The thread for space cadets!

[Timsup2nothin]

While Apple spins a convincing tale that any technology that is more than six months old requires immediate replacement, the military has routinely proven otherwise.

 

[Samson]

Well it is certainly plausible and I lamented at the time we lacked the ability to go find out for ourselves with a probe. Unfortunately the article doesn't give enough detail to make a serious assessment of the claims. It also fails to link to the journal publication as well. It links to the journal's website but not the paper in question and it doesn't give the paper's title to search for it (unless I missed it). Unfortunately I have to go to work and can't go digging on google for it.

I think the paper is "Could Solar Radiation Pressure Explain 'Oumuamua's Peculiar Acceleration?" I cannot usefully read it.

 

[hobbsyoyo]

Thanks I'll try and read it later.

 

[uppi]

I think the paper is "Could Solar Radiation Pressure Explain 'Oumuamua's Peculiar Acceleration?" I cannot usefully read it.

The paper claims that it is not completely impossible for the object to be a solar sail. I didn't check the calculations, but the argument is plausible. It doesn't give any evidence beyond that, so I would file that under "possible, but extremely unlikely".

And: who the hell uses CGS units these days?

 

[CKS]

And: who the hell uses CGS units these days?

Astronomers?
It has been a long time since I've seen stuff measured in dynes; it was really jarring.

They didn't so much use CGS as they did put things into as many different units as possible. For distance, I see mm, cm, m, km, AU, pc, and kpc. They didn't, though, just pick things to make the numbers conveniently sized. 2x10^15 per cubic pc would be much nicer written as 1/4 per cubic AU.

 

[r16]

hey , where is my happy commie spy routine that asks who would have managed to hack a WW II gun laying system ? You know it was supposed to lead to a discussion of why the same gun laying system would then readily to fail to fire a 400 nm ramjet round from the battleships .

 

[hobbsyoyo]

This was a deliciously stupid post from an article on an in-space refueling experiment an American company is trying on the ISS:

A clue to the immediate prospects of orbital fuel depots transferring tons of cyrogenic propellants to a line of waiting spacecraft.

Spoiler: there are NO immediate prospects of that happening. Since NewSpace fans quote it as dogma you would think it is ready to roll out. Nothing could be further from the truth.

Another scam cooked up long ago by the Musk Mob to make the Super Heavy Lift Vehicle seem unnecessary.

Hyping the falcon as good for something other than what it is- a satellite launcher- is one of the worst things that has ever happened to space exploration. The myth that small rockets can be pulled up to a gas pump in space has helped stall any progress for close to a decade

 

[Cutlass]

New NASA recruitment/propaganda short.

 

[Silurian]

The InSight probe has landed.

 

[Broken_Erika]

Martian Great Leader Condemns “Attack” On His Planet

“Mars will no longer accept the constant violation of our proud patriot heritage by small-skull zealot explorers from Earth. We have watched with much patience as you have spent decades probing our weaknesses and resources with lander after lander. First the Viking landers, all the way to today’s probe.”

“Your probes will eventually steal our jobs, they will rape our landscape, they bring microbes and viruses into our atmosphere. Some of them are good probes, I assume, but most of them are very, very, very bad probes.”
.....
“Besides, tell your Yankee leader that we do not accept his kind on Mars. We are a red planet and not an orange one.”

 

[red_elk]

Docking successful

 

[hobbsyoyo]

Virgin Galactic launched the first astronauts from an American vehicle since the Space Shuttle retired.

This test flight had a burn time of 60s, a peak altitude of 82.7 km and top speed of Mach 2.9. This was pretty close to a 'real' flight as the company has stated the ceiling of this vehicle will be around 82ish km. The vehicle was loaded with paying customer payloads (low-g experiments from NASA) to simulate the weight of passengers. It was also the first bit of revenue that Virgin Galactic has generated in something like 14 years, which shows how deep Branson's pockets are and how committed he is to this endeavor.

 

[hobbsyoyo]

SpaceX had a failure during the attempted return to launch site (RTLS) landing of the CRS-16 booster. After successfully lobbing the Dragon spacecraft into orbit, the first stage failed to land. As you can see here, the grid fins seized and the booster began spinning. Because of this, it was unable to steer itself to the landing pad and instead came down over water. It was able to recover from the spin just feet from the water which made for some dramatic footage.

The first interplanetary CubeSats (MarCO) rode along with Insight and provided real-time telemetry for the landing. They acted as a relay between InSight and ground stations. They also gave us this nifty picture of Mars as they sailed off into the void.



