First SLS launch pushed back again to April 2021

Chronological Encyclopedia of Discoveries in Space cover

After being in print for twenty years, the Chronological Encyclopedia of Discoveries in Space, covering everything that was learned on every single space mission in the 20th century, has finally gone out of print.

I presently have my last four hardback copies available for sale. The book sold new for about $90. To get your own autographed copy of this now rare collector's item, please send a $120 check (which includes shipping) payable to Robert Zimmerman to

Behind The Black, c/o Robert Zimmerman
P.O.Box 1262
Cortaro, AZ 85652

"Useful to space buffs and generalists, comprehensive but readable, Bob Zimmerman's Encyclopedia belongs front and center on everyone's bookshelf." -- Mike Collins, Apollo 11 astronaut


"The Chronological Encylopedia of Discoveries in Space is no passionless compendium of information. Robert Zimmerman's fact-filled reports, which cover virtually every spacecraft or probe to have ventured into the heavens, relate the scientific and technical adventure of space exploration enthusiastically and with authority." -- American Scientist

NASA on February 20, 2020 finally admitted that the first SLS launch cannot happen in 2020, and set a new target date no earlier than April 18, 2021.

The previous target launch date in November 2020 was always a pure fantasy. NASA just held off admitting it in order to defuse any political consequences for having a program, building SLS, that will end up taking them almost two decades to complete.

This new launch date is likely the most realistic so far, since the hardware for SLS is actually finally coming together. Nonetheless, if anything at all should go wrong along the way, especially with the full static test firing of the core booster of the first stage scheduled for no earlier than August, then expect more delays, possibly lasting years.



  • V-Man

    What will happen if SLS is somehow delayed long enough for Starship to make a successful manned flight?

    Humiliation and cancellation, or will political inertia be sufficient to keep the program running long enough to fire off a facing-saving mission or two?

  • Fred Kleindenst


    People expressed your thought almost exact in 2017 — they asked what will happen to SLS when Falcon Heavy flies, thus providing proven very heavy lift launch for only 10% or less of the cost of SLS? Well, it has flown, 3 times, and is available to fly as much as needed.

    SLS was not canceled then.

    It won’t be canceled now for the reasons you cite. There is a small chance that a democratic president might want to cancel it for unrelated political reasons.

  • jburn

    You can invest in SpaceX indirectly by purchasing the stock of a company which owns SpaceX stock. It’s a company you are likely familiar with…. GOOGL

  • Ray Van Dune

    Can someone please explain why Spacex is building a bigger booster faster in a field? How can this not be too good to be true? I am certainly impressed with Spacex’s accomplishments, and also ready to believe that SLS is a bloated program, but I just can’t see how Spacex could be so GOOD, and at the same time NASA / Boeing so BAD, as to explain the disparity of results! Are we perhaps being lulled into a fantasy that a starship can be built in a field and still be good enough to safely carry passengers?! But on the other hand, SLS is using EXISTING engines left over from the Shuttle! What the hell have they spent all the money on?

    I am not accusing… I am asking if someone can explain this to me!!

  • Ray Van Dune: As a first attempt to answer your question, which is at the heart of much of what I write, I suggest you start out by downloading the free pdf of my policy paper, Capitalism in Space. I think it will go a long way in explaining the disparity between NASA and SpaceX.

  • Richard M

    Speaking of the disparity between NASA and SpaceX (I mean, after you’ve read Bob’s excellent paper), Robert Zubrin has some harsh comments over at National Review today:

  • Calvin Dodge

    I’m shocked, shocked to see this sort of behavior from a cost-plus contractor!

  • Edward

    Ray Van Dune,
    Robert Zimmerman’s essay, Capitalism in Space, gives a good general view of the differing philosophies between the heritage way of doing space, a way that is heavily influenced by government’s expectations, and the newer way of doing things that newer companies are developing, ways that are influenced less by government and more by a need to get products and services to market quickly and at a price that (non-government) customers can afford.

    However, I see an additional point of view that is more specific to how amazed you are at SpaceX’s ability to be fast and effective. When Elon Musk started SpaceX, he had a limited amount of money, and his first launch vehicle had to work without him spending too much money on it. SpaceX learned some hard lessons when making Falcon 1, including that the market for small satellite launchers just didn’t yet exist, so he skipped Falcon 1 and Falcon 5 and went straight to Falcon 9, where the market already existed. With money tight, it was fortuitous that NASA chose that moment in history to buy commercial services, as SpaceX gained an enterprise-saving contract.

    Still with money tight, SpaceX was able to efficiently finalize its Falcon 9 and begin revenue service. Not having a large pot of cash forced SpaceX to become efficient and fast. The lessons learned included the necessity of rapid, low-cost development and the necessity of going against traditional norms of rocket design. The Falcon 9 second stage is not hydrogen/oxygen, as are most launch vehicles, but uses the same RP-1 that the first stage uses. Fuel efficiency and payload capacity were traded for the cost savings of using a slightly modified Merlin engine rather than developing a second engine. Ground support equipment and procedures were also less complicated due to the use of the same propellants in both stages.

