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whirligig-girl · 7 days ago

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The aliens arrived in their toroidal flying saucers--enormous gossamer-like structures big enough to put Jupiter in the hole. They projected bodies down to Earth on long threads, and complained.

"What happened?" they pleaded with our planetary scientists.

An awfully open-ended question, but the planetary scientists threw up their hands and explained the current state of the field, about the theory of planetary aggregation and various hypotheses to explain how each of the planets ended up where they are today. The aliens nodded along skeptically at times, but they seemed especially disappointed by the Lunar geologists.

"Excuse us," their leader said politely, rising into the sky towards geostationary orbit on a great thread.

And so it was for the next few decades that the aliens set to work correcting what they saw as the great mistakes of the solar system's formation. Perhaps Venus never cooled down enough to avoid a runaway greenhouse effect, or maybe something about its specific volatile mass had been off. Either way, it was the first to be treated. By the time it was done, perhaps 20 years in, it was a blue world with brown continents and white clouds. While another saucer had come to work its magic on Mars, the first saucer returned.

"Eh, we'll need you to give planet two a good head start with the whole biosphere thing. We hadn't bargained on life starting up there halfway through the lifespan of the Sun. If it's no trouble, that is."

A new habitable planet provided the space program no shortage of funding!

Mars was finished, just a few years later, a comparatively simpler job. The aliens advised humans not to interfere with this one just yet, to perhaps give it a few hundred megaannum or so for the life to diversify and develop before contaminating it.

But the saucers didn't leave. They seemed to drift throughout the inner solar system. They took some curious expeditions to Europa and Enceladus--robotic NASA spacecrafts recorded deep probing threads piercing the ice--but didn't seem impressed.

They kept returning to the Moon.

At last, the aliens projected down on their long threads to a university. "You're sure that's how it happened?" they said.

The lunar-planetary scientists showed the alien ambassadors rocks from the Apollo and Artemis expeditions, computer simulations of various types of giant impacts, of synestias and hours-long instant formations and debris disks and gas instability, of an oversized iron core and large low-shear-velocity-provinces.

"We think the water on Earth may even have been delivered through a giant impact from a KBO, though there's some concerns about isotopic ratios."

"No, no," said the alien. "The initial coorbital hypothesis is the correct one."

The alien sighed--it had picked up human body language well over the past 35 years--"This just won't do," it said. It left the building, shaking its head. "It just won't do."

The planetary scientists ran after the alien, as it started reeling its thread back. "Wait!" they said. "What are you going to do?"

"This Moon thing of yours just isn't big enough to hold onto an atmosphere. I'm afraid it's not good enough."

The aliens rose into the sky.

Within a few months the Moon had been lost from the sky, and a years later had been relocated to the L4 lagrange point. The aliens came back, apologetically. "Terribly sorry," they said, "We're in the final phases of the plan," they said.

The Earth Emergency Government representative stepped forward. "Final… phases?" he said.

"Theia was always meant to be a trojan of your Earth, you see. Something must have gone wrong when the gas disk dissipated."

"I don't understand," the representative said.

"My apologies," the alien said, "I'm used to dealing with your planetary researchers."

Many masses of threads now fell gracefully from the skies. When they touched down, they effortlessly bored deep holes. The ground shook. The representative's heart rate skyrocketed.

"It's just that we're going to have to repossess the planet Theia now."

#science fiction #scifi #planetary science #theia #the moon #microfic #flash fic #flash fiction #giant impact

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sadclowncentral · 2 months ago

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wait Lew I have a space law question, how do we decide who gets to put satellites where? like I know there's thousands of satellites in low Earth orbit, how close can someone put a new satellite to old ones? how crowded is that situation? and there's a buncha scientific satellites (the only space thing I know something about) that are all in very similar orbits, who gets to add a satellite to that train? do people fight over spots?

good question! generally, there is a freedom of the exploration and use of outer space, so everyone can do what they want up there as long as they don't violate any other laws - and, as long as outer space remains "free for exploration and use by all States without discrimination of any kind, on a basis of equality and in accordance with international law" (Art I OST). now, what the fuck does that mean, i hear you ask, and to that i shrug and smile politely because we are still figuring that out. outer space is becoming increasingly congested, and it's use is certainly not equal - while the USA owns HALF of the satellites in space, there are many countries who have launched no objects yet, even though many critical infrastructures depend on the access to space. you see the problem.

fights over spots do happen, especially in GEO. this is the geostationary orbit, which is 35,786 km above the equator - satellites here orbit as fast as the earth turns and therefore remains over the same spot of the earth forever, which is crucial for telecommunication (imagine adjusting your satellite dish every minute to watch TV). and those spots are very coveted, as they are very, very limited. there have been multiple attempts of the UN to regulate this on an equitable basis, none of them successful (in my opinion).

equitable access to outer space remains a huge problem and inequalities on earth are often exacerbated in outer space - which is why we need national regulation that actually implements Art I OST instead of ignoring it! (looking at you, US of fucking A)

#space law #HOPE ANY OF THESE ARE READABLE SORRY

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senkusphone · 11 months ago

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Dr. Stone chapter 2D trivia post

Spoilers ahead !

