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SpinLaunch is playing with a different, electric model for mass launching to orbit. It is trying to throw mass into space, but there are challenges.
What’s novel about it? Well, the launcher is a giant solid sling inside a vacuum chamber. It has a big counterweight on a short arm at one end, and a long end that holds the payload at the other. Over 90 minutes or so, it uses electricity to bring the rotating arm with the dart on it up to absurd revolutions per second, about 10,000 gravities of centripetal force.
Then, at exactly the right microsecond, they let the dart go. It goes up through a tube with a light plastic sheet keeping the vacuum in and air out, and continues upward under its own inertia for 10 kilometers right now.
Their goal is to get the device up to the 200 kilogram range and throw satellites with final stage rockets into orbit. //
The parts I have concerns about are the following:
First, while the demonstrator is amazing, as a prototype it’s well below the rule of thumb of quarter-scale by volume for mechanical system prototypes. They assert that it’s a 3rd scale, but that’s by diameter, not 3-dimensionally. As such, it’s a great demonstrator of the principal and as impressive as any piece of awesome engineering that cost $38 million to build, but doesn’t derisk nearly enough of the major technical challenges in my opinion. This is a fairly constant challenge in aerospace, as actual quarter-scale prototypes are wickedly expensive. //
The second challenge is that the sabot, enclosed orbital vehicle, and payload have to be able to survive not only 10,000 G lateral forces, but the orbital vehicle and payload have to manage the rocket forces when they kick in. The sabot is shed by that point, but it’s much easier to build something that will survive extreme forces in one direction than something that will survive extreme forces at right angles to one another.
The payload has to be able to survive both as well, which means that the engineering and packaging of the payload has just become harder. We’re not going to throw iron bars into space for processing with orbital solar smelters. Non-compressible liquids are possible, but liquids like to slosh, so the sudden change of forces would be really difficult to dampen. //
Third, the gripping component of the spinning arm has to be able to support the sabot at 10,000 gs and also release it in a microsecond without causing any wobble. That’s an extreme engineering edge case by itself. //
Just preventing the sabot from crumpling under the stress at the attachment point, or even folding in half is also seriously non-trivial engineering. 10,000 gs at what is necessarily a small set of attachment points around the center of gravity of the sabot leaves dangling sabot under serious strain at either end. The more gs you pile on, the more attachment points you need, and the less ability you have to release them instantly.
A 1,000 kg total package for a 200 kg payload at 10,000 gs is equivalent to 10 million kg of weight on earth. Electromagnets are absurdly strong, but a 3 Tesla magnet only puts out 522 psi, and the strongest electromagnet is 35 Tesla. That degree of magnetic field will also fry a lot of things. It’s unclear to me what their attachment solution is intended to be, but it’s expected to do an absurd job.
Fourth, the rotating arm’s moment of inertia is going to change radically and instantly at release. The buildup of velocity takes 90 minutes, so it’s easy to balance, but the release is instant, with a couple of tons of mass at 10,000 gs disappearing at the long end of the arm. //
Fifth, atmospheric buffeting at release will be non-linear. Hypersonic speeds in the bottom parts of Earth’s atmosphere are non-trivial, which is engineering speak for really hard. To hit orbit, it will be at serious multiples of Mach speed at ground level. So, also very, very noisy. Not a good neighbor.
My intuition — and it’s only a somewhat informed guess — suggests that the combination might not be surmountable on Earth. However, on the Moon or Mars, a lot of things become much simpler. No atmosphere or an incredibly thin atmosphere both eliminate or reduce the need to create a vacuum chamber in the first place, and make the hypersonic sabot’s interaction with the atmosphere immaterial. Much lower orbital velocity requirements mean that the issues related to 10,000 gs aren’t there, just a smaller but still absurd number of gs.
