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Posts posted by sevenperforce

  1. 20 hours ago, Barzon said:
    20 hours ago, tater said:
    20 hours ago, Barzon said:

    If it helps, you can probably get a rough estimate for the dimensions of the habitat from this tweet, if it hasn't been posted already.

    The question is if this is the same vehicle.

    It's probably a safe assumption. If not, well, all we can do is wait for more information.

    I'm pretty sure it's not the same vehicle. The new design has a completely different OML so they would design the interior from scratch.

    To @tater's earlier point, it's possible that they could have the engine(s) protruding into a bulkhead inside the crew cabin, like the New Shepard crew capsule. Not sure how much space would be required, though.

    According to this source, the new HLS lander is 16 tonnes empty and will have a mass of over 45 metric tonnes with full props. But from the lunar surface, it will only need about 2.6 km/s of dV to get to Gateway. Let's say 2.7 km/s for margin. Assuming the BE-7(s) can get into the ballpark of 445 seconds specific impulse, the liftoff mass from the lunar surface will be about 29 tonnes. Liftoff mass for the Lunar Module was 4.7 tonnes and the engine delivered 16 kN of constant thrust, delivering a relatively anemic two lunar gees (0.35 geeEarth). I'm sure the HLS architectures will need more than that. If we say three lunar gees, that's the equivalent of an Earth T/W ratio of 1.4, which is considered pretty sporty. So we'd be looking at needing ~145 kN off the lunar surface, meaning at least three BE-7s are required.

    If they have a cluster of three BE-7s at the center, then you're looking at needing a 2.6-meter-wide circle space for clearance:


    Should be enough to put some storage, at least.


    That's with a notional 6.5-meter OML on the lander, assuming they go right up to the max volume capacity of New Glenn.

  2. 6 hours ago, steve9728 said:
    19 hours ago, sevenperforce said:

    So you could say that Mandarin is as different from Japanese as Japanese is from English.

    Not exactly. The difference in many words between Japanese and Mandarin just be like "turn a corner and you're right there". For example "Your point is correct", in Chinese can be "说得是 (shuō dé shì)", and in Japanese is "そうです (sodesu)". There're lots of other examples like that. Because, well, of course, is inextricably linked to the deep cultural exchanges of all kinds between China and Japan and others where around China, both peacefully and not. That started from very long ago. If must find a similar example like this, I would say is kind like Britain and France.

    On the other hand, doesn't Japanese have a lot of loan words from English as well?

    Maybe the more accurate statement is that Mandarin is almost as different from Japanese as Japanese is from English.

  3. 2 hours ago, JoeSchmuckatelli said:

    To what extent are the 'major' Asian languages related to one another?

    • Are they analogous to English / German where there are many similar root words (even if English's grammatical structure is a hodge podge of Viking and Celt)?
    • ...or
    • Are they analogous to English / Russian where the alphabets are different, the words and grammatical structures are totally distinct?

    They are much farther removed apart than English and Russian.

    The Sino-Tibetan language family consists primarily of Chinese (in most of its various versions), Burmese, and Tibetan. It has no known ties to the Indo-European language family, the Austroasiatic language family, the Austronesian language family, or the Altaic language family, which themselves contain the following:

    • Indo-European: German, English, Russian, Hindi, Punjabi, Greek, Spanish, French
    • Austroasiatic: Vietnamese, Khmer
    • Austronesian: Malay/Indonesian, Javanese, Tagalog
    • Altaic: Japanese, Korean, Turkish, Mongolian

    So you could say that Mandarin is as different from Japanese as Japanese is from English.

    In comparing within the language families, however, there are closer similarities. Japanese and Korean (or Malay and Tagalog) have about as much in common as English and Russian.

    38 minutes ago, SunlitZelkova said:

    The very old Korean and of course Japanese kanji are more or less Chinese characters. Korean uses a modern writing system but the root is the same. So although pronunciation is different, some words are the same. For example, 火星 and 火星. The left is in Chinese, and the right is in Japanese.

    Since Chinese scripts go back so far in history, they were adopted for a number of other languages despite those languages having no recent common ancestry with each other. Just like you can use Roman characters to write transliterated Hebrew even though Hebrew and Latin aren't closely related.

  4. 8 minutes ago, darthgently said:

    Total amateur here, but how important is laminar-ish flow through the throat?

