Tag Archives: spaceflight

595. Apollo 10

Apollo 10 CSM, viewed from the LEM in lunar orbit.

Apollo 10 is a mission that, from the outside, looks unnecessary. It was anything but that. To appreciate it, you have to project yourself back into the state of ignorance that represented best knowledge in 1969.

I was also guilty of underrating it when I taught middle school science. I called it the most frustrating flight in the history of space flight, which was half true and half exaggeration. I also called the Command Module Pilots NASA’s soccer moms because they got to go to the game, but never got to play.

You have to know your audience, and middle school kids are looking for excitement, not “slow and steady wins the race”. And certainly not “they also serve who only stand and wait.”

In actual fact, without Apollo 10, the would have been no moon landings. There were two basic reasons for this. The LEM had only been tested in low earth orbit, not falling into a gravity well and then clawing its way out again. And we had an entirely inadequate understanding of the conditions on the ground at the proposed landing site. We especially needed to fine tune our understanding of lunar gravity for navigation purposes.

As the NASA history website puts it, “a test of the landing radar, visual observation of lunar lighting, stereoscopic strip photography, and execution of the phasing maneuver using the descent engine” were all performed on Apollo 10’s pass over the proposed landing site. If you want more data, check also here.


On May 18, 1969 Apollo 10 lifted off from Cape Canaveral on its way to the moon. Thomas Stafford was Commander, John Young was Command Module Pilot, and Gene Cernan was LEM Pilot. They entered orbit of the moon three days later. Stafford and Cernan undocked the LEM and began their descent fifty years ago today.

John Young was left alone in the Command Module, the first of seven men who would fly around the moon solo while their companions dropped toward the moon’s surface.

Stafford and Cernan fired the descent stage engine to slow the LEM. There followed a long unpowered descent, a rapid flyby of the proposed landing site, and a rise back up to the level of the CSM.

The reports at the time called it a dress rehearsal for Apollo 11, but it wasn’t that simple.

For comparison let’s look at a mission designed to land. At point A on the figure given here, the descent stage engine would fire briefly, changing from the black orbital path to the green one. At point B, a carefully calculated spot nearly half way around the moon, the descent engine would fire again. The descent from 60 miles to about 8 miles would have been in a flat curve, followed now by a very steep curve. The descent engine would continue to fire until the vehicle landed at point C. This is basically the exact reverse of a launch, as shown Monday.

Later, the ascent stage engine would fire, leaving the descent stage on the moon’s surface, and proceed along the second half of the green curve back up to the 60 mile level.

Apollo 10 (red orbit), on the other hand, passed over the prospective landing site and continued on.

This has always been called a dress rehearsal, so one would assume that the ascent stage would separate somewhere near the surface, fire its engines, and continue back up toward rendezvous separately from the descent stage. That’s what I thought for fifty years.

I was wrong. Imagine that. I probably learn more researching these posts than anyone does who reads them.

In fact, on Apollo 10 the descent stage fired again at point D (the red orbit represents Apollo 10), but it was merely a course correction, and the entire LEM continued up to the 60 mile level.

Apollo 11 would leave from the moon’s surface, starting at zero speed. Apollo 10 at its lowest point was at an altitude of 8 miles and a speed of 3554 miles per hour. Dress rehearsal was a considerable exaggeration. It wasn’t that reports were inaccurate; things were just more complicated than the summaries suggested.

It’s a little like science fiction novels. A two line blurb on the back of a 180 page paperback may not actually lie, but it can certainly give a false impression.

At point A on the trip back up for both missions another burn was necessary to get back onto the black curve. However, the CSM had gone its own way; it wasn’t waiting there for the LEM. The final rendezvous for the LEM and the CSM, which were at different places on roughly the same orbit, would be up to the pilot of the ascent stage, and would take an additional three hours.

At this point on all the moon landing missions, the ascent stage would be by itself. For Apollo 10, the ascent stage still needed to separate from the descent stage before performing the orbital insertion burn using its own engine.