The wings program was launched in 2004 to promote the nascent commercial launch industry and the first recipient was Scaled Composites’ test pilot Mike Melvill, who rode SpaceShipOne to the edge of space in 2004. To qualify for the pin, one had to reach 50 miles in altitude. Just after Bezos launched with his brother and some Amazon employees in and autonomously operated Blue Origin in July, the FAA decided to tighten the qualifications for the pin by requiring that those receiving it actually do something to contribute to the safe completion of the flight (other than pay for it). In abandoning the program altogether, the FAA has also thrown out those restrictions and anyone who got weightless in 2021 and applied for the wings will get them.
The same question could well be asked of the LM's descent engine and the main engine on the Apollo service module, however, which did both need to fire in free-fall. In those cases, the smaller RCS thrusters on the LM or CSM were fired first, to "settle" the tankage and separate the fuel from the helium. In the LM case, this "ullage burn" was about 7.5 seconds. The first couple of service module burns -- typically for mid-course correction while en route to the moon -- generally didn't need an ullage burn prior, as the tanks would be full of propellant with little or no volume of helium. SPS burns later in the mission did require ullage burns. The RCS thrusters produced about 100 lbs of thrust each, and four would be used for the ullage burn, yielding roughly 1/200 g acceleration.
The same RCS ullage burn technique would also apply to a situation where the descent engine failed and the ascent engine needed to be used for abort from free-fall, or in flight testing of the ascent engine.
That, in turn, raises the question of how helium ingestion was avoided in the RCS thrusters, since they were also helium pressurized. In those cases, the helium was separated from the propellants by a teflon bladder, so the helium didn't mix with the propellants. This was more practical to do on the smaller scale of the RCS propellant tanks than it would have been for the larger engines.
NASA's Space Transportation System (STS) vehicle, better known as the Space Shuttle, used two single engine Solid Rocket Boosters (SRB) as Stage 0, an engineless external tank providing propellant for the three Space Shuttle Main Engines (SSME) on the orbiter as stage 1, and additional two Orbital Maneuvering System (OMS) hypergolic liquid-propellant rocket engines on the Space Shuttle orbiter as stage 2.
The two solid rocket boosters used roughly 500,000 kg (1.1 Mlb) of a 11-star perforated solid propellant cake of Ammonium Perchlorate Composite Propellant (APCP - a mixture of of ammonium perchlorate, aluminium, iron oxide, PBAN or HTPB polymers, and an epoxy curing agent) each, that provided 124 seconds of burn time with a specific impulse (Isp) of 269 s that provided 12.5 MN of thrust per SRB and the external tank that came in three different configurations (mostly progressively reducing tank's own weight) capacity was 629,340 kg (1,387,457 lb) of cryogenic liquid oxygen (LOX) as the oxidizer and 106,261 kg (234,265 lb) of cryogenic liquid hydrogen (LH2) as the fuel components of the bipropellant LOX/LH2 that provided 480 seconds of burn time with specific impulse of 455 seconds, resulting in 5.45 MN of thrust at sea-level (for the Super Lightweight Tank or SLWT, the last and most advanced of the three versions used with STS).
So to answer your question directly, not counting the OMS propellant as per the specifics of your question, the total mass of all propellants of the SRBs (stage 0) and the external tank (stage 1) was at launch of the STS 1,735,601 kg (3,821,722 lb). The solid rocket boosters provided roughly 83% of liftoff thrust for the Space Shuttle and were the largest, most powerful solid-propellant motors flown to date.
One might imagine that 60+ years of development must have produced large gains, but chemical rocket performance is fundamentally limited by the amount of energy in the chemical fuels, and the 1960s engines were already getting at least 2/3 of the maximum theoretically possible performance (see comparison table below). //
The usual primary metric is specific impulse.
But specific impulse is a somewhat unintuitive quantity to understand, so let's start with effective exhaust velocity, which is the average speed of an exhaust particle (in the backward direction). For example, the Rocketdyne F-1 engines used in the first stage of the Saturn V (the Apollo rocket) have an effective exhaust velocity of 2.58 km/s at sea level.
