Tag Archives: science

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.

582. Newtonian Nukes

Everybody who read the last generation of science fiction juveniles before Apollo knew Newton’s third law:

For every action, there is an equal and opposite reaction.

The demonstrations in popular science books of that same era usually went something like this: imagine a person on a frozen pond wearing ice skates, throwing bricks. Every brick he throws will move him backward. If we could ignore the friction of skates on ice, it would be proportional. That is, if a hundred pound man  . . .

Okay, side issue. Most Americans back then, and even today, don’t think in kilograms or kilometers, nor distinguish mass from weight in everyday thought, so . . .

If a hundred pound man throws a one pound brick at ten miles per hour, it will propel him backward at one tenth of a mile per hour. 1 times 10 = 0.1 times 100. We are ignoring friction from the ice, the atmosphere, and probably a bunch of other things.

So, if you want to go faster, throw more bricks, right? If you throw a thousand bricks, you should be able to go pretty fast, right? Wrong, because the first brick your throw in the new scenario will have to move not only the hundred pound man, but also the other 999 pounds of bricks.

Increasing the amount of fuel carried quickly brings about diminishing returns. More fuel alone is not the answer.

In a Newtonian scenario, the faster the propellant leaves the rocket engine, and the more propellant you use, the faster you can go. LOX and LH are probably near the practical  maximum for propellant speed by chemical reaction. The logical next step would be to use a non-chemical energy source to activate our propellants, such as a nuclear powered rocket. Even that won’t get us to the stars, but it makes sense for travel inside the solar system.

Before Apollo, everyone who read science fiction knew that, which is why the Scorpius and her sisters in the Rip Foster book are nuclear powered. So were the ships in Bullard of the Space Patrol, a marvelous fix-up novel by Malcolm Jameson that no one remembers today. So were the ships in the Dig Allen series (1959 – 1962), six great but forgotten novels, and the ships of the Tom Corbett books, which were not so great and are not completely forgotten.

Star Trek put all these early concepts out of business. Warp speed was a necessity for roaming the galaxy, but it made nuclear rockets look old fashioned. I think that’s too bad. There is still room for them in science fiction, and certainly in real life.

I haven’t mentioned Heinlein yet. The Rolling Stone was nuclear, but he quickly moved on to torch ships, which had the capacity of total annihilation of matter. He never explained how that could be done, but the result would be “propellant” moving at essentially lightspeed. You can’t get faster than that without warp drive. His torch ships roamed the solar system and went on to explore nearby stars.

I stole that schtick for my coreships in Cyan, with a twist. See 23. Star Drives.

In a rational world — which we will probably never inhabit, but we can still write stories about — you would might use chemical rockets to get to LEO (low Earth orbit), nuclear powered rockets to zip around the solar system (fission powered if you were writing in the sixties, fusion powered if you were writing today), and “torch ships” to reach nearby stars. Beyond that, you would need FTL (faster than light) vehicles which, by our present understanding of the universe, are impossible.

Too bad about FTL, but why are we still using chemical propellants in the real world fifty years after Apollo? Fear of nukes, of course. There will be more to say about that on Wednesday.

573: Apollo 9: Full and Complete

Apollo 9 was the first mission to fly full and complete: Saturn V booster, CSM, LM, and lunar rated spacesuits. They weren’t going to the moon, but they were checking out all the equipment that would take astronauts there.

Jim McDivitt was Commander, David Scott was the Command Module Pilot, and Rusty Schweickart was Lunar Module Pilot. Those designations are a bit misleading. Flying any part of a mission frequently took all hands. It took two people to land on the moon and the Commander was the lead pilot with the Lunar Module Pilot in something like a co-pilot’s role.

This was to be the first flight by a full fledged LM. (By this time NASA had dropped the acronym LEM because the word excursion seemed frivolous, but civilians and the media still called it the LEM.) A LEM mockup had flown unmanned, but the LM that flew on Apollo 9 had been much updated since then.

Apollo 9 lifted off on March 3, 1969 into low earth orbit. The Saturn third stage and attached CSM and LM were then moved into a slightly higher orbit, where the CSM separated, reversed and performed its first docking. The multipart cone which covered the LM was jettisoned at this time. (See 569, and animation in the film Apollo 13). The Saturn V third stage separated at this time and the combined CSM and LM moved away.