Also, Voyager 2 entered interstellar space as evidenced by the science data and telemetry it is still returning some 40-odd years later. It's a remarkable achievement.

 

[Samez]

What material are the grid fins made of? From the shape I would have guessed some sls printed steel or titanium, but the deformation looks more like a conventionally milled metal.

 

[hobbsyoyo]

Titanium. Before Block 4 they were aluminum with a cork thermal protection layer.

 

[Broken_Erika]

'Tis the season for a Martian Winter Wonderland.


https://www.bbc.com/news/science-environment-46645321

 

[red_elk]

Cool, they say it's water ice. Huge amount of water!

 

[elmurcis]

Where is Martian under-ice fisherman (not sure how to call it in english)?

 

[Kaitzilla]

I'm kind of ignoring the material of the rings for energy uses. I do not see a practical way to get energy out of the boulders themselves, I only see them as an obstacle to avoid.

But being in the gravity well (where the rings are), would allow you to use elecrromagnetic tethers to generate huge energies from the planet's magnetosphere.

The space shuttle did this once and the tether generated so much current that it melted and snapped in half.

This Hobbs' post needs moar!

https://www-istp.gsfc.nasa.gov/Education/wtether.html

The space tether experiment, a joint venture of the US and Italy, called for a scientific payload--a large, spherical satellite--to be deployed from the US space shuttle at the end of a conducting cable (tether) 20 km (12.5 miles) long. The idea was to let the shuttle drag the tether across the Earth's magnetic field, producing one part of a dynamo circuit. The return current, from the shuttle to the payload, would flow in the Earth's ionosphere, which also conducted electricity, even though not as well as the wire.

​

One purpose of such a set-up might be to produce electric power, generating current to run equipment aboard the space shuttle. That electric comes at a price: it is taken away from the motion energy ("kinetic energy") of the shuttle, since the magnetic force on the tether opposes the motion and slows it down. In principle, it should also be possible to reverse this process: a future space station could use solar cells to produce an electric current, which would be pumped into the tether in the opposite direction, so that the magnetic force would boost the orbital motion and would raise the orbit to a higher altitude.

The first attempt at the tether experiment ended prematurely when problems arose with the deploying mechanism, but the one on February 25, 1996, began as planned, unrolling mile after mile of tether while the observed dynamo current grew at the predicted rate. The deployment was almost complete when the unexpected happened: the tether suddenly broke and its end whipped away into space in great wavy wiggles. The satellite payload at the far end of the tether remained linked by radio and was tracked for a while, but the tether experiment itself was over. It took a considerable amount of detective work to figure out what had happened...

Hehe, boosting an orbit using purely electricity!
How crazy is that?
A shame the magnetic force on the wire/tether causes deorbiting, or it would be a great way to get free electricity.



My goodness, a 12.5 mile or 20117 meters long cable.

Assuming low earth orbit and an orbit crossing the magnetic field lines at a 90 degree angle, we can can calculate the voltage across the wire if we assume 25 to 65 microteslas 20 miles up for the Earth's magnetic field strength.
https://en.wikipedia.org/wiki/Earth's_magnetic_field

10:00 at the Khan academy video
https://www.khanacademy.org/science...wire/v/magnetism-12-induced-current-in-a-wire

20,117 meter cable * 7800m/s orbital velocity * 0.000045? Teslas field strength = 7061 Volts of potential difference across the whole wire?

Later vacuum-chamber experiments suggested that the unwinding of the reel uncovered pinholes in the insulation. That in itself would not have caused a major problem, because the ionosphere around the tether, under normal circumstance, was too rarefied to divert much of the current. However, the air trapped in the insulation changed that. As it bubbled out of the pinholes, the high voltage ("electric pressure") of the nearby tether, about 3500 volts, converted it into a plasma (in a way similar to the ignition of a fluorescent tube), a relatively dense one and therefore a much better conductor of electricity.

The instruments aboard the tether satelite showed that this plasma diverted through the pinhole about 1 ampere, a current comparable to that of a 100-watt bulb (but at 3500 volts!), to the metal of the shuttle and from there to the ionospheric return circuit. That current was enough to melt the cable.

As the broken end whipped away from the shuttle, the plasma established electric contact with the ionosphere directly. The satellite on the distant end monitored the current: after about half a minute it stopped, then it reignited and flowed again for about another half minute, stopping for good when (presumably) all the trapped air was gone.

Huh, reality was 3500 Volts.
Perhaps the cable length wasn't all there, or perhaps the orbit angle wasn't perfectly perpendicular to Earth's magnetic field, or the Earth's magnetic field up there was less than 45 microteslas?

