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That voiceover is unbearably fast - I could only pick out about one word in a hundred!
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"It will take hundreds of flights to be successful from a reliability perspective before humans will fly/land on the moon."

That certainly wasn't true for Saturn 5.
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I'm trying to figure out why the power head is getting optimized here with all sorts of fancy ways of dealing with fragile turbopumps that throws away what was learned with Raptor's power head.

Is the powerhead really the limiting factor on current state of the art methalox engines?

From what Elon says, it's temperature of the combustion chamber that's the problem. It gets very melty.  The other big problem is startup and shutdown sequences for FFSC, but they appear to be very far along on working that out.

Thrust and exhaust velocity is proportional to chamber pressure and temperature (de Laval equation).  If you aren't increasing those, then you aren't increasing Isp or thrust.

The combustion chamber is already 99.5% efficient an knitting the molecules together on Raptor.  What further energy do you think you can extract from methalox?
It gets melty because they use as little film cooling as possible in order to have a good combustion efficiency.
You don't gain anyting by adding more cooling than necessary to the main combustion chamber because it's already burning at close to stoichiometric ratio.

But on a turbine you have so much to gain by going from 800K to 3500K that a little combustion inefficiency is worth it. More pressure also means an higher nozzle expansion ratio so it might ends up more efficient overall anyways.
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ISS Section / Re: Expedition 71 thread
« Last post by Yellowstone10 on Today at 11:15 am »
Visual confirmation this morning that STP-H9 is indeed on EFU-7 (furthest outboard position on the forward edge of the JEM EF). The first picture is from 22 April before the robo ops, the second is from about an hour ago.
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Film cooled turbine blades are typically laser drilled with thousands of small holes that the cooling air bleeds out of.  On a rocket engine that cooling role role would be taken by liquid methane propellant which would burn immediately after it was released through the cooling holes. 

What if that was made a feature instead of a bug so that the methane turbine replaced the injectors as the primary mixer for fuel and oxidiser.  The LOX turbopump would be similar to the present arrangement.  The methane turbopump would be constructed as a spinning sleeve inside the main combustion chamber so running coaxially with the oxygen turbopump.  The pump impellers would exhaust to integrated cooling channels and circulate through the chamber walls, throat and then the bell.  On return the liquid methane would be used to support the sleeve on the walls of the combustion chamber as a hydrodynamic bearing and would travel through the vanes of the turbopump to cool them while being injected into the combustion chamber to mix with the pumped LOX and ignite. 

The rotation speed of the turbine means that there would be good mixing of the propellants similar to a swirl injector.  The turbine blades would remain well cooled even though they are physically placed at the upper end of the combustion chamber.  The combustion chamber temperature local to the turbine section would be intermediate between the LOX inlet temperature of say 800K and the final combustion chamber temperature and combination of evaporative and film cooling would keep the blade temperature under 1300K and with reducing conditions.
That's pretty much how monopropellant turbopumps work, there is a catalyst on the turbine blades so the reaction happends when the monopropellant touches the turbine.

Propellant moves from the highest pressure to the lowest pressure, what makes a turbopump work is that despite the pressure being higher in the fuel injector than on the turbine blades those gases expand as they burn so the flow rate is higher on the turbine than in the injector, which means the turbine gets back more power than it has to give to inject fuel.

That principle would also work if fuel injection was done on the turbine, the small holes only cover a tiny percentage of the area of the turbine so as the fuel burns and expands the overall force on the turbine is increased even if the pressure is reduced.
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https://www.fly.faa.gov/adv/adv_spt.jsp:

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SPACEX STARLINK 6-54, CAPE CANAVERAL SFS, FL
PRIMARY:   04/26/24      2240-0311Z
BACKUP:      04/27/24      2215-0246Z
      04/28/24      2150-0221Z
      04/29/24      2125-0156Z
      04/30/24      2059-0130Z
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I have two ideas for making a better architecture. One is to minimize the requirements on the OS. Launching anything from Mars is insanely difficult and expensive. The mass of the OS needs to be kept down as much as possible. If the OS does not need to handle the loads of a parachute-less landing, then it can be made much lighter. Past studies indicate that a 5kg OS on a 300kg MAV could be landed by the same skycrane hardware that landed Perseverance.

