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Posts posted by RCgothic

  1. I've asked on Twitter but I'm not fully clear - are the bid amounts total for the next phase of development? I.e. divided over years it at least *somewhat* matches the proposed funding.

    Or is it an annual dev cost and the proposed funding is therefore a joke?

  2. On 12/17/2020 at 9:20 AM, Albert ninestein said:

    Sorry for old thread revival. I was googling the (impossible) idea of recycling rocket exhaust in a closed system which this topic shows doesn't work to get forward motion.

    My thoughts that led me here were a closed cylinder with a device at one end that launches a lump of ice backwards towards the rear of the cylinder. If the rear of the cylinder was open then the lump would exit the craft and there would be a positive thrust (I think).

    What would happen if the cylinder was now closed and after launching the lump of ice a series of lasers were fired at it from within the cylinder so it was vaporised before if hit the rear of the cylinder and cancelled out the forward momentum gained from launching it reward.

    Is there any possibile configuration of this setup or do you still end up with the same mass of steam instead of ice going backwards (sorry no drawing but hopefully my description is clear).


    If you vaporise the ice chunk then its water vapour atoms will impact the rear of the cylinder with the same momentum transfer as the solid lump of ice.


    If you can draw an imaginary border around your system such that nothing crosses that boundary, then that system has not exchanged momentum with its environment and shall not be moving today.

  3. 3 minutes ago, RealKerbal3x said:

    I'm not an engineer, but I can't think of an alternative solution that would solve as many problems as the header tanks do. They provide propellant for the landing burn, minimise propellant sloshing as they're always full, and balance the COM for stable EDL. Sure, they had the fuel header pressurisation issue on SN8, but the fact that they're not immediately scrapping newer SNs probably implies that that issue can either be fixed by software or minor hardware alterations. Starship's EDL sequence is incredibly dynamic and successfully drawing sloshing propellant from the huge main tanks during the violent flip maneuver sounds like it'd be harder than simply altering the header tank system slightly.

    As far as I can tell, this means one of two things:

    1. They need more time to fix SN9.
    2. They need more time to scrap SN9 and bring SN10 up to speed.

    Header tanks also insulate the propellant from direct sunlight via the vacuum in the main tanks.

  4. The really ridiculous thing is that for the first half of its development SLS was primarily intended to ultimately send crew to Mars.


    How do you possibly construct a crewed Mars architecture based around SLS and its flight rate. Sure they put out a few fancy graphics, but there's no hope in hell they were ever fuelling that mothership for departure. It's total fantasy.

    Nobody could have predicted SpaceX's success without perfect foresight, but with complete sincerity, SLS Block 1B should be expendable Superheavy with an expendable raptor upper stage and Orion  stuck on top.

    SpaceX could throw together an expendable upper stage *far* faster than EUS will come to pass, and NASA can afford to expend the hardware.

  5. The absolute deal-breaker for me in SLS isn't ultimately the cost, or that it isn't big enough to do capsule and lander to the moon at once.

    It's flight rate.

    A high flight rate could cover all manner of sins. Can't co-manifest a lander? Send up another launch. Can't do Mars return without a mothership? Multiple-flight-construct that thing.

    SLS will never have the flight rate to work unsupported. And this must have been known from the start. I just... I just don't understand how such a crititical component of a crewed BLEO programme gets missed. 

    It's almost like NASA have prat-falled their way into a viable lunar programme:

    "We'll make this booster and capsule to keep the senate happy, but we all know it's never going to acheive anything. Commercial launchers are coming along nicely though. Oh, wait... actually... Huh!"

  6. This series of French tweets has a good round up of pictures:


    "Assembly of SN10 and SN11 prototypes continues as one section prepares to recurve a large quantity of heat shield tiles."


    I'm quite psyched to see what a large collection of tiles looks like. The lunar starship mockup also has a curtain round the bottom, so I'm sure there's lots of work going on in there.


    "The SN9's fins were damaged following the incident with its mount, and will certainly be replaced if the prototype remains essentially in good condition.

    The nosecone of SN10 is in the LowBay and the domes are multiplying."


    The top fin is totalled. Hope the few dents in the cone don't matter much.

    Note that the stand (I *think* is the same stand from before - no damage?) is still being held down by chains and rolls of sheet metal. I... Don't think that's a great idea.

    "On the launch site, launchpad n ° 2 is ready to potentially host SN9.

    Work is resumed on the orbital launch pad and a new crane is being assembled."


    The damaged tent had been stripped. Guessing it needs all-new canvas at a minimum. The orbital launch pad seems to be getting wooden shutters. Good to see some progress, it's been a while.

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