I happen to know a thing or two about rockets, both of the spacebound variety and the more down-to-earth enemy-kaboom variety. While there has certainly always been a group who was interested in rocketry and space missions, I definitely have noticed the past few years see a revival of sorts of interest in the field. I would attribute a lot of that to the lofty ambitions of SpaceX and the game Kerbal Space Program that lets people build and launch rockets and learn a thing or two in the process. But in my opinion, those two alone barely scratch the surface of what there is to rocketry and it does bother me that few tend to look beyond that to see what else there is in the space world. So I thought it might be neat to try to shed light on some of the aspects of space that people really don't think to consider if they themselves aren't involved in working on rockets.
I'll see how interested people are in reading long space diatribes, and how interested I am in writing them, and go from there. From past experience I know that there is a limit beyond which people won't be willing to read on, so I'll try to keep each of these fairly short. In this part, we will focus on two things: the basics of spaceflight and a (highly abridged) history of rocketry, focusing more on the very early and the very recent years of history.
Basic Principles of Rocketry The basic function of a rocket is quite simple: fire go down, pointy thing go up.
Saturn V
The basic design for a rocket really hasn't changed much since its inception; that's the basic concept for how it works and that's pretty much how it's always been. The conceptual and theoretical aspects of rocketry are remarkably straightforward, and based mostly off of the work of famous physicists from centuries past. Of course, the real devil is in the details. As we all know, rockets have an unfortunate tendency to explode at inopportune times, destroying anything and anyone inside. Every time a rocket launches, we all know that there's a not particularly small risk that it will explode in flight, leaving the owner of that rocket to pick up the pieces and spend months or years trying to figure out what went wrong.
Fuel NASA had a really nice article talking about why launching a rocket into space is quite difficult. Bottom line, it takes a lot of fuel used as efficiently as possible in order to generate the kinds of forces you need to be able to beat the gravity of the Earth. The weight of a rocket is disproportionately that of fuel; anywhere from 80 to >95 percent of a rocket's weight is in fuel. It's basically generating a giant explosion and you had better hope that you can control it properly.
While there are other types of rocket fuels used, the ones that generate the massive thrust (the upward force generated by spewing burning gas out the bottom of the rocket) that can actually get you places is pretty much always generated by a chemical reaction optimized to get the biggest bang for your buck in terms of thrust by weight. Those can be divided further into two types of chemical fuels: solid fuels and liquid fuels.
Solid fuels have a very simple design: you place a highly flammable grainy substance into a tube, you light it on fire, and the entire thing ignites and generates thrust until it all burns out. Gunpowder is a great - and early - example of a solid fuel. Light a tube full of it on fire and it will burn until there's nothing left to burn.
The design of that rocket looks quite simple, and it is. Solid rockets are famed for their simplicity, and where that is a priority, solids can't be beat. Rocket missiles these days use solids, and so do strap-on boosters that provide some additional thrust to a rocket. Because missiles are so much more popular than spacebound rockets, most rockets made are actually solid rockets. Their main disadvantages are that they don't burn quite as efficiently as liquid rockets and once you ignite your grain, you can't shut it off (although some clever more modern inventions hope to change that).
Liquid fuels are a whole different story. They involve mixing a flammable liquid, generally liquid hydrogen or a hydrocarbon, in a combustion chamber with a strong oxidizer - usually liquid oxygen (LOX) but also possible is hydrogen peroxide - to generate a nice, powerful explosion.
You can control liquid fuel rockets much more easily than solid fuel rockets but the engine design is always a slight more complicated. But that's the kind of performance you need to actually be able to get into space.
Orbits When an object is moving with its own velocity but is also being pulled by another particularly large object, you get an orbit. The traditional example is shooting a cannon from a mountaintop: the harder you shoot, the further your cannonball will go - until you shoot it hard enough that its velocity allows it to curve all the way around the Earth and circle back. If you shoot it hard enough it will curve away and eventually leave the Earth's gravitational field - the velocity at which this occurs is called escape velocity.
There are essentially three shapes that an orbit can take: elliptical, parabolic, and hyperbolic. An elliptic orbit involves circling around an object in a circular shape, possibly a perfect circle, and is the one of most interest here. A parabolic orbit is what happens when you precisely hit escape velocity, and a hyperbolic orbit is anything faster than that. A missile is, from an orbital perspective, little more than an orbit that at some point intersects the Earth.
