The Guild of Icarus: Aerospace Engineering and Aeronautical Club

[J. Wilhelm]

Artemis I was given the "go" to launch this morning at 1:04 am EST, 6:04 UTC/GMT when a two hour launch window will open. That's tonight for us in the US and today this morning for you on the other side of the pond!

The first stage of the rocket was filled and topped off with oxygen without issues. Liquid hydrogen for the first stage continues at high speed. The upper stage is 18% full with hydrogen, and 44% full with oxygen. No issues reported.

Weather is 90% favourable for launch.

The video feed on NASA.gov is live now:

http://youtube.com/watch?v=21X5lGlDOfg

[von Corax]

The launch was, by all accounts, a roaring success.

https://www.cbc.ca/news/science/artemis-1-third-attempt-1.6651139

[J. Wilhelm]

The launch was, by all accounts, a roaring success.

https://www.cbc.ca/news/science/artemis-1-third-attempt-1.6651139

More than that, it was vindication for NASA employees who have endured accusations of political bias and not being qualified to develop, engineer and conduct the Artemis space program.

The Artemis I mission is proceeding nominally. No problems have been reported so far. At least the SLS launch vehicle operated flawlessly, cementing it's position as the only viable interplanetary launch system at the moment.

[J. Wilhelm]

Some more photos

[J. Wilhelm]

[J. Wilhelm]

NAS Artemis-1 mission has come to and end. The Orion spacecraft has reentered the atmosphere and splashed down off the coast of California after swinging around Australia in a northbound path.

The return mission involved skipping over the atmosphere twice, to slow down from a 24600 mph/ 39600 km/h reentry speed. 

There's a lot of info regarding the orbital Artemis I used to get to and back from the moon.

The orbits of the moon (green) and Artemis 1 / Orion (purple) relative
to the center of gravity between the Moon and the Earth.

Also, I've tweeted/tooted (I'm on Mastodon as well) on details on Orion's reentry thermal protection system and a whole bunch of cool photos. Also, I should note that the ESA was heavily involved with the Service Module, so there's more info on that. I'm not sure if you guys want to read about it. So, I'll stand by to see if I get opinions on this thread!

[J. Wilhelm]

The forum is kind of quiet at the moment. I'll be posting more progress and projects soon, but I thought this quiet period would be a good time to drop this video I found online.

It's the IMAX documentary film "The Dream is Alive" about the Space Shuttle system. This is a presentation by the Smithsonian Institution's National Air & Space Museum & Lockheed Corporation In Association with NASA. The original film was narrated by Walter Cronkite. It's got good sound but it's a bit low, so raise the volume and play in stereo.

https://vimeo.com/541887307

[Sorontar]

I have been thinking (not very hard) and wondering, if a base was set up on the Moon or Mars, with low gravity and not a dense atmosphere, could airships be a cost effective way to get around (rather than landcraft)? Could you use something other than hydrogen or helium or would the problem not be with the gravity and more with the lack of atmosphere, so there is nothing to be lighter than?

Sorry if this has already been discussed.

Sorontar

[J. Wilhelm]

I have been thinking (not very hard) and wondering, if a base was set up on the Moon or Mars, with low gravity and not a dense atmosphere, could airships be a cost effective way to get around (rather than landcraft)? Could you use something other than hydrogen or helium or would the problem not be with the gravity and more with the lack of atmosphere, so there is nothing to be lighter than?

Sorry if this has already been discussed.

Sorontar

Ahh, yes! Da Vinci on Mars! No, I don't think it's been discussed this way before, actually.

In theory, a rigid balloon made from unobtainium containing a perfect vacuum would yield the theoretical maximum buoyancy you could ever get out of any medium (surrounding) of a given non zero density. I think Leonardo Da Vinci posed this very problem.

You get where I'm going. There's a final limit. The problem with buoyancy is that you depend on the ratio of mass density of surround medium or an atmosphere to the mass density inside the envelope to generate lift. In a free body diagram of the floating vessel, the weight of the surrounding medium you're displacing must be equal to the weight of the vessel and envelope for equilibrium, or alternatively the weight of the medium displaced must be greater than the weight of the vessel and the gas contained therein for a positive climb rate (acceleration).

That's what makes wooden and even metal hulled ships so practical in the ocean on Earth, with relatively little volume needed inside the vessel: water is very dense. The space inside a wooden ship approaches the density of air, 1000 times less than the density of water.

Airships on the other hand need to displace far more volume because the ratio of density of water to air (the medium) is 1000, so to lift the same hull weight, the airship's envelope needs to be much bigger than a wooden ship at the density of air. Needs 1000 times more volume than a water craft.

