Comment Re:What bullshit (Score 1) 176
Don't Apple devices (iPhones, iPads, etc.) notify you if a device not associated with your account is following you around?
Don't Apple devices (iPhones, iPads, etc.) notify you if a device not associated with your account is following you around?
Really? My Epson EcoTank ET-3850 including a two year supply of ink cost $246.09.on Amazon. It's a copier and a scanner and it includes Wireless and Ethernet.
Last year these criminals stole over $40,000 from one of my relatives. Local law enforcement told her that there was nothing they could do.
Yup the good old KIM-1 (Keyboard Input Monitor) was my 1st computer also. Technology demonstrator from MOS Technologies for the 6502. 1K of RAM, Kansas City cassette tape interface for program storage and at the beginning hand assembled machine code for programming. Those were the days!
An Acer PC I recently purchased for my wife has a 512 GB SSD that is partitioned as a 256 GB C: for the system and 256 GB D: for data. I added a 1 TB HDD for backup and I suspect it will last her for as long as Windows 10 is still supported and then support a transition to Windows 11.
I recommend the Netflix series Meltdown about the 1979 nuclear accident at Three Mile Island. This series shows the primary problem with nuclear power systems that are managed by for-profit institutions and overseen by an agency subverted by regulatory capture. This is an event that came within a hairs breath of killing untold numbers of people and contaminating a significant portion of the east coast of the United States much like what happened in 2011 at the Fukushima Daiichi Accident.
A 2019 report from NASA’s Office of Inspector General calculated the estimated average cost per seat to be $90 million for Boeing and $55 million for SpaceX. Given Boeing's poor performance NASA should renegotiate.
From the JWST user documentation:
While orbits about the L2 point are inherently unstable, the orbit size is large and the orbital velocity is low (~1 km/s), so the orbit "decays" slowly. However, JWST's large sun shield, roughly the size of a tennis court, is subject to significant solar radiation pressure which results in both a force and a torque. The direction of solar force varies as the observatory's attitude changes from observation to observation. The solar torque is balanced by reaction wheels, but periodically, the accumulated momentum is dumped by firing thrusters. Because JWST operations are event-driven, the observatory attitude profile and momentum dumping cannot be accurately predicted months in advance. These two perturbations increase the acceleration of JWST from its orbit about L2, and necessitates more frequent orbit maintenance (station keeping) maneuvers than other Lagrange orbit missions (which are typically 3–4 times per year).
Thus, for station keeping JWST uses thrusters, while maintaining relative sun-pointing requirements, as follows:
Orbit perturbations along the Sun-L2 axis have the greatest impact on-orbit stability. Thrusters are mounted on the spacecraft bus on the side of the sun shield facing the Sun; those used for orbit correction are oriented as far away from the sun shield as possible, and the sun shield can support a larger sun-pitch angle1 for orbit correction than is allowed for science operations. This architecture allows thruster firing at angles up to 90 from the Sun consistent with Sun avoidance restrictions, which is sufficient to provide orbit correction in all cases.
For momentum management, JWST suffers from massive momentum buildup, as suggested in the question, described here.
During science observations, the observatory will be pointed at a target, in an orientation at which the sun shield center of pressure is not aligned with the observatory center of mass. As solar photons hit the large sun shield, they place a torque on the observatory as a whole. The attitude control subystem (ACS) counteracts this torque by appropriately changing the spin rate on the reaction wheels, with the consequence that angular momentum accumulates in the reaction wheels. Momentum accumulation depends on the solar pitch angle, the roll orientation of the telescope, and the visit duration at a particular pointing position. The angular momentum (spin rate) of the reaction wheels must be managed to be kept within operational limits.
Mission planners are creative in using a technique for momentum management that is passive:
Momentum changes can be managed at some level by the way a sequence of observations is planned; this is done by observing at an orientation that builds momentum in a particular reaction wheel, followed by an observation at an orientation that removes momentum from that wheel.
But, not always, as some need-based science require a quicker slew and orientation which overrides the above momentum management program, and hence "momentum dumping" is performed by unloading the wheels as required.
However, managing momentum is only one of a number of planning constraints. At some point, one or more wheels will need to be adjusted to stay within operational bounds. The planning and scheduling system inserts planned momentum unloads into the schedule as needed, based on the modeling of expected momentum buildup, currently expected to be 1–2 times per week. Each unload activity takes a few hours, in which the observatory slews to a particular orientation to minimize the impact on the orbit and then fires thrusters as needed to allow the spin rate of the reaction wheels to be adjusted.
The orbit will be biased to compensate for mean outward forces associated with gravitation of the planets and radiation pressure on the sun shield.
Above quoted passages are all from the PDF JWST Cycle 1 Documentation for Telescope and Spacecraft found on this page
I dislike the removal of the thumbs down count from YouTube videos.
No the 1918/19 pandemic was three times as lethal as COVID19 has been to date. It killed somewhere between 24 million and 50 million persons worldwide.
A profound modern theatrical interpretation of one of the United States most important founding fathers.
Not at all. But when we start vilifying other nations for practices that our government pioneered it is sort of like the bull frog calling the cat fish big mouth. As they say all's fair in love and war. Also, Chinese culture is far more mature than our own and although there is a tendency to demean their technological accomplishments they are rapidly achieving parity in many fields. Those with a historical perspective are aware that the newly founded United States engaged in similar technological espionage and theft.
When push comes to shove survival trumps everything. Money is the foodstuff of commerce and sales to the world's largest manufacturer of cellular equipment are not trivial. In addition the Defense Department may have a hidden agenda. For all of their bluster about security concerns with Huawei equipment it is our own government that pioneered the modification of commercial equipment to serve intelligence gathering purposes. It is probable that this activity has continued at the component level and that baring sales to Huawei will defeat those efforts.
Not in any particular order:
1) Science Friday
2) Undiscovered
3) Ockham's Razor
4) Spectrum
5) Revisionist History
6) Sum of All Parts
This was exactly my first thought. I'm pretty sure that any attempt to penetrate today's fiber optic cables would be detected. But placing remotely triggerable explosive charges is probable undetectable. I wonder what method would be used to trigger them though.
Why did the Roman Empire collapse? What is the Latin for office automation?