AckSed

Glad to see that the prop-transfer test was a success- *double-take* *searches* Ah! I see hot-gas thrusters are still/back on the menu. I'd hoped for this, if only for the coolness factor. Edit: You know, if this is pulled off first time, we essentially have a functional launch system. Sure, it's far, far too heavy for reusable mode, but expendable would be well within reach.

I can't speak to the first, but yes, concrete will cure in a vacuum: https://space.nss.org/wp-content/uploads/Lunar-Bases-conference-2-518-Lunar-Concrete-For-Construction.pdf In fact, the concrete ended up being stronger, and did not lose as much water as thought. The real challenge is that concrete's compressive strength is not as much of an advantage in lower gravity. If making a pressure vessel out of it, the tensile strength is needed more - and that has historically been lower. Reinforcing it with glass fibres spun out of melted regolith may be needed. Last year, concrete was flown on the outside of the ISS, and made inside: https://www.concrete.org/publications/getarticle.aspx?m=icap&pubID=51738695 Extracting sulphur from troilite (an iron sulphur ore found on the Moon), melting it and mixing in ground-up regolith simulant has been tested, as the same technique's used to make acid-resistant sulphur concrete on Earth. The strength was lower but still fine. However, there are concerns that the sulphur would sublimate away in vacuum, and you do have to pre-heat the mould or you will have voids in the centre. Its advantage is that it's easily recyclable: heat it up and recast it. I've seen one video of railway sleepers made of the stuff being recycled this way. Amusingly, astronaut pee has been considered, as urea acts like a plasticiser in "geopolymer" concrete (regolith plus sodium silicate and sodium hydroxide), allowing the use of less water: https://www.esa.int/Science_Exploration/Human_and_Robotic_Exploration/Astronaut_urine_for_building_a_Moon_base Using it as mortar for sintered regolith blocks is also an option.

https://arstechnica.com/science/2024/04/metafluid-gives-robotic-gripper-a-soft-touch/ tl;dr adding hollow rubber spheres to a liquid allows you to make a colloid that decreases in volume but doesn't increase in pressure when exerting an external force. Thus, if you overpressurise a 'soft' gripper, the force it exerts does not exceed a certain threshold. This lets you engineer behaviours without using any control algorithms or electronics. It can be tuned by varying the size of the spheres, and stepped by adding different sizes of sphere. By reducing the size of the spheres to micrometre sizes and using the right materials, they found that they could also tune the rheology (thickness) and opacity with pressure, as the clear spheres collapsing turned themselves into something like lenses. I love simple things like this that have emergent behaviours. I don't love the resistance the researchers faced because "this was not an interesting idea".

Do I smell the sour pickle-juice whiff of sarcasm about your comment, sir? It would be cool to see, 'tis all.

He had the same apologetic, "please bear with me as I run into more delays" energy about him when explaining Starship V1's current payload, as he did way back when he was explaining to the investors of Tesla why they didn't have their (original) Roadster yet.

It's interesting to see that the Curie kickstage will release the first sat, move up to a 1000km orbit to let the sail go, then come back down, circularise and deorbit itself. Pretty impressive. Edit: Curie engine really is tiny. Edit 2: aww, they're not covering the solar sail deployment.

https://www.space.com/rocket-lab-nasa-solar-sail-tech-launch-april-2024 This slipped under the radar, but it's highly interesting to me. While this is essentially the last whimper of NASA's solar sail missions - Solar Cruiser's funding was cut - it's still a solar sail!

As a postscript to the thread, here is Ivan Bekey in 2000, champion of reusability and SSTO inside NASA, wondering why Shuttle-derived launch vehicles are being considered as "affordable" competitors to the 2nd gen. RLV: https://spaceref.com/press-release/testimony-of-ivan-bekey-before-the-house-science-committees-subcommittee-on-space-and-aeronautics/ The other competitor was the Venturestar. We know how that turned out. :-(

Says here it was carrying a fleet-leader 1D that had done 22 flights: https://www.americaspace.com/2024/02/23/spacex-launches-record-setting-merlin-engine-returns-record-tying-booster-to-safe-landing/

Well of course. Which is why this is designed to track subtle gravitational shifts from the norm in astronomical observations.

That dark energy's a bit elusive and hard to track. I'd better use the BIG lens: https://www6.slac.stanford.edu/news/2024-04-03-slac-completes-construction-largest-digital-camera-ever-built-astronomy

Dig that wood veneer: https://www.esa.int/Science_Exploration/Human_and_Robotic_Exploration/Lunar_I-Hab_mock-up_all_set

That's genuinely impressive. I wonder why it wasn't used before - fragility?

Isn't the E-2 one of the few non-Russian engines using oxygen cooling? And don't they have a Russian propulsion engineer? That might explain it running oxygen-rich.

And this is a card in High Frontier 4 All. It's the "Nuclear Drill" Robonaut. Pretty good card.