Because of physics (conservation of angular momentum), an orbit will be along a flat plane of space. Incidentally, the solar system itself is something of a flat plane; if you go up or down rather than in the direction of the plane you will quickly find yourself among a vast expanse of absolutely nothing. While it's possible to change the plane of an orbit, this requires a rather costly (again, in terms of fuel) maneuver - hence, rocket launch reports tend to talk about the orbital angle and why it's so important to get it right.
Pretty much every rocket is either placing something in orbit, or using an orbit to get somewhere. Two orbital maneuvers are worth talking about: Hohmann transfers and plane transfers.
A Hohmann transfer is a way to change from one orbit to a larger orbit using an intermediate orbit, that allows you to make the transition while using the least amount of fuel possible. It's used for anything from launching a satellite from a lower orbit into a higher Earth orbit to launching a probe from Earth to another planet by taking a larger orbit around the Sun. Of course, this orbit comes with the catch that it's the slowest way to go from point A to point B, but the fastest way (burning your engines at full blast directly toward where you want to go) is a great way to run out of fuel.
An orbital plane transfer is a way to change the plane of your orbit by adding some thrust at the right time in the right direction.
Figure 4.13: Blatant Plagiarism
One particularly important equation in rocketry is, quite aptly, called the rocket equation. It relates the mass of the vehicle (before and after fuel is expended) to the velocity of the exhaust (the fuel you burn and shoot out the back of the rocket) to the change in velocity of the rocket (the "delta V"). This delta V is, in a roundabout way, analogous to fuel, and you try to conserve it. You do an orbital maneuver, you pay some delta V to accomplish it. You run out, and you're just sitting in the middle of a vast expanse of nothing with no way to move around. Similarly, unless you have a good reason to do otherwise, you launch to the east to get some velocity boost from the spin of the Earth, preferably in a place where your boosters won't drop and hit someone on the way down. Hence, rockets are generally launched as close to the equator as possible, to the east, and preferably in a place where people don't live to the east.
An orbit is defined in terms of a certain number of orbital elements, six of which are needed in order to be able to pinpoint the orbit of an object. If you're interested in reading more about them, use the previous Wikipedia link; for now, it simply suffices to say that when tracing an orbiting object, the goal is to get a "six element lock" on that object. That requires at least six independent measures of that object's state, but given that we live in the real world where measurements are imperfect, "the more the merrier" applies. The image below gives one example of a six-element lock on an orbit.
Staging A rocket seldom, if ever, consists of just one engine firing. In general, it's multiple smaller rockets all put together in a cylinder and launched together. Each individual independent piece is a "stage" of the rocket. At the very top lies the package to be delivered. An example of a rocket (United Launch Alliance's Atlas) showing each stage is given below - note the solid rocket boosters on the side of the large "first stage" booster.
The first stage is the big bulky part that gets you into space. As soon as it's done firing, it detaches from the rest of the structure ("stage separation") and falls back to Earth, hopefully into the ocean (or, in the case of SpaceX's Falcon 9 first stage, landing on a pad for that rocket). Generally the biggest and most expensive part of the rocket. In general these are powered by some fuel that does a good job of making a lot of thrust - the consensus these days tends to be around using a highly purified version of kerosene called RP-1 as a fuel, although hydrogen is also used (with lower effectiveness) and methane is being explored as a potential future option (most notably SpaceX's Raptor engine and Blue Origin's BE-4 engine, both in development).
The second stage and on are significantly smaller and use that boost from the first stage to get to where they want to go. When you clear the bulk of the Earth's gravitational pull lifting off, you're left with a much smaller and weaker engine, but any amount of thrust will give you far more bang for your buck. So even very small improvements in efficiency on these engines can make a huge difference. One planned second stage known as the Advanced Cryogenic Evolved Stage (made by United Launch Alliance) will increase efficiency of the upper stage enough to essentially double the amount that the entire rocket can lift into space. Hydrogen or a (nasty, but particularly versatile) compound called hydrazine is often used in the most effective second stage engines, although counterexamples (e.g. SpaceX's Merlin kerosene second stage) exist.
All this work is done in order to get some relatively small package into space - whether that package is a satellite, a lander for another planet, an astronaut inside a capsule, or even a box of chocolates for your special someone living on Venus. If it hasn't become clear yet, gravity is kind of annoying for trying to get anything done in space.
A Brief History of Rocketry I assume that we are all fairly familiar with the history of rocketry during the Space Race; it was a glorious battle of who can be "first" to achieve a certain number of prestigious goals in space travel. If not, or if you would just like to read more about it, Wikipedia's history of spaceflight will be a good place to start - and from there, it's not hard to do a deep dive to learn more about any specific topic you want. Instead, I'm going to focus on the more distant past, the founding era of rocketry, and the much more recent future, covering only the major highlights of the Space Race era.
