A Candidate Detection of the First Hydrostatic Core

The first hydrostatic core (FHSC) represents a very early phase in the low-mass star formation process, after collapse of the parent core has begun but before a true protostar has formed. This large (few AU), cool (100 K), pressure supported core of molecular hydrogen is expected from theory, but has yet to be observationally verified. Here we present observations of an excellent candidate for the FHSC phase: Per-Bolo 58, a dense core in Perseus that was previously believed to be starless. The 70 micron flux of 65 mJy, from new deep Spitzer MIPS observations, is consistent with that expected for the FHSC. A low signal-to-noise detection at 24 micron leaves open the possibility that Per-Bolo 58 could be a very low luminosity protostar, however. We utilize radiative transfer models to determine the best-fitting FHSC and protostar models to the spectral energy distribution and 2.9 mm visibilities of Per-Bolo 58. The source is consistent with a FHSC with some source of lower opacity through the envelope allowing 24 micron emission to escape; a small outflow cavity or a cavity in the envelope are both possible. While we are unable to rule out the presence of a protostar, if present it would be one of the lowest luminosity protostellar objects yet observed, with an internal luminosity of approximately 0.01 Lsun.Comment: 7 pages, 4 figures. Accepted for publication in the Astrophysical Journal Letter

The Dynamometer Hub for the Testing Propellers and Engines During Flight

The need for a device to measure flight resistance, engine and propeller power, and efficiency during flight grew in proportion to the demand for increased flying capacity in military types of aircraft. Here, a dynamometer hub was inserted between the engine and the propeller. Taken as a whole, the tests that were conducted show that though the dynamometer is a sensitive instrument liable to numerous derangements, it is undeniably useful even in its present form, when handled with care and skill. Facilitating, as it does, the possibility of maintaining the fixed position of the engine, the blocking out of the weight effect when the plane is in the sloping position, and the possibility of taking direct measurements of force at the point of transmission, the dynamometer appears to be by far the best solution of the problem of a flying test bench, utilized as a hydraulic balance with the smallest possible measuring stroke and the least tendency to oscillation

Sensitivity, safety, and the law: A reply to Pardo

ABSTRACTIn a recent paper, Michael Pardo argues that the epistemic property that is legally relevant is the one called Safety, rather than Sensitivity. In the process, he argues against our Sensitivity-related account of statistical evidence. Here we revisit these issues, partly in order to respond to Pardo, and partly in order to make general claims about legal epistemology. We clarify our account, we show how it adequately deals with counterexamples and other worries, we raise suspicions about Safety's value here, and we revisit our general skepticism about the role that epistemological considerations should play in determining legal policy

What do you mean “This isn’t the question”?

This is a contribution to the symposium on Tim Scanlon’s Being Realistic about Reasons. We have two aims here: First, we ask for more details about Scanlon’s meta-metaphysical view, showing problems with salient clarifications. And second, we raise independent objections to the view – to its explanatory productivity, its distinctness, and the argumentative support it enjoys

Propulsion estimation techniques

A brief overview of statistical tools needed to perform post flight/test reconstruction of state variables is given. Linear regression, recursive linear regression, and the exact connection between the Kalman filter and linear regression are discussed. The regression connection is expected to serve as an aid in the application of a recently developed analytical method of flight reconstruction to single engine test firing data

SSME propulsion performance reconstruction techniques

In view of the complex flight operation of the Space Shuttle propulsion system together with an expected launch rate increase, the flight performance reconstruction process needs to be performed by automated computer programs. These programs must have the capability to quickly and reliably determine the true behavior of the various components of the propulsion system. For the flight reconstruction, measured values from the solid rocket motors, liquid engines, and trajectory are appraised through the Kalman filter technique to identify the most likely flight propulsion performance. A more detailed data collection program for the single SSME engine captive test firing evaluation is scheduled for startup in September of 1988. Engine performance evaluation for the captive test firing requires a reconstruction process that is similar to the process that is used for the flight reconstruction. Analytical tools that may be used to reconstruct a propulsion system's true performance under flight and/or test conditions are described