the rocket horizontally 100 meters, hovered, and tilted it 30 degrees from vertical.
This is a step toward the goal of using Grasshopper to boost succeeding stages to a high altitude before it returns to its launch pad.
SpaceX CEO Elon Musk’s reasoning: This booster, while “cheap”, costs 50 to 60 million dollars. The fuel costs about two hundred thousand dollars. If we can re-use the booster a thousand times and amortize its capital cost over a thousand launches, the cost per launch will be low.
This is a triumph of servo system design and high-pressure high-flow rate fluid control. The trick is to make the rocket’s engine respond quickly while keeping the servo loop stable. I imagine that the signals from many sensors of all types are monitored by the guidance computer. The resultant control of thrust is impressive.
Yes, there IS a foundation that’s concerned about the possibility of an asteroid striking the Earth. Their motto is “Detect. Deflect. Defend.” This announcement appears on its website, b612foundation.org:
The B612 Foundation is a nonprofit 501(c) 3 organization dedicated to opening up the frontier of space exploration and protecting humanity from asteroid impacts. On June 28, 2012, the Foundation announced its plans to build and operate the first privately funded, launched, and operated interplanetary mission – an infrared space telescope to be placed in orbit around the Sun to discover, map, and track asteroids whose orbits approach Earth and threaten humanity.
Origin of the foundation’s name? Aviator Antoine de Saint-Exupéry’s little prince supposedly came from a tiny asteroid named B-612.
Wow! What a video! Kudos to everyone who helped create this fantastic music video that was just uploaded to YouTube. (And kudos to David Bowie, for allowing this majestic performance of his classic song from, um, 1969.) Until now, David’s performance was definitive. I think that this performance trumps David’s. What do you think?
Published on May 12, 2013
A revised version of David Bowie’s Space Oddity, recorded by Commander Chris Hadfield on board the International Space Station.
With thanks to Emm Gryner, Joe Corcoran, Andrew Tidby and Evan Hadfield for all their hard work.
This is Canadian Commander Hadfield’s last day aboard ISS after nearly five months in space. He arrived December 21 and took command of the space station on March 13. He’s been an active contributor to social networks while aboard ISS. Tomorrow, he will return to Earth aboard a Russian Soyez TMA-07M. God speed, Chris Hadfield!
His photo of Florida:
Let’s boldly go. How will we move data across vast distances as we explore space? I briefly essayed this in Extending the Internet off-Earth. I’ve since learned that Internet pioneer Vint Cerf, ever the adventurer, has been collaborating with others on the Interplanetary Internet, which will probably replace IP (Internet Protocol) with Bundle Protocol (BP). It’s a tall order: in space, propagation delay, multipath, and dropout problems will dwarf those found on Earth or near Earth orbit.
The United Space Alliance, which manages the computers aboard the International Space Station in association with NASA, has announced that the Windows XP computers aboard the ISS have been switched to Linux. “We migrated key functions from Windows to Linux because we needed an operating system that was stable and reliable.”
Apparently computers aboard the International Space Station (ISS) already run various distributions of Linux. I’m not surprised: once installed, Linux is more stable than Windows and techies enjoy having its source code freely available so that they can modify it to suit the mission. Its biggest problem, in my opinion, is its hundreds of dialects.
I just watched the PBS American Experience documentary, Silicon Valley. I loved it! It begins at legendary Bell Labs in New Jersey where William Shockley, John Bardeen, and Walter Brattain invented the transistor in 1947. Eighty-two minutes later, the film concludes at Intel in California, with the introduction of the first microprocessor, the 4-bit 4004 CPU in 1971.
Here’s how PBS describes it:
An eye-opening look at the birthplace of the modern technological era told by the people who shaped it, Silicon Valley is a fascinating reminder of how Robert Noyce and his team of trailblazers led the way in transforming California’s Santa Clara Valley into a worldwide hub of industry and innovation, and laid the bedrock for modern technology.
As astronomical instruments gather more data, the ability to sift through all that data has become critical. A new discipline, dubbed astrostatistics, has appeared within the last ten years. It uses computers, data mining, and statistical analysis techniques to hunt through catalogs of images (at multiple wavelengths) to find obscure astronomical objects that are masked by nearby objects.
One of astrostatistics’ remarkable discoveries is a quasar that existed 13 billion years ago(!). (The universe is believed to be 13.7 billion years old.)