Check out too, my trivia post for the previous chapter.

This changes everything, folks! however, we gotta start from the start.

Chrome's drawn this roadmap, and he seems to pretend to build yet another of his silly storehouse towers like he's done around the globe. Next stop, the moon.

This confused me for a while until it was pointed out to me that "EMU" stands for Extravehicular Mobility unit; which is what we normally call a spacesuit (and I call and EVA suit), and notably it doesn't look muck like these simple, yet decidedly comfy and cute looking jumpsuits.

The graphic depicted below actually shows two trips, if you follow the arrows along the lines, you can see the black ones show a trip from earth orbit to the moon, and the white ones show the return trip, landing in the middle of what loosely resembles the pacific ocean, east of Japan.

In other news, Suika joins the tradition of the space elevator, an idea that has been itching in the back of people's minds since the 1890's

The more detailed explanation of this is a bit more lenghty but I'll keep it simple, so buckle up.

The idea of a space elevator is that a weight with a cable tethering to earth, could keep it tense if the weight is moving too fast (so much so that if let loose it would escape into space, or at least a higher orbit).

This cable can support a vehicle going up along it, bringing any cargo within it to space, using much less energy and resources than a rocket.

How to make a cable that can support its own weight over such a huge distance is the main reason we haven't built one.

A problem that arises from this, is that if the weight doesn't match the rotation of the earth, the cable would get pulled around (eventually breaking or winding around the earth, pulling the weight down, as cartoony as that is), so we need it to hover over one spot.

Now we gotta talk about geostationary orbit, to make this easier.

So, when something is orbiting the earth, it needs to move really fast to combat gravity in such a way that the earth curves away from the object at the same rate it's falling towards it (spaceflight really is the art of falling to the ground and missing it, as the saying goes.)

The farther out you go, the weaker gravity's pull gets, and the slower the satellite needs to be in order to find this balance. Eventually it reaches the point where, if its flying around the equator, it will, at one point, match the speed of the ground spinning beneath, this is at 35786 km above.

Such a satellite appears still in the sky, which is very handy to, as a sidenote, aim a small TV dish at it, and just leave it in place, as you may have at home.

However one must notice that in a space elevator, the satellite (our weight) is not only pulled by gravity but also by the tension in the cable.

Since it's pulled in with a greater force, it falls faster than a normal satellite, and so it needs to also travel faster to avoid falling back to earth.

As a result, it also needs to be further away than a geostat satellite, so it needs to travel a longer way around the earth, and again find the balance of speed with rotation, staying still in one spot while keeping the cable taut.

This is why the weight is shown beyond geostationary orbit here. Yes, this was a long winded explanation for just that.

And after all that, here we all are, ignoring the fact that suddenly petrified hair is flexible.

Perhaps it's like glass fiber / glass wool, and it can be flexible when it's thin enough (yes, glass fiber is just glass but thin, if you weren't aware. Incidentally, most glass fiber is made by a process that works the same as a cotton candy machine... wait this was already shown in Dr. Stone, fu-).

This however doesn't explain how this flexibility hasn't been observed in statues before. Maybe her hair is special after all.

Also special is spider silk, although sometimes overhyped by the media. Spider silk has some outstanding mechanical properties, it's very durable, and it can take a lot of tension and deformation before breaking.

Ruri here makes a reference to her previously stated occupation after the main series. A lot of people took issue with the aftermath of the characters in general, myself included. Still mad at Kohaku joining the police, I'm pretending that didn't happen.

This might be an autism 100 take, but the wheels in this cart are backwards. The flanges should be on the inside, and the taper should be towards the outside.

This geometry helps railway wheels stay on the track, go around bends, and not have to constantly abuse the flanges to not fall off the rails.

The silk road... I really am just googling basic things for you, am I? It was an ancient trade route network joining asia with the middle east and europe. Silk was one of the most famous products traded through the network.

yeesh, I've been typing this for ages (tumblr logged me out while I was writing this post and lost like half of it), and I haven't even gotten to talk about induction motors yet.

A linear motor is just an electric motor that rather than making something spin, it pulls itself along some sort of guide rail. These are in use in some trains but they are not common, the infrastructure cost is much higher than a normal railway.

Why am I talking about trains again...

One way to make it work is by induction.

The tl:dr is that when a magnetic field is moving through a conductive object, it can effectively drag it with it to an extent.

The reason this happens is called Lenz's law; the variation of the magnetic field through the metal causes an electric current to flow through it.