What does 2.58 km/s mean in terms of rocket performance? It means if you build a rocket whose weight is about 63% fuel, and you fire the engine in deep space until the fuel runs out, the rocket will now be going 2.58 km/s faster in whatever direction it was pointing: //
So, what is change in velocity, Δv, good for? In the solar system there are two main uses for Δv: launching from the surface to achieve orbit, and transferring from one orbit to another. The article Delta-v budget has some examples, but the most relevant to Apollo is the Δv to get into low Earth orbit from a sea level launch, which is (very roughly) around 10 km/s. That breaks down as about 8 km/s of required velocity to stay in orbit (any slower and you'll come back down) and 2 km/s spent lifting the rocket against gravity and pushing through the air on the way up. //
So let's take a quick comparison of ve for the F-1 and the SpaceX Merlin engine. This is a relatively fair comparison because both burn RP-1 (refined kerosene) and liquid oxygen in a gas-generator cycle. These characteristics are good for a first stage due to high energy density per unit volume and high thrust, although other fuels have better ve
F-1 2.58 km/s (sea level)
Merlin 2.77 km/s (sea level)
F-1 2.98 km/s (vacuum) 65% of max
Merlin 3.05 km/s (vacuum) 66% of max
Theoretical max 4.61 km/s (vacuum)
The theoretical maximum is based on the total chemical energy in the fuel. //
Finally then, what is specific impulse? It's obtained from ve
by dividing by the gravitational acceleration on Earth:
Isp=veg
where g is usually standard gravity, or about 9.81ms2. The resulting quantity has units of seconds. For example, for the F-1 at sea level, Isp=263s
What is the physical significance of Isp?
Well, consider our rocket from before with 63% fuel by mass. Suppose we start the rocket while it is sitting on the pad, let it just barely lift off, then hover just off the pad until it runs out of fuel (this assumes we can arbitrarily throttle the engine without affecting its performance, which is not realistic, but ignore that). Isp is how long it will hover. That is because, for every second of hovering, we consume 9.81 m/s of Δv in order to overcome gravitational acceleration accumulated during that second. After Isp seconds, all of our Δv is gone.
Glorified Desktop Support Wise, Aged Ars Veteran
NOV 22, 2021 12:56 PM
Cathbadhian wrote:
flerchin wrote:
Congrats Astra. Y'all beat Bezos to the club.BO's perpetual planning has really left them in a terrible place right now. Reputationally, the accumulation of lost contracts, scheduling delays, competitor successes, and rocket delivery complaints (unofficial, of course), don't add up to a company you want to throw cash at.
Well done, Astra.
Now, there could be a question of if BO (and ULA) can reach orbit before one of the small launch companies scale up like SpaceX did. It almost seems like there should be an equation where time to reach orbit is some function of funding, development time, and number of blown up rockets. Surprisingly, too much funding and not enough blown up rockets seems to greatly increase development time, perhaps exponentially.
Statistical Ars Legatus Legionis et Subscriptor
NOV 22, 2021 12:33 PM
DStaal wrote:
jbode wrote:
Damn, that thing was in a hurry to get off the pad.One thing I've learned from KSP that was mildly surprising, and I believe translates to real life: Higher TWR rockets are more efficient to launch. The less time you have to burn at full thrust the less fuel you need to carry, which means less fuel used, etc.
To a degree. Higher TWR also means mass used for additional engines which could just be used for more for more propellant. When you consider economics not just raw performance that is even more important. One ton of engines cost far more than one ton of propellant. Higher TWR also means higher drag losses. Higher TWR means you will hit max Q sooner in thicker atmosphere which may require more aggressive throttling (and thus losing some of the benefit of the mass you paid for).
All that means most orbital rockets tend to fall into a TWR range of 1.2 to 1.6 although there are notable exceptions at either end. Saturn V is sluggish off the pad at a initial TWR of 1.14. Electron has a TWR of 1.8. ///
[TWR: Thrust-Weight Ratio]
"I think that this flight really does prove out the approach we've taken." //
Astra never sought to build the best rocket, the biggest rocket, or the safest rocket. The California-based space company simply wanted to build a rocket that was just good enough, and to do it fast.
