AckSed

Standardised screw threads for nuts and bolts the secret to Crystal Palace's speedy construction: https://arstechnica.com/science/2024/10/how-londons-crystal-palace-was-built-so-quickly/

Resurrecting this topic to talk about monopropellants, spurred by this article talking about a company getting money to develop 'green' monopropellants for satellites: https://payloadspace.com/benchmark-wins-4-9m-afrl-ascent-award/ But to talk about it and why they're 'green', I want to go over the classic and lesser-used monopropellants first. (Monopropellants for thermal and electric thrusters are a different use-case as they take energy from external sources, though they're fascinating nonetheless.) Generally, a monopropellant used as a fuel is fed over a catalyst bed, exothermically decomposing it and using that heat energy to accelerate it through a nozzle. It makes throttling as simple as turning a valve on and off while being an improvement on cold-gas thrusters, which lose energy as they continue to operate. Nearly all monopropellants are used in RCS thrusters, so performance is less desired than storability Hydrazine: With the chemical formula N2H4, it's one of the most popular monopropellants for a number of reasons. First is performance. There's a lot of energy bound up in that nitrogen bond, there's all that light hydrogen for exhaust velocity (vacuum specific impulse of 220 seconds) and it's a tiny bit denser than water, liquid in between 2 deg. C and 114 deg. C Second, storability. The USAF drove the bulk of the research here (because ballistic missiles) and it has a long history as a storable liquid propellant. Not that it's perfect in that regard. Even back in the Apollo era, it was known to slowly decompose in the tank; the tank pressure in Mariner IV rose from 20 psi (1.38 bar) when it completed its flyby of Mars to 80 psi (5.51 bar) two years later when they re-established contact. (Source: "The Status of Monopropellant Hydrazine Technology", JPL, 1968.) The toxicity issues, carcinogenic attributes and the contamination issues are both well-understood and well-known. The images of people in positive-pressure suits working around the Space Shuttle on landing, which used it in its (bipropellant) RCS thrusters are fairly widespread. It's also why the European Union wanted to phase it out entirely under the REACH act, but eventually left in an exemption for spaceflight use. It is still the monopropellant of choice from a performance standpoint. Its derivatives monomethylhydrazine (MMH) and unsymmetrical dimethylhydrazine (UMDH) are also used as either mixtures with hydrazine, or additives in hypergolic bipropellant engines. ------ Green propellants mitigate the cost and risk associated with the transport and storage, cleanup of accidental releases, and human exposure to traditional propellants. Hydrogen peroxide: Always the bridesmaid, never the bride in US rocketry, H2O2 has a long and storied history. The earliest ICBMs and the current Soyuz 1st and 2nd stages (but I repeat myself) still use monopropellant peroxide turbines to power the turbopumps in the RD107/106. Thrusters that use it for RCS are rare, but available off-the-shelf. Indeed, the Vega-C uses H2O2 thrusters as RCS on its upper stage. The performance is OK, with 160s vacuum specific impulse and roughly the same density as water, depending on the concentration. This is the key. Peroxide is a strong oxidiser, and decomposes exothermically and releases oxygen, which means it will react with a wide variety of substances. It decomposes slowly and spontaneously as the temperature rises, which means tanks have to have a vent to equalise pressure. This may be a larger ask on a satellite than on a disposable upper stage. The higher the concentration, the more reactive it becomes. The linked RCS thrusters use 87.5%, which is no joke but relatively easy to ship and handle, as long as you keep the equipment and tanks clean. It can be handled with protective gloves, overalls, boots and eye protection as opposed to full environment suits. 95-98% peroxide, popularly called "high-test peroxide" or HTP, is trickier. Most of the hopes and dreams of the SSTO efforts hinged on it and kerosene, and the British space program were experts at it. As high-energy oxidisers go, it's almost benign but it's still not safe, with splashes on organic materials liable to flare up quickly with a few sparks or even explode. (LOX has the same issue, but something soaked in peroxide looks merely bleached/wet, not visibly smoking with frost.) Further, the stabilisers it is usually shipped with to stop it decomposing in the tank also stop it decomposing when passed over a catalyst, which precludes its use in both certain illegal chemical reactions and perfectly legal rocketry. You have to secure a supplier willing and able to provide it unstabilised at 98%. ------ Dinitrogen monoxide: AKA "nitrous" or "nitrous oxide" or "NOx" or "laughing gas", with the chemical symbol N2O. This is an oxidising gas at room temperature, that can be liquefied, is self-pressurising and can be encouraged to decompose when passed over a heated catalyst bed, or simply heated at sufficient pressure. Its specific impulse can be up to 180s. It is also safe enough to be sold in low-pressure canisters to the public for whipped cream. (Round where I live, it also is used as a recreational drug. :-/) For these properties, it is seeing increasing interest in both monopropellant and bipropellant systems (usually with butane), as it does not decompose, but simply sits there in the tank. ------ Mixed cryogenic oxygen/methane: Only mentioned in Ignition! once, because it's a very, very bad idea. We've said before that a relatively small amount of oxidiser can turn organic material explosive. This is worse. Bright light can make it explode. ------ Energetic Ionic Liquids: This consists of oxidizer salts dissolved in aqueous solutions, called Ionic Liquids (ILs), mixed with Ionic Fuel (IF) or Molecular Fuel (MF), forming a premixed propellant. The propellant blend performances are increased by the addition of other fuel components. The EILs can be further categorized into HAN-based (Hydroxyl Ammonium Nitrate) and ADN-based (Ammonium DiNitramide). They stretch the definition of a monopropellant, but as it's technically all in one tank, it counts. Rocket Labs uses an unknown EIL in its Proton kick stage. This takes us to the header article. ASCENT is actually AF-M315E, which was first developed by the Air Force Research Laboratory way back in 2010. It's a mixture of hydroxyethylhydrazinium nitrate (HEHN) and hydroxylammonium nitrate (HEN), water and an unknown amount of other stuff, including methanol. On first glimpse it's great. It can be handled in the open, without respirators, and only eye protection and rubber gloves. It has a prospective ISP of 235s, better than hydrazine. It has a lower freezing point so the tanks need to be heated less. You can use plastic like polypropylene or PTFE with it (for bladders), You can tip this potent pink propellant into a wood fire with only a "mild burning reaction". It's perfect. Except it's a little finicky about metal tanks, requiring titanium-aluminium-vanadium alloy or platinum/iridium or gold plating for long-term storage and burns hotter than hydrazine. Only now has this company gotten money to redesign the thrusters to cope with the much higher temperatures and eliminate the expensive catalyst bed.