Most of us rely upon our GPS receivers without awareness of our debt to the imagination of Albert Einstein. He published his Special Theory of Relatvity in 1905 and his General Theory of Relatvity in 1915, but for decades afterward, nothing much was done with them; good old Newtonian physics worked just fine for earthbound and even space-bound adventures. The Global Positioning System (GPS, designed in 1973) was the first man-made system that requires relativistic factors to work, because it requires that clocks in different gravitational fields and traveling at different velocities tick in precise synchronism across great distances.
Here’s a good paper by Richard Pogge at astronomy.ohio-state.edu that explains this in easy-to-understand language. Briefly, GPS relies upon precise timing within nanoseconds (billionths of a second) to measure the radio signal transit time from each GPS satellite to our GPS receiver.
Special Relativity predicts that the clocks onboard the satellites will, from our perspective, seem to tick slower because of their velocity relative to us.
General Relativity predicts that a clock near a large mass (Earth) will tick slightly slower than a clock that’s in an orbiting satellite, away from the spacetime distortion caused by the Earth.
1 nanosecond = approx 1 foot at the speed of light
Let’s see . . . the radio signal travels at about 186,000 miles per second, and each satellite is in an orbit of about 11,000 miles, so when a satellite is directly overhead the signal transit time is about 11,000/186,000 or 0.059 seconds. An error of one second will result in an error of 186,000 miles. An error of one tenth of a second will result in an error of 18,600 miles. An error of one microsecond will result in an error of 0.186 miles, and an error of one nanosecond will result in an error of 0.00019 miles, or about one foot.
Because nanoseconds are significant, if General and Special Relativity were ignored, the Global Positioning System simply wouldn’t work. Each day, an error of about 10 kilometers would accumulate to previous errors.
The first lunar explorer has died at age 82. When Neil Armstrong stepped onto the moon’s surface in 1969, he answered the question that was posed by e.e. cummings in a favorite poem:
Who knows if the moon’s a balloon,
coming out of a keen city in the sky,
filled with pretty people?
Neil stumbled slightly when speaking the words, “That’s one small step for a man, one giant leap for mankind.” I don’t blame him. The whole world was watching. Stage fright’s tough just on the local school’s stage. It must have been paralyzing on the moon.
I’m glad that NASA chose such a capable yet modest, dignified man for the role of first man on the moon. Mr. Armstrong made us all proud.
“Armstrong, probably the only man for whom the 20th century will be remembered 50,000 years from now”
Self portrait of Tracy Caldwell Dyson in the Cupola module of the International Space Station observing the Earth below during Expedition 24.
Providing Worldwide Web access to the International Space Station is one thing.
Providing the ability to browse the web from Mars and beyond will be quite another.
Today, the crew aboard the International Space Station (ISS) can browse the web about as easily as you or I can. It’s relatively easy to provide web access, because the ISS orbits at an altitude of less than 300 miles, so packets traverse the radio link quickly and then they travel on terrestrial fiber. [Description of NASA’s Disruption Tolerant Networking for Space Operations (DTN)]
In the future, browsing the web across millions of miles will be tough, because of network latency, which is the transit time required for a packet to travel from sender to receiver, and good old multi-path RF (radio frequency) signal problems familiar to mobile radio users. Doppler shift may also cause trouble.
When we earthlings browse the web, our computer converses with at least two servers: our DNS (domain name system) server, and the desired web server. These conversations take place at nearly the speed of light — 186,000 miles per second. Typical latency across a few hundreds or thousands of miles is so small that we’re barely aware of these conversations.
Once we leave the realm of Earth, though, long distance radio links will cause long network latencies. The distance to Mars varies, but if we assume a minimum of 40 million miles, network latency will approach 4 minutes. (Our mechanical hero, Explorer 1, is 11 billion miles away. Radio signals from it require 14 hours to reach us.) Because of relative movement between transmitter and receiver, there’s bound to be transmission errors, and if just one garbled packet must be resent, it will require 8 minutes.
Some form of FEC (forward error correction) will help, but impose its own overhead. I suppose that frequency diversity may help the multi-path problem, but it will impose a complexity and power-consumption cost. I’ve never tried to use a web browser on such a sluggish network, but I’m sure that it’s frustrating, if not impossible. To some extent, the users could be helped by installing local DNS and caching proxy servers on Mars, but this would work only for frequently visited static pages.
RF signal latency will either halt exploration or force colonization
The Landing of Columbus at San Salvador, October 12, 1492.
Space explorers will eventually need to create their own little colonies far removed from Earth — sort of what the colonists did in the new world. Not only will their new colonies include their own local networks, but quite likely their own dialects, and eventually their own languages. As mankind explores the solar system and beyond, it’s likely that the explorers and colonists will develop their own amenities and technologies. Will their bodies evolve to adapt to their new environments? If so, at what point does it make sense to define them as something other than Homo Sapiens?
