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tater

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    The Quest For Rapid Reusability

    in Science & Spaceflight

    Posted

    22 minutes ago, JoeSchmuckatelli said:

    ...but I do remember when email was new and cool.

    My first email addy was in 83. I've had a total of 5 (1 was an ISP that changed its name, so it might just be 4). Every single 1 has been my first name @domain. Just my first name, properly spelled.

    My current most used is my apple email for my phone. Only downside s that I get people trying to steal it almost daily. Upside is that people who have a variant version screw up, and I get their emails all the time, which is sometimes amusing—like the guy in London who spends £130 a month on his haircut and hair coloring (odd since his hair is gray/white according to his linkedin), and I get all his receipts. I also have his monthly appt schedule, maybe my wife can stalk him (she's in London for a couple weeks as part of getting another postgrad degree, because she needs all the letters after her name, lol).

    Artemis Discussion Thread

    in Science & Spaceflight

    Posted · Edited by tater

    1 hour ago, Exoscientist said:

     Keep in mind Destin also doesn't like the NRHO Gateway, in addition to not liking the multiple refueling launches for the Starship HLS. He prefers an architecture that does go to low lunar orbit.  

     I liked his video, but I think he starts out by fundamentally misunderstanding the mission goal.

    The mission goal for Artemis is a sustainable, and sustained human presence on the Moon, and specifically in a polar site where water is possibly available. It is not, "replicate Apollo." The mission goals were profoundly different.

    Any mission architecture that does not deliver that is wrong from the start. I could see using a frozen LLO for access, but the need for a habitat for at least 2 weeks is part of the equation and over time, I would assume something that can survive night (however many days that is at the chosen landing site given vehicle height, etc).

    So if the mission is some sort of pared down "simple" lander, then the mission must also include placing a habitat on the surface ahead of time. if the hab needs consumable resupply, then that needs to be figured out as well. Any reusable lander will need to be refilled at NRHO (or LLO, whatever). 10s of tons of hypergols delivered to lunar orbit means multiple expended launch vehicles for each lunar sortie.

    In addition to the examples above in the thread on how SS/SH can get things done in a single flight if pared down, if SS is capable of refilling at all—regardless of how many flights it takes—it completely obviates SLS/Orion.

    Artemis Discussion Thread

    in Science & Spaceflight

    Posted · Edited by tater

    59 minutes ago, Exoscientist said:

    But the present SLS can’t send the Orion to LLO and be able to return Orion back to Earth again. That is why the NRHO Gateway was proposed in the first place. But a low cost modification would give the SLS the capability to send Orion to LLO and back again, and also allow a single launch architecture for the Artemis lunar lander missions:

    No, it wouldn't.

    A single launch SLS architecture, even if possible results in a sortie lander like Apollo. Surface stay for 2 measured in hours.

    To be an Artemis mission it needs to have the possibility for FUTURE missions (after the first landing) to be more astronauts, and for 1-2 weeks minimum. So your claim requires redefining Artemis goals entirely to flags and footprints, never better.

    SpaceX Discussion Thread

    in Science & Spaceflight

    Posted

    37 minutes ago, darthgently said:

    My first thought was an island landing pad with refuel support in the Caribbean area located in the most useful location for most launches.  But is is probably less expensive in fuel (considering chill overhead etc) to barge it back, so, yeah

    And what's the savings other than time (and that is assuming zero refurb)?

    Hopping back has all the issues @sevenperforce mentioned, plus it requires possible check/refurb costs—and time. Maybe installation of a nose cone? Then more refurb back at the pad.

    Also, wear and tear. Each such flight adds 2 flights to the total number of uses, with only half of the flights sending a payload. So if they turn out to be good for... 30 flights, you'd be burning half of them on hops.

    SpaceX Discussion Thread

    in Science & Spaceflight

    Posted

    2 hours ago, NFUN said:

    Amazon was getting sued for violating fiduciary responsibilities for not buying SpaceX launches for Kuiper, so Bezos wouldn't've'd much of a say either way

    Buying a few SpaceX launches is win-win for AMZN. They accelerate their progress (and they have a timer ticking with FCC), and get the regulators off their backs.

    Artemis Discussion Thread

    in Science & Spaceflight

    Posted

    1 hour ago, darthgently said:

    Destin asking questions others fear to ask

    Wow. Well done.

    That said, there are a few issues with "simplify," since the baseline is not simple (existing Orion, launched by SLS), causing literally everything else to be less simple.

    If the entire system had been designed from the start with a mission, they would not be having this issue. Hence the usual complaint (at least from me), that SLS is "a rocket to nowhere."

    So we have a bad, required starting point (Orion), and added to that is an entirely different mission from Apollo (here's a link to the PDF he mentioned). Apollo was brief duration stays. Artemis is meant to be longer stays, both to be less rushed, and ALSO because Orion/Gateway won't be back for at least 6.5 days, so that's kind of the minimum stay. If the mission was changed to mimic the simplicity of Apollo within the Orion requirements, then you still need something like the LM, but fit for at least 6.5 days habitation.

    So take a specific observation he makes about hypergolics. He's right of course, but then you need a lot of hypergolics. The lander must be bigger for the required mission duration.

    A lander that is 20t dry needs to be ~90t wet to do the RT from NRHO using methalox. Using hypergols? It needs to be 118t wet.

    What about a 10t lander (~2X the Apollo LM)? 45t with methalox,  59t with hypergolics.

    So that gives us some sense of what the simple solution could look like. A ~60t (wet) lander done with hypergolic props. Except you need a way to send a 60t lander to Gateway/NRHO.

    Interestingly, Starship, assuming a 75t variant (which is actually pretty beefy, could be lower), could send the 60t lander to NRHO (I'm having it fly all the way to Gateway here, else lander needs more dv) with 225t of residual props. That's 285t of payload, including lander. In short, and expended SS could send a 10t dry hypergolic lander to Gateway. Note I assumed a single stage lander.

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