    This philosophy of efficient development bled over into the Falcon Heavy development, Dragon and Crew Dragon development, and even the development of the Starlink constellation. Perfection is too costly for SpaceX, they go for good enough. In developing the reusable first stage, they saved a lot of development costs by turning revenue flights into test flights. Although other companies were (and many still are) unwilling to reduce payload capacity by saving some propellant for recovering spent first stages, SpaceX was willing to compromise overall performance in order to dramatically reduce the price tag on a launch. That compromise has paid off.

    Rapid, low-cost development led to early revenue generation on products that were less expensive than the competition’s. Low cost seems to be SpaceX’s advantage, but rapid development is an important factor to that low cost and to generating revenue before the company becomes insolvent.

    Heritage companies had (have) a philosophy of getting the most performance out of a launch vehicle, of allowing the heaviest payload as possible on each launch vehicle. For them, the price tag was not much of a factor, because their customers had a limited number of vehicles from which to choose, all of which were expensive. Heritage launch suppliers could charge all that the traffic would bear.

    The outdoor construction of various BFR test articles goes against aerospace practices, where flight hardware is built in environmentally controlled cleanrooms. In my experience and in my opinion, this outdoor construction is pure insanity, as there is virtually no contamination control. How can we expect rockets to work properly when there is so much opportunity for contamination? Robert Zubrin, in Richard M’s link, also mentions that more of what SpaceX is doing is madness, according to conventional thinking in the aerospace industry.

    On the other hand, these are only test articles, and SpaceX seems willing to compromise on the contamination issue in order to get their testing program started while they build a facility where they will make their flight hardware. This is consistent with their philosophy of inexpensive rapid development.

    SpaceX is willing to bypass the long pole item — the long lead time construction facility that would otherwise hold up the show (circus tent) — in order to get the development program out of the way sooner. NASA and Boeing did not bypass this long pole item, and they built construction facilities before they started to build their first test SLS booster rocket.

    It is ten years after the announcement of SLS (after seven years of failing to develop Constellation), and NASA and Boeing have yet to fly any development or test articles. SpaceX was testing its first launch and landing of a BFR test article three years after announcing the BFR class of rockets. The heritage philosophy is slow; the SpaceX philosophy is speed.

    On another hand, the third hand (the gripping hand), SpaceX may not be building their fleet of Starships and Super Heavies inside a building after all, bypassing that expense, too. Will that work? Only if the world works differently than the heritage, conventional aerospace industry believes it works.

    Robert Zimmerman’s essay, Capitalism in Space, mentions that not all commercial endeavors will succeed, and SpaceX is no exception. SpaceX had intended to propulsively land Crew Dragon, but that fell to lack of interest by NASA. SpaceX had intended to send a Dragon capsule to Mars in order to explore landing on Mars as well as allow NASA another opportunity to put instrumentation on that planet, but that also fell, and for the same reason. The BFR class of rocket is not guaranteed to work, but if it does then SpaceX changes the entire space industry. Again.

    The lesson for the other private sector commercial companies is to use rapid development in an effective but cost efficient manner.

  • Edward wrote, “..the newer way of doing things that newer companies are developing…”

    I must say I was amused by this line. While your essay is quite good, outlining the effectiveness of SpaceX’s development process, the fundamentals behind this “newer way of doing things” is actually quite old, and has its intellectual foundations in the Old Testament, British culture, the Enlightenment, the American Revolution, and Adam Smith, all prior to 1800.

  • commodude

    Ray Van Dune,

    Long story short, Space-X has a profit motive to successfully build their rockets. The more they build, the less expensive their process is, the more profit they make. Simple economics applied to rocket science.

    NA$A and Boeing have the direct opposite of that. The longer they can keep the development process going, the longer their jobs and budgets are guaranteed. In this model, almost success (aka failure) is rewarded, while success is punished via the termination of the project.

  • pzatchok

    There is no more chance of contamination building the starship outside than building it inside.

    Think of all the contamination it will get waiting on the launch pad alone. Outside in the rain and wind for a week or more possibly.

    I don’t know if you ever heard about it but they have a room at NASA dedicated just to stuff they found inside and on the shuttle when it came back from space. Everything from tools ,obviously, to dead bugs and tree frogs they found hidden inside the shuttle. None of that stuff ever caused a problem.

    What happened to all the water that got inside any rocket waiting on the launchpad in a sudden rain shower? Nothing that effected the rocket and you can bet that someplace and at sometime it has happened around the world.

    Plus think of all the contamination that will get blown into the starship when it lands and kicks up all that dust and dirt.

    Just like your car. Keep the contamination out of the fuel tanks and other liquid tanks like the oil and coolant systems and your car will be fine.

    For years I have argued that NASA demands way to much of its assembly contractors. Surgical cleanliness is NOT needed.

  • Richard M

    Hello Edward,

    “NASA and Boeing did not bypass this long pole item, and they built construction facilities before they started to build their first test SLS booster rocket.”

    Notice that neither did Blue Origin. The cushion of Bezos’s personal wealth, and the more aggressive hiring of legacy aerospace talent for management, has led them to a much more traditional model of development. (Which is not to say that New Glenn can’t or won’t be a successful orbital rocket.)