The Saturn V third stage had it’s own work to do. It’s engines were fired again to change the orbit’s apogee (high point). Once apogee was reached, the engines fired again to achieve a solar orbit. This firing did not achieve its proper objective, so a third firing took place later. Practically speaking, this merely got the third stage out of the way, but it also gave NASA a chance to once again check the flight characteristics of the Saturn stage which would, on subsequent missions, place the Apollo mission on orbit to the moon.

Aside: if you plan to read more on these subjects you will run into the terms S-IVB, which is the designation for a Saturn V third stage, and SPS, which is the designation for the rocket engine in the Service Module.

Now the CSM was flying backward in orbit attached to the LM, and the LM had opened its struts to a landing stance. The CSM fired it’s rocket for the first time (docking had been done on maneuvering thrusters), raising the orbit and providing the first test for the main engine.

Aside again: this mission should have happened before sending a crew around the moon. Although most of the events of Apollo 9 were firsts, a few things like firing the CSM’s main rocket had already been done on Apollo 8. However, the ability of the linked-up CSM and LM to fly under power had not been tested before.

The next day, the CSM/LM made three more burns, changing orbits and testing the integrity of the CSM/LM connection.

On the third flight day, McDivitt and Schweickart (with backpacks) transferred from the CM to the LM by way of the tunnel between hatches. The day was spent testing out the LM, including a six minute burn of the descent stage engine. McDivitt controlled the last minute manually, throttling up and down and shutting off the engine, just as astronauts would do on a actual moon landing. All this was performed while CSM and LM remained linked-up.

The fourth day of the flight, McDivitt and Schweickart returned to the LM. Schweickart spent thirty-eight minutes testing his spacesuit outside the vehicle. He had also been scheduled to crawl over to the CM to demonstrate how astronauts could be rescued after returning from a moon landing, should the two craft be able to rendezvous, but not dock. Space sickness made this maneuver impossible, but everything in the hardware itself checked out.

On the fifth day of the flight, McDivitt and Schweickart entered the LM for the third and last time, and separated from the CSM.

That is fifty years to the minute before this was supposed to be posted, assuming that my math and data from several different sources were all correct. Great plan, but my internet went down for three days. If fact, this post is coming out about three hours late, but at least I made it before Friday slipped away.

The major test of the LM descent stage engine had already taken place on day three. Now, it fired twice, first to raise the LM’s orbit and then to make it more circular. This was done to separate adequately from the CSM.

The descent stage of the LM was now jettisoned and the ascent stage engine was fired for the first time. This burn moved the LM ascent stage to 75 miles behind and 10 miles below the CSM. Over the next six hours, the LM ascent stage achieved rendezvous and docking. The astronauts moved back into the CSM, and the ascent stage was released. By remote control, it was ordered to fire its engines one last time and burned up in the atmosphere. The descent stage remained in orbit until 1981.

The remainder of the flight was uneventful. The CM splashed down north of Puerto Rico. The SM burned up on reentry, as would all subsequent SMs.

Almost no one remembers Apollo 9. It wasn’t the first Apollo into Earth orbit and it never went near the moon. It was a working astronaut’s flight, one more incremental testing of equipment. But when it was over, everything was ready for the moon landing.

Well, almost everything. There was still the matter of maneuvering the LM downward into a gravity well and out again, and the matter of getting good enough close-up views of the moon’s surface to be sure a landing could be done. Those would be the task of Apollo 10, in May.

One last aside: The April issue of the magazine Astronomy has interviews by the astronauts of Apollo 9. It just came out and I didn’t have time to read it before posting this.

550. CSM and Friends

The moon bound Apollo missions sent three things along, a LEM, a Command Module, and a Support Module. Apollo 8 was the only moon bound launch that didn’t carry a LEM, so we will save it for later. CSM was the common abbreviation for the linked Command Module and Support Module. The photo at the top of this post is a CSM.

In the original Mercury spacecraft, (shown here) the single occupant was in a closed space with all his supplies of air and, on longer flights, water and food. Flights were short and maneuverability was minimal. There was no need to store large quantities of fuel or oxygen. The retrorockets which burned to return the craft to earth were outside the vehicle and behind the heat shield; this was also true on the Gemini craft.

