jack1983 Smack-Fu Master, in training
12y
93

The Lurker Beneath said:
Do it on a windy day?
There are risks with too high wind speeds as well. High airflow causes static buildup and turbulence. Hydrogen requires very little ignition energy (well below 1mJ at stoichiometric conditions). So even a gust of wind can set off a combustible mixture.

Cryogenic hydrogen is an absolute nightmare to work with.

paulfdietz Ars Scholae Palatinae
7y
1,168
Using hydrogen as the fuel in the first stage was never a good idea. The density is just terrible, making the first stage much larger. Because the first stage is disposed of so quickly, Isp is less important; what's more important is "density impulse" (density x Isp), and LoX/LH2 is inferior to LOX/hydrocarbon by that metric.

Low density also makes the engines more expensive, as more pumping power is needed for a given thrust. //

paulfdietz Ars Scholae Palatinae
7y
1,168

pokrface said:
Right, but the "first stage" of SLS (and STS) is properly the SRBs.
It's more like the first "half stage". What matters for the argument is the velocity at which a stage is done. Even with the SRBs there, that's not that high (although higher than say the Falcon 9, which ends the stage 1 burn at an unusually low velocity so it can be recovered.)

The SRBs do allow the thrust of those LH2 engines to be somewhat lower, since they don't have to lift the fully fueled stack off the pad themselves. By the time the SRBs drop some propellant is gone. This ameliorates to some extent the relatively poor thrust/weight ratio of the engines (73.1 vs 184 for the Merlin 1D.)

Harrison Schmitt, speaking with a NASA interviewer in 2000, said his productivity in the Apollo suit “couldn’t have been much more than 10 percent of what you would do normally here on Earth.”

“You take the human brain, the human eyes, and the human hands into space. That’s the only justification you have for having human beings in space,” Schmitt said. “It’s a massive justification, but that’s what you want to use, and all three have distinct benefits in productivity and in gathering new information and infusing data over any automated system. Unfortunately, we have discarded one of those, and that is the hands.”

Schmitt singled out the gloves as the “biggest problem” with the Apollo suits. “The gloves are balloons, and they’re made to fit,” he said. Picking something up with a firm grip requires squeezing against the pressure inside the suit. The gloves can also damage astronauts’ fingernails.

“That squeezing against that pressure causes these forearm muscles to fatigue very rapidly,” Schmitt said. “Just imagine squeezing a tennis ball continuously for eight hours or 10 hours, and that’s what you’re talking about.”

Barratt recounted a conversation in which Schmitt, now 90, said he wouldn’t have wanted to do another spacewalk after his three excursions with commander Gene Cernan on Apollo 17.

“Physically, and from a suit-maintenance standpoint, he thought that that was probably the limit, what they did,” Barratt said. “They were embedded with dust. The visors were abraded. Every time they brushed the dust off the visors, they lost visibility.”

Getting the Artemis spacesuit right is vital to the program’s success. You don’t want to travel all the way to the Moon and stop exploring because of sore fingers or an injured knee.

“If you look at what we’re spending on suits versus what we’re spending on the rocket, this is a pretty small amount,” Rubins said. “Obviously, the rocket can kill you very quickly. That needs to be done right. But the continuous improvement in the suit will get us that much more efficiency. Saving 30 minutes or an hour on the Moon, that gives you that much more science.”

“Once you have safely landed on the lunar surface, this is where you’ve got to put your money,” Barratt said.

Sunrise, sunset, moon phase

Darkness fell over Mare Crisium, ending a daily dose of dazzling images from the Moon. //

Firefly Aerospace's Blue Ghost science station accomplished a lot on the Moon in the last two weeks. Among other things, its instruments drilled into the Moon's surface, tested an extraterrestrial vacuum cleaner, and showed that future missions could use GPS navigation signals to navigate on the lunar surface.

These are all important achievements, gathering data that could shed light on the Moon's formation and evolution, demonstrating new ways of collecting samples on other planets, and revealing the remarkable reach of the US military's GPS satellite network.