This current, just like an electromagnet you may have put together in science class, produces it's own magnetic field that interacts with the one coming from outside, hence making the metal react, but only when the field is moving or otherwise changing.

A big advantage is that there needs to be no contact between the source of the field and the moving metal; this is used in all sorts of electric motors even in homes, you'll find them in fans, refrigerators and washing machines, etc.

The train/motor would have a magnetic field underneath with a north-south-north-south-... pattern, which flows towards the back like a river (made by a lot of electromagnets switching in coordination).

As the magnetic river flows backwards, the induced currents in the rail produce their own magnetic field in opposition, pushing the train forward.

How viable is it to use this on a thin cable that needs to pull itself up is another story, and I have my doubts. The electronics involved would be really complex, costly and perhaps even unwieldy, but at least the conductive cable can also be used to deliver power to the elevator with some tweaks.

The structure they begin constructing for the full size elevator is named after the 1979 novel "The fountains of Paradise" by Arthur C. Clarke, in which a space elevator is also constructed.

So, we've made it to this part. As far as I've seen this one panel has been the focus of like 50% of the discussion regarding this chapter.

We all see what he's doing whether we acknowledge it or not; Inagaki should know that you cannot build a relationship on just standing close and gazing with passion; believe me I checked, multiple times.

Wouldn't mind if he hadn't procrastinated on developing Senku's side, the girl has wanted her vegetables since day two (but not day one)

And now, things get really messy, as some mind boggling events lead Ryusui to ask "why, man?"

Look, I've already added 30 images to this post, and I imagine you have seen how this chapter ends, if you haven't, buddy what the heck are you doing here. Have some emoji, I'm not gonna make a second post about this.

🥨✨🦟 ⁉️👱🏼‍♂️🏴‍☠️ 👨‍🚀☠️??

You may be confused, you should.

But after a while I came to a conclusion that I feel is pretty solid, and you may have seen it in the post from earlier.

To summarize:

Ryusui noted that things were going suspiciously well for them, and the sudden disappearance of mosquitoes in the Kanto region ticked him off to something. He sent people to search and indeed found that mosquitos have been petrified within the region, and questions whyman about it, going as far as accusing them of pretending to be Byakuya from the future.

That's where we are left.

The medusa is fully capable of faking the signal they received from "Byakuya". The receiver only detected bursts of petrification beam presumed to be from the future and decoded them as morse code, and it was noted by Balb on discord that if you trace a circle with the center near Tokyo (where the lab keeping whyman is) and a radius reaching as far as Fuji, where they received the message, the circle covers the majority of the Kanto region as stated.

The bursts of petrification would have been invisible to humans, as only the affected species can see them.

So it is assumed that the mosquitos were petrified as a means for whyman to send the fake signal all the way to Fuji, depleting its diamond battery in the process.

However I believe it's also possible the mosquitos were zapped later to make work easier for the people building the space elevator as noted by Kaseki.

Several months if not more must have passed since the Byakuya message and whyman being caught (enough for Kohaku's hair to regrow), and it would be odd that no one would have noticed the lack of mosquitos, their petrified bodies, or the effect their absense would have in the ecosystem.

So why do any or all of this?

Well we know what whyman is largely motivated by, its survival and the spread of its kind across the universe.

So I think it's trying to accelerate human progress for that purpose, so we eventually get to the point where more medusas can be made, or who knows, maybe even succeed in warning the past ones with the time machine.

I also think it's likely this misunderstanding is gonna fizzle out once some dialog is made and Senku basically says yes to that goal too.

Will we get a triple twist and find that the Byakuya message was real after all, and the mosquitos were a separate event?

Will the sengen and kohasen crowds envelop the world in thermonuclear hellfire?

And will this be the true final end of Dr. Stone? hard to tell, but the answers may come next week.

Goodnight.

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newtypezaku · 1 month ago

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Jerid's Sortie Order (1987)

"Hey, Zaku, surely it doesn't take you two and a half years to read a book." It does when you set it aside for several months to watch a ton of hella mid isekai anime, start the first G-Saviour novel and go even slower because of all the hella mid isekai anime, and then forget about both for several more months because you're too lazy to do language practice after work. But I did it eventually!

As with Char's Return, this is a single-player RPG with choose-your-own-adventure branching and turn-based combat. This time, you're Jerid Messa in the final days of his Titans training. When guerrillas take over a Federation base and threaten to use their own experimental technology against them, Bask Om gives Jerid 24 hours to save the day. Summary under the cut.

Setting

January, UC 0087. Buckland Base in Alaska hosts several experimental technologies away from prying eyes. Research into artificial Newtypes has begun. It also has a perimeter defense system powered by Kerberos, a satellite power station in geostationary orbit above the base. Using "Wave Catchers," microwaves received from Kerberos are converted into electricity that can power high-output beam weaponry, which could enhance the defenses of bases without large nuclear reactors. Kerberos itself could also be used as an orbital weapon...