On Gemini flights, the ability to maneuver was critical. Gemini was the program in which astronauts learned how to rendezvous and dock and how to perform space walks. (EVAs; extra-vehicular activities) Gemini was also designed to test the effects of long term weightlessness. There was a need to store large quantities of fuel and oxygen, so a section was added between the crew cabin and the heat shield. It was not accessible from the crew space. You can see it in the silhouette of the Gemini spacecraft shown here.

Gemini could not contain both enough oxygen for very long missions and enough fuel for major maneuvering. Long missions were loaded up with oxygen, but little fuel. Rendezvous and docking missions were shorter and loaded up with fuel.

The trip to the moon would take plenty of breathing oxygen and maneuvering fuel, and a lot more besides. All this, and fuel cells for electricity, were crammed into the Support Module. It also had to act as another stage in the Saturn rocket. It had to have a large engine and fuel supply to use while entering lunar orbit, and when exiting lunar orbit to return to Earth. A comparison of the three photos will show that Mercury and Gemini had only retrorockets for return, strapped outside the heat shield, along with maneuvering thrusters you can’t see in the pictures. The bell of the CSM’s large rocket is clearly visible.

With Apollo, the heat shield was moved back to the base of the crew space. The Command and Support Modules were designed to be separated just before reentry. The Support Module burned up in the atmosphere while the Command Module was slowed by its heat shield before landing by parachutes.

This poster from NASA shows all three spacecraft side by side, at scale, with the LEM thrown in as a bonus.

We’ll look at the Apollo 8 mission itself on Wednesday.

495. Everybody, Two Jobs

Everything about Cyan was designed to give a picture of what might actually happen in the early days of extra-solar exploration. No ray guns, no hovercraft of the Marty McFly type, but hovercraft in the sense of ground-effect machines instead. Some of the technology I chose to give my people was not too far advanced over what we have here, early in the millennium. Why? Because if you are light years from home, you want your gear to work. It is not particularly important that it be up to date, but it needs to be indestructible. (see 253. Handgun Accuracy)

They walked a lot on Cyan. Feet don’t need new batteries.

In real exploration, you can’t expect everybody to survive. That means that you don’t want just one medic, or pilot. Someone has to be ready to step up in case of tragedy, and that needs to be planned in advance.

Which brings us to today . . . I mentioned last week that I have been cleaning out a house I used to live in. Today (May 11, actually, since I write these things ahead) I found an old ms. of Cyan with some notes I hadn’t seen in years.

I wrote the first half of Cyan on a typewriter. Go google it; it’s a crude instrument from ancient days. You actually had to spell words right without spell check, and if you lost something, it stayed lost.

That is why I am posting this now. I had intended to talk about this during the run-up to the publication of Cyan, but I didn’t want to trust my memory for details. Now I have the details right in front of me on a sheet of paper I typed up decades ago.

Except for Keir, everybody on the roster of the starship Darwin had a specialty, and one or more back-up specialties. Here is the list, alphabetically.

        Stephan Andrax    captain (spaceside) – astrophysicist
        Debra Bruner        microbiologist – astronomer – medic
        Petra Crowley       geologist – soils scientist
        Keir Delacroix       groundside crew leader – generalist
        Viki Johanssen      anthropologist – paleontologist
        Gus Leinhoff         zoologist – biochemist – medic
        Leia Polanyi          paleontologist – geologist
        Ramananda Rao  meteorologist – cartographer – geologist
        Tasmeen Rao       first officer (spaceside) – pilot (starship and landing craft) – engineer
        Uke Tomiki           botanist – biochemist – medic

In fact, only weeks into their exploration, a tragedy forces two of the crew to take on the job of one who has died, with unforeseen consequences. You know what I’m talking about, or you will as soon as you download Cyan from Amazon.

In the original iteration of Cyan, the expedition was from a united Earth with crew members from many nations. Stephan and Viki were Scandinavian, Petra was Greek, Keir was French, Gus was German, Debra and Leia were American, Ram and Tasmeen were from Trinidad, and Uke was Japanese. That hopeful future died along the way. In the world that Cyan eventually came to represent, the ever voracious United States, following a world wide financial crisis, gobbled up Canada, Mexico and the Caribbean. The crew members were now all from the United States of North America, but with their various ethnic backgrounds intact.

I like the idea of a peaceful, united world, but even when I began Cyan, America looked hungry. Today — well let’s not open that can of worms. Let’s just say that the less than peaceful Earth that ended up in the novel Cyan represents another attempt at realism.