# Tag Info

68

Added complexity is never welcome in a situation where lives are on the line and help isn't a phone call away. There have been a number of ammonia-related events and those are in systems that should theoretically be a lot more reliable and well characterized than a new CO2 or H2 storage system. If you polled ISS astronauts past and present - basically anyone ...

60

When the shuttle External Tank stopped being painted white, the weight savings was ~600 lbs (~270 kg). This is not a tremendous amount from a vehicle standpoint, but the tank was carried almost to orbit, so weight shaved off it was a direct addition to payload capability, and that amount could be significant for payloads.

54

The "gravity of Mars" is not a number but rather a complex field. The most recent is remarkably detailed, made up to spherical harmonics degree and order 120, described by 29,512 coefficients: These maps are made using orbiters (three orbiters in this case), not landers. A lander/rover can give just one local gravitational acceleration and direction, which ...

24

We can launch from space and in a sense, we already are. If you consider upper stages of orbital launch vehicles that might send spacecraft into higher Earth orbit or even escape Earth's gravity well altogether, we really ignite those when they're already in the vacuum of space. And depending on the launch vehicle's capability and intended trajectory, they ...

23

Lagrange points... can be orbited by asteroids, satellites, and any other useful or interesting object. Assuming two-body motion however... First a quick note; the stability of a Lagrange point itself is not a predictor of the stability of an orbit associated with ("around") it. Are some Halo Orbits actually Stable? (stable orbits about unstable ...

21

I spoke to Mike Lammers, the Flight Director for the ISS and asked him about the mass uncertainty of the ISS; he mentioned that it is ±5000kg or about 1% of the total mass of 411,000kg. Most of the uncertainty comes from waste going back to earth. Every cargo vehicle goes back down with tons of return cargo and trash. There’s no scale on ISS so as the crew ...

20

WD-40 was designed to protect the Atlas rocket from rust and corrosion. The skin of the Atlas was so thin, to save weight, that from the moment it was welded together it always had to be pressurized so it wouldn't collapse in on itself. It needed that protectant because it was unpainted, to save weight. https://en.wikipedia.org/wiki/Atlas_(rocket_family)#SM-...

19

When we consider the mass something is orbiting about, we assume a gravitational potential corresponding to an inverse-square force, which corresponds to either a point mass or, by Newton's shell theorem, a spherically symmetric mass. It is this situation where any 2-body orbital dynamics can be reduced to the Kepler laws, with periods depending on the ...

16

Here's a Map to the Solar System. It details, roughly how much $\Delta v$ you need to get from one place to the next. You can take the rocket equation to quickly calculate your Fuel fraction for any given $\Delta v$. We take the basic form ($m_0$ starting mass; $m_1$ final mass; $v_\text{e}$ effective propellant exit velocity) $$\Delta v = v_\text{e} \ln \... 15 It typically takes a total expenditure of 9400-10000 meters per second of delta-v to reach LEO. Per the rocket equation, delta-v is proportional to the log of the propellant mass ratio, but also proportional to the exhaust velocity of the rocket engines or their specific impulse. Solid rocket boosters have relatively low specific impulse: 275 sec for ... 15 The variations in the centre of mass was handled by the huge gimbal range of over 20 degrees. Also, the heaviest part of the propellant, the liquid oxygen, was placed in the upper part of the external tank. That means that the centre of mass was pretty high, placing it far from the engines, and thereby reducing the deviation angle. 15 Approximately, yes. The gross gravitational effects on the trajectories of the spacecraft and the other object will be the same. The force of gravity between two objects is proportional to the product of their masses; by F = m a, the acceleration of each object cancels out its own mass ( a = \frac {F} {m} ) and so depends on the mass of the other object.... 14 Did the rover actually do a test to confirm the theoretical gravity is truly equal to the actual measured gravity? First off, what would be the point? Secondly, of course they did, but not to perform that test. The Mars rovers were/are autonomous. They needed to know where they were without outside help. To accomplish this, Mars rovers are equipped with ... 14 First, let's get terminology straight: "Tilt maneuver", or "Gravity turn", sometimes also called "Pitch maneuver". It was called "Roll Program" in case of Space Shuttles, because it was connected with a roll, necessary for technical reasons but not contributing to flight efficiency directly. All rockets (and all flying bodies on Earth for that matter) are ... 14 The number is slightly misleading. NASA provides a complete breakdown on the mass. Rover 185 kg Lander 348 kg Almost 2/3rds of the mass that soft landed was in the stand and airbags, only about 1/3rd of the mass of the rover. The bottom line is, Curiosity was more effective in terms of the mass of the rover to the mass of the EDL package. The skycrane ... 14 Historically, the heaviest payloads that reached orbit were the Apollo missions; the third stage of the Saturn V booster plus the Apollo spacecraft combined exceeded 140 tons in low Earth orbit. The lower two stages alone could put over 120 tons in orbit; such a configuration was used to launch the Skylab space station in a single 77-ton piece. Today, the ... 13 Lagrange points do exist between stars. In case of single stars, they are too far away from the stars to have any practical effect. However, in case of the binary stars, the Roche Lobe has its apex located at L1. "RochePotential color" by SamuelHon - Own work. Licensed under CC BY-SA 4.0 via Commons. In case a star's surface extends beyond the Roche Lobe, ... 11 According to Keplerian orbital mechanics, it will never come so close to earth "to get attracted by Earth strong enough to fall on Earth" (unless it will hit the earth directly). Everything entering Earth's Hill Sphere from "outside" is on a hyperbolic orbit, so it is going to pass earth no matter how close it passes Earth (here also: except a "direct hit").... 10 I am going to answer your specific question, to wit: So is EACH IEA a cube 5 meters on a side weighing 7.7 metric tons, or are ALL FOUR of these IEAs, in total, these dimensions? This question was ridiculously difficult to answer, because NASA seems to go out of their way to obfuscate simple info like this. But here goes. First of all, the dimensions ... 10 Absolutely! The parameter that applies is the ballistic coefficient, the object's mass divided by its projected area modified by the drag coefficient. The drag force is given by$$ F_{\text{drag}}=-\frac{1}{2} C_{\text{drag}} A \rho V^2 \,,where: $C_{\text{drag}}$ is the drag coefficient (at orbital speeds and atmospheric densities this is usually very ...

