mikegarrison

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Everything posted by mikegarrison

  1. mikegarrison

    Starship, how many decades did we loose?

    All it takes is one bad COPV and your launch vehicle is scattered in bits downrange or exploded at your launch pad. I don't want it to be highly radioactive when that happens.
  2. mikegarrison

    Starship, how many decades did we loose?

    Gods yes. Save us from this: https://en.wikipedia.org/wiki/Convair_NB-36H
  3. mikegarrison

    Starship, how many decades did we loose?

    This betrays a fundamental lack of understanding of the rocket equation. Yes, "a bigger fuel tank and more powerful engine", but it's SO MUCH bigger, because the mass goes up exponentially. What it really needs is a higher ISP engine. Much higher ISP. Thus the idea of using an air-breathing engine, but now you either carry an air-breathing engine around with you or you need a bimodal engine that is a huge increase in cost, complexity, etc. -- everything you were trying to decrease by going SSTO.
  4. mikegarrison

    Starship, how many decades did we loose?

    Yes it was. It lifted a MASSIVE amount of payload to orbit. Technically it was extremely efficient for its time. As for cost, no, not super cost-efficient. But people forget that the space shuttle was not really an orbital delivery vehicle (even if it was sold as one). It was really a space station that had a week+ endurance in space, science labs, crew life support for more than half a dozen people, etc. Of course it was going to be costly to launch something like that up to space over and over again. You miss the point. Look at Falcon 9. What's non-reuseable? The second stage. Compare the technical difficulty of making the second stage capable of controlled orbital re-entry v. making an entire SSTO capable of controlled orbital re-entry. The latter is much harder because the craft's mass is so much bigger, but you seem to think it would be easier.
  5. mikegarrison

    Starship, how many decades did we loose?

    Apparently I was unclear ... I was assuming all of that when I said "staging technology" and referred to "cost and complexity". Yes, the second stage of a two-stage reuseable lifter has to carry everything needed to land from orbit -- but an SSTO has to carry everything needed to land from orbit AND everything needed to do what a first stage does, which actually means it's even harder (more weight) to safely land it from orbit. The math still works out -- two stages are the way to go. The only (to date) reuseable orbital spacecraft have used two stages (space shuttle, OK, technically "stage and a half") or have been the payload stage of two-stage launchers (X-37, Dragon, upcoming: Dreamchaser, Crew Dragon, CST-100).
  6. mikegarrison

    Starship, how many decades did we loose?

    We know from the math that two stages will always have a huge advantage over one stage. The only offsets for single stage are reduced complexity and cost -- if you can achieve them, which no one ever has. This two-stage advantage only gets bigger as staging technology improves with experience.
  7. mikegarrison

    Hermeus superonic airliner

    Sorry, but that's not true. Right from entry into service the fuel efficiency of the Concorde meant huge ticket prices compared to the 747, and the market immediately chose for value over time. And most of the interest in the Concorde disappeared as soon as it was not allowed to fly overland supersonic.
  8. mikegarrison

    Hermeus superonic airliner

    No, you are missing that they are all related. The 2707 needed that swing wing and stuff because of the lousy fuel efficiency and need for trans-Pacific range. Trans-Atlantic-only wasn't going to work -- Concorde already was there. Flights over land were out. Stopping to refuel negated the speed advantage. Only trans-Pacific was a viable market. But to carry enough fuel to get trans-Pacific needed miracle tech. And any subsonic overland segment needs good subsonic aero, thus the swing wing. And every time the industry has looked at supersonic transport again, the same things (fuel efficiency and overwater flight) keep preventing it, even though we have much better tech these days. Now there is a push to build supersonic bizjets. They are hoping a) the bizjet buyers don't care how much fuel costs, and b) small airplanes make small booms, so maybe they can get permission to fly supersonic over land.
  9. mikegarrison

    Hermeus superonic airliner

    What killed all supersonic commercial airliners is fuel efficiency and rules against overland supersonic travel.
  10. mikegarrison

    How does rendezvous and docking work

    There are also other factors too. It is regulated which propellants you can use around the ISS -- they don't want corrosive chemicals getting onto their space station. I think cold nitrogen gas is allowed, although even that they don't want blasting the station with indiscriminately.
  11. mikegarrison

    Homemade Airspeed indicator

    0.04 kPa at sea level should be about 8 mph. I suspect you multiplied by two where you should have divided (or something like that). Check your math. Dynamic pressure is simple if you are reading static and ram (total) pressure. total pressure - static pressure = dynamic pressure But any instruments are going to have correction factors. It depends on where you measure it. Airspeed indicators have traditionally used pitot tubes that measure both static and total pressure at nearly the same spot.
  12. mikegarrison

    SpaceX Discussion Thread

    Do they later do a controlled de-orbit burn with the second stage?
  13. mikegarrison

    SpaceX Discussion Thread

    Yes, but to discuss why would start to discuss politics, and the mods hate that.
  14. IIRC, the experiment racks are located in a separate compartment from the passengers. I don't know if they envision people buying whole launches for running interactive experiments, but I would guess they would be OK with that if they had launch slots available. Edit: I was only partly correct. https://www.blueorigin.com/new-shepard/new-shepard-payloads/ They do offer standardized racks for payload in the cabin and also payload exposed to the ambient (lack of) atmosphere.
  15. mikegarrison

    Firefly Aerospace Discussion Thread

    It looks a lot closer to the Boeing "totem" logo from the 1930s than it does Tesla.
  16. mikegarrison

    SpaceX Discussion Thread

    The people working with that stainless steel are often less fine about getting rained on.
  17. mikegarrison

    Sierra Nevada Dream Chaser thread

    They will if they ever get F9 launch rates high enough. It would be stupid to have a potential money-making rocket just sitting around with no mission.
  18. mikegarrison

    Running out of air in spacesuit vs removing helmet

    A buildup of CO2 is not as benign (symptom-wise) as just a lack of oxygen. So the exact failure mode matters.
  19. mikegarrison

    Running out of air in spacesuit vs removing helmet

    I believe that was the point of the discussion.
  20. mikegarrison

    SpaceX Discussion Thread

    I wonder if steam locomotives were intentionally designed so that the front plate was the weakest point in the pressure vessel? I mean, you don't want them to explode, but if they do explode, then that's probably the safest way for them to explode.
  21. That's what I referred to. The IDS docks will actually be IDS plugged into PMA plugged into CBM. It would make more sense to have IDS plug directly into CBM and get rid of the possible point of failure of the PMA, except that as far as I know there is no way to remove a docking port without depressurizing the entire ISS.
  22. You can go here to see real Apollo 11 videos. Now that I look at them, I realize that of course the video clip in the OP is fake. Remember the bandwidth for video from Apollo was so limited that it only got 10 frames per second. Anything that moved quickly turned into a smeared ghost image. No way it could capture an image like what is shown in the OP video.
  23. I'm sure that footage is fake.
  24. Reading past the woo-woo hype, it seems like they have found a novel way to get thermal energy to act like other potential energy. Normally it would violate the laws of thermodynamics for a weight to move up against a gravitational field without an external force, but when we use a pendulum it happens. The key is that you start the weight from an even higher position. As it swings down the energy transforms into another type (mgh -> mv^2) and back again (mv^2 -> mgh). With this device, it appears that the heat energy between a hot object and room temperature transforms into another type of energy (probably electrical potential?) and then that energy transforms back again -- except that instead of using it to reheat the initial input like a pendulum swings back up, they use it to further cool the initial input. It doesn't violate physics or thermodynamics any more than a pendulum does.