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Rob:
I don't know enough to respond fully to what you asked in post #1 above. But I will say what I do know.
The cold soak up there in Arctic Canada does present some pretty serious problems operating gas turbine engines. It usually takes a wide-cut fuel to get reliable ignition and operation, when the plane and fuel are that soaked-out that cold or colder. Such fuels would be Jet-B/JP-4 (pretty much the same product sold to different customers with different specs). The JP-8 that most modern military jets burn is not a wide-cut fuel, but a kerosene, rather similar to JP-5/Jet-A/Jet-A-1. Freezepoints vary with the spec a little, but fall in the -58 to -65 F range (-50 to -54 C). Wide cut will successfully go colder than that. Gasoline goes much colder still. It is not the actual freezepoint, but the cold vapor pressure which governs the vapor/air ratio in the combustor cans, that is the real issue.
I am very impressed by the 2 gee maneuver capability at 50,000 ft altitude in that RCAF spec. Service ceilings for jet fighters usually have been in the 50-60,000 foot range since the Korean War, right down to the present day, with exceptions like the U-2 and the SR-71/A-12 family. Service ceiling is defined in the FAR's to be the altitude at which max power climb rate is down to the almost-imperceptible 200 feet per minute. Military specs are similar. There is no maneuver at that service ceiling condition, the airplane can just barely fly unaccelerated straight and level. It's easy to stall at high altitude, and the stall danger is a violent spin, in air too thin to prevent inertia coupling. (BTW, the larger vertical fin on the B-17 from the E model of 1940-onward was a response to this same kind of high-altitude spin risk.)
The "combat ceiling" of 60,000 feet in the spec is not the service ceiling, not with a spec'd cruise at 70,000 feet! That would be one impressive high altitude airplane! I suppose the SR-71/A-12 might be roughly comparable with a Mach 3 to 3.2 max cruise at 85,000 feet. But those planes burned an early version of thermally-stable jet fuel designated JP-7. There is no JP-7 any more, but it would be similar to the kerosenes JP-5, JP-8, and Jet-A/jet-A-1. Wouldn't work well at all in Arctic Canada.
As for burning-out engines in a fast climb, there is a time limitation for operation at full power, because turbine blades, combustor cans, and afterburner/nozzle hardware just gets too hot at the max power setting. You can only do that for a very few minutes. But, it takes full power to climb fast. The "trick" really is being able to handle the heat long enough to get to high altitude at full power, to meet the time spec. If the engine was not designed to operate that long at max power, there is little you can do to meet the tougher short time spec to high altitude.
This effect was manifested in a different way in the Mig-25 Foxbat. That airplane, if carrying no external stores at all, could fly as fast as Mach 3.5. Its engines were short-life at only 500 hours. And you did not overhaul them, you simply replaced them. This obtains because of the max power setting for long intervals required to intercept at Mach 3.5, or to intercept at the redline Mach 2.8 and near-max power with external stores. At max power, engine stuff just gets hot. And at high supersonic, the inlet air is rather hot, which makes the whole problem worse. Carrying stores, the issue was vibration from the aerodynamics around the stores, but with the drag of the stores, it wouldn't have gone much faster, even without vibrations.
If you really want to fly high altitude with handling practicality, you must fly well-supersonic. The U-2 was subsonic, with a service ceiling altitude somewhere around 70,000 feet. But subsonic like that, the difference between stall speed and max speed was only 5 KIAS, even with that huge wing. And that huge wing made landings difficult indeed. The wind can upset you all too easily with a landing speed that low, in an airplane that big.
I hope that answers your question to me.
GW
Note that the Viking landers were low and squat, like the Surveyors and Apollo LM's that went to the moon. The footpads were quite large, too. They pretty much met the criteria for rough-field landings, especially with the far less sophisticated robot guidance of ~50 years ago. Both survived. I am not surprised. Most of the other US Mars landers followed the same pattern, except for the two airbag designs.
As for the frost, depending upon the Martian season, both water and carbon dioxide are frost formers. Most of the Martian year, it is water. But in the dead of winter, it is cold enough to form dry ice, too.
GW
I would also add to the previous post that I think the concerns about in-space refueling are overblown. SpaceX is evolving toward accelerating the docked pair of vehicles at very low gee with thrusters of one type or another, slowly settling the propellants into the bottoms of the tanks. That will work.
Whether this can be done robotically is the real question here, especially since the AI stuff is already proving to be problematical in self-driving vehicles. If the programmers actually address all the possible contingencies, it will work. If they do not, sooner or later there will be a catastrophe. Simple as that. The track record with self driving cars is not promising, as regards programmers anticipating all possible contingencies.
As for the number of tanker flights, I think it is far too soon to be saying that it will take this or that number of flights. This thing is still in experimental flight test, and the final vehicle layout and configuration is still unknown at the detail level required to determine how much propellant payload could be delivered on-orbit. Even the propellant capacity of the vehicle is still evolving. For a full refill, could be anywhere from 6+ to 12+ flights. No one knows for sure yet! Claims "to know" this number are still BS.