Sierra Space working on storing and dropping supplies from orbit for the Air Force: https://spacenews.com/the-air-force-is-exploring-the-potential-of-space-vehicles-to-rapidly-transport-critical-supplies-from-orbital-warehouses-back-to-earth/

Tiny when compared to the Shuttle SRBs; Vulcan's big. The GEM 63XL is built by Northrop Grumman and is taller, wider and heavier than Rocket Lab's Electron: 22m high, 1.63m wide, 53.4 metric tons versus 18m high, 1.2m wide and 28 metric tons. I was thinking it's fortunate that the lower stage is built up enough to withstand the force of 6 SRBs firing at once.

It was originally a Kickstarter project, so that's why it's a little, er, 'quirky'.

Someone needs to check the quality control on those SRBs. The nozzle should not fall off after you light it.

https://arstechnica.com/space/2024/10/ulas-second-vulcan-launch-will-pave-the-way-for-military-certification/ tl;dr ACES or something like it is still of interest to Tory Bruno. They are still developing it and Integrated Vehicular Fluids (the plan for autogenous pressurisation, RCS propellant and power for pumps from recirculated gasses via a small piston combustion engine) though there's no real money behind it (I think). If they do extend the on-orbit lifespan, that extends the variety of missions. Perhaps even propellant depots (maybe for that nuclear-thermal rocket DARPA's touting). Of relevance to the flight is they're looking to try some things out with the Centaur upper stage to reduce boil-off and extend its lifetime in orbit.

Two pieces of news in one, here: first, ESA is building a lunar simulation facility in Germany; second, the lunar gravity simulator is essentially springs on strings, but upgraded to the "Puppeteer" system for greater accuracy and possibly simulating Mars or other gravities: https://payloadspace.com/esa-astronauts-get-new-tech-for-moonwalking-practice/ Call me mad, but this sounds like damn good fun, especially as they plan on a rig not just for people, but for vehicles too.

