RCgothic

I think the idea is that ICPS is only 32 tons and FH has at least 63t of nominal payload, so looking at just those numbers would end up with a stage that's twice as powerful. Unfortunately the largest monolithic payload a Falcon mission has ever carried is 17.5t, with the rest being propellant residuals in the FUS. With a modified adaptor it might be possible to put up ICPS itself with Orion going up separately, but even ICPS doesn't actually have enough DV to send Orion to TLI from LEO (on SLS the core stage helps, but for a simple rendezvous in LEO there'd be no help). Only SpaceX knows whether they could actually fly a full 63.5t on FH as a monolithic payload. Another problem is that Orion/ESM can't capture into LLO and return by itself. The "kick stage" would also have to do LLO insertion. One option is to put up a full falcon upper stage with 63.5t of residual propellant and dock that to Orion in LEO. That would have enough power to send Orion to TLI, but not to also do the full insertion to LLO as would be needed even if the stage were to demonstrate a 3+ day endurance. EUS has way more DV than needed to do TLI and LLO insertion with just Orion (if it has the endurance), but it weighs about 140t at launch (although it has to do a partial burn to reach LEO with SLS) which takes us back to needing SLS (or starship).

I had a look at this yesterday, but I think a 3 yottaton bomb is still several orders of magnitude (10^32) below the kinetic energy of the sun around the galaxy (10^40), and less than the orbital kinetic energy of Jupiter (10^35) or Saturn (10^34), so it's still a little less than a solar system scale Orion propulsion device. It's within shouting distance of the energy required to liberate all of Neptune from its gravitational binding energy (10^33) but not quite.

You'd be insane to have a bomb that large anywhere near a civilised star system. 3 yottatons (3x10¹⁸ Megatons) is a quantity of tnt equivalent to ~500 earth masses and more than a year's solar output in all directions (7.9x10¹⁵ Megatons). Like KSK says ,this is enough energy that (if efficiently transferred) could permanently disassemble the earth over 50 times. If the blast were to last a minute, the bomb would shine 30 million times brighter than the sun (mostly at sterilisating gamma wavelengths). If you detonated it at a pluto's orbital distance, it would still be 5000 times brighter than an earth day for a Pluto located diametrically opposite. If it detonated anywhere within a solar system that system would be sterilised. Some *gift*.

I saw on XKCD a while back the idea to take a swimming pool of water. On the moon our power to weight ratio would be enough to leap like dolphins.

Well Boeing isn't exactly renowned for its judgement.

If SLS were to send the lander as well, if it had twice the payload capacity it still wouldn't be as good as either lander in the current Artemis plans. The co-manifest volume isn't big enough. Alternatively SLS would need both the ability to launch twice as many times per calendar year and to launch twice within a very short interval to supply both the lander and crew. For which, lol, Boeing. And even then, relying on SLS would set back the development of reusability and orbital refilling which are IMO necessary techs which are already long overdue.

Whether it not we have SLS, a lander would have to be developed. The questions are if, without SLS: 1) Could we design a lander as effective as the Artemis landers? A resounding yes. SLS is not sending the lander in Artemis, so we can expect no substantial difference in lander capability here. In fact we can expect an improvement, because for fast transits the round trip DV of LOI, landing and ascent is less than the round-trip DV of NRHOI, landing and ascent, so for the same delivered mass a greater proportion could be devoted to the mission instead of propulsion. 2) Could we get crew to and from rendezvous with the lander? Again, a resounding yes. With a 16t hypergolic propulsion module met in LEO and a docking target in the trunk, Dragon can get in and out of LLO from TLI with reasonable modification. The Falcon upper stage can send over 32t through TLI if falcon heavy puts it into LEO with 63.5t of residuals and it meets the mission there. And this has none of SLS's cost or cadence issues. Such a mission mode could easily support permanent inhabitation.