Early on Saturday morning, Astra proved the value of this philosophy by successfully launching a stripped-down rocket for the first time. The mission hefted a small test payload for the US Space Force into an orbit 500 km above the planet.
The launch came five years and one month after Astra was founded by Chris Kemp and Adam London in October 2016. With this weekend's success, Astra became the fastest company to reach orbit with a privately developed liquid-fueled rocket. With its Falcon 1 rocket, SpaceX required six years and four months. Firefly, Virgin Orbit, and Rocket Lab all needed seven or more years to successfully reach orbit.
To go fast, Astra decided to spend less time designing its rocket and more time testing it in real-world conditions. A first suborbital launch attempt was completed within two years of the company's founding, and Astra has been iterating on the vehicle's design since then. By using iterative design, Astra has had to stomach several failures along the way.
If you saw a rock on Earth like this, and you picked it up, it shouldn't be that heavy," another Melbourne Museum geologist, Bill Birch, told The Sydney Morning Herald in 2019.
The American astronauts calculated critical course-correction maneuvers on their HP-65 programmable hand-held during the rendezvous of the U.S. and Russian spacecraft.
NASA has previously discussed how nuclear propulsion technology could allow the agency to send humans to Mars more quickly than by using traditional chemical rockets.
"Nuclear electric propulsion systems use propellants much more efficiently than chemical rockets but provide a low amount of thrust," NASA has said. "Nuclear electric propulsion systems accelerate spacecraft for extended periods and can propel a Mars mission for a fraction of the propellant of high-thrust systems."
There are multiple types of nuclear propulsion that could be used in space technology. With nuclear electric propulsion, thermal energy from a nuclear reactor is turned into electric energy that powers whatever type of electrical thruster or propulsion tech that a spacecraft uses. With nuclear thermal propulsion, reactors heat up propellants like hydrogen and then the gas from that reaction is ejected, creating thrust. This can create a lot more thrust than electric propulsion systems.
The initiative, however, received no recognition from President Biden. One of Musk’s followers on Twitter asked: “The President of the United States has refused to even acknowledge the 4 newest American astronauts who helped raise hundreds of millions of dollars for St. Jude. What’s your theory on why that is?”
“He’s still sleeping,” Musk responded.
The Biden administration’s apparent refusal to acknowledge the mission comes after it snubbed Tesla, which Musk also leads, by not inviting it to an electric vehicle summit — because the firm does not have unionized workers. //
The Democrats turn their backs on Musk for two reasons. For one, many Democrats are radicalized and hate billionaires. They consider their wealth to be an egregious corruption and proof that the capitalist system is evil. They think the billions of Musk and others like Bezos should be taken from them and given to government programs.
The other part of the Democrat party, namely elected officials, don’t like Musk because it’s useful not to. They feel they have to adhere to the first group’s thoughts and feelings and so they turn their back on them. What’s more, they do it because they want to pressure Musk into adopting systems of control that would put him further under their thumb. As Daily Wire reported above, they snubbed Musk first because he’s not using union labor, and union labor and Democrats go hand in hand. //
While Musk is looking up and thinking about how to bring humanity the stars, the Democrats are looking at you and wondering how they can bring you under their rule. They can’t rightly do that if you’re too busy cheering on and wanting to support their enemies.
Democrats are not about the future of humanity, they’re about the future of their rule.
VAN HORN, Texas, Oct 13 (Reuters) - Having made a career out of playing an explorer of the cosmos, William Shatner - Captain James Kirk of "Star Trek" fame - did it for real on Wednesday, becoming at age 90 the oldest person in space aboard a rocketship flown by billionaire Jeff Bezos's company Blue Origin, an experience the actor called profound.
Full-Scale Model of Apollo 11 12 13 14 Command Module Control Panel (CMCP)
All or nothing. This project will only be funded if it reaches its goal by Tue, September 21 2021 2:03 PM EDT.