In the Bering Sea to the west, Jerid Messa, Emma Sheen, and Kacricon Cacooler are five months into their special training program to become Titans officers. They are aboard the Graf Zeppelin, a massive attack carrier initially developed by Zeon but captured and completed by the Federation. The program is nicknamed "Top Gundam," a portmanteau constructed from the old US Navy's flight academy and the ace machine of the One Year War.

Characters

Jerid Messa: You assume the role of 23-year-old Jerid Messa at the end of his training. As the protagonist, Jerid doesn't come across as abrasive or comically evil as his anime counterpart.

Emma Sheen: A fellow student at Top Gundam. Described as a woman of Eastern descent with graceful features and the air of an honors student.

Kacricon Cacooler: A fellow student at Top Gundam. A rough, veteran-looking guy who Jerid has known for longer than Emma.

Bask Om: A high-ranking officer within the Titans who arrives at the Graf Zeppelin with a dangerous, time-sensitive, mission.

Alaska Native old man: Helps Jerid after a guerrilla encounter in a village. He has little intel but leaves an impact on Jerid by explaining his reasons for living traditionally.

Alaska Native young girl: The old man's granddaughter, who helps rally Jerid's fighting spirit and gives him another reason to complete the mission.

Ex-Zeon soldier: Crash-landed in the region during the One Year War, was healed by the Alaska Natives who found him, and decided to live in their village after growing tired of the war.

Enemy commander: A middle-aged man described as having sharp eyes despite an otherwise scrawny, hollow appearance.

Tom Cruising: Senior Crewman with the local guard. He shows up at the end to congratulate Jerid on his success and remind you that this is supposed to be loosely based on Top Gun.

Mechanics

MS-06MH Marine Hizack: One of three MS that Jerid can select for the mission; it confers an advantage in underwater combat but cannot use beam weapons. Its model number suggests that, despite the name, it's more likely to be the MS-06M/MSM-01 Zaku Marine Type that appeared in Zeta.

MS-09 Dom Blizzard Type: Presumably equivalent to the MSV-R Dom Cold Climate Type. It also appears in the game text as the MS-09F2.

MS-14A Gelgoog

MS-17B Galbaldy Alpha

MS-87D Nashorn: "Zeon's Phantom MS" that saw limited deployment during the One Year War, armed with a hyper rifle.

MSM-10 Zock

MAN-07 Grabro

RMV-05 Guntank Hover: Presumably derived from the RMV-1 as a hovering vehicle, although its in-book art depicts a machine with an upper body that's closer to the original Guntank but with a mono-eye head.

RGC-80 GM Cannon

RGM-79R Gundam Copy Type: Shares the same model number as retrofitted GMs that led to the development of the RMS-179; in the game, though, it's a clone of the original Gundam with Amuro's combat data.

RMS-179 GM II: One of three mobile suits Jerid can select for the mission; it has more HP than the Marine Hizack and is the only unit that can use a beam rifle.

RMS-106 Hizack: One of three mobile suits Jerid can select for the mission. It's used in the training exercises before the mission starts and has stronger armor than either the Marine Hizack or GM II.

RMS-117 Galbaldy Beta

ORX-003 Domingo: Described as the predecessor of the ORX-005 Gaplant, a transformable mobile suit with exceptionally high speed and aerial combat capabilities.

MAX-09 Dura: A behemoth MS nearly 70 meters tall and weighing 685 tons, it was developed from the Big Zam. The Dura has multiple high-output beam cannons, a deflection shield that weakens beam attacks, and, learning from the Big Zam's defeat, sub-arms with close-combat weapons. It is the final boss. Confusingly listed in the book's MS table as the MAX-09, on the back cover as the MAX-07, and in the game text as the MAX-11.

FF-3 Saberfish

M-4A3 Salamander: A hovertank armed with missiles.

Fa-223 Drache: Described as a combat helicopter, but its in-game artwork looks more like the fusion of a Luggun and a Dopp.

Dodai Kai

Story

Aboard the Graf Zeppelin, Jerid, Emma, and Kacricon go through their last big round of combat training. In a simulator, Jerid pilots a Hizack against up to three opponents: a damaged GM II, another Hizack, and the Gundam with Amuro's combat data. After simulator training is completed, the three participate in mock aerial combat aboard Hizacks riding Dodai Kais. (The number of opponents you defeat during the training phase determines how many skill points you start with.)

As aerial training concludes, you're all summoned by Bask Om. He explains that guerrillas have captured nearby Buckland Base -- and by extension, Kerberos, which is controlled remotely -- and are demanding that the Federation government release Zeon war prisoners. Because of the beam turrets powered by the Kerberos satellite, directly attacking the base is not an option. Neither is destroying the satellite itself. What about the Wave Catchers? Their locations are a closely-guarded secret, so they have to be found first.