And there is the long-term boil-off problem. Most anything they are doing will get you days of "stage life", but not weeks. They might get to weeks if the propellant tankage has the header tanks nested inside the main tanks, but only for the small quantities that the header tanks hold. To make it work, they will have to empty and vent the outer main tank, so that the vacuum between makes the tank system into a thermos bottle. The outer tank shell is also the sun shield that stops solar heating of the header tank, but only if there is vacuum between them.
One header tank is nested right now in the flight test configuration up to this point, the other is not. That will have to be rectified for the real mission. But as I said, we are still in experimental flight test with experimental configuration, and these configurations are still evolving. Claiming to already know the final "stage life" is also BS at this stage of the game.
But, what those considerations just discussed prove, is that this vehicle design is NOWHERE NEAR done with very experimental flight test, much less any final development prove-out testing! Precisely because of that, projecting mission schedules using it are still near-100% BS! That's the real effect of the factor-3-ish ratio between "Musk time" and real-world time that we have seen, ever since SpaceX first started flying Falcon-1's expendably out of Kwajalein.
That time ratio is different with each contractor, but all contractors have always had such time ratios. Long ago, that was taken into account by the government when planning military aircraft and space programs, and also for the civilian space program (same crowd of contractors back then). The details have shifted some since then, especially since there are now different pools of contractors for the various military and civil programs that only overlap some now. But it would seem that nobody at today's version of NASA (or DOD for that matter) remembers anything about evaluating and taking into account these time ratios.
That lack shows in how slow (and concomittantly expensive) it has become to actually do anything anymore. The P-51 Mustang went from a sketch on a napkin to a flying prototype in about 100 days. It took another year to re-engine the plane to make it the success that it finally became. And another year or three before they went to the bubble canopy on P-51D, solving the pilot combat visibility issue. That's about 3.5 years from an idea to a fully-successful combat design truly worthy of mass production.
Today that's now running about 25+ years (!!!) for airplanes and giant rockets. I think SpaceX is doing fairly well; their half-reusable Falcon-9 was ready in about a decade from idea to reality, which is way better than the industry usual. I think Starship/Superheavy is going to take them about that same decade to make ready. They are still a tad less than halfway done doing that.
GW
from the Monday 12-8-2025 "Daily Launch" email newsletter, there was a link to a longer article at Space.com, the text of which I copied and reproduced here:
TITLE 'We have lost a lot of time.' Former NASA chief says US needs to start over with moon landing plans or risk losing to China
AUTHORSHIP By Brett Tingley published 3 days ago
SUBTITLE "We have stuck to a plan that does not make sense."
TEXT Former NASA administrator Michael Griffin pulled no punches about where he sees America's current Artemis moon landing program in Congressional testimony today.
Griffin testified alongside other witnesses at a hearing held in Washington D.C. on Thursday (Dec. 4) by the Space and Aeronautics Subcommittee of the U.S. House of Representatives. The hearing, titled "Strategic Trajectories Assessing China’s Space Rise and the Risks to U.S. Leadership," was held to discuss the rapid development of China's space program and what that means for America's long-held dominance when it comes to space exploration.
And according to Griffin and the witnesses at the hearing, that dominance might soon cede to China due to policy decisions that continue to plague the Artemis program, NASA's current planned campaign of moon missions. "Sticking to a plan is important when the plan makes sense. China is sticking to a plan that makes sense. It looks a lot, in fact, like what the United States did for Apollo," Griffin said. "We have stuck to a plan that does not make sense."
Griffin said NASA and two consecutive presidential administrations have stuck to an Artemis moon landing architecture that "cannot work" and "poses a level of crew risk that should be considered unacceptable." The former NASA administrator reiterated a previous recommendation he made to Congress, arguing that NASA's Artemis 3 mission, currently planned for 2027, should be canceled — along with every other Artemis mission — so NASA and the U.S. government can rethink the whole plan for America's return to the moon.
"We should start over, proceeding with all deliberate speed," Griffin said. "We have lost a lot of time, and we may not be able to return to the moon before the Chinese execute their own first landing. Or we may; space is hard and despite the progress that China is making, mission success is guaranteed to no one. But though we may not win at this first step, we cannot cede the pursuit and leave the playing field to others."
NASA and SpaceX's current plan for Artemis 3 and other moon missions in the program relies on a complicated in-orbit refueling system. The current moon landing architecture requires a high number of SpaceX Starship launches in order to refuel the lander that would take NASA astronauts to the moon. The exact number still isn't even known, though SpaceX estimates it could require 12 Starship launches to fully refuel the lander. The concept also remains unproven; SpaceX intends to test Starship's in-flight refueling system on an upcoming launch.
