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zolotiyeruki

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Posts posted by zolotiyeruki

  1. Yeah, I noticed the (significant?) difference in separation time between the two boosters.  I suppose it helps keep them from knocking into each other on the way back to shore?

    That was super, super cool to watch, and the camera shot from the lagging booster, showing the leading booster's landing burn, was sweet!

  2. Here's a guess about the lower part of the image: the part near the checkered line looks a little like a game of Snake, or a spaceship dodging asteroids or maybe going through some sort of hyperspace gate, or getting multiple gravity assists from planets.

     

    Or maybe the checkered line symbolizes a finish line, a race perhaps? Maybe Kerbin is going to blow up and you have to resettle the entire species to another solar system before you run out of time? :D

  3. 19 hours ago, tater said:

    Yeah, watching the live feed from the booster I am usually thinking it is going to miss, the angle above shows me why my intuition is always wrong.

    Yeah, it totally looks like it's going to miss.  It doesn't help that they *aim* to miss until after the landing burn starts and everything is nominal. At that point it adjusts its trajectory to land on the ASDS.

    19 hours ago, Brotoro said:

    The booster comes in at a lot more of an angle than I expected at that altitude. I guess we normally see the ones coming in for landing on the landing pads at Canaveral looking mostly along the direction they are coming from. This is going to make it even more interesting to see a Super Heavy or Starship come in for a landing at 39A if they follow a similar angle.

    The trajectory for RTLS is very different from a droneship landing--an RTLS launch is much steeper, so MECO/separation/SES happen much closer to the pad, horizontally.  So the booster has (and needs) a lot less horizontal velocity to get to the landing pad, compared to an ASDS landing.

  4. 56 minutes ago, RCgothic said:

    Could do. A methane tank leak probably won't end well.

    If it's hit on approach and the tanks depress then the engines will go engine-rich and the landing won't be pretty either.

    If it's on the ground, then it won't be taking off again without pressurised tanks. And the tanks depressurising through a hole could itself cause catastrophic failure.

    And if hit by an explosive munition it's basically game over.

    I'm skeptical that a 0.22" hole in a tank the size of Starship's would cause any huge issues by itself.  The fuel and oxidizer flow is waaaaay higher than what you could squeeze out that hole, and the pressure isn't that high anyway--under 100 psi.  Reentry is short enough that the volume you'd lose through such a hole wouldn't accumulate to an appreciable quantity, compared to the total amount in the tank.  Even if the hole was in the vapor space, the volume in that tank is huge by comparison.

    I'd be more concerned about the bullet getting stopped by the liquid fuel,  sucked into a turbopump, and blowing up an engine.

  5. Ok, dumb question:  Is it worth it to push the engines that far, rather than just slapping a few more engines on?  Musk is talking about an 8% increase in thrust from each engine, which is nothing to sniff at.  But a few extra tons of engine mass on a launch vehicle weighing thousands of tons makes me wonder if it wouldn't be more prudent to baby the engines in order to improve reliability.

  6. Ok, as a moderator for a previous circumnavigation challenge, I feel like I need to lawyer this one a bit:

    1) Do we have to hold a Kerbal?
    2) Only one Juno, but are other engines allowed?
    3) camacju's entry uses a neat exploit that drastically reduces drag.  Is that allowed?

  7. In the video clip, Elon is talking about pressure stabilizing the fairing.  And I'm confused, because I think of a fairing as a (historically) disposable aerodynamic cover that is not pressurized.  Can someone enlighten me?

  8. The idea of launching materials from the lunar surface is intriguing.  The lack of atmosphere and shallow gravity well make it ...well maybe not practical, but perhaps less-unfeasible?  I mean, you can use the Flats on Minmus to get to orbital velocities with no gravity losses, right?

    Let's see, it's about 1700 m/s dV to get from the Lunar surface to LLO.  If you built a long, very straight track, and accelerated craft at 50m/s (5G), it would take about 34 seconds, and require a track (0.5 * 50m/s^2 * (34s * 34s) )= 29km long.  That'd be a pretty substantial civil engineering project.  But using such a system would eliminate most of the need for fuel, along with the nasty issue of kicking up the regolith on launch.

