How much does the Orion capsule (that is, the Crew Module) that splashed down on April 11 weigh? According to NASA's reference guide for Orion, 22,900 pounds.
The guide specifically lists "liftoff weight", and there are a couple of reasons for that. One is that the capsule has reaction control thrusters, which are small rocket engines that allow for fine-tuning the attitude of the craft and small-scale maneuvering, and their propellant is part of that liftoff weight. For this and other reasons, the capsule did not have the exact same contents when it splashed down as when it took off.
The other reason, of course, is that the weight of the capsule depends on where the capsule is in its trajectory. For most of the mission, that weight was essentially zero, since the capsule was coasting in freefall except at a few key points. Units of weight, like pounds, measure force, not mass. At least that's what I was taught in high school physics.
For most practical purposes, though, the pound is a unit of mass. If the door of a bank vault weighs a ton (2,000) pounds, you know it will be a little hard to move, even if it's perfectly mounted on bearings with very low friction so that when you push on it you're not trying to lift its mass. That inertia is due to its mass. If you weigh out a quantity of something, you're interested in how much of it you're getting, that is, the total mass.
You're almost certainly measuring that mass by way of how much that mass weighs on Earth, but it's still mass that you're measuring. Except in specialized applications like calculating load limits or foot-pounds of torque, the amount of force something exerts under gravity is secondary to how much of it you have.
Yes, it matters that a 22lb bag of something is easier to lift than a 44lb bag, but it matters just the same that a 10kg bag is easier to lift than a 20kg bag. You don't need to know the amount of force involved (about 98 and 196 Newtons, respectively) to make that determination and no one is thinking "Hmm ... that 20kg bag will require 196 Newtons to lift" before trying to pick it up.
There are units, the pound-mass and pound-force, that make the distinction between mass and weight. The pound-mass is now defined as exactly 0.45359237 kg, and the pound-force is the weight of this mass under standard Earth gravity of 9.8m/s2.
No one uses this. Well, maybe not absolutely no one, but you won't find anything on a supermarket shelf that says it weighs, say, 1.5 lbm, because no one at the supermarket cares. If you're doing precise engineering or scientific work where the distinction matters, you're not using pounds, but kilograms and Newtons. This is just an example of the distinction I previously discussed between everyday units of measure, which can be pretty much anything, and precisely-defined scientific units of measure.
There are several reasons that SI (metric) units work better than imperial units for scientific work (and why, for example, the telemetry feed that NASA put up during Artemis II showed both SI and imperial units, with SI units first as I recall). One is the consistent use of powers of ten and standard prefixes like mega- and milli-. Another is that SI units have been standard for generations, so anything you're referencing in a scientific context is almost certainly using them. Another is the body of very careful definitions of what each unit means.
A less obvious reason is that SI units carefully make distinctions that we gloss over in everyday use, particularly the mass-weight distinction. During re-entry, when a capsule may be pulling on the order of 5g, it matters quite a bit that the forces on the body of the capsule are much higher than when the capsule is on the launch pad. You want to be talking about Newtons of force and not kilograms of mass when you do those calculations. Using pound interchangeably for pound-mass and pound-force in everyday speech makes good sense when you're buying groceries. Trying to use mass and force interchangeably in mechanical engineering is a recipe for disaster.
To make the distinction completely clear, the Newton is defined as a kilogram-meter per second squared, with no reference to Earth's gravity. A pound-mass weighs a pound-force under standard gravity because we don't really care about the distinction when using pounds. A kilogram weighs about 9.8 Newtons, which helps keep the distinction clear when it matters.
NASA is happy to quote the weight of Orion in pounds and show its speed in miles per hour because the US audience is used to those units. Trying to point out that actually the mass is about 10.4 tonnes and the weight varies is just going to get in the way unless you're specifically talking about the effects of acceleration or microgravity. Using pounds interchangeably for mass and weight is only incorrect if you're doing engineering or science, but then you shouldn't be using pounds at all.
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