Furthermore, Griffin added, the length of time the lander would need to remain in orbit while the refueling flights launch and rendezvous with it would "almost guarantee" the propellant loaded into the lunar lander would boil off before the mission proceeds. "I do not see a way with the current technology we have to overcome those problems, and therefore we should not pursue that line of approach," Griffin said.
Even SpaceX appears to doubt the current Artemis moon landing architecture. In internal company documents obtained by Politico, SpaceX estimates that September 2028 is the earliest timeline for a first crewed lunar landing attempt; however, according to publicly available information, NASA is still aiming for 2027 for that mission.
If Artemis 3 is delayed to late 2028, there will have been an average of two years between the first three Artemis program missions. The Apollo program, by comparison, launched each of its 11 missions an average of once every 4.5 months between 1968 and 1972.
NASA's current acting administrator has even criticized SpaceX for being "behind" on its lunar lander and Starship development. In remarks made in October 2025, acting NASA chief Sean Duffy suggested the Trump administration might be looking for other companies to compete to build and launch NASA's next moon lander. "The president and I want to get to the moon in this president's term, so I'm gonna open up the contract," Duffy told CNBC. "I'm gonna let other space companies compete with SpaceX, like Blue Origin."
But it could be that such programmatic instability is what is holding the United States back from committing to a moon landing program in the long-term, according to Dean Cheng, a China expert at the Potomac Institute for Policy Studies. Cheng told House representatives during the hearing that the bureaucratic structures of the Chinese government allow the nation to stick to plans over longer timelines than the U.S. government system allows. "China sticks to a plan. It creates a plan that sticks to it for decades," Cheng said. "And the benefit there is programmatic stability, budgetary stability, staff stability."
NASA, meanwhile, has been in a period of turmoil that has seen key science facilities lose capabilities, many flagship science missions put at risk of cancellation due to budget cuts, and thousands of personnel lost due to federal workforce reductions.
But whether or not the United States returns to the moon before China, former NASA chief Griffin said that the real risk is "failing to commit to what winning really means in the long run." Many U.S. government officials have stressed that whichever nation is able to establish a sustained presence on the moon first will have the privilege of establishing norms for how other nations can access and use lunar resources. If China manages to get a foothold on the moon ahead of the United States, it may be able to dictate who uses certain areas of the moon going forward, and how.
"I am confident that China fully understands this," Griffin said.
-----
My take:
Here are some high-level people saying essentially the same things I have been saying: how ridiculous our still-evolving mission architecture has been for returning to the moon, and how stupid it was to project a landing date without a lander leaving development testing already in-hand. The only item missing from this article is my comment that this should not be a race to see who is "first" about anything, because we already put boots on the moon over half a century ago! However, to get the politicians to do anything, I guess it has to be some sort of race, because of the technically-incompetent idiots that the politicians usually are. Another stupid race, just like with Apollo.
GW
I dunno what "right wing music" is. Sounds rather contrived to me. Typical of what happens as extremists of one type or another take over your government or your political parties.
But I do know what both far-right and far-left extremism does: install dictatorships. Britain almost was destroyed by the far-right dictatorship of Nazi Germany. We helped them survive and together defeat Hitler. Everybody knows what Stalin did in his far-left dictatorship. All dictatorships are the same. Does not matter what they say or how they got there, it only matters what they do.
And I have noticed that some Brits and some Canadians (and some French and some Germans) have very most definitely noticed the dictatorship currently still being installed in the US. They've seen this crap in action before, we haven't (although the trend toward it was interrupted by the Pear Harbor attack). Its installation is not complete yet here in the US, but there is very little time left to oppose it. Unless you want to do armed revolution in the streets. I'd rather not: incredible amounts of mess to clean up afterward. But I will if I have to.
GW
I kind of figured the "mushroom" Mars building as a hollow masonry column or tower in the center, with beams radiating outwards toward small masonry columns distributed around the periphery. Atop the beams is the slab that supports a thick loose regolith "cap" that is your radiation and meteor shield.
Between the periphery columns is where you add cylindrically-curved transparent and multi-layer panels that each are but segments of a pressure vessel cylinder shape. There will need to be more compressive stress in the columns than the tension-from-bending induced by pressurizing the panels, which otherwise just bear against the columns in a radial-outward direction. That spacing gets set to keep the columns in all-compression. There will be shear in them, that is inherent. But that is the price you pay for a transparent ringwall to get lots of light inside without using electricity, which will be inherently scarce.
This same construction could be done on the moon. You need the same radiation and meteor shielding there. The center column needs a proper foundation, and so does the ring of ringwall columns. This foundation could be an excavation back-filled with size-graded layers of compacted cobbles-and-fines, with the cobbles definitely in intimate contact. You would only need a finished floor pavement across the top layer of gravel-and-fines.