The concept is not new for the topic of exploration on other planets. But material constraints (strength of fabric and weight of fabric) come into the picture (not mentioning exposure to radiation, harsh conditions, etc).

On Mars it's definitely a more difficult task than on Earth. On Mars, you only have 1/3 the gravity, so that helps you, but the atmosphere density is much lower than on Earth, less than 1%. Not as bad as the ratio between water and Terran air, but still a problem. The volume required to lift the same ship on Mars is ~100/3 or say 33 times larger than the equivalent airship volume on Earth.

So it's doable but challenging relative to Terran airship design due to the size of the envelope. There's a silver lining, though: because the average molecular weight of Martian air is higher (carbon dioxide) relative to Mars' low atmospheric pressure (when compared to Earth), the pressure differential between the inside and the outside of any *rigid* envelope is lower on Mars. If this was a nitrogen oxygen atmosphere the pressure differential would be higher. You can take advantage of that low pressure differential if you're willing to entertain a rigid envelope.

You see, to keep the envelope realistically small, some of the methods proposed and studied seriously include a variation of the method proposed by Leonardo Da Vinci: a rigid envelope with a partial vacuum (Yes I know!). No lifting gas involved, regardless of ballast method.

https://www.spaceanswers.com/futuretech/future-tech-martian-airships/

https://www.nasa.gov/directorates/spacetech/niac/2017_Phase_I_Phase_II/Evacuated_Airship_for_Mars_Missions/

Also, there are many scholarly papers on Martian exploration by way of lighter than Martian air craft - I haven't read this one, it's just an example of where to look. Honestly, I haven't even thought about the problem, but it's a very interesting topic.

https://arc.aiaa.org/doi/abs/10.2514/6.1999-896

Alas, the case for a Moon airship is non existent I'm afraid; the medium density is zero, and therefore a sphere made from unobtainium with a perfect vacuum within, would give you zero buoyancy, and the only force acting on the airship is its own weight including the envelope's weight.

Da Vinci will go to Mars, but not the Moon.

[Hurricane Annie]

I remember when Australia II had its legendary winged keel and that was regarded as a such a novel concept. Certainly, the power of the wind can really move you, whatever your craft

Class 5 Land yachts racing and fails on 90 Mile Beach

Everyone wanted a winged keel after that. I recall  the big kerfuffle over the voluminous "skirts " put around the bottom of competing boats , to protect them from the prying eyes of rival teams.

I'm not one for such things usually , those land yachts look tempting though. They could take off  as a recreational adventure sport , now that tourist travel has opened up again

[Hurricane Annie]

I don't post here very often, and much less on the subjecty of sailing. But the last time I kept with sailing technology it was the late 1980s and I was a young lad starting college in San Diego, which is what introduced me to the America's Cup and that disastrous international scandal between New Zealand and the United States. The issue being lawsuits back and forth over what kind of technology could be used to meet the race requirements, and after a bitter complaint from the USA over certain technology used by New Zealand, the Americans decided to retaliate by bringing a rigid-sail catamaran as allowed by the loopholes in the vaguely defined rules of the race...

https://en.wikipedia.org/wiki/1988_America%27s_Cup

But after not paying attention to the sailing technology over the last 3 decades, I saw today on NBC Sports Network the latest race beween the UK and Italy in the 2021 Prada Cup which is taking place between January and February of this year (currently ongoing).

https://www.skysports.com/more-sports/sailing/news/30786/12185095/36th-americas-cup-stevie-morrison-talks-development-favourites-and-the-prada-cup

What I saw gobsmacked me. The easiest description of the craft is a racing craft with dual articulated hydrofoils, each *with functional ailerons*, on a hull that acts as a lifting body (airfoil cross-section), naturally a wing plus a sail, and oh yes, the thing can cruise up to 45 knots and turn "on a dime" to tack using said ailerons and rudder. No engine of any kind, just the wind, and the hull barely gets to touch the water.  So there's so much going on that I'm going to post one of the races, and let you marvel at these craft.

Full Race Replay | Day 1 | PRADA America's Cup World Series Auckland, NZ

From a non engineering or nautical design perspective -
I've never been much taken with watching sail boat competitions. They were a bit boring. I avoided them. Until a friend mentioned some international yacht race in the South Island that was being televised. [She is more interested in rich boaties, than actual boats]. She mentioned the scenery , so I switched on .

