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About cryogen

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  1. Spiegel's source is an astronomer who's part of that group (or at least has inside information).
  2. That's not really fair; JWST has an enormous wavelength range, even more logarithmic range than Hubble. JWST spans 600 nm - 28.5 μm between two cameras (NIRCam and MIRI), while Hubble's cameras span from 115 nm to 1.7 μm, up to 2.4 μm when NICMOS was still operating. https://directory.eoportal.org/web/eoportal/satellite-missions/j/jwst
  3. It's probably invisible, actually. Hydrogen gas has very little emissivity; it's transparent and doesn't glow when heated. Check out photos of the RS-25 engine (shuttle launches, or SLS engine tests); they're almost totally invisible, except for a faint blue glow. Even that glow is probably caused by steam (this person suggests chemiluminescence from radical recombination, I assume OH radicals), and wouldn't show up in a pure-hydrogen exhaust stream. RS-68 engines, by contrast, have an orange-pink glow, despite using the identical LH2/LOX fuel as RS-25. The difference is that RS-68 is an
  4. I think you're thinking of the upper stage engines. NASA planned on using (an update of) the J-2 engine, the one from the 2nd and 3rd stages of Saturn V, as the upper stage engine for SLS. (And prior that, Ares I and Ares V). They ended up dropping it in favor of RL10. https://en.wikipedia.org/wiki/J-2X
  5. You got it. The reason Orion exists is there was a project to go the moon and so they designed this capsule, an analogue to the Apollo CM. Around 2010, the moon project was cancelled, but there was a political rift, some politicians tenaciously held their grip on Orion's budget. So we keep building it. There's no reason any more, only rationalizations and inertia.
  6. Here's a useful article about super-sized EELV derivatives: https://www.cbo.gov/sites/default/files/109th-congress-2005-2006/reports/10-09-spacelaunch.pdf I don't think there's much market for heavy EELV's (at least at ULA pricing), given that Delta IV Heavy launched only 9 times in the past 12 years. And none of them were commercial launches. As for USAF, they can't buy many more Atlas V's because of the RD-180 embargo.
  7. I think the answers in this thread about MLI are only partly right (as is the Wikipedia page on MLI). From some research, it looks like multi-layer insulation (MLI) can use either aluminized or goldized Kapton; while the aluminized version has a deceptively "gold-color" appearance, there's a different type that uses actual gold (Au), the element, vacuum-deposited on Kapton film. This makes sense, since gold has pretty unique radiative properties; it has significantly higher α/ε ratio than aluminum -- it's a "warmer" material in direct sunlight. Here's one source, a NASA technical doc
  8. That's characteristic energy, C3. It's not a delta-v figure per se; it's equal to v∞2, i.e. the asymptotic limit ("at infinity") of the Earth-relative velocity as you leave the Earth's SOI. Squared. So if you're leaving Earth with a C3 of 130 km2/s2, you're departing with an Earth-relative heliocentric velocity of more than 11 km/s. It has a wikipedia page: https://en.wikipedia.org/wiki/Characteristic_energy It's often used to measure launcher performance (on the x-axis): https://www.nasa.gov/sites/default/files/files/NAC-July2014-Hill-Creech-Final.pdf
  9. Ozone as a rocket oxidizer was studied in depth in the 1950's. In theory you could get 20-30 seconds increase in Isp from it, over plain oxygen. It's thought too unstable to be practical. Here's an excerpt from John D. Clark's Ignition!: An informal history of liquid rocket propellants, which is out of print (and currently sells for $2,904 on Amazon ) (reposting my own comment from an older thread)
  10. Here's the paper (33 pp), http://arxiv.org/abs/1510.06387
  11. Cool! That guy with the blue wire running out of him... Might be that they're running a neutral gas atmosphere in there, and that's his personal air line.Those are "SCAPE suits", used when working with highly toxic rocket fuel (i.e., hydrazine and nitrogen tetroxide). They're at positive pressure for leak safety (just like biohazard suits). The blue hoses are air supplies. So that photo was likely taken when they were fueling the satellite before launch. http://sci.esa.int/rosetta/33116-scape-suit-training-is-given-by-the-csg-safety/ http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/201100
  12. I recommend J. D. Clark's "Ignition" for a scary history of Cold War-era propellant labs. Some of the craziest fuels researched were Hydrazines / N2O4 (we're still using this... ) Fluorine compounds (liquid F2, ClF3, ClF5, OF2, O2F2...) Ozone (O3) Beryllium (metal, beryllium hydride...) Boranes (B2H6, B5H9...) Mercury (metal, dimethylmercury...)
  13. The problem is that Pluto has little gravity (vesc = 1.2 km/s), so the Oberth effect gives you no help with capturing into orbit. Any realistic trajectory arrives at Pluto with a very high vinf, and all of that has to be cancelled with propulsive delta-v. New Horizons' flyby was at a relative speed of 11 km/s, which would be impossible for chemical propulsion to cancel. If you work out the orbit equations, more realistic speeds would give you ridiculously long flight times, like 30-50 years! What you'd need is high-Isp propulsion to decelerate to Pluto from a high vinf. Since this happens ve
  14. The chemical propulsion variants descend from lunar orbit to low altitude, to get exactly the same Oberth boost. They'd be nuts not to. On that note, does anyone have a mirror of that paywalled .pdf on NASASpaceFlight? It's a US government publication, so it should be in the public domain, by statute. We're all missing details here. I wonder if you could you use SEP spirals from LEO to lunar orbit? (It's like a 2:1 to 3:1 mass ratio savings). How critical is the van Allen belt radiation for that, and could you maybe avoid it by spiraling in the polar direction? (I've been curious if you could
  15. Strontium is problematic because it's difficult to shield. Beta radiation itself doesn't go far but, when it stops, the impact creates secondary x-rays (bremsstrahlung) that are a lot more penetrating. It doesn't help that 90Sr's betas are very energetic -- 2.28 MeV from its daughter 90Y. NASA appears (?) to consider it impractical. There are lots of (heavily-shielded) 90Sr generators, but none in space (as far as Google knows). The US tested a prototype (SNAP-17A) intended for space satellites -- this before solar photovoltaics were practical -- but it didn't fly. I can't find information abo
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