Physicists While not precisely related to rocketry, it's worth acknowledging the physicists who laid the foundation for rocketry. Among them are Galileo, Copernicus, Kepler, and of course Newton. Einstein's work on both general and special relativity also contributed to the space world. I won't spend much time on them, but they certainly deserve mention.
Chinese Fire Arrows The idea for solid rockets goes back to ancient China and the invention of gunpowder. The Chinese found that if you strap a small capsule of gunpowder to a flighted arrow and lighted the capsule, you would get a primitive form of powered rocket flight. This was essentially an early form of solid rocket.
An early prototype of the Grad missile system.
Liquid Rockets Three individuals are mentioned among the founders of the liquid rocket: Konstantin Tsiolkovsky, a Russian; Robert Goddard, an American; and Hermann Oberth, a German.
The three pioneers and their respective successors
Tsiolkovsky was the first pioneer of rocketry who laid much of the groundwork for the physics of space travel. While in his own lifetime he never managed to build rockets, he did create the rocket equation (also known as Tsiolkovsky's Rocket Equation). His work was noticed by an American physicist named Robert Goddard, who created the first rockets. Compared to modern, 99% fuel efficiency rockets, his were rather primitive - he used gasoline and liquid oxygen and only managed a 63% fuel efficiency, and a top speed of 550 mph. In his time, his work was scarcely acknowledged and he died before the advent of the rocket era.
Enter Hermann Oberth, and his student (and an important player in American rocketry), Wernher von Braun. They improved upon Tsiolkovsky's principles and Goddard's designs to create some of the first viable rockets, starting with gasoline/LOX mixtures but eventually moving on to many alcohol-based rockets (I always imagine drunk German rocket scientists pouring vodka into a rocket). One of their most famous works was the V-2 rocket, one such alcohol-LOX combination which, while ineffective as a weapon, did help make future rocketry possible. Though their work was ultimately used for rockets "that go to the wrong planet" in Nazi Germany, their work was indeed eventually used for the right kind of rockets.
As an aside, although it's not commonly used anymore (due to there being better fuels), alcohol is actually a pretty good fuel. It makes a very nice, hefty flame.
Space Race After WWII, the missile technology developed by the Germans was improved upon to create space rockets. The Sputnik program put the first satellite into orbit, then a research capsule, then two dogs, and finally a dog with a human dummy. The Vostok program put multiple humans into space, including the first man (Yuri Gagarin, Vostok 1) and woman (Valentina Tereshkova, Vostok 6). Mercury launched the first American (Alan Shepard) and first American orbit around the Earth (John Glenn). And of course we have the Apollo 11 mission, in which Neil Armstrong, Buzz Aldrin, and Michael Collins the Forgotten (the pilot who didn't leave the craft) landed on the Moon. This is the best known era of spaceflight; I need not describe it in excruciating detail.
Aftermath Shortly after the 1969 Moon landing, interest in space sort of rapidly fell apart. On the Soviet side, many attempted projects ended in unfortunate failure due to budget issues and one particularly glaring flaw (a lack of development of hydrogen engines, which would have been great for a Moon mission). The US sought to create a cheap rocket and created the rebuildable ("reusable") Space Shuttle, which was anything but. The Soviets, and later Russians, undertook some projects, but for many years mostly just kept the lights on, making upgrades to their vehicles but hardly being in a position to make anything new and special - though this capacity did survive the collapse of the USSR and the following disaster.
One new development that was actually interesting during the 1970s and on was the launch of space stations, including Skylab, Mir, and eventually the International Space Station. Each had their own degree of success, but it's hard to deny that the ISS was by far the most successful - it's still orbiting and still one of the most important achievements of spaceflight. Much of the modern work in spacefare involves servicing this station. In a large way this was the dawning of a much more cooperative era, in that the ISS was built with the help of multiple nations rather than as part of a race.
Era of Old Spacers At the turn of the century, one particularly interesting development was the development of a commercial space market - launching satellites for private companies for money. Although a satellite is an expensive thing to make and launch, a well-planned satellite can rake in hundreds of millions of dollars over its lifespan, easily paying for its launch costs many times over. The European aerospace giant Aerobus created the Arianespace organization to launch commercial payloads, and took a leading position in that market. The Russian space program, suffering from a sudden and severe collapse in potential government funding in the 1990s, kept afloat by selling launches, most notably on its Proton heavy rocket (also Sea Launch, but that's a story for another time).