That was the plan, but things didn’t entirely go well. Just before the separation, the LEM began acting up, corrected itself, then seconds later started a rapid roll. It was later determined that this was due to erroneous computer input. Stafford and Cernan quickly separated and regained control, but it was another of those close calls which could easily have led to a deadly outcome.

The crew rendezvoused and docked with the CSM, then returned to Earth. The ascent stage engine was fired again and went into solar orbit. The necessary data had been obtained for the moon landing in July.


At present, I plan for this to be my last full Apollo mission post. Everybody will cover the anniversary of Apollo 11. Everybody has already watched the movie Apollo 13, and I covered the other landings in 187. The Rest of the Landings. Of course, I reserve the right to change my mind.


594. Into Orbit

Fifty years ago last Saturday, Apollo 10 left for the moon. As you read this, depending when you click in, they are/were part way there. The mission’s big events will have their anniversary Wednesday, and that is when the main post will come.

Meanwhile . . .

From the fifties onward, there were dozens of books by people like Arthur C. Clarke and Wily Ley that explained in great detail how  we would go to space. I read most of them — at least every one I could get my hands on. There were a lot of people like me then. A lot of them spent the last decades working for NASA.

Now our knowledge of the universe is vastly greater, and most kids today know more than the best informed knew then. Still, some basic things get missed, because “everybody already knows them”.

Actually, they don’t. Here is an example, which I need to get out of the way before I talk about Apollo 10 on Wednesday.

Imagine, a rocket leaves Cape Canaveral with rocket engines flaming. The engines only burn for a  fairly short time, for reasons of efficiency; then the rocket coasts upward into orbit.

Right. And wrong. There is one more important thing that happens, but rarely get mentioned any more. A second critical burn has to happen at the high point of the initial orbit (apogee).

A rocket heading for orbit leaves the pad vertically, but it immediately begins to roll over. It needs to gain altitude to get above the atmosphere, but it also needs to gain velocity horizontally, so its upward path is a precisely programmed curve that begins vertically and ends horizontally (i.e. tangent to the surface of the Earth). This tangent is reached long after the rockets have ceased firing, at apogee, roughly half way around the Earth.

Caveat: everything in orbital mechanics is more complicated that the explanation you will get from someone like me. Nevertheless, this should be close enough for our purposes.

Let’s assume that the orbital insertion burn did not happen at apogee. Our craft would have achieved enough speed to reach its orbital altitude, but not enough speed to remain there. It would immediately begin to descend.

Think of a high fly ball to center field — up, then down again. Same Earth, same gravity, same result.

Such a rocket leaving Earth would burn up on reentry. If it were launched from an airless body like the moon, it would end up in an elliptical orbit with its low point very near the surface.

Instead, if all went well and the secondary burn took place when the rocket had reached its orbital altitude, it would change from a sharply elliptical orbit to a more nearly circular one. This is the normal way things get done.

You’ll need to have this in mind when we look at Apollo 10’s “dress rehearsal” on Wednesday.

586. Slogging Toward Space

One of the things I have to offer is a viewpoint that reaches back half way through the twentieth century. That can be a problem, actually. I don’t want to talk about the good old days. Fortunately, I never thought the good old days were all that good. They were, however, both exciting and hard.

It has become almost cliché to point out how little computing power the Apollo 11 computer had, but there are a thousand other instruments which we take for granted now, which were also not available during the early space program. I used a few of them myself, early on.

Some of these instruments became fossilized into early science fiction, as in Slip-stick Libby, one of Heinlein’s regular characters. Slip-stick was a slang term for a slide rule, an instrument of sliding scales which was used in computation. It was only good for estimating to about three significant figures. I learned to use one in high school in 1966. Early Texas Instrument portable calculators made them obsolete a few years later, although you will still see them in use at Mission Control when things began to go bad in the movie Apollo 13.

