New answers tagged

3

I'm not entirely convinced by the "expendable" argument of the other answers. Let's look at the reasons why you would want to give a name to a craft: When you need to distinguish between more than one vehicle. Any mission with more than one spacecraft (e.g. rendezvous) will need an easy-to-use way to distinguish between the two vehicles. Sure, you can ...


1

ANone is correct that launchers traditionally haven’t gotten names because they’re expendable; it’s a shame to give a perfectly good name to a rocket that’s going to be in use for less than an hour. Note that the space shuttle orbiters got individual names, because they were flown repeatedly; the expendable booster & ET portions of the space shuttle ...


4

Probably the same reason small-holders often don't name their pigs. "The spent lower stage of the ShinyRocket(tm) for project-put-thing-in-sky was jettisoned over the Pacific." Sounds better than if you'd given that same piece of hardware a name. This in keeping with the observation that the bits that weren't expected to meet a fiery end shortly after ...


0

I imagine designing three legs around the two side cores of a Falcon Heavy would also be quite a bit more difficult, since (assuming equal spacing) two of the legs would be quite a bit closer to the cores.


0

Load on an individual leg in a 4-leg-design is less than a 3-leg-design. (load distribution optimization). Thus, the total weight of 4-leg-design was less than 3-leg-design (stress handling vs material density optimization).


5

The main advantage of three legs is on uneven soil: they will always all contact the ground, while with 4 legs one might be up in the air. This isn’t a concern for space x since they land on a flat launchpad or barge. Here the 4 legs increase the stability by increasing the tipping tolerance (as seen is other answers)


22

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 ...


83

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 ...


1

I've found something like this in famous book "Ignition! An informal history of liquid rocket propellants" by J.D.Clark, 1972. " And when you have a turbine spinning at some 4000 rpm, and the clearance between the blades is a few thousandths of an inch, and this sticky, viscous liquid deposits on the blades, the engine is likely to undergo what the British, ...


4

Note that payload performance is often hard to compare apples-to-apples as different providers will use different reference orbits (200 km, 28 deg, vs 500 km SSO, etc). Pegasus (US), Electron (US/NZ), Kaituozhe-2 (China), Kuaizhou-1A (China), and Hyperbola-1 (China), Shaviyt (Israel), and Safir (Iran) are currently operational in the sub 500 kg to LEO ...


2

Cryogenic: the propellant has to be cooled to keep it in a liquid state. At room temperature, it's a gas. Oxygen, hydrogen for example. These propellants need careful handling because they are at very low temperatures. Storable: the propellant is a liquid at room temperature, so the rocket can sit on the launch pad with propellants on board without needing ...


4

Based on page 31 of the document referenced in the question, the author appears to use the term for engines that use one cryo propellant and one storable one (for example, liquid oxygen and kerosene). It's not a term I have heard before. Prop: integer variable defining the type of propellants used for new design rocket engines. The following ...


4

People think that rockets push on the air, and that without air there is nothing to push on. This is a very common misconception I think: people with physics or other science backgrounds (like me) have spent a long time more-or-less unconsciously training ourselves not to think like this intuitively, to the extent where we may end up thinking that people ...


6

What are the parameters of determining the launch capabilities of a rocket? The main parameter is "payload to orbit", but you have to specify which orbit you're using. In the answer by ASRI_306, 'payload to GTO' is used (i.e. geostationary transfer orbit). Strictly speaking, that's incomplete because there is more than one transfer orbit. 'GTO 1500' means ...


7

In the list of current operational launch vehicles, this is how GSLV stacks up. This is a comparable list, to compare it to N-1, Proton, R-7 would be an apples-to-orange comparison. Vehicle Deliverable Payload to GTO (kg) 1. Long March 4B/4C 1500 2. Long March 3A 2600 3. Soyuz STA-A/B w/ Fregat ...


3

Simply answered. Although the rocket is smaller, the cost of launch infrastructure, licencing, insurance, down range tracking & saftey don't scale down with rocket size. Also the cost to R&D the small vehicle isnt that much less than one around the size of electron, and this cost has to be recouped across your launches. In short you end up with a ...


1

The weight of all electronics needed for an orbital rocket is nearly the same for a small and a large rocket. If there is a single engine only within each stage, the number of telemetry chanells will be somewhat smaller and thus also weight. The same is true for battery weight needed to power the electronics. It won't be very efficient if electronics and ...


2

Why isn't there a rocket to launch a single cubesat? There is! However it remains to be seen if it is necessarily a good business idea. From this answer to Will JAXA try again to launch TRICOM-1 with the “world's smallest orbital rocket” SS-520-4 again? From Wikipedia's S-Series_(rocket_family); SS-520-5 The second attempt at becoming the ...


12

N2O4/UDMH is the choice if you need a non cryogenic storable hypergolic fuel. But UDMH is toxic and carcinogenic and should be avoided if possible. LOX/UDMH is not storable and not hypergolic. There are a lot other fuels to be combined with LOX and they are not toxic or carcinogenic and thus easier to handle. There are combinations of LOX with higher ...


13

You need a massive facility that can maintain a near vacuum while dealing with the engine exhaust. There are (were) a couple in the US. Plum Brook Station (Part of NASA Glenn) includes the In-Space Propulsion Facility (picture from this informative paper) Arnold Engineering Development Center (run by the DOD) includes the J-6 Large Rocket Motor Test ...


4

The oxygen tanks on the Saturn V had anti turbulence vanes to prevent the lox from forming vortices. These were considered undesirable both for flow purposes and to avoid stray magnetic fields. My dad ran the lox plant at Woomera rocket range in Australia. He told me the lox pipes to the Blue Streak and Black Knight rockets had to be grounded to avoid ...


1

That depends entirely on what rocket and airplane you are comparing, of course. However, with regard specifically to the large rockets used for spaceflight against commercial aviation, yes. Orbital speed is approximately 8 km/s for Earth at a low orbit. A typical commercial jetliner flies at speeds of around 0.25 km/s. That's all it takes to know which is "...


0

It depends a bit on how you define cost and how many launches you consider. In the very-large-launch limit, where capital cost can be spread widely, some people think a tethered space elevator is the right solution. More hypothetical are dynamic elevators like the space fountain: The launch loop: Or laser launchers: There’s a systematic catalog in ...


0

Everything I've seen from Mercury to Apollo has been in imperial units but that doesn't mean they used metric and converted it all over before handing it over. There is a pretty good article here that talks about the Apollo guidance computer. The computer was programed to use SI units, which is basically metric with a new name, but everything entered into it ...


0

For me the answer to using nuclear power to get to orbit absolutely requires tapping into the electrical grid and not carrying the propulsion with you. For example, a space elevator, or a high velocity projectile to bring raw material up along with in space manufacturing. Alternatively, if you want the benefits of a high velocity projectile, without the ...


10

Rockets don't actually mostly go up, they try quite hard to go up as little as possible. While flying, gravity is always accelerating you downwards at 9.8 m/s^2. This means that any fuel spent accelerating upwards is wasted, as gravity will pull you back to earth eternally, no matter how much fuel you burn (unless you reach escape velocity, but it will ...


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