    The flow itself isn't laminar at the throat, but that IS the location of the choke point, with subsonic flow on one side and supersonic flow on the other side. And so it's the point of greatest temperature and pressure.

    They might place the gimbal location just downstream of the throat, so there is a fixed portion of the nozzle and a gimbaling portion of the nozzle. That's a good trick, as Anakin would say. Still not a straightforward problem though.

  5. 1 hour ago, darthgently said:

    Which brings up the possibility the readable numbers on the shirts are intentionally wrong just to mess with ppl :)

    We know that the Blue Origin website labels something as a hydrogen pump which, if zoomed in on, clearly says oxygen pump. So the web/marketing team may be just wildly inaccurate in general.

    16 hours ago, tater said:

    My estimate on the dia if the engines was off a little. I put the dia at 1.2m for Be-7, guess it is closer to 1m. Makes fitting them in the lander even easier.

    Can't remember if I said this before or not, but if they really are going with a nozzle-only gimbal (which is still a shocking choice for a regeneratively-cooled nozzle), then that also decreases the space required for gimbal authority.

    Assuming 10° pitch and yaw authority (not necessarily representative; just picking a round number), an engine that is 80" x 37" will need a circle 60.2" in diameter to accommodate gimbal from the thrust structure at the top of the engine, but will need a circle of only 47.4" in diameter to accommodate gimbal from the nozzle:


    When you think about a lander with where the engines are clustered with 2 or 3 in a line, that extra gimbal clearance starts to add up. So I can see why they would want to go with a throat gimbal for that reason. Throat gimbals also allow for slightly lower overall fixture weight since the engine load mount doesn't move (the mount still needs to be able to transfer the off-axis load; it just doesn't have to do so while also moving).

    What's unclear is whether these advantages are worth the added complexity of running both cryogenic cooling loops AND superheated high-pressure rocket exhaust through a flexible throat.



  6. I don't know that this has been posted before, although it's fairly old news.

    The Blue Origin store is selling a t-shirt with engine dimensions:


    If you go to the sale page and look closely, you can read the engine dimensions (given in height x diameter):

    • BE-3PM: 115" x 27"
    • BE-3U: 175" x 99"
    • BE-4: 150" x 76"
    • BE-7: 80" x 37"

    Main takeaway: the BE-3U is a honking big engine. Bigger than the J-2, bigger than an RVac, and bigger than the largest RL-10s.  Unless I miss my guess it will be the largest upper-stage engine ever flown, whenever it finally flies.

  7. 1 hour ago, darthgently said:

    My assumption was that as the g-screen ramped up, orbital velocity would become less necessary, so as the g-screen ramped up to max, orbital velocity would be ramped down to zero.  So no tangential velocity to deal with.  And, as implief by @sevenperforce, any mutually exclusive mix of g-screen and orbital_velocity could be dialed in one would assume

    The trouble is with how inertial and gravitational mass are handled, I think.

    Everything in Earth's SOI is attracted toward the center of Earth, regardless of its mass. Even photons, with no rest mass, are deflected by Earth's gravitational well, albeit only slightly due to their great speed.

    And so reducing the effects of gravity on an object -- "screening" some portion of its gravitational mass -- wouldn't change the free-fall behavior of the object. If you "screen" 99% of the mass of a 1-tonne object, you will be able to lift that object 10 meters off the ground with relative ease, exerting just slightly more than 98 Newtons of force and expending only 981 Joules. However, if you then release that object, it will accelerate downward at 9.81 m/s2 just as if there was no gravity screen at all, and so all 1000 tonnes of its inertial mass will impact the ground at 44.3 meters per second, releasing 981000 joules of energy.  This creates an infinite energy glitch and I think it also potentially violates the Copernican principle.

    The natural "fix" is to reduce the vehicle's felt perception of gravity. But this really mucks things up, because now you start to drift away from Earth relative to the sun, etc., because if the felt perception of the sun's gravity dropped by 99%, your 30 km/s orbital velocity around the sun would immediately become an escape trajectory.

  8. 3 minutes ago, darthgently said:

    It seems unintuitive that a g-screen could tell the difference between galactic, solar, and planet/moon gravity and would simply screen the sum of all of them.  Hard to be logical about something not very logical though

    Yeah, there's a problem here.