But the pièce de résistance for Firefly's first Moon mission might be the daily dose of imagery that streamed down from the Blue Ghost spacecraft. //

Dtiffster Ars Praefectus
9y
3,725
Subscriptor
TylerH said:
Given the amount of fuel needed to return to Earth, probably somewhere around the middle.

The prop to lift back off is at least 1.1 times the dry mass + up mass, but 78% of that is LOX which goes in the bottom tank. We don't know if the liftoff prop will just be in the tanks or in some kind of a really large header in the tank (as a boil off mitigation), but I would assume if there are headers they will be at or near the bottom of the of their respective tanks. Thus atleast 41% of the landed mass would be LOX and be very near the bottom. The legs and engine section will also be fairly substantial and very low. The methane for liftoff would be another 11% and only about a third of the way up the rocket. Much of the rest of the mass is tankage, but that center of mass is also probably no more than a third of the way up. The habitat section and equipment is high up, but it's less than 15% of that lift off mass. The CoM of the whole thing on landing/liftoff is probably only 25-30% up from the surface. It is much less tippy than your initial intuition would lead you to believe. //

https://www.youtube.com/watch?v=M2P-z_cXsOs

https://youtu.be/IpA9DORDkeE?si=oNmwnzJs6_UwzjPb

https://www.flickr.com/photos/fireflyspace/albums/72177720313239766/with/54395270843

Intuitive Machines announced on Friday morning that its Athena mission to the surface of the Moon, which landed on its side, has ended.

"With the direction of the Sun, the orientation of the solar panels, and extreme cold temperatures in the crater, Intuitive Machines does not expect Athena to recharge," the company said in a statement. "The mission has concluded and teams are continuing to assess the data collected throughout the mission."

Athena, a commercially developed lander, touched down on the lunar surface on Thursday at 11:28 am local time in Houston (17:28 UTC). The probe landed within 250 meters of its targeted landing site in the Mons Mouton region of the Moon. This is the southernmost location that any probe has landed on the Moon, within a few degrees of the lunar south pole. //

NASA has accepted that these commercial lunar missions are high-risk, high-reward. (Firefly's successful landing last weekend offers an example of high rewards). It is paying the companies, on average, $100 million or less per flight. This is a fraction of what NASA would pay through a traditional procurement program. The hope is that, after surviving initial failures, companies like Intuitive Machines will learn from their mistakes and open a low-cost, reliable pathway to the lunar surface. //

Fortunately, this is unlikely to be the end for the company. NASA has committed to a third and fourth mission on Intuitive Machines' lander, the next of which could come during the first quarter of 2026. NASA has also contracted with the company to build a small network of satellites around the Moon for communications and positioning services. So although the company's fortunes look dark today, they are not permanently shadowed like the craters on the Moon that NASA hopes to soon explore.

"Every single thing was clockwork... We got some Moon dust on our boots." //

Firefly Aerospace became the first commercial company to make a picture-perfect landing on the Moon early Sunday, touching down on an ancient basaltic plain, named Mare Crisium, to fulfill a $101 million contract with NASA.

The lunar lander, called Blue Ghost, settled onto the Moon's surface at 2:34 am CST (3:34 am EST; 08:34 UTC). A few dozen engineers in Firefly's mission control room monitored real-time data streaming down from a quarter-million miles away.

This unusual photograph, taken during the second Apollo 12 extravehicular activity (EVA), shows two U.S. spacecraft on the surface of the moon. The Apollo 12 Lunar Module (LM) is in the background. The unmanned Surveyor 3 spacecraft is in the foreground. The Apollo 12 LM, with astronauts Charles Conrad Jr. and Alan L. Bean aboard, landed about 600 feet from Surveyor 3 in the Ocean of Storms. The television camera and several other pieces were taken from Surveyor 3 and brought back to Earth for scientific examination. Here, Conrad examines the Surveyor's TV camera prior to detaching it. Astronaut Richard F. Gordon Jr. remained with the Apollo 12 Command and Service Modules (CSM) in lunar orbit while Conrad and Bean descended in the LM to explore the moon. Surveyor 3 soft-landed on the moon on April 19, 1967.

