90

I can't speak for why SpaceX made the decision. However, while three legs won't wobble, four legs are less likely to tip over. SpaceX has demonstrated tipping over is a major problem. Dr Peterson of The Math Forum explains... There are different kinds of stability! A three-legged stool is guaranteed not to wobble, because the ends of its legs always ...


65

The boosters do not have the range to get to Africa because they aren't going fast enough. If you look at the graphic below it shows a Falcon Heavy mission. The side boosters do not get very far downrange at all so they return to the cape. The drone ship for the core booster was located 1236km downrange, Africa is over 6000km downrange. The graphic came ...


44

Because of accidents of geography and history. Both of the main US launch sites are where they are because rockets occasionally crash, and, for fully fueled heavy lift vehicles, worst-case impacts have yields approaching that of nuclear detonations. So they were sited to fire out over the ocean for the longest possible distances to minimize potential ...


38

As with most things space, it all comes down to tradeoffs. The most efficient rocket is one that is purely expendable and has no mass that does not contribute to getting the payload towards orbit. If the aim is to reuse the rocket, you need a mechanism to achieve control in the upper atmosphere, a method to control descent rate and a method to achieve a ...


35

The first manned Soviet flight was Vostok 1 in 1961, and the first Soviet flight with a multiperson crew was Voskhod 1 in 1964. The Wikipedia article that you linked intends to say that Soyuz 1 was the first Soyuz mission with a crew. The anecdote about the wolves and bears comes from Voskhod 2 on March 19, 1965: For the Soviet crew of Voshod 2 [sic], their ...


34

Earlier on Musk indicated it may be possible to fly a block 3/4 booster more than twice but it would depend on the missions flown, with LEO missions like this Commercial Cargo mission being easier than GTO missions. I suspect this booster and the previous one that did two cargo missions could be reused if SpaceX wanted to but they are choosing to move ...


30

It is not so much that in the 21st century it is hard or expensive to make a fairing. Rather they are just REALLY REALLY big. 13 meters by 4.6 meters. That is about 40 feet long, and 14 feet wide. The common description is that a school bus would fit in it. (Sort of like the Space Shuttle cargo bay size). These need to be very light, as every gram/...


30

No, the pad will not be used for propulsive capsule landings. As requested by NASA, SpaceX have stopped pursuing propulsive capsule landing. The landing legs have been removed from the design, for instance. The pad is for a helicopter: Most notably, GO Searcher is being fitted with a helipad that will be used to rapidly transfer astronauts from Crew ...


25

This is explained in the Apollo Program Summary Report. A floating command module has two stable positions; stable II is upside-down and undesired. It was discovered that three identical uprighting bags was not enough to get out of the stable II position, so the Z-axis bag was made smaller: 4.4.4.4 Uprighting system [...] In addition to the overall weight ...


24

The test they were doing didn’t require parachutes. Data-taking ended right after the capsule separated from the tower. Since the capsule’s behavior after that was not part of the test, it could be an inert item. To extend the test through parachute deployment, the capsule would have to be much more complex with the parachutes, deployment system, and a ...


24

A stool with three legs that are rigid, are of a fixed length, and have a fixed orientation with respect to the seat of the stool is superior to a chair with more than three rigid, fixed length, fixed orientation legs in one and only one regard. And that one regard is completely irrelevant in the case of landing legs. The landing legs on any landing space ...


23

In addition to the other answers, a fixed site in Africa would limit the available launch inclinations to a narrow band. A ship can be positioned anywhere in the ocean.


22

The fairings are large structures, made in a way that's difficult to automate. The structure consists of an aluminium honeycomb core with carbon fibre inner and outer panels laminated onto it. Carbon fibre is a labor-intensive material. Then there's the quality assurance that makes everything rocket-related expensive. Roof boxes, OTOH are injection ...


22

If you check the Reddit Wiki listing all the SpaceX Falcon 9 first stage cores, you will see that they are flying the Block 3 and Block 4 boosters only twice. What is interesting has been that they still often fly them on the second flight with legs. They have been using these flights to test the edges of the flight envelope. In some ways, the Block 3/4 ...


