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[Madman198237]

Space is a pretty good insulator but starship is not, as evident by the condensation and ice patches forming immediately upon prop load,

Starship has good enough insulation for the purpose; remember that that is formed in air which conducts heat a lot more readily than vacuum and it's due to the substantial time it takes to load the Starship, which lets the whole thing cool down dramatically. Once in space, that stainless steel hull will reflect most of the sunlight striking it, while on the dark side the temperature in earth orbit is like 20 Kelvin or something like that? It's not quite the universal background 3 K but it's close.

In short, the actual rocket scientists who set this up do in fact know what they're on about. They won't lose all their propellants no matter how long the mission goes.

Autogenous pressurization is just "use the propellant to pressurize the propellant tanks" but IIRC the precise way SpaceX is doing it relies on the exhaust from their gas generators, which is a great place to get hot gas to pressurize the propellant tanks, which does bring along some CO2 and H2O because those are the products of the reaction. I could be wrong there, I'd have to go back to whatever EverydayAstronaut or Scott Manley video mentioned it.

The reaction control/attitude control (same thing) thrusters use the gaseous component of the tanks, but as far as I have heard the larger methalox thrusters that are going to use the liquid component to aid in thrust, because even in 1/6 gravity you do still need a good amount of force to land the 120+ ton (depends on how much fuel it's burned at this point) Starship on the lunar surface.

[Starver]

ISTR early (Starhopper? Falcon 9?) "rapid self-disassembly" was caused by the internalised helium tank failing and/or being failed by another element, causing overpressures.

There's pros and cons in all the different solutions to the pressurisation problem (including feeding 'waste' gases back in and using header-tanks), but I suppose I have to trust the people who have actually been building and launching these things (mostly) successfully as having done their homework/etc to do it in one of the least-worst ways... 

[Madman198237]

There was a Falcon 9 launch (CRS-7) that failed when liquid oxygen infiltrated the carbon composite laminate of a liquid helium tank, and then froze solid, forcing apart layers of the carbon composite until the helium tank failed and overpressured the oxygen tank, causing that to fail, which destroyed the vehicle.

Liquid helium is EXTREMELY cold (~20K) which is why it can freeze liquid oxygen which is already very cold (~80K), and the COPVs (Composite Overwrapped Pressure Vessel) are kept under incredible pressure so they can keep the main propellant tanks pressurized without being too huge.

[Starver]

Sounds about right. I also recall a different instance (not SpaceX, I think) when an internally-slung helium tank came entirely loose from its mountings/vent-valve within the larger tank (launch forces upon manufacturing insufficiencies?) and thus vented improperly into the outer-tankage to similar effect. (All this determined from secondary sensors and/or by examining the bits that were recovered, either and both of which are technical feats in themselves, when you think of it...  )

[jipehog]

The reaction control/attitude control (same thing) thrusters use the gaseous component of the tanks, but as far as I have heard the larger methalox thrusters that are going to use the liquid component to aid in thrust, because even in 1/6 gravity you do still need a good amount of force to land the 120+ ton (depends on how much fuel it's burned at this point) Starship on the lunar surface.

If so, then Starship would have to use its main engines to launch from the lunar surface. Without a launchpad, we would have to deal with the same situation we saw in the recent launch with destructive regolith bits flying that could damage the ship.

Autogenous pressurization is just "use the propellant to pressurize the propellant tanks" but IIRC the precise way SpaceX is doing it relies on the exhaust from their gas generators, which is a great place to get hot gas to pressurize the propellant tanks, which does bring along some CO2 and H2O because those are the products of the reaction. I could be wrong there, I'd have to go back to whatever EverydayAstronaut or Scott Manley video mentioned it.

I think I understand now. They are utilizing the residual ullage gas for control authority cold gas thrusters venting, however, for the landing they would need higher thrust for which hot gas thrusters combustion engines are utilizing for which you argue that ullage gas --which include exhaust from the oxideizer pump gas generator spin up process-- will not be useful or instead that feeding lox --of which should be in abundance-- directly to the hot thrusters would be far more efficient. That make sense.

Once in space, that stainless steel hull will reflect most of the sunlight striking it [..] They won't lose all their propellants no matter how long the mission goes.

I assume the last sentence is hyperbole. Heat would be added to the system from ambient and onboard sources, which would eventually cause the oxidizer to heat.

For common missions, like injecting satellites into orbit, it is much more cost-effective to just accept the boil-off and save on insulation weight or added complexity from active cooling. While it is possible that for the 10-day journey (3 in transit + 7 on the lunar surface ?), the only adjustment that Starship HLS would need to do is to top off its tanks (or add some insulation for the header tanks). I am curious as to what is their estimation for daily boil off get a sense of perspective.

There's pros and cons in all the different solutions to the pressurisation problem (including feeding 'waste' gases back in and using header-tanks), but I suppose I have to trust the people who have actually been building and launching these things (mostly) successfully as having done their homework/etc to do it in one of the least-worst ways... 

This isn't an exercise in trust, but fun time of figuring something new with no up to date readily available documentation. Unless you are holding on me

[Madman198237]

If Starship's lunar landing engines can land it on the surface safely, then they're powerful enough to lift it back OFF the surface. Basic physics, after all. At absolute worst (just barely greater than 1-to-1 thrust-to-weight when on the lunar surface) the landing engines can still lift Starship high enough above the surface to let the main engines light without blasting rocks into themselves.