I was completely taken aback by the modern racing yacht designs. They were perching on the water ready to strike, with giant metal insect legs straight out of a scifi movie. It got me watching

[J. Wilhelm]

SNIP

From a non engineering or nautical design perspective -
I've never been much taken with watching sail boat competitions. They were a bit boring. I avoided them. Until a friend mentioned some international yacht race in the South Island that was being televised. [She is more interested in rich boaties, than actual boats]. She mentioned the scenery , so I switched on .

I was completely taken aback by the modern racing yacht designs. They were perching on the water ready to strike, with giant metal insect legs straight out of a scifi movie. It got me watching

Indeed, sailboat racing was never something I knew much about or watched. The only reason I knew something about it, is because when I moved from Mexico to the US, I settled in San Diego, right when the controversial America's Cup was taken back by Dennis Conner with the 12 ft long rigid sail (wing) catamaran "Stars and Stripes 87.". The ship was docked right next to a park and shopping center I frequented, so I got to see the ship in person

[J. Wilhelm]

In other news, I very seldom post anything by SpaceX, but a couple of days ago the complete Starship two stage rocket was launched for the first time.  While SpaceX and Elon Musk enjoy near cult (or full cult) status online, it's during this launch that you see the real limitations of the so called "iterative design," where systems are designed partially, tested to failure, then redesigned and flown again, over and over, until you have a viable system.

In the past, this design approach applied to Falcon 9 and Heavy Falcon vehicles has forever changed the field of rocket, forever changing the expectation of a rocket as a disposable vehicle.

Unfortunately, while the approach was very successful on the development of rocket stages, the philosophy has come back to haunt SpaceX, because when you design a rocket you have to design "Stage Zero" otherwise known as the launch pad.  It looks like the initial shock from engine start and acoustics generated by the enormous thrust of Starship cracked and literally pulverized a "bench" styled launch platform known as the "launch ring." The launch ring was only standing on top of a concrete platform.

Aerospace engineers who work at NASA developing launch platforms, explain that gas pressure is enough to crack concrete and inject high pressure gases into the soil, with enough power to lift large pieces and repeat the injection process, eventually creating a vertical jet of burning gases and debris flying upwards at high angles. For that purpose, "thrust diverters", basically a system of channels, tunnels and ramps are built upon a massive platform to divert the flow sideways in a safe manner.  In spite of SpaceX' collective human expertise, they chose to not built a diverter for what is basically the biggest, most powerful rocket ever assembled. Speculate at will why they chose not to do build a diverter (Baffled, we're debating that decision among the engineering community right now).

The end result was a giant crater in the ground with debris including very large chunks of concrete flying very far away from the launch pad, impacting launch facilities and much further than that, covering the township of Boca Chica in "sand" made from pulverized concrete and regolith soil in the area. There were some interesting souvenirs found by locals and tourists to be found all around.

Piece of a hexagonal thermal insulation tile on Starship's hull.
Now you know how the tiles are attached (metal clips).

It's quite probable that some of that blown debris flew upward and impacted several engines and one hydraulic system. It's also unlikely that the FAA will grant SpaceX permission to launch again anytime soon without a complete redesign of the launch pad. So it's all speculation right now, but I wager this is going to set the Starship program many months if not years back. Bad news for NASA too, since the Starship 2nd stage was selected as the Lunar Lander for the Artemis Moon program. It may be time to restart the bidding process and select a fallback landing vehicle from the other two industry conglomerates who submitted their bids to NASA, which will probably sound like music to various State Senators in Congress, not to mention aerospace companies.

I'll let rocket aficionado Scott Manley tell the rest of the story as it happened a couple of days ago.

http://youtube.com/watch?v=w8q24QLXixo

[mizzarrogh]

Interesting, Honestly spaceX does not interest me as much as the vintage technology, but i was a bit suppried when i red Your post here since this is basic knowledge that has been known for decades (at least since the 1940s), even smaller rocket engines, like the Russian RD-253 will do this on a platform constructed this way. However i think the Russian base are made with a tunnel system made of a special concrete mixture, i am not sure what it is, but it seem to be many times stronger than regular concrete, the modern mixtures used in the Swedish nuclear powerplant walls are even stronger and i seen videos where they crashed a decommissioned fighterplane into a test piece and the plane was literary pulverized, but the concrete wall barley had a dent, regular construction concrete had been pulverized with a fraction of that force.

[von Corax]

The latest from today's Hackaday: Sharkskin Coating Reduces Airliner Fuel Use, Emissions.

[morozow]

Comrades! Happy Cosmonautics Day!