50

Starship alone is not capable of orbital flight, but it is capable of high suborbital flights sufficient for testing reentries. The booster's only use is as a first stage for Starship. It could only be put into use immediately if a Starship has been developed and built to stack on top of it. And it is expected to be much quicker and easier to develop than ...


49

Salt does all sorts of unpleasant things to just about every building material humans use. Hot salt spray, such as you'd get from a rocket launch, is even worse: spraying something with hot saltwater is one of the techniques used for corrosion testing. Build a launch pad over the ocean, and you'll need to clean it off after each launch to try to keep the ...


46

There are several compelling engineering and design reasons why a bigger spaceship makes sense and several reasons why making a mini-starship does not make sense for SpaceX specifically (and their vision). First and foremost, Elon Musk has made it clear that his goal for the company and the future isn't to provide cheap satellite launch capabilities, it's ...


43

Musk is creating a Starship "production line", because obviously, he wants a lot of Starships. This aligns with the company's goal of "making humanity a multi-planetary species". As for "where is the market?": It doesn't exist yet. Currently, SpaceX's attitude towards space is "build it and they will come". Many large scale investment organizations ...


40

Neither has much financial purpose without the other. A BFR cannot perform any useful function without an upper stage, and that is the BFS. Since the whole platform is a major investment in a new architecture, they are starting with the smaller piece - the BFS. Since it uses some of the same engines as the BFR, it can act as a testbed for both BFR and BFS ...


40

Sorry for the length of this, but it brings up some interesting facts and possibilities. The moons you mention, Titan, Europa, and Enceladus, are three very different places. Titan has a relatively large surface gravitational acceleration (as far as satellites go) and a very thick atmosphere; Europa has a relatively large surface gravitational acceleration ...


38

In my experience, I've noticed that SpaceX uses a lot of temporary components until such temporary components need to actually be tested. Since the legs of MK1, MK2, and most probably MK3 will never see uneven soils rather than concrete landing pads, they will most likely just have simple legs. After a few successes with MK3, we should start seeing much more ...


33

In the question you mention about why Falcon 9 uses four legs to land instead of three, there are multiple great answers. One of them by @David Hammen states that: "Another factor is that the Falcon has nine engines, one in the center and the other eight around it in an octagonal or square-like arrangement. The bottom part of the thruster reflects ...


30

Elon Musk stated in a news conference after the Falcon Heavy launch that the BFS will be the focus because they think they understand designing booster rockets pretty well, and thus they decided to focus on the more difficult piece first. He answers this in response to a question that starts at 20 minutes 52 seconds here, and speaks specifically to starting ...


30

F9 can enter engine first because it isn't returning from orbital speeds. While fast, it's a fraction of the speeds something returning from orbit (or further) comes in at. So the engines are out as an entry surface, you need more protection. One way to achieve this is Dragon-style: put a heat shield on the bottom, and engines in the sidewalls. Great for ...


30

Anyone know what the story is? The main driver for the large number of engines on the BFR first stage is the desire to use a common engine design (albeit with different optimized nozzles) for both the booster stage and the interplanetary spacecraft stage. Building and maintaining only one type of engine makes things more efficient, and is a strategy that ...


29

Starship is a 9 meter wide vehicle. The first stage (Super Heavy) will be mounting 35 or 38 or some other number in that range of sea level engines. As you can imagine that will take at least three separate rings of engines. 6 in the center, then two more rings with the rest. The Starship is the same diameter as Super Heavy, and the inner ring will be ...


23

While this seems lightly ill conceived, it actually makes sense. Super Heavy is going to be very large, as these things go. 70m tall, 9m wide, and while not very dense, still quite heavy. Not very easy to move around. The plan is to land close by to make moving it back to the launch pad easier. Original plan was notionally to land back on the launch ...


23

Since the term "grain" already in use in the solid rocket context, I'm favoring the term "cereal". Cereals contain about 66–76% carbohydrates -- mostly starch (55–70%) plus some sugars and cellulose. Cellulose combusted with gaseous oxygen yields surprisingly good specific impulse, up in the 240 sec range; sugars with potassium nitrate ...


21

This has been answered before, but I chose not to just mark it a duplicate because there is one new reason for the header tank unique to Starship. In a Reddit AMA in 2017 where Elon Musk answered questions about the original ITS design, he answered a question about the header tanks: Those are the header tanks that contain the landing propellant. They are ...