The US at this time was not really at the top of its game. While I could describe it myself, this report does a better job than I could do, so I'll just quote it instead:
The period spanning the late 1980s to the early 1990s was a particularly difficult era for spaceflight in the United States. After the tragic Challenger disaster in 1986 and the Titan rocket launch failures quickly thereafter, all military launches were halted for almost a year. The fall of the Soviet Union in 1991 led to a decline in the U.S. defense budget, which included military program consolidations. There was also a growing concern that the commercial space launch market could shift away from the United States. The United States needed a new launch vehicle that could provide assured access to space for the military and stay cost competitive over time.
The full report, in fact, gives some nice insight into US Old Spacers - I recommend reading it. Long story short, though, the US was in a pickle because they feared they would be locked out of the growing commercial space industry, their military launches would see trouble, and they needed to create some reliable, cheap rockets to stay afloat. One company, General Dynamics, eyed the Russian RD-170 engine - a monster of a kerosene engine with excellent performance capabilities and a better design than anything they could have made themselves. They made a joint venture with the engine producer, NPO Energomash, to build what was essentially a half-size version of that engine - the RD-180. It was used in the Atlas rocket, which was eventually purchased by Martin Marietta, which after a merger became Lockheed Martin. Another rocket at that time of interest was the Delta series, a hydrogen rocket that eventually got into the hands of Boeing. While they both eventually developed some rather fantastic launch records, the Atlas was clearly superior for most launches, being a far less convoluted design with a fantastic engine.
The plans that the US had for getting into the "growing commercial market" never really materialized, mostly because the market itself never materialized. So it started to be the case that the most important customer for these organizations was the Air Force itself. They wanted to keep two lines of rockets online to ensure that they would never be in a position where they couldn't launch one of their rockets; in the case of military satellites, the cost isn't so much the lost satellite as the cost of what the satellite won't be doing for you, the battle it won't win. Ultimately, Boeing and Lockheed merged their two rocket businesses into the United Launch Alliance, which they claimed would reduce logistics costs and give the US Air Force cheaper launches. Whether or not that's true, ULA is known for two things these days: being very expensive, and not losing a single rocket in the entire history of the joint venture.
I know that India, China, and others started to really develop their space chops at this time, and I wish I could talk more about them. But I simply don't know enough about them to give any meaningful opinion here. I'll make sure to talk about them more if I end up learning more.
The New Spacers on the Block The most recent development, the one we've all seen develop before our eyes, is the advent of a group of New Space companies which sought to break into the space industry. Funded mostly by the funds of wealthy individuals, they set out to accomplish some lofty goals - create space tourism services, create cheap rockets, colonize Mars, and many more.
Their successes were rather limited in most cases, but one particular New Spacer stands out: SpaceX. Headed by Elon Musk, a man of many talents and an ego the size of Donald Trump, he sought to make fully reusable rockets that would be able to travel to Mars.
Will SpaceX reach those goals? Hard to say. Personally I have my doubts - but even so, it's hard not to acknowledge what they did bring to the table: a focus on designing rockets to reduce cost. Many of their design decisions, while suboptimal from a performance perspective, do make the rocket much cheaper to build. They also chose to build much of their rocket in-house to reduce the size of their supply chain. And they have offered launches for far cheaper than their competitors (possibly at a loss), forcing those competitors to do all sorts of things to try to be competitive with their low price. Some may wonder if they are in over their heads with some of their plans - but it's hard not to acknowledge the things they did do, including designing for cheaper manufacturing and landing a first stage booster (certainly a technical feat).
Blue Origin, perhaps, deserves a parting mention. Bankrolled by Amazon billionaire Jeff Bezos, they have designed a reusable suborbital rocket which they have reused before - and are creating a large, powerful methane engine - the BE-4. ULA, forced to find a replacement for their RD-180 engine due to political troubles with Russia, has played the role of a guardian angel of sorts for Blue Origin - helping them design and improve the BE-4, so that they will sell ULA a good replacement for a new rocket.
So that's about where we are today and how we got there. I know that I skipped over quite a lot of history in each era. You'll have to forgive that; this is already getting pretty long and if I get any more exhaustive then I'll be writing to an audience of no one.
Conclusion With the advent of the New Spacers, spaceflight has certainly taken an interesting turn towards a cost-based focus. Whether or not any one of those New Spacers will ultimately succeed, many of the expensive, yet highly skilled, Old Spacers have been forced out of their comfort zone and into a much more competitive environment.