Eventually the propellants (NOT just the oxidizer) will evaporate...but it will take a long time if the vehicle is designed reasonably. Also, the lunar missions planned for Artemis are I think 3-4 weeks total? Up to two on the ground plus a longer transit to and from Gateway.

[jipehog]

According to Musk they are building a "massive water-cooled, steel plate to go under the launch mount". Any how it would look like, or if it would be sufficient?

Eventually the propellants (NOT just the oxidizer) will evaporate...but it will take a long time if the vehicle is designed reasonably. Also, the lunar missions planned for Artemis are I think 3-4 weeks total? Up to two on the ground plus a longer transit to and from Gateway.

Do anyone have any info on Artemis mission (detailed is good, I enjoyed reading and going over the engine schematics before) same with any data that would allow to quantify how long is long time?

Btw does starship has any hidden radiators on its exterior or plans to add them (like with apollo), if not what it would do for heat management? Any sense in tapping those huge tanks full of freezing material to dump heat into?

[jipehog]

Any thoughts on aerospike rotating detonation engine?
https://www.youtube.com/watch?v=RVxgyz_avQM

[jipehog]

NASA selects Blue Origin to develop second Artemis lunar lander
https://spacenews.com/nasa-selects-blue-origin-to-develop-second-artemis-lunar-lander/

[Starver]

I had a soft-spot for the Dynetics ALPACA, but... hey. Mass problems.

(It maybe reminded me of some of the games that I've played far too much in the past.)

...and if SpaceX can't sort its issues out, who knows if Artemis 3 also has to use it/be kept back until it can be. Not that we can be sure New Glenn is even viable for the job yet, either.)

[jipehog]

From what I hear they fixed the problems, its now just matter of price point and Blue origin was able to incorprate much of their advantage and with Bezos deep pockets offer a more attractive option.

Is there any major advantage to Blue Origin proposal over spaceX? it seem like smaller a starship an unnecessary duplication of effort.

----

continues to be an important partner to AFRL as we build hypersonics capabilities and remove America’s dependence on foreign propulsion systems for launch

https://spacenews.com/air-force-research-lab-to-fund-development-of-ursa-majors-rocket-engines/

Any notion of what foreign dependence they try to shave off? Two engines are mentioned 4k and 200k pound force, so some sort of missile smaller than MLRS, and some sort engine weaker than Raptor presumably for a small launch vehicle.

[Culise]

Any notion of what foreign dependence they try to shave off? Two engines are mentioned 4k and 200k pound force, so some sort of missile smaller than MLRS, and some sort engine weaker than Raptor presumably for a small launch vehicle.

They're almost certainly referring to Lockheed/ULA's Atlas V which uses RD-180s sourced from Ukraine and Russia.  Between the war and the sanctions, both suppliers are no longer supplying, which means that once we use them up, there will be no replacements.  Likewise, the Northrop-Grumman's Antares was a joint venture with Pivdenne Design Bureau in Ukraine.  The Antares 100 uses AJ26s repurposed from Kuznetsov NK-33 engines imported in the 1990s, and the Antares 200 series was intended to use RD-181s manufactured in Dnipro.  As such, the war and resulting disruption of production put the brakes on plans for the 200 series, and the replacement will use American-built replacements.

[Madman198237]

Atlas V is gone; all remaining launches are sold and I think all the boosters for them are built.

What they're talking about is the previously existing (and already rapidly vanishing, the war has just hastened the process) dependence, and those ventures using Ukrainian parts since obviously the supply of those parts is now in jeopardy.

[jipehog]

I am confused these engine seem to be very different, both in size and thrust, from RD-180 and is far from being complete certified (or did I get my metrics wrong?). And USA already have the tried and true raptor, and several other space engines in various stages of completion/testing.

Meanwhile this articles says that

The engine would be used to build target vehicles simulating hypersonic missile threats.

[Culise]

I am confused these engine seem to be very different, both in size and thrust, from RD-180 and is far from being complete certified (or did I get my metrics wrong?). And USA already have the tried and true raptor, and several other space engines in various stages of completion/testing.

Meanwhile this articles says that

The engine would be used to build target vehicles simulating hypersonic missile threats.

Two different engines, two different roles. The Draper is the hypersonic missile engine to "build hypersonics capability".  The Arroway is the staged combustion engine for medium and heavy launch vehicles to "remove America's dependence on foreign propulsion systems."

Otherwise, it is worth remembering that this is being said by someone who is selling something, specifically rocket engines.  As I said and as Madman concurred, the Atlas V is down to what we have left to use up over the course of the next six years; no new ones are being constructed, and once the last of the Kuiper Systems and Boeing Starliner orders are launched, that will be the last of them.  The Antares 100 was likewise used up in 2014, and the very last Antares 200 series is slated for use July this year.  To my recollection, all other US launch vehicles already use domestic engines.  The Arroway can conceivably replace the RD-180 or RD-181 if clustered once certified, but more likely, it's just a combination of an appeal to patriotism and supply security.