If their demands aren't met within 30 hours, the guerrillas will use Kerberos to attack colonies. An organization as proud and just as the Titans could never allow a laser to strike a colony; the very idea is preposterous. Due to Minovsky Particle interference, someone has to locate and destroy the Wave Catchers and then call for reinforcements using laser-line communication from the Buckland Base control tower. The mission is assigned to Jerid, the one with the highest marks among the three trainees.

Once Jerid selects a machine and weapons, he departs the Graf Zeppelin in a high-speed capsule to one of two locations on the Alaskan coast. The mission area is a 6x4 grid and moving to an adjacent cell takes two hours, although this is reduced to one if a high-mobility item is equipped. All objectives must be achieved within 24 hours.

Jerid is free to roam the grid, encountering various enemies (defeating them earns more skill points) and procuring items that will help him later. Several, such as infrared goggles, are for the eventual infiltration of Buckland Base. Others are additional ammo or different weapons for his MS, in addition to repair docks that fully restore the unit's HP but require two hours to use. A few areas are also protected by minefields.

With the exception of two Alaska Native villages, the region is sparsely populated. He is more likely to run into a guerrilla than a civilian, although the latter do have items and information if you are able to converse. A young girl in one village gifts him a protective amulet that fits neatly into the breast pocket of his normal suit, which certainly isn't foreshadowing anything.

After destroying all three Wave Catchers and crossing the minefield outside Buckland Base, Jerid breaks into the facility in search of the communications room. There are infrared sensors along the way that must be avoided and gun-toting troops guard most routes. After reaching the room and sending the laser communication, the enemy commander and his men attack, but Jerid survives a gunshot thanks to the protective amulet. He still blacks out.

When Jerid wakes up, he's in a large dome under the base where the enemy commander has graciously provided him with his MS, repaired and rearmed, for a fight to the death against two artificial Newtypes loaded with Char and Amuro's combat data. Seeing the Gundam, Jerid recalls a family trip to Ireland where he met a girl who showed him a commemorative photobook of the machine. Jerid defeats both and the commander angrily prepares to destroy the dome from the inside, but since Jerid successfully called for help, Emma and Kacricon arrive to prevent the dome from collapsing on him.

Upon exiting the dome, the enemy deploys its final card, the Dura. It immediately bathes the area in fire and threatens to destroy the Graf Zeppelin approaching offshore. Jerid, Emma, and Kacricon all fight together and eventually bring the lumbering hulk down. (Although it's not a game over if either Emma or Kacricon die, this does lead to a bad ending where Jerid dies from extreme fatigue at the end of the mission.) With the Dura's defeat, the Buckland Base staff are rescued, as are civilians from the two villages who were captured after you left. You are reunited with the young girl, who reminds you of the one you met in Ireland years ago.

Jerid, Emma, and Kacricon return victorious to the Graf Zeppelin. Jerid does a victory roll on the deck, causing Bask to spill hot coffee on himself in the control room because, remember, this is Top Gun. At the debriefing, Bask promotes them all to Lieutenant Junior Grade and offers them the chance to become Gundam Mk. II test pilots (Two months later, the AEUG infiltrates Green Oasis and any character growth that Jerid experienced while completing this mission is lost when he encounters an autistic teenager.)

So there you have it!

Most of the story is contained the prologue and epilogue, as there's no canonical path to completing the mission. Only the Wave Catcher cells and the young girl's village are hard requirements, but given where they are relative to each other, you need to find a high-mobility item as early as possible. Same deal with items for base infiltration; you need at least two of the infrared goggles, wire rope, and landmover to reach the comms room before getting caught. There's probably also a fine line you have to walk between avoiding battles and fighting them for skill points, because repairs are expensive time-wise.

Dunno what's next; I certainly have no shortage of books to try!

#mobile suit gundam #zeta gundam #jerid messa #jerid's sortie order #gundam

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7crowsinadress · 6 months ago

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Ok SO I’m taking some orbital mechanics and aerospace classes right now and we’re learning about different orbits and what they’re used for. Low earth orbit is generally used for observation satellites, medium earth for navigation, and geostationary is where a lot of the broadcasting satellites are. As previously mentioned, I am experiencing terminal levels of Mad Max Brainrot.

SO:

With the Vuvalini, when they see the satellite, it is moving. Geostationary broadcast satellites, like the ones that would be broadcasting the shows, don’t appear to move in the sky. You know what does? Lower earth orbit observation satellites. You know what’s also in low earth orbit? The ISS. That could very well have been a tin can full of corpses they were reminiscing at.