In truth, though, I often find this era slightly disappointing - it almost seems like much of the interesting aspects of spaceflight are being ignored in favor of just focusing on SpaceX. What I tried to do here was to give a much broader picture - the physics of a rocket, some of the technical challenges, and many of the players and where they are coming from. Time allowing, I'll probably go into more depth on some of these; much was omitted in order to make this at least somewhat shorter than it was originally planned to be. If anyone wants me to talk about anything specific, let me know.
In any case, props to anyone who actually read through my diatribe - and bonus points to anyone who reads all the links as well. Hope you enjoyed it!
Sure, I could take a stab at it. I don't know much about their plans in depth, and I don't know if they even published them because I just don't follow SpaceX much. But I could give some insight into what it entails.
First of all, I think it goes without saying that 2018 isn't happening. SpaceX is not known for keeping its deadlines and even if they were, "optimistic" would be too soft a word to describe that deadline. What I think they're banking on is to be able to launch for Commercial Crew on their stated May 2018 deadline, and then with minor reconfiguration use the same type of mission to go moon orbiting. From a "common sense" perspective it kind of does look just that easy. What's the essential difference between launching astronauts to the ISS compared to launching them to the Moon? Seems like just a couple of minor tweaks and you're good to go.
Well it's not actually quite that easy. For one, they haven't even quite finished up the comparatively easy task of launching astronauts to the ISS yet. The trajectory of events suggests that even without any more "anomalies" in their rockets, they won't be able to meet 2018. So on that alone 2018 probably won't be happening. And it's also unclear to what extent they will be delayed by the fact that SpaceX has a gigantic backlog of mildly-to-severely annoyed customers who have to deal with endless delays on their launches. The most significant of those customers is of course NASA, which is already rather frustrated with some of the delays they've been seeing from that end.
But that only has to do with when it's going to happen, not if. And for that I suppose the most important question to ask is, how are they going to launch it, i.e. on what craft? The Falcon is plenty strong for standard heavy lift capacities to LEO, but it loses its potency very quickly for going too far past that. Of course I don't have access to particularly strong technical data for Falcon performance, but I do know that they have a rather inefficient second stage compared to their competition. I believe Musk said something along the lines of "our competitors may have a more efficient second stage, but ours is much cheaper to make because we use the same engine as for our first stage." Unfortunately, that really starts to bite you in the ass when you're trying to go to the Moon or further rather than just go to LEO or even GEO.
The current Dragon which I think they're going to try to rate for humans weighs a good six metric tons dry. When it's full of people and life support and cargo, it'll probably be at least ten, if not more to account for the fact that you have to do a lot more to keep Moon-bound humans in check compared to ISS-bound ones. That's a hell of a lot of stuff to launch into GEO, much less to the Moon. That alone is more than current Falcon capacity (they're rated up to 8, they've launched 6 to GEO before). 360,000-400,000 km vs 36,000 km is the difference between the Moon and GEO. Maybe Falcon Heavy could make the trip, if it ever comes online. That's supposed to be later this year but they've delayed it so many times that I can barely keep track. And that's still a maybe, I just don't know if FH could do it. And to be fair I don't know if SpaceX does either.
Incidentally, that's kind of what killed the Soviet Moon program: weaker upper stage engines. The technical leadership at the time had a grudge against hydrogen engines and that's been a weakness of Russian space that extends to present day. Hydrogen turns out to be really good for second stage engines, and while Russia makes the best kerosene engines (great for first stages!), their hydrogen game needs work. SpaceX as well is a kerosene shop, though they are working on a methane design (whose functional capabilities I am far less familiar with due to fewer examples of it being used).
An orbit of the moon with people has been done before so there's no reason to think that it can't be done again, in principle. Enough money and time and it would be done, easily. But SpaceX is still working out the kinks in their rockets which yet still are short of where they would need to be to make them suitable for carrying people without a well-placed fear of explosion, much less to do the same with a Moon-bound group. But there's a reason why pretty much all of the Old Spacer folks take the view that they are in over their heads with this one.
As a chemist, the fuel side of things has always been of particular interest to me. Have you read Ignition! An informal history of liquid rocket propellants by John D. Clark? I read it in college and loved it – it's very in-depth and well-written. Problem is, it's also copyright 1972. Do you know if there are any other books that could offer a more updated history? I have no idea, for instance, if anybody still uses UDMH/nitric acid, or if anybody ever got boranes to work as fuel, or what people usually use these days for monopropellant. Is nitric acid even still used?