10

How close would the Tesla Roadster with Starman have to get to Earth in order to become attracted and fall on Earth? tl;dr: If Roadster approached the Earth with $v_{inf}$ of 3000 m/s and an impact parameter of about 24,000 km from Earth's center (about 3.8 Earth radii), Earth's gravity would deflect it just enough for a grazing collision. From Wikipedia's ...

9

First of all, the difference in capacity is actually greater than you included. Dragon launches without a fairing, thus there is an increased capacity as a result of launching without the fairing. The exact mass isn't known. Okay, so what else might be different in the cargo capacity? Here's a few things: The Dragon might not be structurally capable of ...

9

One thing mentioned was that it allowed the vehicle to lift more mass. All things being equal, I fail to see how tilt can increase the ability to increase the potential energy of the payload. All things weren't equal. The Shuttle was not an axially symmetric vehicle. The Shuttle roll program was performed starting about ten seconds after launch and lasted ...

9

In rocketry, the two fundamental parameters of the Rocket Equation, $m_0$ and $m_f$ are referred to as wet mass and dry mass respectively. And, as you can guess, physics doesn't care what comprises the dry mass; everything has to be included. While with other crafts, when writing specs, one can just drop the variable crew/payload and give a neat constant ...

9

Closed trajectories around the stable Lagrangian points (L4 and L5) are not elliptical and do not follow Kepler's laws, so there's no value of M you can use. The same is true for the quasi-periodic Lissajous "orbits" around the unstable points L1, L2 and L3.

8

Indeed it's extremely difficult to accurately determine the mass of a comet without flying something past it at close range. Even if you assume an average density (which is not particularly safe, as little is yet known about the internal makeup of comets and how that varies from body to body), no earthbound telescopes (including Hubble) were able to resolve ...

8

The International Space Station is a far more capable vehicle than any of its predecessors. This comes at a cost, and that cost is mass. There's a problem here: Doubling the electrical power more than doubles the mass needed to produce that power. Things don't scale linearly. You can see this in the animal kingdom. Given equal sized images of the skeletons ...

8

The products of combustion, apart from gases, are small solid particles, 'ash', that slowly floats down to the lower atmosphere and, eventually, to the surface.

8

I believe the plan is for SpaceX BFR to be able to take 150 tons into space: Reference SpaceX Mars Official Website

8

I haven’t seen very many detailed mass breakdowns of engines that call out the mass of the gimbal system. For the Apollo Service Propulsion system, the gimbal actuators alone contributed about 20kg to the 300kg engine according to the original spec; that’s a lower bound since it doesn’t include the gimbal mounting & bearing itself, but suggests that ...

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