20

SSTO on Earth requires about 9400 m/s of ∆v depending on the exact acceleration profile and other factors. Ascent from Mars' surface to low Mars orbit requires only about 3800 m/s, and from there it's another 2500 m/s to break out of Mars orbit and get on a trajectory to intercept Earth -- a total of 6300 m/s. Allocate another 300 m/s or so for touchdown on ...


20

It's pretty simple: Beresheet has a dry mass of 150 kg. Starship has a dry mass of 120 t. So even though Super Heavy is 10 times as powerful as Falcon 9, that's nowhere near enough to make both situations similar – even without needing also fuel for the return.


19

It's probably going to be less of a concern than you'd guess. The icy worlds of our solar system have essentially no atmosphere, so the surface materials will sublimate directly to vapor and be dispersed rather than melting and freezing the landing pads into place. Fairly little of the surface will be disturbed to begin with. The gas expansion which ...


19

Falcon 9 reentry is only designed for first stages, with a reentry burn that is pretty minor - on the order of a few hundred meters/second. A second stage, reentering with far more velocity than a first stage, can't shed the extra velocity with a cheap burn, because the total delta-v necessary for that would be about as much as the second stage was capable ...


19

By the time Starship launches for Mars, SpaceX may have changed the number of legs several times. They redesign as quickly as the Haggunenons of Vicissitus Three evolve during lunchtime. Plausible guesses for factors favoring three legs, at the moment: lighter less aerodynamic drag, if the legs also act as fins send a scout beforehand to choose a boulder-...


19

Bob Zubrin, of Mars Direct fame, has been critical of the SpaceX Mars plan. He suggests that it makes no sense to send a full Starship too Mars, instead use it to launch the Mars vehicle and just use Starship to bring payload and fuel. Most of the concern revolves around the fact each Starship sent to Mars is committed for almost two years. In normal ...


18

Russell Borogove's answer gets to the root of the issue. They wanted minimum 6 engines on the BFS, which meant that the BFR had to have several times more, and they picked the number 31. 31 nozzles, however, is not a record. The Soyuz has 5 cores. The centre core has 4 main and 4 vernier nozzles, and the side cores have 4 main and 2 vernier nozzles each, ...


18

tl;dr: at an apparent magnitude of about +18.5 you need a several meter telescope and a dark sky. Hubble can do it too. So by reflected sunlight, definitely not by eye. The exhaust from a Methalox (CH4 + LOX) engine barely makes any light in the visible, so no help there. Starting with the math from this answer: I'm going to characterize the 55 x 9 meter ...


17

They are COPV (Carbon Overwrap Pressure Vessels). They are high pressure gas tanks. Basically a steel tank with carbon fiber on top to make them stronger so they can hold very high pressure gasses. People have gotten close up 'spy photos' of the label which suggests the latest ones (used on SN3) say CNG only (Compressed Natural Gas, aka Methane, aka CH4). ...


15

If you want an easy way to think about it, imagine how bright it might be in low Earth orbit, 240 miles up (which is just a bit lower than the International Space Station). However bright that is, it will be only a millionth as bright when it’s near the Moon, 240,000 miles away (and so a thousand times the distance). Is it likely that it will be bright ...


14

There are no published/proposed abort modes for ascent. We can speculate that some incidents can be survived by letting Starship tumble free and light it's own engines to burn to a low orbit or land depending on altitude and velocity, but that capability has not been proposed by SpaceX. Landing redundancy is provided by carrying 7 deep throttling, sea level ...


13

Environmental impact may be a major consideration The effect on the local water environment from that sort of blast into it could be severe and far reaching in the neighborhood around a water based launch pad. Also if there are any abort or need to dump fuel or uncombusted fuels from explosions could also have massive impacts that are immediately spread due ...


12

Pretty much certain it's a flyby. Grey Dragon mission was a flyby. To send a mission to the surface of the Moon would require many refueling missions, and I can't imagine that would be the case. Also, the tweet that started everything says so. SpaceX has signed the world’s first private passenger to fly around the Moon aboard our BFR launch vehicle


12

Quick answer is all I have time for now -- if someone wants to do a more detailed and referenced answer, please feel free and I'll delete this: While it's very big, its mass is not that high, and gravity is low. On Mars, for instance, it needs about 150 tons of fuel, plus 100 or so tons of vehicle (mass) to get back to orbit. Under Mars gravity thats only ...


11

SpaceX has been developing a methane/LOX engine called Raptor which is about 2 times more powerful than the Merlin engine. (This is the first Raptor iteration at around 400Klbs thrust. The first Merlin (1A) was 75Klbs, current version is closer to 200Klbs. So expect performance growth). 31 engines at about 400Klbs thrust gives about 12.4 million lbs of ...


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