Anyways, thanks for this, and I'll try to keep an eye on the blog section for more LL rocketry posts.
Well shit. I wrote up a response for you then it got lost somehow. Let's try it again.
My book recommendation is Rocket Propulsion Elements which is considered the go-to book these days on rocket design. Pick an edition that works best with your budget-modernity requirements balance; it's one I use as a reference if I need a few quick pointers on rocketry. Though a simple answer to your question would be that rocket fuels have been remarkably consistent throughout the ages. Methane is the fuel that people think will be the future and both Russia and the US are researching new methane engines. Blue Origin in particular is testing the world's biggest methane engine and will be back to it (after their test exploded) shortly. ULA is helping them. SpaceX is working on an all-methane engine, the Raptor. Russia has a few R&D projects on methane as well.
As for UDMH/hydrazine, it's still in use, but it's nasty shit that is on the way out. ULA uses it in their Centaur upper stage in small quantities on the Atlas as a monopropellant. They're phasing it out with ACES, which will eliminate the need for a monopropellant. Russia uses it as a fuel on the Briz-M upper stage (Proton and optionally Angara), but that's about the most unfortunate upper stage ever created, responsible for many launch failures over the years, and it's being phased out on the Angara in favor of some still in development hydrogen-based options (which is probably why they only launched the one Angara so far). Hydrazine is still the monopropellant of choice though; to explain the successor options, all of which are quite fancy, would probably require a separate discussion on upper stages.
Don't think borane ever went past experimental. Nor nuclear.
Huh. Thanks for the response and reccomendation, especially after losing a response you typed. Clark's description was that for any application where you needed something 1) storeable, and 2) with good specific impulse, UDMH as fuel and nitric acid as oxidizer couldn't be beat. But also as a chemist I know enough about those two chemicals to avoid them like the plague. Hell, the reagent grade nitric acid we've got at work is nasty, nasty stuff, and that's nowhere near the purity of white fuming or red fuming nitric acid. I should look up some of these successors - it seems like the thermodynamics are such that you don't have that many chemical reactions out there that could give more bang for your buck.
Nope, not really. Rockets already pretty much function at the asymptotic limit of thermodynamic efficiency. Most improvements these days come from some new designs of integrated plumbing systems that simply reduce the need for fuel consumption. Might cover that if I'm still interested in writing by then.
Hydrazine is one of the nastiest compounds I've ever had the displeasure to have to deal with. Go figure, people want to move away from it.
Great post, thanks for the read. Hope to see more!
Side note: I believe the 'Chinese Fire Arrow' picture you included is actually a Korean piece - I recall seeing that one in person earlier this year, and a reverse image search seems to confirm it.
We know this is all a SUBTLE attempt at feeding information to the North Koreans. I'M ON TO YOU LL!
=p
<3 I've never delved into the science behind rocketry but this was an interesting read and I'll probably get on wiki to look up more later. Space flight is something I wish humanity would invest more time into. Our future is out among the stars, not blowing each other up here on this rock.
Yup, that specific model of the fire arrow is a Korean device. You are correct about that.
Glad to see that at least a few people are interested enough to read what I typed up. If and when I write more of these, though, I want to focus not just on "the basics of rocketry" (which I think I covered well enough for most purposes in just this post) but some of the more unusual and/or less commonly appreciated aspects of rockets. If you want more on the basics, I could always recommend some readings that would help you learn.
But I would like to ask: is there anything specific anyone is interested in knowing more about? I have my own set of pet topics that I want to cover, but if there's something specific anyone is interested in, let me know.
I thought I remembered JimmyJRaynor being a moon landing truther. Posting that video again reminded me of where I knew that from. Here he is on a blog I posted a couple years ago:
On October 16 2015 05:01 JimmyJRaynor wrote: lol, there is no evidence our circulatory systemS ( notice the plural) can withstand true low gravity. the space station people are experiencing 90+% of the gravity we experience... (G*m1*m2)/(r^2) .. just plug in the #s urself and do the math on your own.
its been 44 years since these long distance missions allegedly happened. put it this way, If the longest plane ride from 1929 to 1980 were 3 kilometers then i'd have doubts about the authenticity of Lindbergh's transatlantic flight. i feel the same way about the Apollo missions.
here is Buzz claiming we'll be back on the moon by 2010.