The Dark Ars Tribunus Angusticlavius
8y
11,841
The lander's four shock-absorbing legs have some give, sort of like the crush zone of a car, according to Will Coogan, Firefly's chief engineer for the Blue Ghost lander. The legs have an aluminum honeycomb material inside, and they connect to bowl-shaped footpads with a ball-socket joint to give the spacecraft some flexibility in case it comes down on a slope or a rock.

That's basically a copy of the Apollo landers. Apollo had crushable aluminum honeycomb in the legs and bowl-shaped feet attached to the legs with ball joints. The statistical analysis was that Apollo's system had a 99.9% of not fully crushing the honeycomb as long as the landing velocity was below 4 feet per second horizontally and 7 feet per second vertically (1.22 m/s and 2.13 m/s). All of the landings were well under those velocities:

https://arstechnica.com/civis/attachments/1740667805423-png.103726/

NASA Technical Note TN D-6850 Apollo Experience Report - Lunar Module Landing Gear Subsystem by William F. Rogers (June 1972).

D-6850 Apollo Experience Report - Lunar Module Landing Gear Subsystem

https://ntrs.nasa.gov/api/citations/19730010151/downloads/19730010151.pdf. //

EarendilStar Wise, Aged Ars Veteran
8y
148
SkyeFire said:
Lunar conditions are brutal. Two weeks of brutal daylight (plus unfiltered solar radiation) followed by 2 weeks of total darkness. A few lunar probes have managed to survive the night and reboot once they got some sunlight again, but none of them survived more than a few day/night cycles. The thermal swings tend to destroy the electronics and power systems.

This entire bath and forth made me realize I don’t know how the temperature swings of the moon and Mars differ. I was reading thinking “How is this thermal swing different than Mars, a place we operate electronics for far more heat cycles than this?”.
Allow me to share what I found:

Commonly accepted average temps for Luna:
-180°C to 105°C
Mars:
-130°C to 22°C

That’s quite the difference!
Does anyone know why Mars nights are warmer? Is it mostly due to ground surface absorption of radiation, and not losing most of it until the next day cycle? The (limited) atmosphere retaining some heat? ///

Shorter nights on Mars

The math that makes refueling from the Moon appealing is pretty simple. "As a rule of thumb," write the authors of the new study on the topic, "rockets launched from Earth destined for [Earth-Moon Lagrange Point 1] must burn ~25 kg of propellant to transport one kg of payload, whereas rockets launched from the Moon to [Earth-Moon Lagrange Point 1] would burn only ~four kg of propellant to transport one kg of payload." Departing from the Earth-Moon Lagrange Point for locations deeper into the Solar System also requires less energy than leaving low-Earth orbit, meaning the fuel we get there is ultimately more useful, at least from an exploration perspective. //

the researchers decided to focus on isolating oxygen from a mineral called ilmenite, or FeTiO3. It's not the easiest way to get oxygen—iron oxides win out there—but it's well understood. Someone actually patented oxygen production from ilmenite back in the 1970s, and two hardware prototypes have been developed, one of which may be sent to the Moon on a future NASA mission.

The researchers propose a system that would harvest regolith, partly purify the ilmenite, then combine it with hydrogen at high temperatures, which would strip the oxygen out as water, leaving behind purified iron and titanium (both of which may be useful to have). The resulting water would then be split to feed the hydrogen back into the system, while the oxygen can be sent off for use in rockets.

(This wouldn't solve the issue of what that oxygen will ultimately oxidize to power a rocket. But oxygen is typically the heavier component of rocket fuel combinations—typically about 80 percent of the mass—and so, is the bigger challenge to get to a fuel depot.). //

The team found that almost all of the energy is consumed at three steps in the process: the high-temperature hydrogen reaction that produces water (55 percent), splitting the water afterward (38 percent), and converting the resulting oxygen to its liquid form (5 percent). The typical total usage, depending on factors like the concentration of ilmenite in the regolith, worked out to be about 24 kW-hr for each kilogram of liquid oxygen. //

Obviously, we can build larger arrays than that, but it boosts the amount of material that needs to be sent to the Moon from Earth. It may potentially make more sense to use nuclear power. While that would likely involve more infrastructure than solar arrays, it would allow the facilities to run around the clock, thus getting more production from everything else we've shipped from Earth.