Another nearly obsolete instrument from the Apollo era is the theodolite. I learned to use one in the same class. We took it out to the back lot of the school for some practical examples of the uses of trigonometry. We didn’t call it a theodolite, however. We called it a transit, which is somewhat less accurate. Real surveyors called it a gun.

A transit measures elevations and angles. You level the instrument on its tripod and align it to true north, then you look through a telescopic sight, with crosshairs, at a distant target, usually a rod with red and white inch markings.

(We’re talking sixties here — everything in America was in inches, feet, and miles.)

This instrument was used in surveying everything from house foundations to radar installations before lasers replaced them. It gave you direction. It didn’t give you distance. For that you walked, dragging a measuring device called a chain.

The dictionary will tell you that a chain is a unit of length equal to 66 feet, subdivided into 100 links. It may not tell you that a chain (of length) was represented by a heavy, physical, steel chain that the rod man dragged behind him — for thousands of miles during a career.

Today, laser radar does it all.

An alidade or plane table worked like a transit except that it was attached to a narrow steel plate which moved freely on a plywood table. It was used for mapping. You would slide the alidade around on the table, over a sheet of paper, take your sightings, and use the edge of its base as a ruler. It allowed you to  draw a map as you went. I used one of them two years after high school at an archaeological site in Bay City, Michigan.

To fully understand what a tremendous undertaking the space program was, you should remember that a line of radio/radar stations was built all around the world to track spacecraft in orbit. At the same time, the same Russian missiles which scared American into the space race had to be watched for. A line of radar installations (the DEW — distant early warning — line) was built across Canada for that purpose.

The building of these two sets of installations was an immense undertaking. Even before the first foundation was laid, the positioning of these instruments had to be determined to the highest possible tolerances. This was done by survey engineers working with transits and doing their calculations by hand, with rod men dragging chains. A slide rule might provide estimates, but after that it was paper, pencil, and mathematical tables — which had themselves been calculated by hand.

The word calculator first meant a person who calculated such tables. By hand.

These engineers didn’t all come from Harvard, or other prestige colleges. There were thousands of them, possibly tens of thousands, and they came from every college in America. Bear that in mind as we contemplate the present college entry cheating scandals.

Speaking of which — prestige colleges my &#^$%!  Math is math, whether you learn it at USC or Palomar Junior College.


I want to introduce you to a survey engineer you have never heard of. He is a distant in-law, a fine man I only met once. I ran across a decades old newspaper clipping of his obituary the other day, and it triggered this post.

I’m appending a copy of that clipping, minus family matters, to give you an idea of how the space race, and the missile defense of America, looked from the mud below. The gentleman’s name was William Mussetter.


Mr. Mussetter graduated from Willmington College in 1917 and also attended Haverford College in Haverford, Pa. He retired after working 40 years in government service as an astronomical geodetic engineer. He served with the US Coast and Geodetic Survey, Army Map Services, InterAmerican Geodetic Survey United States Department of Foreign Services where he worked in many different countries.

Mr. Mussetter was a veteran of World War I, serving as a second lieutenant. In World War II he served as a captain and taught artillery.

At the end of the World War II, Mussetter received a call from Washington, D. C. He was assigned to head a survey group to be based in Panama and to work in south America, principally on the west coast of Chile, Peru, Ecuador, Columbia to Venezuela. This project lasted four years.

The Mussetters came home to Wilmington and he worked with the Ohio State University doing contract research for the U.S. Air Force. There was a need to connect the continents of the world, locating them with respect to each other, then to lay out guided missile courses from Cape Canaveral to the Bahamas. [This means during the early testing of IRBMs and ICBMs, before they began to be used to launch space vehicles. The same tracks were used through Mercury, Gemini, and Apollo. See 578. That Odd Spiral.]

In 1953, he transferred to the U.S. Army Corps of Engineers to define the Earth’s parameters, its diameters, flatness at the Poles and other data. [We are talking about building the DEW line here.]

