Engineering topics

Fletcher, James C.

Publications and source records attributed to Fletcher, James C..

4 records

NASA NTRS1992

Polyimide processing additives

A process for preparing polyimides having enhanced melt flow properties is described. The process consists of heating a mixture of a high molecular weight poly-(amic acid) or polyimide with a low molecular weight amic acid or imide additive in the range of 0.05 to 15 percent by weight of additive. The polyimide powders so obtained show improved processability, as evidenced by lower melt viscosity by capillary rheometry. Likewise, films prepared from mixtures of polymers with additives show improved processability with earlier onset of stretching by TMA.

Fletcher, James C.↗

NASA NTRS1989

Space - 30 years into the future

A prognostication is made of the topics which a NASA administrator might be addressing at an AIF convention held 30 years from the date of the present work (1987), in 2017. The administrator is envisioned as discussing progress in SETI research to date, as well as outlining a follow-on program to SETI which would conduct its searches from the far side of the moon; if some form of verifiable contact with extraterrestrial intelligence had been made by 2017, the hypothetical administrator is seen as arguing for an effort to respond to that communication.

Fletcher, James C.↗

NASA NTRS1989

A digitally controlled system for effecting and presenting a selected electrical resistance

A digitally controlled resistance generator is described, in which resistors having values selected according to an expression 2(sup N-1)(R), where N is equal to the number of terms in the expression, and R is equal to the lowest value of resistance, are electrically inserted into a resistive circuit in accordance with a parallel binary signal provided by an analog-to-digital converter or a programmable computer. This binary signal is coupled via optical isolators which, when activated by a logical 1, provides a negative potential to some or all of the gate inputs of the normally on field effect transistors which, when on, shorts out the associated resistor. This applied negative potential turns the field effect transistors off and electrically inserts the resistor coupled between the source terminal and the drain terminal of that field effect transistor into the resistive circuit between the terminals.

Fletcher, James C.↗

NASA NTRS1989

A strategy for Mars: The case for Mars III - Keynote address

Plans for defining a Mars mission and developing the technologies needed for a Mars mission are discussed. The information about Mars obtained from the Viking mission is reviewed. The establishment of a lunar base and the role of such a base in a manned mission to Mars are examined. The problems of a long-term mission in microgravity, the possible development of artificial gravity, the Mars Sample Return mission, and various scenarios for a manned mission to Mars are considered.

Fletcher, James C.↗