#did this make any sense to anyone but me #the only way I’m getting through this class is by associating it with my current fixation #mmfr #mad max fury road

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spacetimewithstuartgary · 13 days ago

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Using multimode propulsion for more efficient trips in space

Over the span of two projects, researchers at the University of Illinois Urbana-Champaign investigated using a propulsion concept known as multimode propulsion to get spacecraft to the moon and developed a technique to design optimal multimode transfers.

NASA provided the team with four real mission scenarios. The goal was to explore how a multimode propulsion system that integrates both a chemical high-thrust mode and an electric low-thrust mode—while using the same propellant—can succeed. They examined using a standard 12-unit CubeSat to accomplish four distinct missions.

"We showed for the first time the feasibility of using multimode propulsion in NASA-relevant lunar missions, particularly with CubeSats," said aerospace engineering Ph.D. student Bryan Cline. "Other studies used arbitrary problems, which is a great starting point. Ours is the first high-fidelity analysis of multimode mission design for NASA-relevant lunar missions."

The study that looked at four NASA-relevant lunar trajectories, "Lunar SmallSat Missions with Chemical-Electrospray Multimode Propulsion," is by Cline and Joshua Rovey from the University of Illinois, Khary Parker and José J. Rosales from NASA's Goddard Space Flight Center, and Stephen West from Space Exploration Engineering. It is published in the Journal of Spacecraft and Rockets.

Cline said one of the advantages to multimode propulsion over a hybrid system is there can be a big savings in the dry mass of the spacecraft. Needing only one fuel tank, for example, saves mass and volume.

"Multimode propulsion systems also expand the performance envelope," he said. "We describe them as flexible and adaptable. I can choose a high-thrust chemical mode to get someplace fast and a low-thrust electrospray to make smaller maneuvers to stay in the desired orbit. Having multiple modes available has the potential to reduce fuel consumption or reduce time to complete your mission objective."

There are also advantages over hybrid propulsion systems which have multiple propulsion modes but each use a separate propellant.

"I can choose to use high-thrust at any time and low-thrust at any time, and it doesn't matter what I did in the past. With a hybrid system, when one tank is empty, I can't choose that option."

Cline said, to complete each of the design reference missions for this project, they made all the choices manually—that is, when to use high-thrust and when to use low-thrust. Because it was all manual, the trajectories weren't optimal. Following this work, Cline developed an algorithm, a set of equations, to automatically select when to use high-thrust and low-thrust to ensure that the resulting trajectory is optimal.

"This was an entirely different beast where the focus was on the development of the method, rather than the specific results shown in the paper. We developed the first indirect optimal control technique specifically for multimode mission design. As a result, we can develop transfers that obey the laws of physics while achieving a specific objective such as minimizing fuel consumption or transfer time," Cline said.

Cline first solved a simple two-dimensional transfer between Earth and Mars that decides the optimal times to use high-thrust, low-thrust, or just coast. He then solved a three-dimensional transfer to geostationary orbit that minimizes fuel consumption.

The study that developed the method, "Indirect optimal control techniques for multimode propulsion mission design," is by Cline and Alex Pascarella, and their faculty advisers, Robyn Woollands and Joshua Rovey. It is published in the journal Acta Astronautica.

"We showed the method works on a mission that's relevant to the scientific community," he said. "Now you can use it to solve all kinds of mission design problems. The math is agnostic to the specific mission. And because the method utilizes variational calculus, what we call an indirect optimal control technique, it guarantees that you'll get at least a locally optimal solution."

Cline said multimode propulsion is emerging, enabling, and enhancing. "It's an emerging technology because it's still being developed on the hardware side. It's enabling in that we can accomplish all kinds of missions we wouldn't be able to do without it. And it's enhancing because if you've got a given mission concept, you can do more with multimode propulsion. You've got more flexibility. You've got more adaptability.

"I think this is an exciting time to work on multimode propulsion, both from a hardware perspective, but also from a mission design perspective. We're developing tools and techniques to take this technology from something we test in the basement of Talbot Lab and turn it into something that can have a real impact on the space community."

IMAGE: Earth–Mars minimum-fuel trajectory when the CubeSAT is coasting, as well as in mode 1-low thrust and mode 2-high thrust. Credit: Acta Astronautica (2024). DOI: 10.1016/j.actaastro.2024.07.020

#science #space #astronomy #physics #news #astrophysics

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tracybirds · 2 years ago

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hey um. what's geostationary orbit and why is it impossible for TAG's TB5 to achieve?

Hello!! I'm assuming you're coming in from the stack of memes I made lol so welcome welcome, this is my well-known pet peeve and I will happily explain because it involves my favourite subject - physics!

"Impossible to achieve" isn't quite accurate - my argument is formed purely on the observational evidence of where it is, such that when the show makes references to TB5 being in geostationary orbit it doesn't make sense because it's simply.... not.