Lunar exploration is undergoing a renaissance. Dozens of missions, organized by multiple space agencies—and increasingly by commercial companies—are set to visit the Moon by the end of this decade. Most of these will involve small robotic spacecraft, but NASA’s ambitious Artemis program aims to return humans to the lunar surface by the middle of the decade.

There are various reasons for all this activity, including geopolitical posturing and the search for lunar resources, such as water-ice at the lunar poles, which can be extracted and turned into hydrogen and oxygen propellant for rockets. However, science is also sure to be a major beneficiary.

The Moon still has much to tell us about the origin and evolution of the Solar System. It also has scientific value as a platform for observational astronomy. //

Several types of astronomy would benefit. The most obvious is radio astronomy, which can be conducted from the side of the Moon that always faces away from Earth—the far side.

The lunar far side is permanently shielded from the radio signals generated by humans on Earth. During the lunar night, it is also protected from the Sun. These characteristics make it probably the most “radio-quiet” location in the whole solar system, as no other planet or moon has a side that permanently faces away from the Earth. It is, therefore, ideally suited for radio astronomy. //

At that time, most of the matter in the Universe, excluding the mysterious dark matter, was in the form of neutral hydrogen atoms. These emit and absorb radiation with a characteristic wavelength of 21 cm. Radio astronomers have been using this property to study hydrogen clouds in our own galaxy—the Milky Way—since the 1950s.

Because the Universe is constantly expanding, the 21 cm signal generated by hydrogen in the early Universe has been shifted to much longer wavelengths. As a result, hydrogen from the cosmic “dark ages” will appear to us with wavelengths greater than 10 m. The lunar far side may be the only place where we can study this. //

Moreover, there are craters at the lunar poles that receive no sunlight. Telescopes that observe the Universe at infrared wavelengths are very sensitive to heat and therefore have to operate at low temperatures. JWST, for example, needs a huge sun shield to protect it from the sun’s rays. On the Moon, a natural crater rim could provide this shielding for free. //

But there is also a tension here: human activities on the lunar far side may create unwanted radio interference, and plans to extract water-ice from shadowed craters might make it difficult for those same craters to be used for astronomy. As my colleagues and I recently argued, we will need to ensure that lunar locations that are uniquely valuable for astronomy are protected in this new age of lunar exploration.

Bloomberg calls for cancellation of the SLS rocket. In an op-ed that is critical of NASA's Artemis Program, billionaire Michael Bloomberg—the founder of Bloomberg News and a former US Presidential candidate—called for cancellation of the Space Launch System rocket. "Each launch will likely cost at least $4 billion, quadruple initial estimates," Bloomberg wrote. "This exceeds private-sector costs many times over, yet it can launch only about once every two years and—unlike SpaceX’s rockets—can’t be reused."

Several types of astronomy would benefit. The most obvious is radio astronomy, which can be conducted from the side of the Moon that always faces away from Earth—the far side.

The lunar far side is permanently shielded from the radio signals generated by humans on Earth. During the lunar night, it is also protected from the Sun. These characteristics make it probably the most “radio-quiet” location in the whole solar system, as no other planet or moon has a side that permanently faces away from the Earth. It is, therefore, ideally suited for radio astronomy. //

Radio waves with wavelengths longer than about 15 m are blocked by Earth’s ionosphere. But radio waves at these wavelengths reach the Moon’s surface unimpeded. For astronomy, this is the last unexplored region of the electromagnetic spectrum, and it is best studied from the lunar far side.

Observations of the cosmos at these wavelengths come under the umbrella of “low-frequency radio astronomy.” These wavelengths are uniquely able to probe the structure of the early Universe, especially the cosmic “dark ages”—an era before the first galaxies formed.

At that time, most of the matter in the Universe, excluding the mysterious dark matter, was in the form of neutral hydrogen atoms. These emit and absorb radiation with a characteristic wavelength of 21 cm. Radio astronomers have been using this property to study hydrogen clouds in our own galaxy—the Milky Way—since the 1950s.