He worked with a survey team measuring the arc of the Meridian at 30 degrees East Longitude from the Mediterranean Sea at Egypt to South Africa, down through Egypt, the Sudan, Uganda, Belgian Congo, Tanganyika, and into North Rhodesia; 4800 miles. [Many of these names no longer exist.] He also did some survey work for the Aswan Dam on the Nile River.

In 1964 he was sent to Antarctica, to Byrd Station, and the South Pole.

He had retired in 1964, but during the last four months of 1964, he worked in Peru, S. A. on a contract for a hydro-electric project; and in 1966 he was sent back to Afghanistan for three months, to inspect the work that was begun in 1961, and complete the Tri-lateration of Afghanistan.


All this without a computer. Imagine that.

578. That Odd Spiral

This is the track of Sputnik, the first satellite launched from Baikonur Cosmodrome at latitude 46 degrees north. Launches from Cape Canaveral followed paths that were more flattened out because they were launched from 28 degrees north.

The orbital path shown above was to be found in thousands of publications at the dawn of the space age. Everyone carried the image in their heads, but today I had a hard time finding it on the web. My how times change.

Every space geek in 1960 would have known everything in this post, but then Star Trek came along. Kirk and Spock, and especially Uhura, went at warp speed and walked around on the floor like it was a sound stage in Hollywood. No weightlessness there. Then Star Wars came along and all veracity went out the viewplate.

There were a lot of very basic principles of physics that governed the space program, which Hollywood had to ignore.

Let’s begin on the ground. The Earth rotates eastward at a certain number of miles per hour. (We are channeling 1960 here. None of the published reports on space used the metric system back then.) Any geek with a pencil could figure out rotational speed by dividing equatorial circumference (25,000 miles to any 1960’s space fan, forget the decimals.) by the length of the day. !042 miles per hour eastward at the equator.

A spacecraft in low Earth orbit flies at 17,500 miles per hour. Actually that varies, but that was the figure in all the space enthusiasts books at the time. If you launched a rocket eastward, you started with about 1000 mph of free speed. If you launched westward, it would cost you 2000 mph of extra speed. You wouldn’t gain the natural advantage, and the rocket would be going 1000 mph the wrong way as it sat on the ground.

Everyone launched eastward.

There was actually another reasonable option, launch north or south. We’ll look at that choice at the bottom of the post.

Actually you don’t get all of that speed advantage. The circumference of the Earth is less as you move northward, lowering the eastward speed. If a United World wanted to choose the most advantageous place for a spaceport, it would be at high altitude somewhere on the equator. That happened frequently in science fiction.

Neither America nor Russia had a far southern point suitable for a space port. America’s best choices were Texas and Florida — the same two states Jules Verne pointed out in From the Earth to the Moon. Florida had the added advantage of having the Atlantic ocean to eastward, which provided a place to drop first stages and failed rockets, without landing on anybody’s house.

Russia built in the desert at the same latitude as Portland, Oregon, but they always chose secrecy over other factors.

Launching eastward is an exaggeration, of course. Straight east from either site won’t work; launches had to be aimed south of east to bring the center of the orbit into line with the center of the Earth’s gravity.

You might think that a launch from Canaveral would return to Canaveral after one orbit, but that isn’t true. The Earth is rotating eastward, so a spacecraft launched from Canaveral will pass over a spot about a thousand miles west of Canaveral on its first return. And so forth. Which is why the cosmonauts were a thousand miles off target after one extra orbit in yesterday’s post.

All this gives us that odd spiral at the top of the post.

In fact, you could launch a spacecraft into orbit from any point on Earth as long as its orbital path circled around the Earth’s center of gravity. Further south is simply more efficient.

You could even launch satellites due north, and we do, from Vandenberg Air Force Base on the west coast of California. Such satellites also spiral around the Earth, but they cover every part of the Earth eventually. Weather and spy satellites use this orbit.