The next question is, Are we descendants of colonists from a distant planet?
Voyager 1 is leaving the solar system. That’s 11 billion miles from Earth!
NASA announced that Voyager 1, which weighs about 1500 pounds and was launched in 1977, is apparently at the edge of the solar system and is now entering interstellar space. It’s not likely to collide with any stars: the nearest star is about 4.5 light-years away, and at Voyager’s current velocity (about a million miles a day), it would require 40,000 years to travel that far. (Outer space is huge beyond my imagination.) In any case, it’s not headed in that direction.
It’s impossible to learn about Voyager 1 and its sister, Voyager 2, without being amazed. It was originally projected to have a lifetime of perhaps 12 years. It’s been almost 35 years since its launch, and it’s still transmitting data back to Earth, 24×7. Its transmitter output power is a puny 20 Watts!
Meanwhile, back on planet Earth, for about 8 hours every day, the huge 70 meter diameter dishes of the Deep Space Network (DSN) listen to the incoming data from Voyager 1 at the slow speed of 160 bps (bits per second). (The old Telex system operated at 110 bps and the first modem that I had operated at 300 bps, c 1978.) These bits now require about 14 hours to travel the 11 billion miles from Voyager 1 to Earth.
Very rarely, commands are transmitted from Earth to Voyager 1.
If any of this captures your interest, you’ll find much more detail in Wikipedia:
Everyone who was or is associated with this project should be proud of this amazing achievement. And just in case either Voyager is ever found in a scrapheap in Alpha Centauri, it can serve as a jukebox to play, among other selections, music by Chuck Berry and Mozart. (What, no Bach?!)
The only constant is that everything changes.
Go with the flow!
Amateur radio operators quickly become familiar with the 11 year sunspot cycle, because solar activity dramatically alters the propagation of radio signals around the earth. I guess that from a young age (I obtained a ham radio license at age 16) I became comfortable with the idea that nothing in the universe stays the same. My sister points out that at one time the area around Philadelphia resided at the equator, and shark remains are found in Kansas, which was once at the bottom of a huge sea.
Naïf Al Gore and his horde of naïfs shout that human activity is overheating the planet. If earth’s ice caps were melting (well, at least the northern one is; our southern ice cap is actually growing), how do these pseudo-scientists (Al Gore flunked out of divinity school!) explain the shrinking of the ice caps on Mars? Are Martians’ SUVs heating their atmosphere?
More likely, Mars — like Earth — is responding to cyclical changes in solar emissions. The simplest explanation is usually the correct one. (See Occam’s razor. )
If you’re reading this, you probably are to some degree fascinated with things technical. They’re great . . . until they break. Then somebody’s got to repair them.
Repairing technical systems is always challenging, especially when they’re mission critical, you’re far from home, have few spare parts, and are stressed by a tight schedule. I’ve been under pressure to repair critical systems, but never in the way that the most recent Hubble repair mission members were. It’s a fascinating documentary: 7 crew members trained for 2.5 years for this repair mission. If they failed, the Hubble telescope might never again work.
I was intrigued to see that even in space, repair technicians encounter reluctant fasteners, bolts that simply can’t be removed, and Phillips head screws that strip out while trying to remove them . . . plus while “floating” (at 13,000 miles per hour) in space they have other problems, including torque reaction every time they try to turn a fastener.
It was 40 years ago today that Apollo 11 astronauts stepped unto the moon’s surface.
Was it done by computers? Not exactly. Apollo 11 had about 74 kilobytes of data storage and 4 kilobytes of volatile memory — about the same as today’s washing machine and far less than your laptop computer. Supposedly. when Neal Armstrong saw that the lunar lander was about to set down on a point, he took control and with a joystick guided the lander to a landing on a smoother surface. They had about 30 seconds of fuel in reserve. That’s how close to the edge this mission was.
NASA can’t find the original videotapes of the historic Apollo 11 moon mission. They were apparently taped over(!) decades ago when NASA needed fresh tape to store data. (. . . and we’re supposed to turn over our health care to these people???) The tape story: http://www.collectspace.com/news/news-071709a.html
Addendum: In 1972, a friend and I drove to Cocoa Beach to watch the Apollo 17 lunar mission (the last one) lift off at night, propelled by the awesome Saturn V missile. Although we were about 20 miles from the launchpad, birds awakened and began singing, mistaking the firey glow of the missile for a rising sun. The ground shook as if there were an earthquake — from 20 miles away!