So strap in, I'll go through this as clearly as I can but feel free to ask follow up questions :D Or just generally hang out lol TAG is a fun time despite the handwave-y physics ahaha :D

1. What is geostationary orbit?

Geostationary orbit is the specific orbit where a satellite/space station/whatever moves with the exact same period as the Earth's rotation i.e. 24 hours AND is placed so that the object is directly over the equator, it will move in that orbit at the same rate as the location it is over, so that it will always be over that position at all times. This gives it the name "geostationary", implying that the Earth doesn't move relative to the orbiting object, or if you look down you'll always see the same place.

Both conditions must be met for geostationary orbit to occur; an orbit with a greater or lower period will fall out of step with the Earth fairly quickly, and if not on the equator, you'll get a related type of orbit known as a geosynchronous orbit which will move up and down relative to the equator rather than staying put.

Furthermore, I won't take you through the calculation (1 | 2 | 3), but using Kepler's Third Law which is sufficiently accurate for this scenario, this orbit must always be ~36,000 km above the Earth, or the quoted 22,500 miles in the show. That is the main evidence in the show that implies that the writers intended for TB5 to be in geostationary orbit, like TOS was written to be.

However....

2. Why can't TB5 be in geostationary orbit?

It's not that it can't, it's that it isn't! There's two main reasons for this that I return to when grumbling about this to my friends (they are long-suffering on this point lol thank goodness they're reasonably good-humoured about it...)

Reason 1: The size of the Earth from TB5

This is the most damning evidence. Let's make some visual comparisons.

This is what the Earth looks like from the International Space Station which maintains an orbit about 400 km above the surface of the Earth (in a region known as Low Earth Orbit).

It's a little more complicated to show what Earth looks like from geostationary orbit as many satellites in this region are communication relays or broadcasting satellites (very appropriate for TB5 it must be said!!) But that being said, this is a full disk image of Earth from Japan's Himawari 5, a weather satellite in geostationary orbit.

Now take a look at the animation in TAG and decide for yourself what was being used as inspiration!

But I'm a physics nerd, so I won't take blind faith in some pictures! No, no - if there's a specific height that an orbit must maintain in order to remain in this orbit and the size of the Earth doesn't change, then it should follow that the Earth must be some kind of stable "apparent" size that we can figure out. Think about a freestanding house from 40 m away. It doesn't matter in which direction the 40m is, the house takes up the same space in our vision. The same follows here.

Once again, I'll gloss over the calculations ( 1 | 2 | 3) and simply state that from geostationary orbit, the Earth should take up no more than about 20° of our field of vision. In comparison the visual angle of the Moon is about 0.5° so it's still going to look really big!! But not as big as you'd see from the ISS :P If you make both hands into fists, place them next to each other and hold them at arms length from your body, that would be the approximately the width of the Earth from geostationary orbit.

So TB5?

....might be a wee bit closer than that 😂

Reason 2: The locations on Earth

This one's a little looser, but it illustrates my second point - in order to be geostationary, TB5 needs to..... stay over one location? Like okay sure it has rockets and engines so that it's able to move around, we've seen them plenty of times. But that doesn't change that fact that even when these are not in use, TB5 is never in one place.

Here's some examples…

The Strait of Gibraltar (Spain and Morocco) | 1x07 (Runaway)

Looks like Japan in the background to me | 1x07 (Runaway)

Ireland and Great Britain | 1x08: EOS

Cheating a tad, but he's only just launched so it's reasonable to assume that here TB5 is over SE Asia | 2x02 (Ghost Ship)

None of these are examples where John's manoeuvred TB5 into position like he does in Skyhook (1x11) and Impact (2x09) so it's reasonable to assume that TB5 is following its assigned orbit... and its not geostationary!

Moral of the story: TB5 could be in geostationary orbit, there's nothing stopping it! But uh... it's not. Thanks for listening ;D

All images stolen either from the thunderbirds wiki, or I've attached a click through link to their origin :)

#thunderbirds are go #hello yes it's me chattering about geostationary orbits again #sorry not sorry

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eugiesblog · 5 months ago

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cuz i dont believe in paywalls ✌️

1. A Beautiful Crescent Moon

When: after sunset on Friday, June 7, through Monday, June 10

Where: above the western-southwestern horizon

There are four nights each month when a gorgeous crescent moon appears at dusk in the western sky, but most of us miss it. We don't know if it's there and/or if it's cloudy. So here's a forewarning that a crescent moon will shine close to the stars of Gemini, then Leo, across one long weekend in June. Just look west—and if you have binoculars, use them. You will see not only the spectacular crescent but also "Earthshine" subtly lighting up the "dark side" of the moon.