    If you wanted to go whole hog and get the payload on an escape trajectory back to earth, you'd need 2400m/s, and a 58km rail...

  9. I suspect/hope that dramatically reduced launch costs will dramatically increase demand, for two reasons:

    1) Supply and demand curve.  Drop the price of something, and you'll get more customers.  The lower price, IMO, will unleash all sorts of ideas that have never been considered before because of high launch costs.
    2) Lower launch costs per ton will have a compounding effect on the cost of the actual payload, because your launch costs per kilogram are now $333 instead of $10,000 (or $2,500ish on F9).  You no longer have to spend boatloads of money on engineering the lightest parts with the strongest (expensive) materials in order to fit within a tight weight budget.  Since you can now launch 10x as much payload for the same cost, you don't have to worry quite as obsessively about failure rates, either.  It may also enable more of a "throw science at the wall and see what sticks" approach.

    I watched the Smarter Every Day video about how they measured each layer of JWST's sun shield, within a few thousandths of an inch, in a clean room environment, just so they could validate their computer simulation model of how it would behave in space.  This effort took several people several years, and is a teeny tiny portion of the overall engineering cost of the project.  If SS/SH reduces costs as much as it's projected to, all sorts of lower-engineering-cost alternatives become viable.

    If I were NRO, I would be salivating right now.  Apply JWST's folding mirror approach to a spy satellite, scale it up so it just barely fits in SS, and all of a sudden you're reading Putin's mail.

  10. 28 minutes ago, mikegarrison said:

    It's kind of amazing to me about how sentimental people are about the Hubble Space Telescope, compared to all the other space probes before and since.

    Goes to show, I guess, the value people place on pretty pictures. We are a very visually-oriented species.

    I think Hubble's a bit unique in that 1) It's still close to earth, and 2) still operational, and 3) it's famous to people of today.

    Here's a probably-silly idea:  Launch a hubble replacement on SS into the same orbit, and recover Hubble on the same mission!

  11. 8 hours ago, Beccab said:

    - EVA will be at a lower altitude (310 km) for increased safety

    Can someone explain to me why EVA is safer at a lower altitude?  I mean, you're still inside the Van Allen belts, and if something goes wrong, you're in the same trouble at 310km as you are at 850 miles.

  12. That was some pretty sweet footage of stage separation, SES and boostback burn.  That's a nice perk of RTLS!

    I noticed that the entry burn has a pretty high TWR--my rough timing-it-with-a-stopwatch estimate is something like 30m/s^2 deceleration, which means its actual TWR is about 4.  I suppose that shouldn't be a surprise, since the thing is almost empty at that point, and you want to minimize gravity losses, but still...

  13. On 11/7/2021 at 1:26 PM, camacju said:

    @zolotiyeruki are my entries ok? or would i need to re-fly the missions?

    Hi!  I sincerely apologize for this taking me so long--I finally got a chance to look at your 27 circle entry craft, and from what I can see, I don't have any issues with the craft. Sure, the tail surfaces aren't quite touching the fairing, but they're close enough and meet the spirit of the challenge.

  14. 1 hour ago, JoeSchmuckatelli said:

    Can one of you smart guys explain this? 

    Why does a rocket engine, designed for high-heat operation, require a thermal protective cover?  (And what dictates when you need one vs when you dont)

    thanks in advance

    *Some* things inside a rocket engine are designed to handle high-heat stuff.  And most of the hot stuff is on the inside.  There's plenty of stuff outside the combustion chamber and bell that don't react too well to super high temperatures.  Recall during some of the earlier SS hops, there were things catching fire under the skirt, from residual fuel burning after an engine shuts down, or turbulent airflow sucking burning stuff back up.

  15. 1 hour ago, tater said:

     


     

    Can someone run through the math of this for me?  That's a humongous difference in payload to orbit.  I understand that disposable SS would not need heat shield tiles, fins of any sort, or fuel for deorbit and landing, plus fuel to get those things to orbit.  Does all that add up to 100 tons worth of savings?

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