The other idea is to move requirements to the cheapest locations. High Earth orbit is a far cheaper location to operate in than any Martian orbit. Mars orbit is a much cheaper place to operate than the Martian surface.

My architecture would replace the current Earth return orbiter with three different spacecraft. I call these the Catcher, the Transporter and the Quarantine spacecraft.

CATCHER
This spacecraft would be waiting in low Mars orbit when the MAV launched. It would rendezvous with and capture the OS as soon as possible after launch. It would then boost itself into a long term stable orbit and wait. This approach minimizes the chance of being unable to locate the OS in orbit. It also minimizes the demands on the MAV for orbital altitude and precision. It would be a small spacecraft with a high fuel fraction and a very long lifetime. It would have to be funded now, but the next two spacecraft could be funded later when money is available.

TRANSPORTER
This would fly to Mars to rendezvous and dock with the Catcher. It would pick up the OS and would fly back to a high Earth orbit. It would use solar electric propulsion. It would be much smaller than the current Earth Return Orbiter (ERO). The ERO carries a 90kg Earth Entry Vehicle (EEV) to Mars and back. The Transporter would only have to return a 5kg OS to Earth. That requires something a little more capable than the Japanese sample return mission to Phobos, which isn't enormously expensive. That mission, the Martian Moons Exploration (MMX) mission, is estimated to cost $417 million.
MMX mission article: https://arstechnica.com/science/2020/02/ambitious-japanese-mission-to-phobos-moves-into-development-phase/

QUARANTINE
This is the largest and most complex of the three spacecraft. Located in a high Earth orbit, it would receive the OS from the Transporter. It would unload the sample tubes from the OS, do whatever sterilization is required, and load them into the Earth Entry Vehicle (EEV). When planetary protection approval is received, it would send the EEV to the surface. This avoids sending the EEV on a round trip to Mars and back. It also avoids sending complex sterilization hardware to Mars orbit. Being in Earth orbit allows near real time communications so the robot arm for sample tube transfer could be operated from the ground.

This is a more complex architecture than the current one. However, two stage to orbit launch vehicles are more complex architectures than single stage to orbit, yet they are much easier to build than single stage to orbit launchers. Sometimes splitting things into multiple stages cuts cost.
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Commercial Space Flight General / Re: Perigee Aerospace
« Last post by TheKutKu on Today at 10:01 am »
https://m.mk.co.kr/news/it/10998084

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On the 23rd, Perigee Aerospace announced that it will tentatively launch Blue Whale from Jeju on the 27th of next month, at the latest within the first half of this year. The launch will use ‘Setesia 1’, a Perigi Aerospace marine launch platform, in the west sea of ​​Jeju. The plan is to launch Blue Whale from a launch pad located at sea, perform a suborbital flight, and then drop it to the sea level within a safety control radius. Perigee Aerospace said, “This launch will verify the flight capabilities of Blue Whale, which we developed ourselves. If the launch is successful, it will mean that the performance and stability of the propulsion, structure, and flight control systems of the launch vehicle have been verified.” explained.
This launch will also carry a payload. It will be launched carrying micro-satellite components from domestic space company Cairospace and Spacelintech's space medicine platform. Perigee Aerospace said, “In addition to verifying the launch vehicle, we will also verify the space technology of domestic New Space companies.”

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3) JPL has been dithering about whether to do two landers (both of them a bit larger than Perseverance) or one lander (a lot larger than Perseverance).  Either way, packing the fetch hardware and the MAV in are volumetrically challenging.  This doesn't have that problem.

Originally they were concerned that Perseverance wouldn't still be operating when the Sample Return Lander (SRL) arrived. So the plan was to cache the samples and pick them up with a fetch rover built by ESA. As the size of the MAV grew from 300kg to over 450kg, it eventually became impossible to accommodate the fetch rover on the same lander. One possible solution was to put the fetch rover on a second lander.

The unexpected success of Ingenuity gave NASA another option for collecting the samples. And Curiosity continued to perform well, so the estimate of the likely life time of Perseverance increased. The fetch rover was dropped, and the plan shifted to using Perseverance to deliver the samples to the SRL, with Ingenuity type helicopters as a backup.

Given the mission delay they may have to change plans again, and I'm not sure what they are going to do.
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