9

The ion propulsion was run continuously to compensate for drag immediately. The drag force varied strongly during each orbit (i.e. changing from night to day), typically between 4 and 12 mN on its 1 m² surface. Absolutely not. The drag coefficient was about 10 times higher. The low $c_W$ that can be reached in a dense atmosphere mostly comes from flow ...


8

In addition to the space weathering phenomenon described by ebv, optical surfaces can and do get dirtied by other mechanisms as well. In particular, outgassing from the rest of the spacecraft and produce various compounds that may recondense on lenses, especially if these surfaces are cooler than the rest of the spacecraft exterior, which they sometimes are ...


6

Roughly how much lower was GOCE's drag compared to a typical spacecraft, or to a sphere of the same mass. Did it have a drag coefficient as low as a real Ferrari? GOCE's drag coefficient was higher than that of a typical spacecraft. From Geul, J., E. Mooij, and R. Noomen. "GOCE statistical re-entry predictions." Proceedings of 7th European ...


4

There is a gray area here, but probably yes. If it were called a "suborbital flight" the assumption would be that the orbit's path would intersect the surface of the Earth. Since the perigee of your orbit is in the denser part of the atmosphere but does not intersect the surface, if it weren't for the drag force the spacecraft would continue to ...


4

The lower the orbit, the higher the drag. Since the drag force is roughly proportional to area, but the resulting acceleration is force divided by mass, then the denser the spacecraft, the less it is affected by drag. The simplest way to fight drag is to carry a lot of fuel, and use it often. This will make the spacecraft less dense as the tank empties, ...


4

Following @JCRM's lead: rocket horsepower questions to the rescue! See this answer and this answer for derivations and explanations. Power If we assume that most of the kinetic energy of the air molecules striking the spacecraft is converted to heat (perhaps it's more like half or 2/3) then we can use the concept of "rocket power" which is really ...


4

It literally eats away at surfaces made of certain materials. It's pretty crazy. According to Space Mission Analysis and Design ("SMAD", 3e, by Wertz and Larson), Atomic oxygen (which I'll call ATOX thanks to user1209304's comment), is "the predominant atmospheric constituent" from 200 to 600km, and is a dominant force above 170km (around which it actually ...


4

JAXA's Tsubame satellite is planned to orbit to altitudes as low as 180 km, using an ion engine to reboost. It was launched in January 2018 into an initial orbit at ~480 km, its orbit will be gradually lowered over a period of 2 years. The Super Low Altitude Test Satellite "TSUBAME" (SLATS) is the first Earth observation satellite to use a super ...


3

Per Space News, reviewing the applications, VLEO in this context is below 350 km orbit. Of the four, SpaceX is by far the largest with 7,518 satellites constituting what it calls a “very low Earth orbit,” or VLEO constellation that would operate slightly below 350-kilometers. What is interesting to me is the comment that follows: At that altitude, ...


3

Yes, there are a number of different technologies that I'm aware of that are being developed specifically to enable and assist satellites in operating sustainably in lower altitude orbits. The DISCOVERER project (European Horizon 2020) has the aim of developing some of these foundational technologies and Skeyeon, an emerging US company, also has some patents ...


2

My understanding is that the "Direct Simulation" part refers to the fact that rather than solving equations governing the flow (as in Computational Fluid Dynamics) it directly simulates the particles interacting with the surfaces. Rather than modelling each atom, they are grouped into "molecules" representing a large number of atoms, and ...


2

I've been able to find a few rocket bodies and payloads that have done so, at least for some period of time prior to decay. These objects might have been in a state of decay prior to entering in these low objects. The two satellites I could find were MOLNIYA 2-12 and MOLNIYA 1-30. I don't know if they were actually able when they did so, but they certainly ...


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