There was nothing actually wrong with the TMI reactor itself. It was mainly a failure of procedures and instrumentation. How the accident began: For a start the reactor should never have been at power with both the auxiliary feed water pump stop valves for the secondary loop locked off. The control room operators didn't even notice because the indicators were covered (in one case possibly by an overly fat belly!). This was a major breach of the operating license. The reactor should not have been operating. Then an improvised filter-cleaning procedure caused water to get into an instrument line and spuriously turn off the main feedwater pumps leading to a turbine trip. When the turbines are tripped, they no longer remove heat from the secondary loop, causing the temp and pressure in the secondary loop to rise. This is usually corrected by dumping steam and back-filling with feedwater. Except all the main and aux secondary loop feedwater pumps are all effectively inoperable and the operators don't know. In fact they can see the aux pumps running, but don't know they're doing nothing due to their stop valves being closed. So the secondary loop is getting hotter and depressurised by steam dumping without replacement. The operators don't understand the situation. The primary circuit is affected by the secondary loop, as the amount of heat that can be removed in the steam generators is greatly reduced. A brief aside on pressure control in the primary circuit: There's a pressuriser in the primary coolant loop that contains a steam bubble. Pressure can be increased by turning on heaters in the steam bubble to increase its pressure. Pressure can be also reduced by spraying cold water into the steam bubble to reduce its temperature, or by a solenoid operated pressure relief valve. The level of water in the pressuriser can simultaneously be adjusted by adding or removing water to the primary loop. Generally in the absence of coolant addition/subtraction an increasing pressuriser water level indicates increasing primary loop temperature (and due to expansion compressing the steam bubble - pressure). Back to the accident: So with heat not being removed from the primary loop, the primary loop gets hotter, and the coolant expands. It pushes into the pressuriser, compressing the steam and increasing the primary loop pressure. This is when the pressure relief valve is commanded open and sticks open. But it's not enough to keep the pressure down with the reactor at full power, so the reactor is tripped and the control rods inserted, reducing reactor power to ~6% resulting from decay heat which is still substantial. But the pressuriser level continues to rise even as the primary loop pressure is falling. The operators haven't been trained for these parameters disagreeing. The pressure is falling due to the steam bubble getting vented through the stuck valve, and the level is rising due to the decreased pressuriser bubble and another steam bubble forming invisibly to the operators in the reactor pressure vessel (due to boiling in the low pressure) then displacing coolant into the pressuriser. There is basically already a minor loss of coolant accident in progress, but the operators take far too long to work this out. It's exacerbated by bad instrumentation - the control panel doesn't show the valve's actual position, what it reports as valve position is just the solenoid power status, and as the valve is stuck this is incorrect. There was a temperature sensor downstream from the pressure relief valve that could have helped indicate coolant was passing the valve, but as it was not considered safety critical its display was located on a panel that the operators weren't likely to notice in the heat of crisis. Pressuriser level rising uncontrollably is normally bad - if the steam bubble disappears the primary loop effectively "goes solid", and therefore could be subject to large pressure excursions as the "incompressible" coolant fights its pressure vessel. The operators have been trained never to allow this as it can cause a loss of coolant accident. So they turn off the primary coolant feed to try and lower the pressuriser level. This is *exactly* the wrong thing to do during an actual loss of coolant accident! It stops the falling coolant level in the RPV getting topped up, and stops cold coolant being introduced to keep the temperature down. By the time the operators work out their mistake enough coolant has boiled off that the fuel has overheated and melted. How to fix the TMI reactor design: Better operator training. Interlocks to prevent reactor operation with safety critical systems locked off for maintenance. Better control panel layouts. Revised, more reliable pressure relief valve. Safety critical valves to have indicator switches to report their actual position, not merely their solenoid power status. The actual reactor design was a good and safe design. Despite the accident and radiation release there's no direct evidence of harm to anybody off-site. Reactors for lunar bases: The main challenge for reactors in space is heat rejection. Earth-based thermal power plants (not just nuclear) generally need to reject heat to the environment, and the best way of doing that is by releasing steam or using bodies of water as heat sinks. Neither of those is especially possible in space, and radiators are very much less effective at heat dissipation so they'd need a lot. Water for the primary coolant loop is also very heavy, which could be prohibitive. Perhaps a space-based reactor would be better off using a high temperature gas-cooled or liquid-metal cooled design rather than a conventional PWR using water and steam cycles. Gas is a lighter coolant than water, and liquid metal would allow a denser, more compact and therefore potentially less massive reactor as a result, and both could have higher temperature exhausts which would make their radiators more effective. It could also be better to use much higher military/weapons grade fuel enrichments as the mass of fuel to be transported would be a lot lower, and again they'd have higher power densities allowing smaller less massive reactors as well. I'm speculating a bit though. Presumably there are some NASA papers somewhere with some concrete plans, my experience is of AGR and PWR reactors.

Yes, easily. That's the power of rendezvous.

The payload envelopes Falcon and Vulcan can fit any crewed capsule ever flown and every space station module bar skylab.

SLS never wasn't obsolete. F9, Falcon Heavy and Vulcan are all perfectly capable of supporting lunar Earth Orbit Rendezvous mission modes. It'd would have been better cheaper and more frequent to spend SLS's budget on the surface mission rather than the marginally useful rocket to nowhere.

10 in January alone. 120 by year end at this rate!

Your copied text is interfering with dark mode again, @Exoscientist btw. When I rounded up to 60t, it was on the basis that SLS Block 2 Cargo can do 46t to TLI but B2 Crew can only do 43t. There's a 3t penalty associated with the LAS and the intermediate payload fairing (which does get carried through TLI). I inadvertently used 6t, (because apparently 46-43 is difficult math) but with sevenperforce's DV correction it comes out roughly the same anyway: A lander from scratch, stretched ESM, and an SLS Block 3 upgrade would not be better/faster/cheaper than the current approach.