bush said they're going back in 2006 and it gets cancelled in 2009 before we can begin to compare the progress made during the '62 to '68 time frame.. when JFK yapped at Rice and men were orbiting the moon 6 years later.
when humans actually go 1,000+ kms off the earth's surface on a consistent basis i'll start to pay attention to this stuff....
so far.. its all talk.. with them always trying to reach into the taxpayers pockets to get more money for SPAR/MDA Space Missions. my stance is zero federal tax money for SPAR.. and i'm voting accordingly on October 19th.
they can have all the pie-in-the-sky fantasy world plans they want.. just don't ask for Canadian federal taxpayer dollars for this crap which is all a waste of money.
as i said there are dozens of other examples of big yap about returning to the moon. i'm too lazy to list them all here and it would take things off topic. if you want another 30 or so examples... i'll PM them to you.
Buzz can be forgiven for thinking that in 15 years, we might go back to the Moon. It was attempted a few times, for sure. And we wouldn't need to build a Saturn V caliber monstrosity to do it either - modern advancements in engine plumbing provide some rather impressive boosts in lift capacity that would be able to make that trip far more possible. But it would still take a very optimized design to get humans to the Moon and back successfully, whether or not you land. We should be able to move past that in a few decades, but we simply are not there yet. I don't think SpaceX has the rocket to make the trip in 2018, at any rate.
JJR: I never particularly understood why people are consistently so aggressively opposed to your thoughts on Lagrange points. Though I'm not entirely sure that your points on low-gravity environments are correct (and admittedly I am not much of an expert on the physiological aspects of human spaceflight), I do know that there is some talk at NASA about launching people into some Lagrange points as a Mars trial. For a number of reasons, including studies of background radiation over a prolonged journey.
ChristianS: Man, you certainly threw some shade at rocket scientists/engineers - even if you didn't mean for it to come off that way. I'm sure you'll be happy to know that the fuels other than hydrazine (which is falling out of favor over time) that people have ultimately settled on - kerosene, methane, and hydrogen - are fairly clean in the grand scheme of things. And personally - I think a lot of the innovations will come not from better fuels, but from better energy integration within the rocket system. As I mention a lot, small differences on the upper stage can make a big difference in how much you can actually do - will probably cover that eventually.
Incidentally, I met Freeman Dyson once, a couple of years back. He came off to me as an old man reciting the tales of his youth. Only his stories weren't about catching gigantic sea bass and visiting the old haunted house, but rather about nuclear propulsion rockets, analog computing, and genetics. Was a fun guy, if a bit unorthodox in his methods and his research foci.
Haven't read that blog in a few years, dunno how much I'd stand behind it. I don't remember feeling like I was throwing shade at the time. I remember arguing that rocket scientists are somewhat natural enemies of environmentalists, since their whole job involves building giant towers of chemicals and lighting them ablaze – a practice that will, in the best case, dump a large amount of things like CO2 into the atmosphere, and in the worst, accidentally spill some pretty toxic chemicals by the metric ton. Even kerosene or methane aren't exactly things environmentalists would be excited about spilling into the environment.
But that's not to say I think that rocket scientists are irresponsible with regards to the environment. NASA is doing some great work for the environmental research, after all, and in the end cars, rockets, plsnes, power plants, and all the rest of modern technology has an environmental impact. I do think that concepts like the nuclear propulsion rocket are absolutely insane from an environmental perspective, and we're all lucky Dyson never got the chance to try them out. But the point of that blog was not to insult either Dyson or rocket scientists; it was mainly to give some of the reasons that Dyson's opposition to the dominant scientific position on climate change isn't wholly unexpected, and should be taken with a grain of salt.
@JJR: You say I half-read your post. Were you not expressing skepticism about the veracity of the moon landings in that post? Because your wording seemed fairly unambiguous.
Yeah, I know you didn't mean it that way. But I could see why people would look at it as such. But for kerosene and methane the result is just carbon dioxide, a little carbon monoxide, and water. I don't think it's the biggest concern of most simply because there are much bigger fish to fry. Rockets just are not that big in terms of overall emissions.
Hydrogen isn't an exception either, though, considering it's made out of hydrocarbons, usually methane. Steam reforming is the process I'm most familiar with, and as far as I know the most popular. The carbon just comes out on the ground rather than in the air.
I think JJR's message looks like something along the lines of "we haven't been to the Moon in so long that one might wonder if we were ever there at all!" Which I guess could be interpreted as Moon truthing but in context is more about being disappointed at how we just haven't gone back in so long.