Southeastward launches from Canaveral and Baikonur don’t cross over the far north or the far south.

What about a satellite exactly circling the equator? In low Earth orbit, it would circle the Earth about every 90 minutes. The moon, a quarter of a million miles further out, circles the Earth in 29 1/2 days. Clearly, even for math challenged enthusiasts, the further out the satellite, the slower it travels in orbit. At some distance from the center of the Earth, it would take a satellite one day to circle the Earth. Seen from Earth, it would appear to hang in one spot above the equator.

Everybody should know that, because that is how communication satellites work. The first person to recognize the fact and calculate the distance was Arthur C. Clarke, known even to non-SF readers from 2001, a Space Odyssey. The connection between science and science fiction has always been close.

577. The First Space Walk (2)

The space suit worn by Alexei Leonov on the first human space walk. On display at the Smithsonian National Air and Space Museum. Author: Nijuuf

This is the rest of Tuesday’s post. If you haven’t read it yet, take the time to do so, or this won’t make much sense.

Alexey Leonov had extreme difficulty reentering the airlock. His space suit had over inflated; the boots and gloves had slipped beyond his toes and fingertips, and his suit had increased in girth. He had to vent part of his rapidly depleting oxygen in order to bring his suit down in size, and even then he entered the airlock head first, instead of feet first as planned. Once inside the airlock, he had extreme difficulty contorting his body to close the outer door. All this time, his body was heating up dangerously; surrounded by vacuum, there was nothing to carry away the heat his body was generating.

Once air pressure had been restored in the airlock, Belyayev opened the inner door and Leonov was safe. For the moment. As he said in an article for Smithsonian’s Air and Space magazine in 2005, “the difficulties I experienced reentering the spacecraft were just the start of a series of dire emergencies that almost cost us our lives.”

The mission had achieved it’s goal and it was time to return, but just before the scheduled time for firing retro rockets the cosmonauts discovered that their automatic guidance system was malfunctioning. It took time to prepare for manual entry, so they had to wait one orbit, which would make them miss their return point by a thousand miles. (To find out why it would be a thousand miles, see the post coming on March 25.) Most of that orbit they were out of radio communications. (The Americans had built a string of radio relay stations around the world to maintain constant communication with their astronauts, but the Soviets had not.)

When communications were restored, ground control asked them where they had landed.

Their orbital path was set; the moment of firing their retro rockets would determine where on that orbit they would land. They chose a target just past the Urals. Using the clumsy and difficult manual backup equipment, they achieved the correct attitude and fired the retro rockets in the conical rear portion of the craft called the orbital module. The orbital and landing modules were supposed to separate ten seconds after retrofire. They didn’t.

The two cosmonauts knew immediately that something was terribly wrong. Instead of the steady press of force against their backs as they decelerated, they found themselves whipped about by confused forces that exceeded ten gravities. A communication cable between the two modules had failed to release, and now both modules were whipping about each other, tethered by the cable.

Finally, about 60 miles up, the cable burned through and the cosmonauts were freed. The drogue chute deployed, and then the main. All was peaceful and in order – briefly. Then it became dark as they dropped below cloud cover, the final rocket fired to slow them to landing speed, and they touched down in six feet of snow.

They were 1200 miles beyond their intended landing point.

They blew the explosive bolts to release the hatch. It didn’t open. They had landed in the middle of a forest and the hatch was held shut by a tree. By yanking violently they dislodged it and it fell away, lost in the snow.

They made their way out of the spacecraft and waded through snow to a small clearing. Those back at headquarters had not heard their landing signal, but a passing cargo plane had. It circled, and was soon joined by other planes and helicopters, but none of them could land in the rough taiga. Pilots threw a bottle of cognac; it broke. They threw warm clothing which got caught in the trees, but at least two pairs of wolfskin boots made it to the ground.

