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68 votes
Accepted

Why vent $CO_2$ and $H_2$ waste products to space on ISS?

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 ...
uhoh's user avatar
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60 votes
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Is the mass of paint relevant in rocket design?

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 ...
Organic Marble's user avatar
57 votes
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Did the Mars rovers actually confirm the gravity of Mars?

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 ...
Mark Adler's user avatar
  • 58.2k
25 votes

What is the "mass" of a Lagrange point?

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 ...
uhoh's user avatar
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21 votes
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How precisely do we know mass of the ISS?

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 ...
Mark Omo's user avatar
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20 votes

Is the mass of paint relevant in rocket design?

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 ...
Greg's user avatar
  • 4,287
19 votes

What is the "mass" of a Lagrange point?

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 ...
leftaroundabout's user avatar
15 votes
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Why is Curiosity so light compared to Opportunity?

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/...
PearsonArtPhoto's user avatar
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15 votes
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How did the Space Shuttle maintain thrust/weight balance

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 ...
SE - stop firing the good guys's user avatar
15 votes

Did the Mars rovers actually confirm the gravity of Mars?

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 ...
David Hammen's user avatar
  • 74.9k
15 votes
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What is the largest and/or heaviest object that could be sent to space?

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 ...
Russell Borogove's user avatar
15 votes
Accepted

Does trajectory of an object orbiting a planet depend on the object's mass? (With hypothetical Apollo example)

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 ...
Russell Borogove's user avatar
13 votes

Common usage of "dry-mass"

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 ...
SF.'s user avatar
  • 55k
12 votes

With increased space exploration missions, are we affecting earth's mass?

With increased space exploration missions, are we affecting earth's mass? In theory, yes. In practice, no. The amount of mass we send into space is completely negligible compared to the huge mass of ...
David Hammen's user avatar
  • 74.9k
11 votes
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How close would the Tesla Roadster with Starman have to get to Earth in order to become attracted and fall on Earth?

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 ...
CallMeTom's user avatar
  • 3,298
10 votes

What determines the orbital speed around a Lagrange point?

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 ...
pericynthion's user avatar
  • 10.1k
10 votes
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Does the size of a satellite have an effect on orbit?

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}}=-\...
Tom Spilker's user avatar
  • 18.3k
10 votes

How close would the Tesla Roadster with Starman have to get to Earth in order to become attracted and fall on Earth?

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 ...
uhoh's user avatar
  • 149k
10 votes

Why will Starlink Gen2 be so big and heavy?

"Just a Flying Router" This is... not the half pound plastic wifi router in your house. I don't think there are firm numbers out yet, but the speculation I've seen is that bandwidth on a ...
codeMonkey's user avatar
  • 1,693
9 votes
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Why is the Dragon small compared with the Falcon 9 LEO payload

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 ...
PearsonArtPhoto's user avatar
  • 121k
9 votes
Accepted

Where to find the best values for standard gravitational parameters of solar system bodies?

If you consider the ephemeris files put out by JPL as the final say in terms of simulations, then the data they put in the PKC files alongside the ...
Kaushik Ghose's user avatar
9 votes
Accepted

Why are all possibly habitable exoplanets higher mass than Earth?

There is a nice Wikipedia article about the transit method for finding exoplanets by detection of the light intensity drop caused by the planet when passing before its central star. Unfortunately this ...
Uwe's user avatar
  • 49k
9 votes

With increased space exploration missions, are we affecting earth's mass?

The earth gains about 43 tons of mass every day in meteorites and space dust. We are not only not decreasing the mass of the earth with our space program but are not even keeping it from growing.
John Meacham's user avatar
8 votes

What happens to materials which burn up during reentry?

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.
xxavier's user avatar
  • 729
8 votes

What limits miniaturization of space probes?

Aside from optics and communications, there are other limitations to miniaturization. For example, smaller objects become harder to track if communication is lost. Our current orbital debris tracking ...
called2voyage's user avatar
  • 23.7k
8 votes
Accepted

What size payloads could we feasibly launch from the moon with a mass driver?

Short answer: Yes. Big. Long answer: There's no law that says this technology doesn't scale. Railguns functionality is dead simple. You apply a current to two rails and bridge across which produces ...
Dragongeek's user avatar
  • 19.1k
8 votes

What is the largest and/or heaviest object that could be sent to space?

I believe the plan is for SpaceX BFR to be able to take 150 tons into space: Reference SpaceX Mars Official Website
Robs's user avatar
  • 181
8 votes
Accepted

How much mass does a gimbal mechanism add to a rocket?

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 ...
Russell Borogove's user avatar
7 votes

What limits miniaturization of space probes?

What is driving the payload weight currently? Optics. You need a big camera with a big lens if you want pretty, high resolution pictures. There is no way around this. It's physics. Communications. ...
David Hammen's user avatar
  • 74.9k
7 votes

What savings allowed James Webb telescope to be lighter than Hubble?

As far as the primary mirrors are concerned, HST's mirror was made out of silica glass, and had a mass of 826 kg. The primary mirror of the Hubble telescope measures 2.4 m (8 ft) in diameter and ...
lordcheeto's user avatar

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