 Have you ever looked at the Apollo missions list and wondered why it starts at Apollo 4? Or if you're not an epic space nerd, did you know that the first flown Apollo mission was Apollo 4? So what exactly happened to Apollos 2 and 3? Hi everyone, I'm Amy, this is The Vintage Space, my little corner of the internet where we talk about all things mid-century that I love, and a lot of that happens to be Apollo-era spaceflight. This is something maybe really obscure that you've never noticed or thought about. The Apollo missions go from the tragedy of the Apollo 1 fire to Apollo 4 without any mention of Apollos 2 or 3. It's actually a pretty interesting story, albeit a really inside baseball kind of nerdy story, about how mission naming conventions worked in the early space age. The Saturn V that launched the Apollo missions to the moon was part of the Saturn family of rockets, the Saturn I, the Saturn 1b, and the Saturn V. Of course, there's more to these rockets than just stages, but this gives us a good sense of how they fit together as a family. The Saturn I was the smallest in the family. It used an S1 first stage manufactured by Chrysler. The bulk of this stage was the cluster of nine propellant tanks, one larger internal tank and eight surrounding it. These tanks fed a mixture of RP1 or rocket propellant 1 and liquid oxygen to the eight H1 engines that got the rocket off the ground. The second stage was an S4 built by the Douglas Aircraft Company, powered by six Pratt & Whitney RL10 engines, burning a mix of liquid hydrogen and liquid oxygen. Next in the series was the Saturn 1b. This rocket was the same as the Saturn I, but with the more powerful S4b upper stage. It still used liquid hydrogen and liquid oxygen, but instead of the six Pratt & Whitney engines, the S4b used a single J2 engine. The Saturn V represented the most powerful rocket in the series. Where the previous rockets used two stages, this one used three. The Boeing-built S1C first stage used RP1 and liquid oxygen to power the five F1 engines. The S2 second stage, built by North American Space Division, used five liquid oxygen and liquid hydrogen-powered J2 engines. The third S4b stage was the same as the upper stage of the Saturn 1b. NASA started Saturn I launches in 1961 with boilerplate Apollo spacecraft and ballast payloads to study the rocket's development and later the spacecraft's development. After right off the bat, the agency used a straightforward naming scheme, a letter denoting the rocket and test type, and a number denoting the specific launch. There were ten Saturn I launches labeled S-A for Saturn Apollo or A-S for Apollo Saturn followed by the number. Whichever letter came first was the emphasis of a specific test. The serial numbers or internal designations for Saturn I missions went from SA-1 to SA-10, but the missions were a little different. SA-1 through 5 were rocket development tests. Then the designation changed to the 100 series numbers, marking the shift into Apollo tests. AS-101 to 105 were the first Apollo hardware launches. There were some other tests early in Apollo's development that used a different but still consistent designation. Hardware tests using a little Joe rocket were labeled A. A-1 through 4 were these Apollo hardware tests. As Apollo advanced towards manned missions, NASA began using the upgraded Saturn I-B. These missions had the internal designation of SA for Saturn Apollo, but their mission numbers used A-S for Apollo Saturn followed by a 200 series number. The 200 series was reserved for the Saturn I-B. Three Saturn I-B tests launched in 1966, while the interim Gemini program was coming to a close. AS-201 launched on February 26 as a suborbital test of the Saturn I-B and a Block I Apollo command module as its payload. AS-203 on July 5 was another suborbital flight to test the command module's heat shield. AS-202 was a test of the Saturn I-B rocket. The next mission in the Saturn I-B sequence, AS-204, was a simple but vital Earth orbital test of a Block I command module with a crew scheduled to launch on February 21 of 1967. When the spacecraft for the AS-204 mission, spacecraft 12, arrived at the Candy Space Center on August 26, 1966, it was protected by a cover emblazoned with Apollo I in capital letters. The mission was publicly known as Apollo I, the first in the series of manned missions that would culminate in the lunar landing. From here, NASA's plan was to have Apollo II launch on a duplicate of Apollo I's mission to gather additional data from the relative safety of Earth orbit, even though the Block I model couldn't support the lunar mission. Only the Block II could dock with the lunar module and thus support the lunar landing mission. We'll have a whole video on why NASA built two versions of the Apollo spacecraft right up here. Apollo III would then debut the advanced lunar-capable Block II command module. But it wasn't long before this plan fell apart. Spacecraft 14, the spacecraft for Apollo II, was badly behind schedule, and many within NASA began questioning the value of a second Block I mission. Not to mention, the agency had abandoned the practice of duplicating flights after Gus Grissom repeated Al Shepard's suborbital mission in 1961. The standard practice had become to take steps forward and achieve a new goal with every