Measuring a massive 82" wide, 33" tall, and 7" deep, all representing that same vision of teamwork, peaceful exploration, engineering accomplishment, and pioneering spirit.
"You can now take the controls of a historic NASA spacecraft — literally.
A team of Hollywood prop and visual artists are offering replicas of the Apollo command module control panel. The museum-quality reproduction features every switch, knob and indicator that was used on board the first three missions to land astronauts on the moon and to bring the Apollo 13 crew safely back to Earth.
"It is here where the impossible becomes possible," team leader Mark Lasoff, an Academy Award-winning artist whose credits include the 1995 feature film "Apollo 13," wrote about the control panel. "It is here where humans and machines interface. It is here where every vital operation, including navigation, propulsion, communication and life support is calculated, calibrated and controlled intricately."
"It is both an engineering feat and a work of art," Lasoff wrote of the flight deck." //
Measuring an expansive 82 inches wide, 33 inches tall, and 7 inches deep (208 by 84 by 18 cm), the replica control panel was designed using the original blueprints for the NASA spacecraft. Lasoff and his team also used 3D scans of the Apollo 11 command module produced by the Smithsonian's National Air and Space Museum to verify their details.
The Kickstarter campaign is offering the full-scale metal replica for $3,900.
America's next trip to the moon may suddenly be delayed bit thanks to...PDFs?
A U.S. federal judge has granted the Department of Justice a week-long extension in its lawsuit with Jeff Bezos' space company Blue Origin. The reason? Large PDF files. //
According to Blue Origin, there are "fundamental issues" with NASA's decision. The company also claims that the agency was supposed to provide multiple awards.
However, the process has been delayed due to PDF problems. PDFs are a proprietary file format created by Adobe used primarily for documents. Attorneys for the U.S. Department of Justice say there have been a myriad of issues related to the PDF format.
According to the DOJ, there is more than 7 GB of data related to the case. However, the U.S. Court of Federal Claims' online system allows for only files of up to 50 MB in size to be uploaded. //
Instead of using the online file system, the U.S. government will transfer the documents for the case to DVDs.
Both Blue Origin and SpaceX agreed to the extension. NASA's contact with SpaceX is currently on pause until Nov. 1 due to the lawsuit. This latest development would seemingly extend that for another week.
Space exploration is currently on hold thanks to a lawsuit and a slew of pesky PDF files.
This is a revisitation of a post that I published in 2011, with the title “The Hubbert hurdle: revisiting the Fermi Paradox“ Here, I am expanding the calculations of the previous post and emphasizing the relevance of the paradox on the availability of energy for planetary civilizations and, in particular on the possibility of developing controlled nuclear fusion. Of course, we can’t prove that nuclear fusion is impossible simply because we have not been invaded by aliens, so far. But these considerations give us a certain feeling on the orders of magnitude involved in the complex relationship between energy use and civilization. Despite the hype, nuclear energy of any kind may remain forever a marginal source of energy.
Post revised and readapted from “The Hubbert hurdle: revisiting the Fermi Paradox” — Published on “Cassandra’s Legacy” in May 2011
https://cassandralegacy.blogspot.com/2011/10/hubbert-hurdle-revisiting-fermi-paradox.html //
It seems clear that planets are common around stars and, with about 100 billion stars in our galaxy, organic life cannot be that rare. Of course, “organic life” doesn’t mean “intelligent life,” and the latter doesn’t mean “technologically advanced civilization.” But, with so many planets, the galaxy may well be teeming with alien civilizations, some of them technologically as advanced as us, possibly much more.
The next step in this line of reasoning is called the “Fermi Paradox,” said to have been proposed for the first time by the physicist Enrico Fermi in the 1950s. It goes as, “if aliens exist, why aren’t they here?” Even at speeds slower than light, nothing physical prevents a spaceship from crossing the galaxy from end to end in a million years or even less. Since our galaxy is more than 10 billion years old, intelligent aliens would have had plenty of time to explore and colonize every star in the galaxy. But we don’t see aliens around and that’s the paradox.