This kind of graded, compacted backfill is a load-spreader that spreads high bearing pressures upon the surface into lower pressures that the regolith can safely bear, lower down. All of this is well-known civil engineering "dirtwork" stuff. In the absence of data, use only 30 degrees off vertical as the load spreading angle. Here on Earth, angles vary from 30 to 45 degrees, with 34 degrees as the common "default" value. But we have water content, the moon and Mars do not. So use the min 30 degrees for safety. You must go deep enough so that the weight upon the larger footprint area at the bottom of your excavation is a pressure at (or under) the safe bearing pressure of the regolith. You will be excavating and backfilling quite deeply. This is big machinery work, not pick and shovel stuff.
Regolith (on the moon and on Mars) has low bearing strength because the rocks in it are not in direct contact, and they are not properly size-graded. It resembles nothing so much as "Earthly sand dune sand" in its strength and cohesion. There's a bit more cohesion on the moon than Mars, because the particles are sharp on the moon. But neither has a high safe bearing pressure. 0.1 to 0.2 MPa is all that we know of, based on "sand dune sand" here. That would be "fine, dry, loose sand".
Sealing against loss of atmosphere by percolating gas could be done with sheet polymer liners on the inside, bonded together, and to the inside constructed surfaces.
That kind of excavated foundation would replace the need to develop a Mars or moon "concrete" in the foundation, but not the beams or the roof slab. That "solution" remains to be discovered: a castable reinforced "concrete" usable in vacuum at at very cold temperatures. But the machinery to do this, and to prepare the backfill materials, is really big and heavy, and will need copious amounts of electrical power to run! You are looking at something near 500-1000 HP per excavator machine, and each weighing several tons. Just like here!
This can be done. But you CANNOT stint on any of this work! That would be far too unsafe to bet lives on!
GW
EDIT UPDATE same day: if you cannot develop a suitable moon/Mars concrete, then the alternative is steel beams and a steel plate for the roof slab. Just more weight to ship from Earth, but then EVERYTHING about this kind of building construction becomes things we already know how to do.
Regarding post 32 above, more "I-told-you-so" stuff showed up in today's (5 Dec 25) "Daily Launch" from AIAA:
Ars Technica
Congress warned that NASA’s current plan for Artemis “cannot work”
In recent months, it has begun dawning on US lawmakers that, absent significant intervention, China will land humans on the Moon before the United States can return there with the Artemis Program. So far, legislators have yet to take meaningful action on this—a $10 billion infusion into NASA’s budget this summer essentially provided zero funding for efforts needed to land humans on the Moon this decade. But now a subcommittee of the House Committee on Space, Science, and Technology has begun reviewing the space agency’s policy, expressing concerns about Chinese competition in civil spaceflight.
-----
My take:
Finally, it is just beginning to dawn on the politicians running NASA's show that they have been seriously miss-running it! About time! Actually, far too late! Announcing an expected landing date without a lander (and a rover) almost done with development, was just UTTERLY STUPID! But that's EXACTLY what you get when you let incompetent politicians be the top managers. Always has been, always will be.
This return-to-the-moon thing should not be another space race in the first place. The US put boots on the moon 56-53 years ago. It should no longer be about "who does something first". It should actually be about going there to do something significant and perhaps even useful.
Congress took over managing NASA by the end of Apollo. We have spent the last half a century puttering around with men in orbit (WITHOUT doing artificial spin gravity work !!!), while sending probes to other planets from the one part of NASA not so badly micromanaged by Congress until recently. Before Nixon killed all manned spaceflight outside LEO (not just Apollo!!!), the plan was US boots on Mars in the 1980's!!!
EDIT UPDATE same day: NASA killed NERVA just as it was ready to fly as an alternate 3rd stage on Saturn-5, when Nixon forbade manned flight outside LEO, based on the reasoning "who needs the rocket if we aren't going to go?" They learned that kind of "reasoning" from Congress!
See what Congress micromanaging NASA REALLY did?
GW
There are very good technical reasons why pressure vessels have round shapes based on spherical or cylindrical geometries, and arches supporting weight are more like parabolas in shape. Static pressure acts equally in all directions at once, weight does not.
If you build only a pressure dome, it will have to have a spherical membrane shape in order not to be too thick and too heavy. The usual idea is to make it transparent to visible light so that things could be grown under it. That forces you either to glass, or to structural plastics. Glass is vulnerable to impact fractures, and the structural plastics fail fairly quickly when exposed to harsh UV. Neither option can provide much in the way of radiation protection.
If you build arches to hold up a regolith radiation shield, which can also provide meteoroid impact protection, you will be using the more paraboloid shape. This thing has to stand up under the weight of the regolith, even when not pressurized. You cannot have it both ways: you must build it before you can pressurize it and live in it. But, your real problem is then getting visible light into it so that you can grow stuff.