Because the Universe is constantly expanding, the 21 cm signal generated by hydrogen in the early Universe has been shifted to much longer wavelengths. As a result, hydrogen from the cosmic “dark ages” will appear to us with wavelengths greater than 10 m. The lunar far side may be the only place where we can study this. //

The Moon also offers opportunities for other types of astronomy as well. Astronomers have lots of experience with optical and infrared telescopes operating in free space, such as the Hubble telescope and JWST. However, the stability of the lunar surface may confer advantages for these types of instruments.

Moreover, there are craters at the lunar poles that receive no sunlight. Telescopes that observe the Universe at infrared wavelengths are very sensitive to heat and therefore have to operate at low temperatures. JWST, for example, needs a huge sun shield to protect it from the sun’s rays. On the Moon, a natural crater rim could provide this shielding for free.

Experts in South Korea are convinced that bricks moulded from microwaved stardust could produce materials on site and boost humanity's hopes of living on the lunar surface.

The scientists said: "NASA has announced the Artemis Mission aiming for a long-term presence on the lunar surface. However, infrastructure expansion such as lunar base construction plays a vital role.

"Yet transporting construction materials from Earth to the lunar surface via landers incurs a significant cost of $1.2 million per kilogram.

"To solve this problem Korea Institute of Civil Engineering and Building Technology has developed technology for producing construction materials using in-situ resources from the Moon."

Meanwhile, it was revealed recently that space fanatics could be able to watch TV coverage from the Moon when man returns there for the first time in over 50 years for the Artemis III mission.

We're standing by for news on NASA's decision on what to do about Orion's heat shield. //

The central piece of NASA's second Space Launch System rocket arrived at Kennedy Space Center in Florida this week. Agency officials intend to start stacking the towering launcher in the next couple of months for a mission late next year carrying a team of four astronauts around the Moon.

The Artemis II mission, officially scheduled for September 2025, will be the first voyage by humans to the vicinity of the Moon since the last Apollo lunar landing mission in 1972. NASA astronauts Reid Wiseman, Victor Glover, Christina Koch, and Canadian mission specialist Jeremy Hansen will ride the SLS rocket away from Earth, then fly around the far side of the Moon and return home inside NASA's Orion spacecraft. //

NASA's inspector general reported in 2022 that NASA's first four Artemis missions will each cost $4.1 billion. Subsequent documents, including a Government Accountability Office report last year, suggest the expendable SLS core stage is responsible for at least a quarter of the cost for each Artemis flight.

The core stage for Artemis II is powered by four hydrogen-fueled RS-25 engines produced by Aerojet Rocketdyne. Two of the reusable engines for Artemis II have flown on the space shuttle, and the other two RS-25s were built in the shuttle era but never flew. Each SLS launch will put the core stage and its engines in the Atlantic Ocean. //

Artemis III's launch date is highly uncertain. It primarily hinges on SpaceX's progress in developing a human-rated lunar lander and Axiom Space's work on new spacesuits for astronauts to wear while walking on the Moon.

NASA spent $11.8 billion developing the SLS rocket, and its debut was delayed five years from an original target date in 2017. But for Artemis II, the readiness of the Orion spacecraft is driving the schedule, not the rocket.

Anders - who was a lunar module pilot on the Apollo 8 mission - took the iconic Earthrise photograph, one of the most memorable and inspirational images of Earth from space.

Taken on Christmas Eve during the 1968 mission, the first crewed space flight to leave Earth and reach the Moon, the picture shows the planet rising above the horizon from the barren lunar surface.

Anders later described it as his most significant contribution to the space programme.

The image is widely credited with motivating the global environmental movement and leading to the creation of Earth Day, an annual event to promote activism and awareness of caring for the planet.

Speaking of the moment, Anders said: "We came all this way to explore the Moon, and the most important thing that we discovered was the Earth."