TSS-1R mission
Four years later, as a follow-up mission to TSS-1, the TSS-1R satellite was released in latter February 1996 from the Space Shuttle Columbia on the STS-75 mission.[6] The TSS-1R mission objective was to deploy the tether 20.7 km above the orbiter and remain there collecting data. The TSS-1R mission was to conduct exploratory experiments in space plasma physics. Projections indicated that the motion of the long conducting tether through the Earth’s magnetic field would produce an EMF that would drive a current through the tether system.

TSS-1R was deployed to 19.7 km when the tether broke. The break was attributed to an electrical discharge through a broken place in the insulation.[7]

Despite the termination of the tether deployment before full extension, the extension achieved was long enough to verify numerous scientific speculations. These findings included the measurements of the motional EMF,[8] the satellite potential,[9] the orbiter potential,[10] the current in the tether,[11] the changing resistance in the tether,[12] the charged particle distributions around a highly charged spherical satellite,[13] and the ambient electric field.[8] In addition, a significant finding concerns the current collection at different potentials on a spherical endmass. Measured currents on the tether far exceeded predictions of previous numerical models[14] by up to a factor of three. A more descriptive explanation of these results can be found in Thompson, et al..[15] Improvements have been made in modeling the electron charging of the shuttle and how it affects current collection,[11] and in the interaction of bodies with surrounding plasma, as well as the production of electrical power.[16]

A second mission, TSS-2, had been proposed to use the tether concept for upper atmospheric experimentation,[17] but was never flown.[18]

19,700 meter cable when it broke.
3500 Volts
STS-75 had an orbital period of 90.5 minutes, so 7727 m/s orbital velocity.
Earth's magnetic field was 19,700 * 7727 * x = 3500
x = 23 microteslas?

Could read the paper on it I suppose since actual scientists know a lot more.
The current-voltage characteristics of a large probe in low Earth orbit: TSS-1R results
https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/97GL02958


The magnetic force opposing the conducting wire's orbit through Earth's magnetic field?
https://courses.lumenlearning.com/p...gnetic-force-on-a-current-carrying-conductor/

With a constant flow of 1A of current, it would be 1* 19,700 * 0.000023 = 0.4531 Newtons applied to the entire 19,700 meter wire.
1 Newton accelerates 1 kilogram 1 meter per second every second.
Would need to know the mass of the 19,700 meter cable and attached satellite.

Only need to lower the orbital velocity from 7727m/s to 7637m/s to deorbit like the shuttle, a loss of 90m/s
https://space.stackexchange.com/que...enough-to-commit-the-space-shuttle-to-landing

Call the cable+satellite 518kg
https://space.skyrocket.de/doc_sdat/tss-1.htm

It should lose 90 meters per second in orbital velocity and start crashing into Earth after 518 / 0.4531 * 90 = 102,891 seconds or 28.5 hours conducting 1 Amp.
A bit over a day to crash.

No idea if these calculations are even close.
In reality, the thing stayed up there for over 3 days at least.
Can't seem to find how long it stayed up in Earth's orbit.

The TSS 1R mission was a reflight of the Tethered Satellite TSS 1. Five hours after deployment began on 25 February 1996, with 19.7 km (of 20.7 planned) of tether released, the tether cable suddenly snapped near the top of the deployment boom. The TSS satellite shot away into a higher orbit. TSS instruments could be re-actived and produced science data for three days until battery power ran out. An independent review panel was formed to review the TSS-1R failure.

**Edit**
Sigh, it was 0.48A, not 1A
https://www.americaspace.com/2014/0...cond-flight-of-the-tethered-satellite-part-2/
=========================

I also want to plug the spinning wheels that make it so satellites and spaceships don't spin out of control.

14:25 WTF is that?!
1968 production values

 

[elmurcis]

Only need to lower the orbital velocity from 7727m/s to 7637m/s to deorbit like the shuttle, a loss of 90m/s

Its magic how much prograde and retrograde bursts (even with small thrust) can impact orbit at right points of orbit.

Spoiler :

Managed to reach 4000 km perfect circle orbit in Orbiter with regular Atlantis Space Shuttle (with big fuel tank still attached ) and manual controls (if don't get nose down quickly enough after start - will get really high but with too slow orbital speed to get around Earth) just by doing short bursts at perigee to get up apogee and at apogee to get up perigee (and oposite way to get down back on Earth, using atmosphere (precise retrograde trust at apogee and can get perigee at altitude you want ) to slow down a little bit before actual entry - going directly into Earth atmosphere from high altitude orbit would be little more unrealistic and dangerous to space ship structure that is designed to do that from 110 km orbit.