Arches are only one way to hold up weight. Beams are another, and can be curved, too. Beams and columns with a slab atop can also hold up regolith shielding, but leaves you free to make the side walls transparent, especially if you use a round floor plan. That way, mirrors outside can direct lots of visible sunlight into the build through those transparent side walls between all the columns that hold up the beam and slab roof.
It sort of looks like a mushroom with a shower-curtain ringwall hanging from the perimeter of the cap. And with a round floorplan, that ringwall is an efficient cylinder pressure vessel. The UV danger will drive you to safety glass, but you will need multiple layers of it anyway for thermal insulation.
I came up with this notion for Martian building construction several years ago. It does require some sort of Martian "concrete" for the foundations and the reinforced beams and roof slab. It was posted on my "exrocketman" site January 26, 2013 as "Aboveground Mars Houses". That old article has no search code, you'll have to use the archive navigation tool to reach it. Left side of the page. Click on year 2013, then on "January", then on the title if need be.
The enabling technology will be a Martian concrete. All the rest is stuff we already know how to do. I don't think "icecrete" will do, it will sublime away because we need a habitat to be warm inside.
GW
There may or may not be large quantities of easily-recoverable ice on the moon near its poles. We still do not know with real ground truth. Remote sensing still often lies to you, precisely because too many inferences have to be made.
But if easily recoverable ice exists, then LOX-LH2 should be producible powered by a mix of solar and nuclear electricity (remember, the day/night cycle is a month long!). All it takes is electricity to do purification, electrolysis, and liquifaction.
If you have a single stage, reusable lander rigged to use LOX-LH2 propellant, you can use it to ferry some of that same LOX-LH2 propellant to orbit. You refuel the lander on the surface. It uses less propellant to launch cargo into lunar orbit and return, done that way.
That being the case, what purpose does a lunar space station serve? Why build 2 propellant production plants? Just use the one you need on the surface, and ship product to orbit for transit elsewhere.
That approach makes more sense to me, because you get the same effect while building less infrastructure.
Now, if you intend to use LOX-LCH4 propellants, you will have to ship carbon from Earth or elsewhere, and it needs to be pure, and in powder form. There is no easily recoverable carbon on the moon.
Extremely dilute concentrations of anything are not easily-recovered resources. That is why sea water has never been "mined" for the uranium that is there, in extremely dilute concentrations.
GW
Copied from my post 26 above:
"NASA needs somebody else to respond with a different idea from either of these two. But, with the landing scheduled for only 1 or 2 years way, there is no reality to NASA's plans, either! The Apollo LM took 4 years paper to flight, and that was a crash program where money was secondary. This is not. The downselect was driven by insufficient money in the first place. This lander cannot be done "from scratch" in 1-2 years, even if it were a crash program."
Now see this from the Wednesday 12-3-2025 issue of AIAA's "Daily Launch" email newsletter:
"Ars Technica
NASA seeks a “warm backup” option as key decision on lunar rover nears
By the time the second group of NASA astronauts reach the Moon later this decade, the space agency would like to have a lunar rover waiting for them. But as the space agency nears a key selection, some government officials are seeking an insurance policy of sorts to increase the program’s chance of success.
-----
My take on it:
Told ya so, didn't I? No reality at all to the Artemis plan and schedule.
They announced a landing date without a working prototype for a lunar lander, and no fruitful effort at all toward a rover. What kind of "planning" is that? What kind of "management" is that? None, I would say!
And just how are they going to address these needs while laying off 25-50% of their workforces? Answer -- they cannot!
All of which proves my point here: the NASA we knew and loved no longer exists.
It was slowly being destroyed by Congress using it for porkbarrel politics the last several decades, and here in the last several months, the destruction has been sped up enormously by this administration, which is demonstrably anti-science, and also apparently only interested in warfighting technologies it can purchase more over-the-counter than by developing them.
GW
Just an update on my solar installation. It's been 16 months since installation. On average, my electric bills are around a third to a quarter of what they once were (it varies with season and weather). The meters run backwards on most bright sunshiny days. Which means I am selling power back to the electric coop (we have a rural electric coop for service out here in the boondocks). Our coop has lower prices than the big utilities, and its service has far fewer outages. Typical of rural coops vs the big utility companies, actually.
The installation that can sell power back like that has to meet the technical requirements of the coop. That's why I cannot be stand-alone on my solar with a battery. They do not allow that kind of connection. Their sine wave is what my system detects in order to phase-in correctly. It does not operate without that signal.
GW
Last I heard, NASA recently reduced the remaining contracted Starliner flights from 6 to 4, with 1 of the 4 to be the unmanned qualification flight Boeing still must fly. That's down to 3 paid crew delivery flights.
We will soon see if Boeing will fulfill its side of the contract, or just abandon the program to cut their losses. They will never make any profit off of this vehicle from their NASA contract. There might, or might not, be other customers for Starliner, though. We will see.
GW
I am glad to see Blue Origin entering the orbital launch fray. They do have an impressive design in New Glenn. It's smaller than Starship/Superheavy, so it fills a different payload mass niche.