flight. Not long after the final Gemini mission splashed down on November 15th of 1966, George Miller of the Office of Manned Spaceflight canceled Apollo II. The missions were reorganized, so Apollo II would now debut the lunar module on another Saturn 1B flight, and Apollo III, a high-Earth orbit mission with both the command and lunar modules, would also be the first manned Saturn V flight. This was the standing order for Apollo missions at the beginning of 1967, and each had an assigned crew already in training. Then NASA was struck with its first major setback. During a routine pre-launch test, a fire ripped through the spacecraft 12 and killed the Apollo I crew. The ensuing accident investigation revealed flaws in management practices and fundamental issues in the spacecraft's overall design. The review board recommended dozens of changes to the spacecraft. Apollo and the command module prime contractor North American Aviation were facing substantial redesigns, which promised to delay the whole program. The fire also forced Apollo management to reconsider its mission schedule. The question became whether it was worth launching the Apollo Block I flights at all. With so many changes pending, was there anything really to gain from launching a version of the spacecraft that couldn't go to the moon? Towards the end of April, the decision was made to cancel all manned Block I flights, and with the lunar module also behind schedule, Apollo missions would start with an Earth Orbital Block II command module only flight, followed possibly by a lunar orbital command module only flight. Reassessing the Apollo schedule brought a change in naming conventions. The widows of the Apollo I crew asked NASA to retire the mission designation in honor of their husbands. Moving forward from here, NASA had two options, both of which George Miller outlined in a letter to George Lowe, deputy director of the manned space flight center. The agency could proceed in sequence and name the first mission after the fire Apollo II, or it could count the unmanned Saturn 1B test flights as part of the Apollo series and retroactively rename them to have sequential Apollo designations. AS-201 would become Apollo 1A, AS-202 would become Apollo 2, and AS-203 would become Apollo 3. This meant subsequent flights following the fire would begin with Apollo 4. On April 24th, 1967, NASA's Office of Manned Space Flight announced that AS-204 would officially be recorded as Apollo 1. AS-201, 202, and 203 wouldn't be renumbered in the Apollo series, but subsequent missions would be named, beginning with Apollo 4. Apollo 4 marked the first Saturn V flight and brought with it a new naming scheme. Internally, the missions were denoted SA for Saturn Apollo and given a 500 series number. SA-501 was publicly known as Apollo 4 and it launched on November 9th, 1967, with a Block 1 Command Module with Block 2 elements installed as a spacecraft and rocket test. Apollo 5 launched on the Saturn 1B intended for the Apollo 1 mission on January 2nd, 1968, so it was known internally by the same designation, AS-204. But its alternate notation of SA-204 slash LM-1 speaks to its goal of the first test flight of the lunar module's Ascent and Descent engines. Since it was only an engine test, it didn't even fly with legs. Apollo 6, internally AS-502 was another Saturn V test flight with a modified Block 2 Command Module and a lunar module test article. Apollo 7, internally AS-205 was the first manned Apollo mission. It launched a Block 2 Command Module on a Saturn 1B into Earth orbit on October 11th, 1968, doing what Apollo 1 had intended more than a year and a half earlier. It was the flight that got Apollo back on track and the familiar, steady sequence of missions from this point on points to the program's success. Apollo's 8 through 17 had the internal sequential designations of SA-503 to SA-512. SA-513, originally earmarked as the launch vehicle for Apollo 18, was the final Saturn V to fly only instead of going to the moon, it launched the Skylab space station into orbit. SA-514 and 515 were two unused Saturn Vs intended for Apollo's 19 and 20. The pieces are now on display at the Johnson and Kennedy Space Center as part of full Saturn Vs. To finish out the Saturn 1B story, SA-206, 207 and 208 were the three Skylab missions and SA-210 was used for the Apollo Soyuz test program. SA-209 and 211 were built but never used and SA-212, 213 and 214 were built in part before being scrapped. I hope that little weird insight into Apollo naming conventions and mission numbering answered a question some of you guys didn't even know you had about the lunar program. Or maybe it just gave you good fodder for your next cocktail party chat. I want to remind you guys that my new book, Fighting for Space, is available however you like to consume books as is my first Breaking the Chains of Gravity. I have links for both in the description below. I want to give a special shout out to my Patreon supporters and YouTube members, who you guys truly make these videos possible, especially throughout the pandemic. I wouldn't have been able to keep creating content without your support, so thank you so much. That's going to do it for me for today. Thank you so much for spending a little bit of your day with me and I will see you guys next time.