    But while Blue Origin has been going slow and steady, SpaceX has raced out and grabbed the bulk of the orbital launch market, and will very likely beat them out for the Air Force Phase II award.

  • sippin_bourbon

    I am not count Blue Origin out, either.

    They hired legacy talent, and the methods are more traditional and methodical, but those folks have been freed from being in the government program.

    Contractors want the government program to be drawn out to make more money, keep their jobs longer, because they count on the agency heads to keep going back to the well of tax payer money.

  • Edward

    You wrote: “the fundamentals behind this ‘newer way of doing things’ is actually quite old

    Once again, I have been caught using shorthand. The “newer way of doing things” was supposed to apply strictly to aerospace, because it is the general method of development in most industries, where a new product has to get to market in 18 months, otherwise the competition will have their version of your product on the market and scoop your company. Ouch.

    This “newer way of doing things” is isn’t even new in aerospace, so my shorthand caused me to misspeak twice in one phrase. That makes it twice as amusing, to me.

    In the 1950s, rocket development was fairly rapid. For instance, the Scout was designed in 1957 and its first successful launch was in 1961. Although the Scout is a small rocket, I think it is a good example. The Saturn V was also rapidly developed. Although the F1 engines began development in 1955, the Saturn V rocket (launch vehicle) started development in the early 1960s (my recollection is 1962, not to be confused with the Saturn I development, which started earlier), and its first manned launch was 1968 and first unmanned test flight was a year earlier.

    This “new” way is half a century old in the space industry, it just fell out of favor. Probably because competition went away and complacency set in. The “all the market will bear” business practice is also not new. It is what happens when a monopoly sets in.

    COTS (now Commercial Resupply Services) and CCDev (now Commercial Crew Transport) were supposed to change the complacency and change the high pricing business practice. It has worked wonders.

    So, what happened to rapid development of our launch vehicles? Was it the Space Shuttle, which took more than a decade for first launch? Perhaps it was the ISS, which took 15 years from approval to the launch of the first module and another decade to complete construction. It couldn’t have been that we lost our rocket-building capability in the dry years between the Shuttle and COTS, because we have several new launch vehicles and a few more still in development.

    I think that it was the complacency that the monopolistic governments had as sole suppliers of launch capability. The U.S. certainly had no urgency in replacing the Space Shuttle, which failed to lift quite as much as it had supposedly been designed to launch, or to be inexpensive or to turnaround rapidly. A monopoly has little incentive to improve its product.

    You wrote: “Think of all the contamination it will get waiting on the launch pad alone

    You aren’t thinking about the interior of the fuel tanks and other interior parts that do not get exposed to the elements. Interior contamination, such as propellant tanks or lines, can cause bad things to happen to the rocket engines, including rapid unscheduled disassembly.

    What happened to all the water that got inside any rocket waiting on the launchpad in a sudden rain shower?

    If it got inside, then the rocket was faulty.

    Keep the contamination out of the fuel tanks and other liquid tanks like the oil and coolant systems and your car will be fine.

    So, were those car parts of yours built in the back yard or indoors in a building with filtered air and no leaks in the roof? That’s what I thought. And that is for parts that don’t rapidly, violently disassemble when there is a little contamination.

    SpaceX will have to spend time and other resources eliminating both the contamination and any ill effects, after the fact. It is a tradeoff in order to get their test articles flying sooner.

    Surgical cleanliness is NOT needed.

    Actually, it is. SpaceX is using corrosion resistant steel (Stainless Steel(R)), which is good because there is a source spraying salt into the air just a few hundred meters east, but material choice not a guarantee against corrosion. Any contamination on an optical surface messes up that surface’s ability to perform as designed. Since every surface radiates heat to space, or collects heat when it faces the sun, contamination makes Starship’s thermal characteristics questionable, so the designers need more flexibility in their environmental control for the ship (I am so glad that I am not a thermal engineer). This may require more power than would otherwise be necessary, in yet another tradeoff that SpaceX is probably making in order to reduce the cost of launch and spaceflight. With questionable thermal characteristics, the power source would have to be heavier than would otherwise be necessary.

    Since satellites and deep space probes are built indoors in climate controlled environments (temperature, humidity, particulates, etc.), their thermal characteristics are reasonably well understood. This means that they do not require extra solar panels or larger RTGs or whatever their power source. Camera lenses and other optics also remain clean, so their performance is not degraded. Keep in mind that satellites and other payloads are placed within the shrouds while indoors, not outside.

    High performance requires serious cleanliness.

    Richard M,
    I purposefully did not mention Blue Origin or Virgin Galactic. They have deep pockets and seem to be in no hurry to build their suborbital tourist businesses. It looks like New Shepard will take nine years to develop, which isn’t so bad when compared to SLS.

    Commercial space will win out over government space, because government space takes so long. The traditional contractors are in a competition with commercial suppliers (Boeing is competing with itself), and this will be felt hard, once SLS is replaced by commercial vehicles. Blue Origin and Virgin Galactic may lose all their tourism customers if SpaceX’s Starship can make orbital tourism possible sooner and for the same or lower price.

Leave a Reply

Your email address will not be published. Required fields are marked *