Meanwhile, SpaceX has been proving out the "rideshare" concept with its Falcon-9. That is to be the technique by which the giant Starship/Superheavy can address the market for smaller payloads.
A rocket sized about right for a given payload offers the possibility of a sooner date to launch, but at a somewhat higher price. The "rideshare" option offers the lowest price, but at a longer wait time before launching, trying to fill the "seats".
I think both are good approaches, and actually the two companies will offer services that are as much complimentary as they are competitive.
Being so much bigger with an upper stage that is also a fully-qualified entry vehicle, I think SpaceX has the longer row to hoe, before their vehicle is considered safe and reliable. Blue Origin still has a similar row to hoe with New Glenn, but not one quite as long as Spacex's, because Blue Origin's upper stage is not reusable.
It's apples and oranges. I did the best I could to compare in a realistic way.
GW
From AIAA's "Daily Launch" email newsletter for Tuesday 12-2-2025:
New York Times
Russian Launch Site Mishap Leaves Country’s Space Program in Limbo
The launchpad Russia uses for sending astronauts and cargo to the International Space Station is out of commission after a mishap last week during the liftoff of a Soyuz rocket. The rocket itself headed to space without incident, taking three astronauts — Sergey Kud-Sverchkov and Sergei Mikaev of Russia and Chris Williams of NASA — to the space station. But the force of the rocket’s exhaust shoved a service platform used for prelaunch preparations out of its protective shelter. The platform fell into the flame trench below.
-----
My take on it:
I'm surprised that something like this hasn't happened before. Although, if it had, we probably would not have learned much about it publicly. There's precious little reported here. They will apparently require some facilities repair and replacement before they can launch again. That leaves only SpaceX's Falcon-9/Dragon as a means to send people to ISS, since the Boeing "Starliner" is still in unqualified limbo. There's Cygnus and the Japanese vehicle for cargo.
I bet there are some at NASA wishing Dreamchaser had been funded.
GW
Rather than modify the grid you already have working, why not just artificially increase the mass flow rate? If you are running 1 bar at the nozzle entrance with 2 kg/s, and you want 10 bar, then just analyze with 10*2 = 20 kg/s. Don't mess with the mesh. That way lies error and madness, far too easily.
Once you have an answer you like, you can rescale it to the "right" size very easily: just hold a constant mass flow per unit throat area, and change both by the same ratio. Not in the CFD code, just in your reported results.
GW
Balancing the rotor:
You seem to have put an all-thread through the centerline of the hub. Try static balancing it upon a level table, while sitting atop that all-thread. I have a car tire balancer that works the same way, with a bubble level. Static balancing a car tire works up to about 70 mph (110 kph) driving speeds just fine. You need dynamic balancing to go faster, though. There's basically an rpm limit to what you can achieve with static balancing.
GW
It's not the identity of hydrogen that makes the big difference. It is merely the interplay of mass flow rate, throat area, the effective c*-velocity of the chamber conditions, and the resulting chamber pressure. Hydrogen vs something else merely changes the c*-velocity, by several-to-many percent, but not by really large factors. The temperature is higher but the molecular weight is lower. Those effects upon c* are in the same direction, though (see below).
All species, no matter how they are heated, must obey the nozzle flow rate equation: wnoz = Pt CD At gc / c* where CD is the discharge efficiency of that choked throat: effective A / geometric A, and is usually rather close to, but never exactly equal to, 1.
As for c*, there is an equation for it, too: c* = square root of (gc R Tc GF / gamma), where GF is a function of gamma, but it is always pretty close to 2.9 in numerical value. The square root reduces the effects of large changes in Tc. The molecular weight shows up in the gas constant R, which is the molar universal value divided by the molecular weight. That is actually the bigger change with non-combustion heated hydrogen, simply because the molecular weight is greatly lower than that of most other species, and the effect is only reduced some by the square root.
GW
PS: the GF is (gamma + 1)/2 raised to an exponent that is (gamma + 1)/(gamma - 1). We have modeled hydrogen's gamma as 1.4 from cryogenic to 1000 K, decreasing linearly to 1.286 as the temperature increases to 3000 K, with molecular weight constant at 2.016 throughout that temperature interval. Beyond 3000 K, dissociation changes all those numbers. It is not molecular hydrogen anymore.
This 180-about interpretation falls right in line with my observation that you cannot trust remote sensing enough to bet lives on it. You have to "go there" to find the truth! That is as true today as it was before Mariner 4 in 1965. And ever since.
By the way, before the Mariner 4 flyby, Mars's atmosphere was thought to be mostly oxygen-nitrogen like Earth's, just a lot thinner at a surface pressure near 85 mbar. The flyby caused a 180-about back then to the vision that Mars was much more like the airless moon. Until we sent orbiters and landers there, then we gradually learned the real truth. Especially with the landers.