21

The first Block I version of the capsule used three bags of the same diameter (43 inch). The later Block II used one smaller bag (34 inch). The volume of the small bag was 49.43 % of the larger ones. So they wanted to try a smaller bag with half the volume and calculated a 34 inch diameter bag. Source: https://airborne-sys.com/wp-content/uploads/2016/10/...


20

The usual answer - $. Booster recovery was only marginally worth it for STS - once you witnessed how every screw and nut was taken apart, cleaned, and reassembled, you began to wonder why not just build a new one. That said, it is a wonderful thing for problem resolution if you get the hardware back to look at. Here are some pictures I took at the STS-...


20

SpaceX was testing a more efficient, faster landing technique. The test produced useful telemetry data. See Musk's tweet and photo. Normally, the terminal phase of Falcon 9 first-stage landing finishes with a single engine firing. This attempt used three engines for the landing. By firing three engines instead of one, the final deceleration of the stage ...


20

Aside from the technical aspects, Africa is comprised of a couple of dozen different countries, all with their own rules and politics, but none of which would appreciate a botched booster landing in their urban centers. Even one incident like this would be enough to make sure no more flights happen.


20

In the Apollo era, landing guidance had gotten quite precise and there wasn't a "huge flotilla" waiting; Apollo 8's recovery force was the largest, with 6 ships waiting for it in each of two landing zones, but groups of 2-3 were more common. The recovery ships were usually positioned a couple of miles away from the designated landing point, and the ...


18

The reports indicate the seas were high enough they did not want to send people on board to weld it down. Further reports suggest the seas were up to ten foot swells, and remember that the ASDS barges are very large and flat. They did not use the Octobgrabber/Xoomba, because the attach points it uses on a Falcon 9 core, are modified and not available on a ...


17

The answer is on this National Geographic page about the best pictures from NASA's official photographer Bill Ingalls: If you love space, odds are you’ve admired the work of Bill Ingalls. He has been NASA’s senior contract photographer for 30 years, a job that has taken him across the world—but not yet beyond it—to cover major moments in space exploration. ...


16

SpaceX has decided that reusability is a critically important goal to keep long-term costs down, therefore they've designed in the ~15%-30% performance margin they need to achieve reusability (the lower figure for mid-Atlantic barge landing; the higher figure for boost-back to the launch site). Cost is critical for SpaceX because Falcon 9 has to compete ...


16

It seems to me very unlikely that this would actually occur. One would have to get the fuel out to the barge, fill the rocket, monitor the mission to return, and run the risk of losing the rocket, etc. The cost to have the barge return is minimal in comparison, and in fact, the cost is probably about the same regardless of if there is a booster on top or not....


16

Wings are heavy. They also add mass to the rocket's structure, because it is loaded horizontally when flying with wings rather than vertically as it is at launch. At the time Energia was developed, control systems were not developed enough for a vertically landing rocket. However, now that we have that ability (as Blue Origin and SpaceX have demonstrated), ...


15

The FH side boosters should be almost equivalent to the F9 first stage (at least the Block 5 ones) - the difference will be mostly in mount points and the nosecone instead of the interstage. The center core is a bit more different with reinforcements to handle the forces. So from hardware standpoint the landings are the same thing. (One of the probable ...


15

From the article: Tuesday’s launch was more focused on testing the launch abort system itself. The parachutes on Orion have been tested 47 times.


14

Local scrap metal dealers collect and recycle them. See this link for some more information.


14

It is purely down to trajectory. The side cores detach relatively early after the launch. This means that they are not so high nor do are they travelling so fast Eastbound. There is therefore enough fuel left in the side boosters to allow the "boost back burn" that allows them to change direction and get back to the original landing site. The centre core ...


13

SpaceX designed the Falcon 9 for reuse. They have several iterations, starting with the 1.0 design (with the tic-tac-toe grid of engines). The switch to the 1.1 design with the Octaweb, was distinctive and was finally able of landing. The current model is Block 3, 4, or 5 (Block 3's have all been flown, and Block 5 is about to fly, end of April as I write ...


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