The light was failing. The cosmonauts returned to their craft for shelter. Leonov was walking in calf deep sweat still trapped in his space suit from his space walk. Both cosmonauts stripped, removed the liners from their space suits and wrung them dry, then put the on again along with the wolf skin boots. They abandoned the useless space suits and crawled into the landing module for the night, well aware that the taiga was filled with bears and wolves, and that this was mating season, when they were most aggressive.

The hatch was out of reach. The lights failed, but the circulation fan ran all night, adding to their misery. The temperature dropped to 22 below zero.

A rescue party arrived on skis the next morning; they chopped trees to build a small log cabin and a big fire. The cosmonauts spent a second night, then skied out to where a second, larger party had chopped down enough trees for a helicopter to land.

I guess they made ‘em tough in those days. I suspect they still do.

576. The First Space Walk (1)

I posted this in 2016, under the title Spacecraft Threatened by Bears. The title was snarky but accurate. Back then I had few followers, so it seems time to post the amazing story again.

My admiration for the people of the early American space program is boundless, but the Russians were no slouches either. They were the first to perform many feats, including the first space walk, during the flight of Voskhod 2 on March 18-19, fifty-four years ago.

I had the great good fortune of living through the early days of manned space flight. I was nine years old when the Russians orbited the first satellite, and the early manned flights came when I was in high school. I watched every American launch with fascination and envy, but the Russian launches were shrouded in secrecy. I knew only the bare minimum that all Americans knew. I’m not sure the president knew much more.

During those early days, nothing was routine. Every mission was dangerous. They still are, of course, but not so much as then. American failures were there for all the world to see, while the Soviets kept their’s secret.

After the breakup of the Soviet Union, information about the early Russian space program became generally available, but by then few people cared. I did, and I sought out the stories.


Oceans are big targets and landing in water cushions the fall. That is why Americans always splashed down. The Soviets were unwilling to land their craft anywhere outside of the USSR for reasons of security. Their hard landings had an effect of the design of their spacecraft.

The first six manned Soviet spaceflights were aboard Vostok craft, which came down on land — hard. Vostok astronauts wore space suits throughout their flights and landed by personal parachute separate from the capsule. Before the second generation Soyuz spacecraft came on line, the Soviets launched two additional manned missions on modified Vostoks called Voskhod.

On Voskhod, an additional rocket was added to the spherical descent module to fire at the last minute. This softened the landing enough so the cosmonauts could remain within the descent module all the way to the ground. Since ejection seats were no longer used, the weight saving allowed Voskhod 1 to carry three astronauts.

Voskhod 1 cosmonauts flew without space suits, as did early Soyuz missions. Voskhod 2 cosmonauts Belyayev and Leonov wore space suits because they were scheduled for the first space walk.

American space walks first took place during the Gemini program (see post 87). That craft had two hatches but no airlock; both astronauts were in vacuum during the entire spacewalk.

To exit his Voskhod in space, Leonov used an inflatable airlock (see drawing above), leaving Belyayev in the craft and unable to aid him. I had known this for several years but just in the last few days found out why. Russian electronics within Vostok and Voskhod were air cooled. American electronics were not. This meant that if a Voskhod were opened to space, the electronics would overheat.

On Voskhod 2, Leonov crawled into the airlock, sealed the inner door and opened the outer one. Belyayev remained in the pressurized descent module.

For ten minutes, Leonov remained within the airlock but exposed to the vacuum of space, then he slipped free and floated on a tether for another ten minutes. He was called back in to terminate his space walk, and his difficulties began.

(Or perhaps they had already begun. Some sources state that he “experienced a disorienting euphoria” during the space walk and other sources state that he suffered bends like symptoms after the space walk was over; I haven’t been able to confirm these statements.)

This post concludes on Thursday.

575. Textbook: The Rolling Stones

This is a continuation of the post Learning Spaceflight.

For someone reading this post today, it will require a bit of imagination to recreate the head space I’m talking about. Think 1952. Sub-divisions and interstate highways were brand new. NASA was still three years in the future. Heinlein wrote a science fiction juvenile called The Rolling Stones in the year Mick Jagger was still twelve years old.