You need to take remote sensing results with a grain of salt. A big grain of salt. About like a salt lick block. Even today. Although it has gotten a bit better than it was 60 years ago.
GW
Not knowing where to put this, I put it here.
I see The New Glenn flew successfully today, including landing the booster on a barge. The second stage put the twin craft on their way to Mars.
The delay yesterday was too high a radiation environment due to the solar flares. Those Mars craft were judged at risk.
GW
I have split up the stuff discussed in posts 607 and 606 just above into two separate topics: (1) what is required of a vehicle design to be capable of rough-field landings on the moon, Mars, or even Earth, and (2) how to go about building the landing pads for vehicles not capable of rough-field landings, which involves spreading concentrated loads over larger areas to reduce bearing pressure, as well as rocket jet blast erosion.
I re-wrote and expanded these as two articles that will be posted on my "exrocketman" site in December and January. As soon as the search codes become available, I will post them here. The articles have not yet been posted, so there are no search codes for them as of yet. I did the research and was able to quantify the proper load spreading angle to use, as 30 degrees off vertical. That would be for the load-spreading ability of the layered packed rock substrate underneath the finish paved surface of the landing pad. The more concentrated the applied loads are upon the paved surface, the deeper the stone-backfilled excavation must be.
GW
These are good concepts, but they require being proven effective, before you risk lives upon them. To the best of my knowledge, that has not yet been done for any of these. Going to the moon to experiment with them in situ under harsh conditions, is a pretty good reason for going back to the moon, among others.
GW
Regarding the images Tahanson43206 posted for me in post 606 just above:
The "design for landing" image is what I estimated for a lunar "Starship" variant properly equipped for a rough-field landing on the moon. Mars would be similar, but the numbers would be different, and it would be very difficult to protect such legs during Mars entry. There are two critical design criteria a rough field lander must meet: (1) The transient pressure underneath the pads (or other contact surfaces) during the touchdown event cannot be allowed to be any greater than the bearing strength of the lunar regolith, which is rather similar to Earthly sand-dune sand. (2) The minimum span across the polygon created by the landing leg outer contact points must exceed the height of the vehicle center of gravity above the surface. These two critical design criteria were amply demonstrated appropriate by Apollo, and by Surveyor before it. There are too many today who ignore, or never learned, these well-established criteria. It shows in the recent overturned commercial lunar landers.
The "how to build a landing platform" image shows how roads and foundations are properly built upon weak soil, so that heavy concentrated loads do not crush or penetrate the paved surface. These techniques were developed and used with great success by the Romans, and are still used today. Unfortunately, doing it "right" is quite expensive, so today our roads are built with inadequate excavation and inadequate quantities and size-grading of the rock fill underneath the paved finish surface. So, they do not hold up nearly as well as the old Roman roads. Big heavy trucks do the most damage, by crushing the substrate down, "rutting" the road.
The image of the "Blue Ghost lander" is not what I sent, but it is the Firefly Aerospace commercial lander design that was actually quite successful landing on the moon. Note the squat low form relative to the leg pad span, and the large size of the landing pads. It meets the same criteria that the Apollo LM and the Surveyor probes were designed to. So, success at a rough-field landing should not be much of a surprise.
As for vehicle designs that do not meet rough-field criteria, they should not be sent to the lunar surface until a hard-surfaced, strong landing pad surface has been constructed. The same applies to Mars, most of its surface is similarly weak. The load-spreading effect of the backfill-rock substrate is how you spread a concentrated large force on the surface onto a much larger area at the bottom of the excavation, which reduces the applied bearing pressure to what the regolith or soil below can actually withstand. This is all civil engineering "dirtwork" just like what we do on Earth, except for the final pavement finish surface. To land rockets, that finish pavement must be both heat-resistant and blast erosion resistant. Concrete usually requires some repair after a rocket landing, but concrete as we know it is unavailable on the moon (or Mars). Some sort of tough, resistant tiles laid like flagstones might work. But they need to be thick, and as heavy as possible, not to get ripped away by jet blast shear forces. Laying such tiles directly upon the weak regolith will NOT work!
GW
Actually you don't need anything but pencil and paper to do analyze nozzle expansions, although having a spreadsheet or something to automate the iterations required to find Mach number from Area ratio helps. That's what you usually have to do, to have a vacuum bell. Bear in mind that there is no such thing as an "optimal vacuum rocket nozzle design", there are only constrained designs, the usual constraint being how big a device will actually fit behind your vehicle?
Pick your constrained Ae/At. Determine from it (and gamma) your exit plane Mach number. From Mach, determine the exit plane pressure ratio to chamber pressure Pe/Pc. Pick either an 18-8 degree curved bell shape to be detailed with method-of-characteristics, or else a 13 degree half angle conical bell. The conical bell is a bit longer, but will have identical performance! The performance index is kinetic energy efficiency nKE = (1 + cos(avg half angle))/2.