    I'm currently sitting on a chair being pulled toward the center of the Earth at 9.81m/s2, which is the equivalent of being accelerated at 9.81m/s2 for an object in free-fall. More importantly, this is the equivalent of being at the apogee of a highly eccentric 6378 km by 6.7 km orbit around the center of the Earth, with an apogee velocity of around 361 m/s (if you're clever, you can use that to determine my latitude). I rapidly come to notice this orbital path (and the change in orbital velocity relative to my fixed surroundings) if I jump off a ledge. A device or machine that could "screen" gravity and cancel my weight, leaving my inertial mass intact, would be the equivalent of stopping my orbit from being an orbit: transforming my apogee velocity of 361 m/s into a pure tangential velocity.

    Thus if gravity was "screened" and turned off for me, I would continue moving at 361 m/s in a straight line, while the surface of the Earth continued to move under me at 361 m/s along the 39th parallel, in a circle. After four minutes, both of us would have traversed 86.6 km, but Earth's surface would have done so along one decree of circular arc, causing it to drop away underneath me by 972 meters. After twenty minutes, both of us would have traversed 433 km, but Earth's surface would now be 24 km beneath me. After an hour, Earth's surface would be a whopping 225 km beneath me.

    A g-screen, then, would result in a perceived vertical levitation effect which increases quite rapidly with altitude for the first three hours, then increases more slowly, reaching a maximum of 361 m/s (or more, if you're at a lower latitude) after 6 hours.

    However, this becomes a problem when you start looking at other orbits. Earth is orbiting the sun. If I "screen" gravity for my spaceship, my 30 km/s of orbital velocity I share with Earth is transformed to tangential velocity. After ten minutes, my straight trajectory will have drifted 1068 meters away from Earth's near-circular trajectory. After an hour, it will be 38 km. So my rate of drift relative to the surface of the Earth will be different if I am on the daylight side or the night side. (Fortunately, the rate of the sun's rotation around the center of the galaxy is slow enough (in rad/sec) that drift between my vehicle and the sun is not a significant issue.)

    I suppose the easiest way to fix this is to posit that the g-screen, while very efficient, is not QUITE 100% efficient, and so portions of the ship still experience SOME gravitational attraction, which anchors the ship to the planetary surface at least a little. That would fix the drift problem, but I'm not sure what it does to orbits themselves, since the inertial mass of the vehicle is still intact.

    3 minutes ago, darthgently said:

    +1 on the Firefly mechanic being the most "sensible"

    Agreed. It was a good balance. Not Star Wars handwavium, where everything floats for no visible reason, but also not so detailed that it introduces obvious contradictions or otherwise adversely impacts the plot.

    Another reasonably good system (which I suppose approximates the Star Wars thing to some degree) is the "gravity rail" approach. There's some sort of superconducting loop which "locks" a vehicle to whatever spot in the local gravitational gradient where it finds itself, without using up any energy. That allows an object to experience gravity (and have the objects in or on it also experience gravity) while floating, but also while following the local curvature of space so that it doesn't drift. However, such a system doesn't allow you to follow the terrain; if you run off a cliff you'll stay at the same elevation, and if you try to drive up a slight hill you'll plow straight into it.

    Perhaps the superconducting hoverloop thingy stores energy relative to your own gravitational potential, so when you drop off a cliff, it absorbs more energy in cushioning your fall, and when you need to ascend a hill, you lose potential energy in your hoverloop while gaining gravitational potential energy. But this suggests some maximum altitude to which a speederbike can ascend...

  9. On 5/28/2023 at 11:10 PM, magnemoe said:

    This, the magic gravity plates who are so common in  science fiction. And yes using it to hover or get into space would be an valid use case for them. It would be much more efficient than an helicopter unless the process was pretty inefficient. It would be very inefficient for creating gravity inside an ship as it would require the energy to hover the inside all the time. Worse you have the gravity 90 degree of the direction of trust. 
    Why? because planes and ships are oriented this way :) 

    I believe that in the Firefly universe the ships like Serenity have two systems that work like this: a g-screen and a g-field. The g-screen insulates the bulk of the ship from the effects of gravity, so that the engines don't have to fight against gravity during the climb to space. The g-field, on the other hand, produces a directional gravitational field for discrete objects within the ship to allow the use of decks, chairs, bunks, and so forth. It's reasonably clear that although these use similar technology, they are two separate systems. Both the g-field and the g-screen, while requiring a lot of energy to set up, require very little energy to keep going and decay slowly after a power loss, slow enough that issues like oxygen and temperature are more pressing.