2. A Big Star And A Big Moon

When: after dark on Wednesday, June 19

Where: east-southeast

Antares, the brightest star in the constellation of Scorpius, is an anchor star of summer skies. A red supergiant star 12 times the sun's mass, it's one of the biggest stars in the night sky. You can see it in the east tonight after dark, close to a big, bright, waxing gibbous moon.

Where: east-southeast

A noctilucent clouds display of June 20, 2021.

3. Noctilucent Clouds

Where: northeastern night sky

When: evening twilight

Stargazers at latitudes between 50 and 70 degrees north of the equator may be able to observe noctilucent clouds this month. These “night shining” clouds or “space clouds” comprise icy dust and form about 50 miles up. They form mostly during June and July because the sun never sets far below the horizon. They're best viewed with the naked eye or binoculars during twilight.

People gather for sunrise at Stonehenge, on June

4. Midsummer Night’s Eve

When: Thursday, June 20

Where: sunrise and sunset

The solstice marks the start of summer in the northern hemisphere and winter in the southern hemisphere. It's when the planet's north axis is at its maximum tilt towards the sun. The moment of the solstice is at 15:51 EDT, but to witness it, you should try to watch the sun rising (at its farthest northeast of the year) and/or setting (at its farthest northwest). Solstice comes from the Latin words sol and sisto, meaning sun and stop, as the sunrise and sunset points remain the same for a few days.

5. The First Full Moon Of Summer

When: moonrise where you are on Friday, June 21

Where: east

Tonight's the night to see June's full “Strawberry Moon” rising in the east during dusk. Since the sun is at its highest in June in the northern hemisphere, the moon is at its lowest, with the “Strawberry Moon” the lowest-hanging and latest rising full moon of the year. Much like the sun in December. Occurring just a day after the solstice, the first of summer in the northern hemisphere is also called the “Hot Moon” and the “Planting Moon.”

The SpaceX Falcon Heavy rocket lifts off from

6. A Big Rocket Launch

When: 5:16 p.m. EDT on Tuesday, June 25

Where: Kennedy Space Center, Florida (SpaceX YouTube channel)

If the schedule sticks, today will see a SpaceX Falcon Heavy rocket—on only its tenth outing—launch the NASA/NOAA GOES-U satellite into a geostationary orbit. It will launch from Kennedy Space Center, Florida, with the launch window opening at 5:16 p.m. EDT.

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sklira · 4 months ago

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静止軌道上空のあなたへ | cosmomule

#cosmomule #静止軌道上空のあなたへ #to you on geostationary orbit #my post #musik #one of the best things ive heard in a while #cosmomules EPs are incredible along with everything else he's been a part of

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enriquemzn262 · 2 years ago

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Colombia just put its second satellite into orbit. Congrats! Even with how easy satellite launches have gotten, that's still not something plenty of nations are capable of.

Micro-satellite, but yeah, thank you! The ultimate goal is to get a proper geostationary satellite up and running, for both communications and mapping.

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humanspaceflightday · 7 months ago

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BULGARIA - Workshop on "Humanity’s space past, present, and future" - Yuri’s Night 2024.

On April 12, 1961, Yuri Gagarin became the first human to fly into space, becoming the most famous person on Earth. For years, this date has been celebrated as World Aviation and Cosmonautics Day, and the global initiative Yuri’s Night has been created to popularize topics related to humanity’s space past, present, and future.

Traditionally, we at Ratio participate in the global celebration, and this time we have prepared a series of interesting topics through which we will fly together.

The Yuri’s Night space crew consists of Victoria Todorova (Systems Engineer), Ralitsa Velikova (Software Engineer), Elka Terzieva (Engineer), and Simon Jenner (Axiom Space). With them, we will orbit around several topics, while in the meantime, we will enjoy a special thematic selection of music and lights suitable for a space party.

Space exploration would be impossible without space rockets, and at Yuri’s Night, we will learn more about how they work. We will discuss what Q-MAX means and why everyone celebrates when the rocket passes it, even though it is still flying and has not reached space yet. We will raise the topic of radiation sources in space and understand the various effects that radiation can have on electronics in space. We will also examine types of random-access memory that are radiation-resistant. Of course, when talking about space, we cannot overlook astronauts, and we will learn more about the preparation of an astronaut before flying into space.

We will ask a series of space questions, including:

Can we launch space rockets from Bulgaria? What are geostationary satellites (GSS) and what are the nature of their missions? What are the ways to deal with non-destructive errors caused by radiation? We expect you on April 12 with a large dose of space science to celebrate together the historic journey of Yuri Gagarin and World Aviation and Cosmonautics Day.

Yuri’s Night Bulgaria 2024 2024-Apr-12 @ 07:00 PM - 2024-Apr-12 @ 10:30 PM София, Bulgaria

#Cosmonautics Day #yuri's night #geostationary satellites (GSS)#space science #12 april #International Day of Human Space Flight #bulgaria

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