CFvac = (Ae/At)(Pe/Pt)(1 + gamma*nKE*Me^2) There is no backpressure correction term -(Pa/Pe)(Ae/At) because out in space Pa = 0.
Vacuum thrust Fvac = CFvac*Pc*At.
The nozzle mass flow rate wnoz depends upon c* ("characteristic velocity"), Pc, At, and the nozzle throat discharge coefficient CD that reflects boundary layer thickness. Wnoz = Pc CD At gc/c*. The flow rate drawn from tankage wtot is bigger than wnoz by the amount of any flow rate tapped off, used to drive turbopumps, and then dumped overboard without going through the nozzle. The dumped bleed flow fraction BF is dumped/wtot. Wnoz = wtot(1 - BF).
You must use wtot for your Isp calculation, because it is directly related to the mass ratio of the vehicle. This Isp = Fvac/wtot. Or you can divide the one relation by the other t tobtain Isp = CF c* (1 - BF) / (gc CD).
All you need to enable this is c*. That is chamber temperature and gas properties as c* = square root of [gc R Tc GF / gamma] where the gamma factor GF inside the square root is GF = c3^(c3/c1). In turn c1 = (gamma - 1)/2, and c3 = (gamma + 1)/2.
That's all there is to it.
As for the area ratio-Mach relation, it is Ae/At = (1/Me)(TR/c3)^c4, where c4 = c3/(2*c1). Now, TR = Tc/Te = 1 + c1*Me^2. You can find Ae/At directly, but finding Me is iterative, because the equation is transcendental in Mach.
As for the Pe/Pc ratio, PR = Pc/Pe = TR^c2, where c2 = gamma/(gamma - 1). Then Pe/Pc is just 1/PR. If you have a gamma and an Ae/At, you know Mach, and you know Pe/Pc. Given an nKE, you know CFvac. So you know thrust. And if you know CD, you know wnoz. If you know BF and wnoz, you know wtot. So if you know Fvac and wtot, you know Isp.
GW
I don't really know anything about "sulfacrete", except that the notion is to slurry rocks and fines into molten sulfur and let it cool off and solidify. That presents raw sulfur to the environment, because it is the matrix in a composite reinforced by the rocks and fines. If that gets hit by a rocket plume with H2O in it (and almost all do), that creates H2SO4 sulfuric acid anhydride, which is a strong acidic corrosive. Here on Earth, that's less of a problem, because there is much in the environment that is alkaline, which can help neutralize it. But on the moon or Mars, nearly all the rock and regolith materials are from volcanic-type rocks, which are also generally acidic. I think you will have an acid contamination corrosion problem with anything sulfur-based as a building material. But I could be wrong.
GW
I see in the news that NASA finally threw open the lunar lander thing to all of industry, seeking a "plan B". So far, there have been 2 responses, one from SpaceX, the other from Blue Origin, the same original HLS contractors NASA selected, then finally downselected to SpaceX. The news reports provide no clue as to what SpaceX and Blue Origin "plan B" items really are.
You can pretty much bet that the SpaceX "plan B" is still some variant of its Starship modified to land on the moon, which is exactly what they were contracted to do in the first place. You can also bet that the Blue Origin "plan B" will be based on the "Blue Moon" lander they were designing right up until the downselect. They both have too much effort invested in those ideas to switch horses now. Simple as that!
Both are too tall to be stable for rough field landings on the moon (they violate the "stance wider than the cg is tall" criterion that was successful with Surveyor and the Apollo LM). And, you have to worry also about landing pads sinking deep into the lunar regolith, because it is no stronger than an Earthly sand dune! I do not know how loaded the Blue Origin pads would have been, but as of yet I have seen nothing out of any SpaceX designs that take dynamic (transient) bearing pressures during touchdown into account. They only have touchdown experiences on a hard pad or steel deck.
NASA needs somebody else to respond with a different idea from either of these two. But, with the landing scheduled for only 1 or 2 years way, there is no reality to NASA's plans, either! The Apollo LM took 4 years paper to flight, and that was a crash program where money was secondary. This is not. The downselect was driven by insufficient money in the first place. This lander cannot be done "from scratch" in 1-2 years, even if it were a crash program.
The original SpaceX and Blue Origin ideas have about 2 years under their belts now. Some variants of those are the only feasible things that might get done in another 2 years. And that could ONLY happen if NASA funded both contractors at a crash program level, from now until then. That's the only way to have a viable option AND a viable backup option! Common sense says so!
But it ain't going to happen that way, people!
All you need do is look at what is happening to JPL to understand what has already been happening at the rest of NASA. So far, 25% of workforce laid off, and they were by far NASA's most capable people! Demonstrably so! THAT is what this government is really doing!
Just as I have always recommended: "look ONLY at what they really do; do NOT listen to what they say or promise!"
GW