One thing that is not clear from this NASA report is the important detail about net effect of using hydrogen 'only' with a LENR heat source (and assuming low exhaust temperatures as a given). This is in the context of hydrogen "brisance" balanced against the massive weight reduction advantage of NOT requiring oxygen.
Often this subject material comes under the category of "specific impulse." http://www.mail-archive.com/[email protected]/msg15977.html This swing into "rocket science" may sound a bit unclear to most of us, so let me try to make it little more transparent. When hydrogen is oxidized there is an expected shock wave and a resultant brisance leading to an impulse that provides most of the acceleration due to thermal expansion combined with shock - but this acceleration comes at the expense of a steam molecule with a molecular weight of 18 amu. Yes, there is high heat and a shock wave which is the standard for comparison to other alternatives (some of which require less mass for the a specific impulse which is comparatively better on the bottom line). In contrast to the "standard rocket fuel" (H2 and O2) there can be a nine to one potential advantage in ditching the oxygen, when the hydrogen can be adequately heated without it. But the shock wave can only derive from converting liquid H2 to a gas at the normal temperature range of the reactor, which is less than combustion. Yet it is still far more than adequate, due to the low temperature of liquid hydrogen. Your brisance, in effect, comes on the low end of the scale. This is a bit confusing: that high heat does not guarantee anything approaching a linear relationship with acceleration (or shock wave). And it is not that simple, but there are no secrets here. With fission, temperatures could be near the reliability limit of metal containment, but still much lower than combustion, and with similar specific impulse - and with LENR probably half of the exhaust temperature that is expected from fission, but with much lower overhead and a good specific impulse. Almost no shielding would be needed with the T-effect (hopefully). Lower exhaust temperature is almost meaningless since pressure provides acceleration - when the specific impulse (compared to the mass) is more favorable. A standard nuclear reactor is heavy, toxic, and its slight advantage in exhaust temperature is not worth the downside problems. Not so for LENR, even with a much low exhaust temperature it is far superior in specific impulse "on paper". Thus we see a unique convergence of advantages when oxidizer is eliminated - that strongly favors LENR, if it can reach even modest average exhaust temperatures, without the downside risks of fission. This is precisely why NASA is so interested ! Plus, the shock wave of (low temperature) exhaust from H2 may be only slightly less than the oxidized hydrogen in any event ! This is the big surprise which we have learned going back 60 years from research with peroxide and entropic explosions. The message is this: heat is secondary to other properties in fueling a shock wave (such as ion mobility and reaction time). Many do not appreciate this, but the data about "entropic explosions" is solid and unassailable - and the remarkable advantage of peroxide to provide thrust in contrast to its negligible chemical energy - this gives hope that LENR plus H2 with NO oxidizer will be far superior. BTW - you sit behind an "entropic explosion" (which is waiting to happen) every time you get in your car. That is what a "airbag" technology is all about - you definitely do NOT want high heat release in this case, but you do want high specific impulse (since you car has already made impact by the time the reaction starts). Jones From: Chemical Engineer LENR Rocket Fully Reusable SSTO Vehicle powered by Low Energy Nuclear Reactions (LENR) Propulsion