In the interests of full disclosure, I was five years old that year, so I must have read it six or seven years after publication.

In those days, those of us who were in love with the idea of spaceflight were getting our fix from science fiction, and mostly from juveniles. PBS was seventeen years in the future, and NOVA was twenty-two years in the future.

I recently re-read The Rolling Stones. It was never my favorite novel. I would give it one star for plot and no stars for its obnoxious characters.

The Stone family lived on the moon. The slightly underaged twins wanted to buy a spaceship and flit around the system on their own, using money they had made from an invention. Dad said, “No,” but never fear. He bought a larger ship and took his whole family along, first to Mars, then to the asteroid belt.

If my tone sounds facetious, chalk it up to how irritating all the characters were, but as a textbook on how to fly in space, The Rolling Stones was top notch.

Here is an example. Leaving Luna for Mars, the Stones opt for the most economic orbit. This puts them in a long line of craft who have made the same decision. They fuel up on Luna then drop down to pass close to the Earth because . . .

A gravity-well maneuver involves what appears to be a contradiction in the law of conservation of energy. A ship leaving the Moon or a space station for some distant planet can go faster on less fuel by dropping first toward Earth, then performing her principal acceleration while as close to Earth as possible. To be sure, a ship gains kinetic energy (speed) in falling towards Earth, but one would expect that she would lose exactly the same amount of kinetic energy as she coasted away from Earth . . .

The mass of fuel adds to the energy as they drop deeper into the Earth’s gravity well, but the fuel is expended at perigee so it does not subtract from the energy as they move away. I’m interrupting RAH and explaining it myself because he took too many paragraphs, but that’s where I learned about gravity well maneuvers. By the time I got to college my main interest was ecology and then anthropology, so I never studied engineering or orbital mechanics. I still wish I could have done both but, in truth, most of my knowledge of space travel came from Heinlein, Clarke, Ley, and Goodwin, with lesser lessons from Gamow, Coombs, Hoyle and dozens whose names I no longer remember.

Later on, the Stones headed out for the asteroid belt. They . . .

shaped orbit from Phobos outward bound for the Asteroids six weeks later. This was no easy lift like the one from Luna to Mars; in choosing to take a ‘cometary’ or fast orbit . . . the Stones had perforce to accept an expensive change-of-motion of twelve and a half miles per second for the departure maneuver. A fast orbit differs from a maximum-economy orbit in that it cuts the orbit being abandoned at an angle instead of being smoothly tangent to it… much more expensive in reaction mass.

Of course. That makes perfect sense.

I watched the first part of a NOVA program the other day called The Rise of the Rockets. I turned it off about ten minutes in muttering kinderspiel. At least that’s the word I’m choosing to use in this family site. That happens a lot. NOVA covers fascinating subjects, but they tend to dumb them down. The old dudes did it better, even in their fiction.

However, they didn’t always get it right. Regarding the asteroid belt, RAH said . . .

But it was not until the first men in the early days of the exploration of space actually went out to the lonely reaches between the orbits of Mars and Jupiter and looked that we learned for certain that the Asteroids were indeed fragments of a greater planet — destroyed Lucifer, long dead brother of Earth.

Back in the fifties when The Rolling Stones was written astronomers had not yet decided if the asteroids were an exploded planet or an unformed one, caught in the tidal stresses of Jupiter’s gravity. RAH chose the more exciting option. Today we know better. Too bad. I always wanted to write a novel called The Last Days of Lucifer. I guess I still could, as steampunk.

In the fifties, we knew little about the universe and not all that much about the solar system. A lot of what RAH and others wrote has been killed by current knowledge. He had a non-human civilization with canals on Mars and intelligent talking dragons in the swamps of Venus. But he knew his math, and his rockets always got where they were going by following the rules of physics that NASA uses today.