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Everything posted by DDE

  1. No. The mirror gets burnt through near instantly - see @Kryten's note on efficiency. Using a high-albedo material for all of your armour (good example - aluminium) is a potential mitigator. But, basically, you're ought to go looking for a strong, heat-resistant material. Aerogel (OK, not necessarily strong), basalt fibre, boron carbide or nitride, carbon-reinforced carbon...
  2. A gas laser is still a laser. It still produces a beam; the hot gas exhaust is a byproduct of using a different medium. The operational version of Skif was to use a CO2 laser to engage targets over hundreds of kilometers.
  3. U. wot. m8!?
  4. I dare say that power isn't even the key limitation, it's the energy coupling. Bullets are more efficient at demolishing targets than beams; whatever power source you come up with for your laser, I can plug it into a railgun and get superior mileage in all but a few very specific situations.
  5. @tater, http://heavens-above.com/ Didn't spot a thing on my first attempt thus far. My stargazing spot of opportunity was right under the landing approach to Vnukovo, though.
  6. A kerolox rocket engine is a lot more efficient than any chemical airbreathing system, even if used as just the first stage. With non-chemical airbreathing systems, you move into very vague territory, so see And as to @tater, Or what time period the authors are into.
  7. Scramjets can handle only about a third of requisite dV.
  8. Well, if anything, there is a history of chucking cubesat-like spacecraft into Lunar orbit from passing manned ships.
  9. https://arstechnica.com/science/2017/07/spacex-appears-to-have-pulled-the-plug-on-its-red-dragon-plans/
  10. @tater, I agree with @kerbiloid that this system is overdesigned for LES work alone. Basically, there's no point of having it around at all if you're not using it for propulsive landing. If you can recover a fairing, why not recover a fairing with some expended solid motors strapped to them?
  11. I was unaware that they've completely ditched the use of the trunk for fuel carriage.
  12. But if they are now opting for a parachute landing (what I'm taking from Musk's quote) why even have the engines?
  13. Highly unlikely, especially because the things most affected - computers and crews - would still be present and just as vulnerable. You need high thrust, thrust even VASIMR can't provide. Control drums to full reflector, stand by to engage atomic rocket thrust!
  14. And it's been nuked by Mattis anyway.
  15. Moon orbits are a menace, viciously unstable. The proposal was to put it at an Earth-Moon Lagrange point instead, but funding for such an op was pulled along with funding for Apollo 18-21. Other than that, there was no real obstacle. Lunokhod 2 kinda reached the dark side by operating very near the limb. https://www.xkcd.com/676/
  16. ...and then we arrive at the dual problem of single-point failure - how much of SpaceX philanthropy will endure should Musk take an accidental brick to the head? I also still suspect that no national government would take a serious colonization effort lying down; from a purely psychological perspective this is an unacceptable affront.
  17. Except the entry barriers are so freakishly high that nobody's willing to properly sink their teeth into it. For instance, creation of propellant ISRU infrastructure is likely costlier than using oversized vehicles for BLEO missions, given how few BLEO missions we launch and how few we will keep launching for the foreseeable future.
  18. http://astronautix.com/l/loxammonia.html Methane would also combust quite readily. Because I assumed that @sevenperforce's claims were solidly out of the solid-core reactor territory (pun not intended) in terms of core tmperature.
  19. @Casualnaut, I think the explanation may be much more mundane - the same graphics artist reused models from the old study. Wouldn't be the first time the people doing graphics for spiffy NASA presentations did something really stupid. Also, old North American Rockwell MEM lander projects featured nearly indistinguishable habitat, rover garage and return vehicle-carrying landers.
  20. Yeah, but whatever your lightbulb's operating temperature, hydrogen will always have better Isp. Although I do think the other remass materials are unjustly ignored given the reduced tankage size.
  21. A fair question. Some suggest nowhere because radiation encourages mutation, bootstrapping evolution. Protection against radiation is two-fold. In the long term, radiation causes cancer; high cell replacement tempo would only make the tumors grow faster, we need more enhanced DNA repair mechanisms instead. Refer to Deinococcus radiodurans ("Conan the Bacterium") and Thermococcus gammatolerans. Short-term acute exposure (Acute Radiation Syndrome) is much simpler and boils down to, indeed, quick replacement of dead cells, especially white blood cells, and handling the various free radicals produced by radiolysis; there's a reason it's billed under "toxicology". We're already seeing the first radiation protection meds, such as Ex-Rad (keep your Fallout jokes about you). Ultimately, pantropia, and radical adaptation of humans to whatever environment they are going to face, is just one solution to the problem of truly Earth-like planets not existing.
  22. Yet at the same time they talk about a Moon base... I'm afraid the SLS is to blame, not Mars, assuming this isn't a malicious maneuver to spread more pork.
  23. @jsisidore, a "suit" capable of reliably shielding against lethal amounts of gamma rays would look something like this, which they used to handle the ejected reactor fuel in Chernobyl: We're talking significant amounts of high-density armour plating all around. It's easier to do with a reactor because it's immobile and you can mix distance and directional shielding to further mitigate the thickness required. I know the Chernobyl liquidators also used lead breastplates, but these were widely considered utterly ineffective.
  24. Bam, here's a classic RL-10: And bam, here's it in Nertea's cryogenic rockets pack: They're generally used to reduce interstage length, not to change ISP dynamically, though.