    When the ship's main pulse drive is activated, the surge of power allows for the g-field and the g-screen to be aligned together, which effectively cancels the inertia of the entire vehicle and allows for very high acceleration. Feels very much like the sort of of stuff that @Spacescifi using goes on about. He should really just borrow the Firefly mechanic and be done with it.

    One unanswered question (I think) is how far the effects of any g-screen system actually extend. Ordinary objects are in free-fall, but free-fall itself is actually an extremely eccentric orbit around Earth's center of mass. If you cancel that, are you floating relative to Earth, or are you also floating relative to the sun? Relative to the galaxy? 

  10. 2 hours ago, Terwin said:

    The fairing would not be for aerodynamics, but to protect the vessel from the heat and radiation.  This is not an issue in space because the pusher-plate acts as an umbrella and there is nothing else to redirect it.

    In atmosphere, the pressure-wave becomes an issue that the pusher plate cannot stop as it will engulf the entire vessel.  The pressure wave is also bringing lots of vessel melting heat and any radiation that misses the pusher plate can bounce off air molecules and radiate the vessel.

    Ah, I see where you're coming from.

    Do you know of any studies reviewing the effects of atmospheric Orion?

    With the radiation problem, I suspect that high enough standoff would make it work. The plasma envelope is opaque to x-rays so as long as the standoff distance is greater than the initial fireball radius there shouldn't be problems there. The flash will certainly transfer quite a bit of energy to the surrounding air, but air is famously quite transparent and so the amount of energy that is absorbed and re-radiated before the ship is out of range of the blast should be low.

    The shockwave propagation around the pusher plate might be a bigger problem.

  11. 38 minutes ago, JoeSchmuckatelli said:
    54 minutes ago, sevenperforce said:

    FAA should investigate the incident.

    They probably are / already have.

    Strong suspicion that FAA simply asked SX what happened (beyond what everyone could see) and SX gave them open access.

    No need to shut SX down for months for some hyped up Congressional Inquiry like dog-and-pony show.

    Smart folks from the FAA look at what happened and what SX plans to do about it, write a report... done.

    Yes, they are absolutely already investigating.

    The suggestion by Bob seems to be that because there was something he thinks was a failure, that means we can infer a failure in the FAA's oversight process, and that means we can infer a fundamental flaw in the FAA oversight process, and that means we can infer that FAA is incapable of rectifying the fundamental flaws in its oversight process, and that means we can infer an independent commission is necessary to fix the inferred problems in the FAA.

  12. 5 minutes ago, Exoscientist said:
    23 hours ago, sevenperforce said:

    If there's an actual problem, then we should identify the problem, characterize the problem, and determine whether it was a lapse in oversight or an unknown unknown...not create an independent commission to tie things up endlessly with no actual goal or objective.

     So you’re saying the FAA should investigate itself?

    I'm saying the FAA should investigate the incident.

    Because that is its job.

    There is no indication or suggestion (other than wild unsourced and unevidenced speculation) that that FAA ought to be investigated as an institution.

    Failure investigations and process lapse evaluations happen all the time across industry and regulators.

  13. 3 hours ago, RCgothic said:

    That really is a vastly superior design.

    Putting the capsule at the bottom is very Kerbal, very New Space, and very clever.

    I'm still unsure where the engines are. Can this be used to physically drop cargo pods, or would the vehicle need to land and offload cargo robotically?

    3 hours ago, RCgothic said:

    Now for maximal effectiveness of refilling ops they just need to sort out their reusable second stage for New Glenn.

    Fingers crossed.

    Re-entry from orbit is just an inherently hard problem. I'm not sure how they do it. The four options seem to be (1) the DC-X/FHUS concept, (2) the Starship body flap approach, (3) the Shuttle/X-37/Dream Chaser approach, and (4) the Stoke/Chrysler SERV approach. Number 4 clearly won't work for a New Glenn upper stage (unless they do a radical redesign and replace the BE-3Us with BE-7s), and you'd need separate landing engines for Numbers 1 and 2. So a winged, wheeled vehicle seems like the only possibility.

  14. 1 hour ago, Terwin said:
    8 hours ago, SunlitZelkova said:

    Would it be possible to launch a nuclear fusion rocket propelled interstellar ark using nuclear pulse propulsion from a ground site in the far north? I.e. stage one is an Orion, stage two is a Daedalus.