In terms of the Moon, though, the most interesting mission in recent times was the LPRP "crash a rocket into the Moon to find water" mission. It was forgotten as quickly as it happened, but those of us who paid attention could see its significance: it makes a lunar infrastructure development that much more feasible in the long term.
Sure, the actual volume of CO2 produced by rockets is tiny compared to something like cars, so it's not a big issue. Wouldn't hydrazine burn even cleaner? Seems like the product would just be nitrogen and water. Maybe I came off too critical back then, but I absolutely think responsible rocket science shouldn't bother any but the most extreme environmentalist (i.e. Someone who thinks basically all modern technology should be abandoned due to its environmental impact).
JJR seemed fairly unambiguous. Between saying nobody's been more than 1000 km out, saying there's no evidence humans can survive zero gravity, and the word "allegedly" I don't know how that could mean anything other than "I don't think the Apollo missions really happened."
The real problem with hydrazine is the unreacted stuff being a monster of an environmental hazard. I know far too many cases of hydrazine-related deaths. See wiki. Whereas hydrocarbons are fairly benign and quite biodegradable unreacted.
JJR can clarify himself of course - and I'll let him do that. But that's how I interpreted it anyways.
Great blog post! 5/5 I finally got around to reading it just now. I have a my written blog post in similar style that I should really finish off and post.
Your info on orbits was especially helpful to me (Hohmann transfers will not sound esoteric to me any more). You asked for ideas so one area I would like a nice little explainer on is the various types of Earth orbit such as LEO, GEO, and SSO, and the others that I can't remember the names of.
As a teenager I was always bothered by the phrase "it's not rocket science", because rocket science principles seemed pretty straight forward to me. Now I think the phrase is meant to be "it's not rocket engineering" because that seems to be where the major difficulty lies.
Quick question: why is the ignition charge at the top of the solid fuel rocket? Seems a bit counter-intuitive to me.
Editing notes: "ego the size of Donald Trump" should be "Trump's" instead I think. The sentence about Michael Collins strongly implies that he was actually on the Moon.
On orbits: I think the best I could do is to offer you a number of readings that would get you a good understanding of them. I can't think of a good way to strike the right mix of comprehensive and accessible, because at the same time the idea behind them is simple, yet there are so many that you could devise an entire class on learning the ins and outs of various orbits. This page and this page should give you a nice, clean introduction to a few of the most important kinds of orbits, and why they matter. If you want a list, Wikipedia has a nice one that you can deep dive if you have that old fashioned sense of wonder that comes with learning new things. If you want a deeper understanding of why certain orbits behave as they do and where their use comes from, beyond just "orbit X is best for application Y just because I said so," then I would recommend that you learn orbital mechanics. I can recommend a book - Bate, Mueller, and White's Fundamentals of Astrodynamics, a relatively easy read for a science book written in the no-nonsense style that you might expect for a book written for Air Force cadets. In any case, take your pick.
As a teenager I was always bothered by the phrase "it's not rocket science", because rocket science principles seemed pretty straight forward to me. Now I think the phrase is meant to be "it's not rocket engineering" because that seems to be where the major difficulty lies.
If Wikipedia is to be taken at its word, then "rocket science" is merely a branch of rocket engineering - the one that deals with the design of rockets. Which is certainly a tough task, but that's an engineering task nonetheless. An interesting little factoid for the curious.
Quick question: why is the ignition charge at the top of the solid fuel rocket? Seems a bit counter-intuitive to me.
What you really need to answer this question is simply to understand how the solid fuel actually burns. The first factor is that it has its own oxidizer as part of the grain itself, so you don't need to have access to air; it will burn from the top just as well and that's a nice place to squeeze in a pyrotechnic device as opposed to on the exposed bottom of the rocket. What you do want is to have a clean, even burn along the length of the tube so you don't have the top of the grain tube just sit on its ass forever. So in fact what is happening is that the igniter is lighting the center of the cylinder of fuel grain along its entire length in such a way that it combusts outward from that center. And it just burns outward until there's nothing left, then it's done. A very simple design, with none of the hassle of the constant fuel mixing and pressure control of liquid engines.
"ego the size of Donald Trump" should be "Trump's" instead I think.
When talking about Trump, gotta use Trumpian grammar . Bigly.
The sentence about Michael Collins strongly implies that he was actually on the Moon.
He was. He was the guy who sat inside the lunar lander when Neil Armstrong and Buzz Aldrin made their moonwalk. He was the pilot, and he had to do his job instead of getting on camera and receiving the major glory for walking on the Moon, go figure.
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