Recent content by mfb

Not the first, and not the last either. They routinely test engines beyond their flight requirements, and sometimes actively to destruction. It's likely this explosion was unplanned but we don't know what parameters they tested without a statement by SpaceX.

7-8 m/s is an orbital velocity close to the surface of Phobos, Mars' larger moon. People on Earth can sprint faster than that, but trying to run on Phobos would be really awkward as every "step" becomes a huge leap that has you tumbling around in a way that's hard to control (without rocket...

Nuclear weapons are only very mildly radioactive before detonation. Various spacecraft launched with 4.4 kW of thermal power from radioactive decays of Pu-238 while a typical uranium-based nuclear weapon might have a few milliwatts, or a million times lower radioactivity. The same system that...

The physics is sound, despite some people dismissing the idea because they don't understand it. It's unclear if they can make the launcher cheap and reliable enough and find enough customers to make it economically viable, but that's an engineering and marketing problem not a physics problem...

It is a (planned) launch date! SpaceX has filed a notice to mariners (NOTMAR) along the flight path.

The beach and the highway will be closed on June 1 for "flight testing activities". They performed a wet dress rehearsal already, this could be a repetition or maybe even a launch date. Surviving reentry is the key goal for SpaceX’s fourth Starship test flight

Quarterly statistics: https://brycetech.com/reports/report-documents/Bryce_Briefing_2024_Q1.pdf In the first quarter of 2024, SpaceX launched 429 tonnes, or 87% of the global mass to orbit. Its main competitor, ULA, launched 1.3 tonnes. Everyone else combined launched ~65 tonnes (China 31...

No earlier than May 25 for Starliner, they are still working on the helium leak. The ISS schedule is free until early June at least or maybe even early July, if it gets delayed beyond that then ISS scheduling could shift the launch further. A Falcon 9 booster has flown for the 21st time, going...

Essentially all satellites have power, almost always via photovoltaics. Batteries are used to make it through the shadow of Earth. Almost all satellites have propulsion to maintain their orbit and attitude. The two things you want to add are already essential components of almost all spacecraft.

Starliner delayed to May 21. This time it's a helium leak on Starliner. The valve on Atlas has been fixed.

The magnetic field bends particles in phi but not in eta. You might see bremsstrahlung from (relatively low energy) electrons. You can make this plot separately for electrons, positrons and photons to check.

Starliner launch delayed to mid-May A valve in the Atlas V has to be exchanged because excessive vibrations might have damaged it.

A valve issue. Again. Remember June 2023? Or August 2021? Edit: It's a valve issue on the rocket this time, not a Starliner problem.

9 hours and 30 minutes. Still on track for a launch. NASA coverage will start about 4 hours before launch.

You don't need to guess the units of the answer, you need to work with units. ##F = CI \rho \frac{v^2}{2} A = 0.5 \frac{1.225 kg}{m^3} \frac{(20 m/s)^2}{2} 0.1 m^2 = 12.25 kg \frac{m}{s^2} = 12.25 N## This formula is assuming all of the wing has the same velocity relative to the air. Your...