July 20, 2018
Website Notice

Note: This website (moonviews.com) has not been regularly updated since 2014. Now that the project’s data has been submitted to NASA, this website will no longer be updated but will be maintained as an online archive of the LOIRP’s prior activities. Thank you for your interest in – and support of – our project. //

The Lunar Orbiter Image Recovery Project (LOIRP) is a project to digitize the original analog data tapes from the five Lunar Orbiter spacecraft that were sent to the Moon in 1966 and 1967; it is funded by NASA, SkyCorp, SpaceRef Interactive, and private individuals.[1]

The first image to be successfully recovered by the project was released in November 2008. It was the first photograph of the Earth from the Moon, taken in August 1966. On February 20, 2014, the project announced it had completed the primary tape capture portion of the project.[2] One medium resolution image, most of one high resolution image and parts of three others are missing, apparently due to lapses at the time they were being recorded.[3] The rest of the Lunar Orbiter images have been successfully recovered[2] and have been published in NASA's Planetary Data System.

This image (click on image to enlarge) shows the sequence of images that were read out during what is termed “priority” readout vs the “final readout”. The priority readout was an opportunistic scanning of processed photos on the lunar orbiter before all of the images were taken. The photo process with the 70mm film began with an image being simultaneously taken by the 610 mm high resolution camera and by the 80 mm medium resolution camera. In a process remarkably similar to the old polaroid dry process instamatic cameras, the film was dry processed by a “bimat” dry processor. The bimat would separate from the film (most of the time) but would sometimes due to the timing would leave artifacts on the image, which are readily identified on the film.

The film would then be fed into the readout looper where it could be scanned and the images sent back to the Earth. During the mission when photographs were still being taken the film would run one direction through the looper. After all of the images were taken a command would be sent to cut the bimat and then the film could be read in the opposite direction.

Thus when we start with a low numbered tape, the first images that come off are from the priority readout in ascending order. However, the ascending order is not linear, jumping because images are still being taken and the film advancing while the spacecraft cannot transmit.

At 12.56 pm on 21 July 1969 Australian Eastern Standard Time (AEST), mankind took its 'one giant leap' and 600 million people watched as Neil Armstrong walked on the Moon.

Our Parkes radio telescope, Murriyang, famously supported receiving the television signals on that momentous day. Although many people think the Parkes telescope was the only station receiving the signal, it was the 26-metre antenna at NASA's Honeysuckle Creek space tracking station near Canberra that was the prime station assigned with receiving the initial TV pictures from the Moon and Neil Armstrong's first steps on the lunar surface. (The Tidbinbillla deep space tracking station, today known as the Canberra Deep Space Communication Complex, provided support to the command module in lunar orbit.)

Eight and a half minutes after those first historic images were broadcast around the world, the television signal being received by the larger 64-metre Parkes radio telescope, Murriyang, was then selected by NASA to provide the images for the following two hours and 12 minutes of live broadcast as the Apollo 11 astronauts explored the Moon surface.

“I’ve spent the past week in Mountain View, California, hanging out with a group of Lunar Orbiter Image Recovery Project (LOIRP) hackers who are working out of an abandoned McDonald’s on the NASA Ames base. For more than five years, LOIRP technologists (or techno-archeologists, as they prefer to be called) have been reverse-engineering analog tape drives and developing new software in an attempt to unearth some of the first images of the moon that were taken by unmanned lunar orbiters in advance of the manned Apollo missions of the late 1960s. Upon entering the building (affectionately called “McMoon’s” by those who work within it) for the first time, I was greeted by familiar architecture. The drive-thru windows, menu light boxes, stainless steel counters, fiber glass tables and the ghosts of corporate brand ephemera all remain. However now they coexist under a jolly roger with a literal mountain of vintage 2-inch tape reels that contain trapped data, refrigerator-sized Ampex tape drives, an army of Mac workstations and a seemingly endless supply of analog tape decks, monitors, cables and soldering supplies.”

The 2024 total eclipse is in the books. Here's how it looked across the US.

And God said, Let there be light: and there was light. And God saw the light, that it was good: and God divided the light from the darkness. And God called the light Day, and the darkness he called Night. And the evening and the morning were the first day."

The steady rhythm of the night-day, dark-light progression is a phenomenon acknowledged in ancient sacred texts as a given. When it's interrupted, people take notice. In the days leading up to the eclipse, excitement within the Ars Orbiting HQ grew, and plans to experience the last total eclipse in the continental United States until 2045 were made. Here's what we saw across the country.