    Beyond the already existing issues with developing nuclear fusion and nuclear pulse propulsion, is there anything that would cause an issue?

    In the story I am writing, a nuclear war occurred nearly a century ago, but climate change is destroying humanity and the Soviets and Americans team up to evacuate a portion of their nations to a nearby star system. Because nuclear weapons and rockets were banned following the war, the project must be carried out in secret in Alaska.

    Nuclear pulse propulsion works in space because the pusher-plate works as a shield.

    In atmosphere, the heat an radiation can bounce off of air in addition to conduction and other methods of heat propagation that are not an issue in space.

    While a ground-launch Orion is more realistic than a star-trek shuttle, you would need a fairing that probably weighs more than the rest of the ship put together to have anything survive to orbit, and even that would be highly questionable.

    In-atmo-launched nuclear pulse propulsion would actually be slightly MORE efficient because the air provides an additional reaction mass. However, getting off the ground initially is...challenging. Most designs would use solid boosters or similar tech to get moving before the pulses start dropping.

    The pusher-plate would still act as a reasonably good shield in-atmo although the standoff distance might need to increase. Alternatively, it might be better to decrease the standoff distance and use a smaller nuke in-atmo, thus trapping more of the radiation behind the shield and relying on the increased impulse from aerodynamic remass to make up for the smaller nuke size.

    Average acceleration isn't significantly different than an ordinary vehicle so the fairing is not a big deal.

  15. 8 hours ago, mikegarrison said:
    16 hours ago, Nuke said:

    they were using a tougher material than any previous rocket. as i understand it the fts was more or less an off the shelf model that was designed to rupture aluminum tanks. solving the problem seems just a matter of using a bigger explosive device. 

    I certainly hope that's not true, because it would be pretty careless of them if so.

    The Shuttle and STS booster segments are steel, so using a similar FTS charge would make sense.

    It wouldn't necessarily be careless if they ran the numbers and they looked appropriate.

    3 hours ago, Nuke said:

    were talking maybe less than a few grams of explosives, as little as necessary, its just that starship needed a little bit more. steel just doesn't propagate cracks the way aluminum does.

    Shocking how much my prior experience comes into play here, LOL.

    Crack propagation in steel is a well-studied phenomenon in the field of transportation pipelines, although it primarily focuses on stress corrosion cracking (SCC) and other fatigue-based crack propagation. That's what you end up with in thick steels at ordinarily temperatures which are subjected to large internal pressure gradients. Rapid crack propagation in rupture scenarios can follow existing crack structures, but it is much more likely to burst at one point and then have a directional propagation through the steel at the local speed of sound. I remember one instance (I won't name the provider) where fatigue-based cracking weakened a particular bend in a pipeline, and then one day they had to abruptly shut down flow in an offshoot line several miles downstream. The spike in oil pressure from that shutdown propagated backward along the pipeline through the flow and intersected the existing standing-wave pressure gradient at that joint, causing a constructively-additive pressure excursion at the precise point of the SCC fatigue. The resulting rupture released all that energy in a beautiful sinusoidal wave for about 8' along the length of the pipeline. You could actually see where the crack propagation dropped below the speed of sound and stopped.

    Of course we only figured all of this out AFTER an entire LAKE of crude oil got dumped into someone's farmland, but I digress.

    All that to say: the relationship between rapid crack propagation, ductility, and tensile strength is a complex one, made all the more challenging by temperature. They may have been expecting crack propagation that happened in ground tests but didn't happen under cryo conditions, or they may have simply been relying on the rupture to cause tank implosion.

    4 hours ago, Nuke said:

    as for off the shelf, that seems to be the way things go for safety equipment. you want a tried and true design, and features more than a standard demo charge (telemetry and long range remote detonation are the big ones). whether they were left over from falcon testing or obtained by a supplyer of space hardware, idk.  scott manly did a video on that not to long ago. 

    SpaceX uses the same FTS explosive initiator, detonator, and linear shaped charges used by NASA on the Shuttle and STS main tank and boosters. Although the shaped charges are linear, they do not run the full length of the tanks.

  16. 15 hours ago, Nuke said:

    perhaps instead of pumping down the chamber, replace air with deuterium/tritium mix. then you just need a basic fission core to set it off. thermonuclar desing usually focuses the x-rays on a smaller volume, but if you could reflect the x-rays back into the sphere and let it bounce around long enough, it may impart fusion level energies, you could also pressurize the hell out of the thing being underground to get the density you need. but i dont know enough about nuclear weapons design to know if that would work or not. 