There seems to be a discrepancy in some of the DV maps I've been using. Depending on whether it's 680m/s or ~820m/s - if the latter I get about 10.7t additional mass required to get to LLO with a 15t payload and return with ~100m/s margin for free-flight and rendezvous. So that's 60t to TLI required, as near as matters, to land an Apollo LM on the moon using SLS and Orion. I already think the Apollo LM is far less capable than we need, a 2t Cygnus derived lander ludicrously, even dangerously so. A lander with an ascent stage that light could only be done by cutting margins beyond the bone. Hydrolox is also absolutely not a propellant you consider in the same breath as breath as reliability and endurance. And as for timelines, regardless of the challenges facing Starship and *Blue Origin* HLS, a clean slate design is starting five years behind Starship and 3 years behind BO. If Starship or BO HLS can't meet Artemis III and IV timelines at this point, then it simply can't be done. The timeline needs to change, not the lander. Spaceflight timelines are *never* improved by starting from scratch mid programme. *Never*. I have a lot of sympathy for blowing up the timeline to acquire greater mission scope and craft capability. We should do this to rework the mission architecture to get rid of SLS and Orion. But a skeletal lander proposal does the opposite - it trashes the timeline to make everything worse.

I do agree a larger service module on Orion would be better, given where we've ended up. It would actually improve SLS Block 2's co-manifest payload to NRHO as well, as SLS B2 can throw more combined mass of Orion/ESM and payload to NRHO than Orion can actually brake into that orbit and still return. SLS might *possibly* be able to do a single stack Apollo style mission with an Apollo LM *if* the ESM is upgraded with an additional 6.5t of propellant and 0.6t dry mass. The total mass to TLI would then be ~ 55t including the payload adaptor and intermediate fairing. Block 2's stated capabilities are 49t to TLI, so on paper it's a no-go although they might be sandbagging a bit. But I don't know why we'd want to. Which is what we keep coming back to in this discussion. Apollo style with SLS gets ~3days on the surface every other year and a few hundred kg of samples each time at most, after a multi-year delay to develop a lander that small. Artemis HLS style gets potentially months on the surface per crew launch and tonnes of sample return, with scope to bypass SLS entirely and go multiple times a year and an architecture that also works for Mars, with landers that have already cut metal. I just don't understand why anyone would prefer Apollo-style.

The early statements from BO were "we'll recover New Glenn from the first flight" to which everyone's response was "believe it when I see it". As said, they no longer have any recovery assets so it looks like they've walked back from that statement, and trying a few test landings over water first would indeed be prudent.

IFAIK we've identified no pad or barge hardware and their ship has been sold so probably not, but then this is BO so something might materialise out of nowhere. I'd assume not for now though.

https://spacenews.com/spacex-targets-february-for-third-starship-test-flight/ Next flight hardware ready in Jan, FAA license expected Feb after closeout of IFT-2 mishap investigation actions. Not forthcoming on what those actions are.

I have spent a fair amount of time on fastener tightening in my career. Basically, if the fastener isn't tight enough to bind the joint without slip, then it will fret and chafe and fatigue and fail under repeated load cycles. Castellated nuts and cotter pins are a *terrible* way of securing a bolted joint. The nut has to have enough clearance to get the pin in which means in practice it can back off a little. Depending on torque and wear it's not unusual to shear the pin entirely. At best this will temporarily retain a nut that's come a bit loose before the bolt fails. The best way to make sure a nut doesn't come loose is to ensure it's correctly fastened to begin with (and the best way to do that is with a stud puller) and definitely not with a castellated nut. Yikes.

Following a successful mission by Vulcan, the peregrine lander has suffered a propulsion anomaly that nearly resulted in its battery depleting and solar arrays not pointing towards the sun. The team conducted an improvised manoeuvre to get the spacecraft oriented correctly, but the propulsion failure may be a serious issue. Peregrine Mission 1: Lunar spacecraft back in contact and battery being recharged after 'propulsion anomaly' | Science & Tech News | Sky News

Even if it was a knife-edge of mostly exactly 120s tests with a few falling short (which this data isn't), that would *still* not say anything about raptor's reliability because 3rd party observers have no idea what's being tested or what the abort criteria are. It could be GSE faults. It could be test aborts more conservative than flight. It could be testing above 100% throttle. It could be deliberate tests to failure. Nothing can be inferred definitively from this data.

You don't know those were all supposed to be 120s burns.

https://xkcd.com/2876/ The Range Mischief Officer has modified the trajectory to add a single random spin somewhere in the flight, but won't tell us where.

So that's 98 launches total? So close!

Also we just don't do things the same way anymore even where the production drawings are explicit. We wouldn't braze a load of individual cooling pipes for instance, and would have a very hard time following any drawings calling for that. We'd 3d machine instead.