Paradoxes are often extremely useful scientific tools. They state that two contrasting beliefs cannot be both true and that’s usually powerful evidence that some of our assumptions are not correct. The Fermi paradox is not so much about whether alien civilizations are common or not, but about the idea that interstellar travel is possible. //
But let’s imagine that an alien civilization, or our own in the future, avoids an irreversible collapse and that it moves to nuclear energy. Let’s assume it can avoid the risk of nuclear annihilation. Can nuclear energy provide enough energy for interstellar travel? There are many technological problems with nuclear energy, but a fundamental one is the availability of nuclear fuel. Without fuel, not even the most advanced spaceship can go anywhere.
Gravity is the weird, mysterious glue that binds the Universe together, but that's not the limit of its charms. We can also leverage the way it warps space-time to see distant objects that would be otherwise much more difficult to make out.
This is called gravitational lensing, an effect predicted by Einstein, and it's beautifully illustrated in a new release from the Hubble Space Telescope.
In the center in the image (below) is a shiny, near-perfect ring with what appear to be four bright spots threaded along it, looping around two more points with a golden glow.
This is called an Einstein ring, and those bright dots are not six galaxies, but three: the two in the middle of the ring, and one quasar behind it, its light distorted and magnified as it passes through the gravitational field of the two foreground galaxies.
Because the mass of the two foreground galaxies is so high, this causes a gravitational curvature of space-time around the pair. Any light that then travels through this space-time follows this curvature and enters our telescopes smeared and distorted – but also magnified.
Editor's Note: Aug. 3, NASA issued a statement over social media sharing that the space station "was 45° out of attitude when Nauka's thrusters were still firing & loss of control was discussed with the crew. Further analysis showed total attitude change before regaining normal attitude control was ~540°. Station is in good shape & operating normally." //
According to the report, Scoville took over mission control after the docking. It was actually his day off, but he was on site because he'd helped to prepare for the module docking and wanted to see how it went. He ended up taking over from the previous lead, Gregory Whitney, who had a meeting to attend, after docking, thinking it would be smooth sailing from there. But soon, a caution warning lit up.
"We had two messages — just two lines of code — saying that something was wrong," Scoville said.
After initially thinking the message could perhaps be a mistake, he told The New York Times, he soon realized that it was not and that Nauka was not only firing its thrusters, but that it was trying to actually pull away from the space station that it had just docked with. And he was soon told that the module could only receive direct commands from a ground station in Russia, which the space station wouldn't pass over for over an hour.
The crew, working together with ground teams, helped to counteract Nauka's thrusters by counter-firing thrusters on the Russian module Zvezda and Progress cargo ship. Additionally, 15 minutes after starting to fire, Nauka's thrusters stopped, though Scoville said he didn't know why the thrusters did so.
But this combined series of events and counteractive measures allowed the team to get the station to stop moving and return to its correct position.
"After doing that back flip one-and-a-half times around, it stopped and then went back the other way," Scoville told the New York Times.
On Monday (July 26), astronauts said goodbye to a cornerstone of the International Space Station and captured stunning images of the compartment burning up in Earth's atmosphere.
A Russian Progress cargo vehicle towed the module, called Pirs, away from the space station and down through Earth's atmosphere to ensure the module burned up completely and reduce the odds of any large chunks making it to Earth's surface.
"Quite a strange feeling to see a part of your ship fly away in mid-air (so to speak — no atmosphere here duh)," European Space Agency astronaut Thomas Pesquet wrote in a statement shared with the photographs on Monday. //
Russia had launched its Pirs module in 2001; since then, the module, which served as a port to the space station, hosted more than 70 different capsules and supported Russian cosmonauts conducting extravehicular activities, or spacewalks. //
To make room for Russia's new science module, dubbed Nauka, which launched on July 21 and will arrive at the station on Thursday (July 29), Pirs had to go. Yesterday's fiery retirement ceremony marks the first time a major component of the International Space Station has been discarded.