Most of these companies do operate small to medium-sized constellations (a lot of cubesats are for EI; Planet has 300, with 150 active), but how do you compete (they ask) with a company that has demonstrated the ability to both build at least 6000+ satellites in a few short years, and operate more than 4000, and launch more often, with more mass, than the next largest country? Indeed, quite a few of them have taken advantage of their Transporter missions to get up there. It's a bit like hearing that, oh, I don't know, Greyhound buses will start shipping their own robotic workers to the premises of the business that you work in. Since they own the transport company, they can charge ticket prices to themselves at cost, the business saves money and you're left competing with workers that do not get tired, need breaks or complain about working conditions. In desperation, you quit, then sign on with another company that designs and builds their own robots, but they've lost the first-mover advantage, the robot-worker market has already begun to race to the bottom and Greyhound worker-robots are frickdamned everywhere. Analogy ran away from me there. Point is, I'd be nervous too, and, like some of these other companies, hoping I could latch on to the coattails of Starshield.

Earth-imaging companies worried Starshield (which, among other things, could also do earth-imaging) might start eating into the money they receive from the government: https://spacenews.com/earth-observation-companies-wary-of-starshield/

Hydrosat, the infra-red imaging company mentioned in the film, that sells its services to farmers to increase their yields, has broadened its reach: https://spacenews.com/hydrosat-extends-reach-in-latin-america/

MAXAR's SEP unit bus is ready to be attached to the Gateway PPE module, and is now in propulsion testing at NASA Glenn: https://payloadspace.com/an-electric-solar-powered-future-maxar-space-systems-ppe-to-propel-nasas-artemis-gateway/

Radian progressing to flight-testing of a model: https://spacenews.com/radian-aerospace-begins-tests-of-spaceplane-prototype/

One key technology is molten oxide electrolysis, where it doesn't care if it's Lunar regolith or marginal Earth basalt, it can extract iron, silicon and aluminium just the same, with oxygen as a byproduct.

Not only that; Phil Eklund is an ex-aerospace engineer who has been refining High Frontier (with the help of others in Ion Game Design) for decades. To give an idea of how grounded this is in speculative space science, there are citations in the game manual, every faction is real or based on a real organisation, and every piece of technology is listed in an appendix, each with a citation to the design or concept it originally came from. It's a time-capsule of 2020 astrofuturism. I love it. Edit: if you're willing to put up with the clunkiness of VASSAL, there is a free HF4All module. The downloadable rules are available on Ion Games' website and it has a solo mode.

I highly appreciate him showing what his initial thoughts were and how his process evolved. That's good stuff.

Looks good, looks really quite good.

Cool and amusing way to calibrate the spacecraft before it goes off to image Jupiter's moons: https://www.esa.int/Science_Exploration/Space_Science/Juice/Juice_confirms_that_Earth_is_habitable

This is exactly how the Appendix in the boardgame High Frontier describes its (inhabited) space-mining operations: the robots are on the surface of the benighted spacerock while the workers are orbiting in an artificial-gravity habitat and telepresencing in.

Totally. ...the beat of that thruster firing was unexpectedly good. With the violin recital, I think we can call this the most musical flight of Dragon so far. :-)

The 'trunk' also being a berthing mechanism/docking port may also be a bit of future-proofing. Say Orbital Reef becomes a thing and they decide an expanded ring is more optimal. Redesign the trunk, a solid rocket booster extra and away you go.

Heeere am I/Rolling in a tin can: https://europeanspaceflight.com/nasa-greenlights-next-phase-of-italian-lunar-habitat-project/ Thales Alenia given the go-ahead to make the... modest mobile moonbase.

Is this a case of, "Anything Bezos can do, I can do better"?

Oh yeah, thanks to that documentary, I now know what the 'can' on the end of the robot arm is for - it's a launch mechanism for smallsats. I was a bit confused when they called it an air-lock, but that is how it works: dock 'can' to docking port, equalise pressure, open airlock; load smallsats, close hatch, vent, attach robot arm, undock and use arm to point firing mechanism away from station.

Very Iron Man. "OK, cut the power."