    Unfortunately it won't. You need a spark plug and a plasma source like Fogbank, and neither of those are going to be approximated by a giant-reflective-sphere arrangement.

    On 5/21/2023 at 3:09 PM, darthgently said:

    It would be far more efficient to simply run the same nuclear materials through a modern nuclear power plant design.  And there would be no tsunamis or massive fish kills either.

    I don't particularly feel like running the numbers atm but I am guessing that you would need at least multi-megaton-class nukes before the accessible energy from thermonuclear fusion pulses would exceed the output of simply shoving the fission materials into a modern reactor.

  17. 1 hour ago, CBase said:
    5 hours ago, sevenperforce said:

    Activation of FTS at 30+ km altitude might simply be something we've never experienced before.

    Good point. Are there any kind of information whether it was some problem transmitting the FTS signal (maybe not redudant via starlink ?), processing the signal, igniting the charge or time / pressure for enough structural damage to rip it apart ? Would we have seen the charge going off on the video ? I mean on the test tank it looked pretty obvious. But if it wasn't going off, was dynamic pressure or integrity really an issue ? Or maybe antenna / processing ?

    Starship+Superheavy, like Falcon 9, uses an AFTS. So there is no signal at all. Rather, the ship itself knows where it is and detonates itself if it flies outside of an acceptable corridor.

    What happened with the Starship test launch was twofold. First, the range of acceptable launch profiles was quite high (since they had contingencies for thrust shortfalls) and so the acceptable corridor was extremely broad. Second, when it finally did fall outside of its acceptable corridor, it was at 38 km and tumbling slowly with relatively low aerodynamic stress. The FTS charges popped holes in the tanks, but there was enough residual head pressure in the tanks that they maintained structural integrity for almost a minute before finally imploding and then ripping apart.

    Scott Manley has a video where he highlights the moment that the FTS charges go off and you can clearly see propellant spewing out while the tanks remain intact.

    Had the AFTS fired lower in the atmosphere or while under significant acceleration (either due to gravity or thrust), the FTS charges would have caused immediate tank collapse and breakup. But being so high in the atmosphere while traveling relatively slowly was a different matter.

  18. 54 minutes ago, mikegarrison said:

    There were a *lot* of things that went wrong. Blaming it all on "the FAA delegated too much to Boeing" is over-simplifying to the point of being dangerous.

    To be clear, I was saying that the FAA's lapse was over-delegation. The more serious lapses were within Boeing for sure. 

  19. 55 minutes ago, JoeSchmuckatelli said:

    I don't understand the hesitancy /resistance to oversight. It's not like this is rocket science, or anything.  We should absolutely trust the judgment of a politically appointed administrator to know what is in everyone's best interests. 

    Eh, there's no resistance to oversight to be found here.

    I've worked in the federal government -- specifically in the field of accident investigation, root cause evaluation, and process lapse mitigation. Specifically with methane, liquid hydrocarbons, and cryos, in fact. The feds on the ground performing certifications and evaluating process trees and double-checking industry work aren't political appointees. These offices are staffed with absolute nerd lifers whose entire personalities revolve around personal pet peeves that just happen to align with public safety. Bureaucracy moves slowly, but that can be a good thing in the world of safety, because political pressure doesn't often transfer downstream very well.

    Where you see problems are political and administrative overrides, like Challenger. All of those people on the ground doing good work are useless when the higher-ups simply overrule their objections. If that happens, it's definitely a reason for Congressional or other oversight of the regulatory agency, but fortunately that sort of failure is quite open and notorious.

    Calling for an "independent review" of something which still has not been shown to even constitute a failure doesn't seem like oversight; that seems like political posturing in its own right. I'm reminded of that scene from The Phantom Menace:

    Chancellor Valorum: "The point is conceded. Will you defer to allow a commission to explore the validity of your accusations?"

    Queen Amidala: "I will not defer. I've come before you to resolve this attack on our sovereignty now. I was not elected to watch my people suffer and die while you discuss this invasion in a committee!"

    If there's an actual problem, then we should identify the problem, characterize the problem, and determine whether it was a lapse in oversight or an unknown unknown...not create an independent commission to tie things up endlessly with no actual goal or objective.

    49 minutes ago, Pthigrivi said:

    At the same time I don't think the FAA or the environmental review imagined SpaceX would be ejecting a few hundred tons of pulverized concrete over a 5m radius in a wildlife refuge. 

    I haven't looked at the environmental review closely, but given that a pad RUD was one of the possible failures, I can't imagine what actually happened being WORSE than what the environmental review was prepared for.  If the whole stack had blown up on the pad it would have been a lot more destructive than what actually happened, and with a much bigger radius, too. The 2020 Beirut explosion had a yield of approximately 1.1 kilotons TNT equivalent and did this:


    A Starship+Superheavy pad RUD would have a yield of at least three Beirut explosions and possibly up to nine Beirut explosions. Again, I cannot imagine that the pyroclastic pad launch (which blasted chunks of concrete as far as a kilometer but only sent fine particulate matter and dust significantly beyond that) was as bad as an RUD would have been. Dust and particulate matter certainly went beyond the expected debris field, which is cause for investigation, but that's already being investigated by the FAA.

    49 minutes ago, Pthigrivi said:

    Im happy to see those plates go in and I hope they work. Seems like a lot of headaches and raised doubts could have been avoided by putting them in first. 

    You and me both. In hindsight it was more of a gamble than they thought, although I think it was more of a program/schedule gamble than a public safety gamble.

    44 minutes ago, darthgently said:

    I'm wondering if part of the delay of the FTS was underestimating how much stronger that flavor of SS is at cryo temps.  The (apparently) unexpected resilience of the craft while doing flips in thick air seems to somewhat support this possibility

    Thick air, yes, but how thick?

    38 km is certainly much lower in the atmosphere than the altitude where separation was intended to take place, but it is still MUCH higher than ordinary aerodynamic altitudes. At a speed of 500 meters per second and an air density of 0.41 g/m3, the dynamic pressure is 1.95% of the dynamic pressure on the SR-71 and a scanty 0.24% of the dynamic pressure on Falcon 9 at MaxQ. It's the equivalent of a semi-truck doing slow donuts while sliding across an icy parking lot at an average speed of 20 mph -- definitely out of the ordinary, but nothing you'd expect to crumple steel (at least not from aerodynamic forces).

    Has there ever been an FTS activation at that altitude? Challenger blew up at around 15 km. Activation of FTS at 30+ km altitude might simply be something we've never experienced before.

  20. 6 hours ago, SunlitZelkova said:

    Something something 737 MAX something something.

    Not saying independent review is needed, just that the FAA is not that reliable.

    IIRC, the FAA's lapse over the 737 MAX came from delegating too many of the certifications to Boeing and just taking their word for it.

    If the delayed effect of the Starship AFTS is considered a failure (and again, that's something I'm assuming, not something that's necessarily evident), then there's value in the FAA looking at whether a similar lapse was involved. Did the FAA simply trust SpaceX's assurances that the AFTS would produce an immediate RUD without verifying? Or was the delayed effect an unintended consequence of enhanced structural integrity that no one at SpaceX or the FAA could have anticipated? If the former, then it would be worthwhile for the FAA to look at its review process to see if it is unjustifiably delegating certifications in other areas. If the latter, then it falls into the "unknown unknown" category and increased oversight isn't going to make a lick of difference.

    And ^^THAT^^ is how you properly handle root cause evaluation and mitigation of process lapse during a failure investigation. Not by demanding an undefined, ill-conceived "independent review" with no meaningful goals or realizable objectives.

  21. 13 hours ago, magnemoe said:
    14 hours ago, Terwin said:

    Are you suggesting that yelling 'do better' on the internet after an experimental vehicle launch with no crew or payload experienced anomalies that did not injure any of the many many bystanders is an insufficient argument to tear-down and rebuild from scratch every involved agency and organization?!?!??!

    Clearly every technical failure requires that we abandon all faulty technologies and start over with wood and bone tools!

    No experience with bones outside the one inside me and in food.
    But wooden shafts has lots of problems. 

    I don't understand all of this insistence on using these new-fangled wooden tools. That's a fast way to get splinters, if you ask me. Fists and dirt clods were good enough for my grandpappy and they should be good enough for me.

  22. 24 minutes ago, tater said:

    Still, the cut out for 2-3 engines could be a frustum of a cone such that there is room at the exit end (~1.2m/engine, plus gimbal needs), but less room at the top.

    Indeed. Made even more advantageous if the bell alone gimbals rather than the entire thrust structure.

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