Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “spruces”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 253 records · Page 14
All sourcesNASA NTRSDOE OSTI
NASA NTRS1988

Comparison of measured C-band scattering coefficients with model predictions as a function of leaf area index and Biomass

The backscattering coefficients for black spruce and aspen at an incidence angle of 50 deg obtained using a helicopter mounted C-band scatterometer are related to leaf area index (LAI) and biomass for several dates while leaves are present. These data are compared with estimates obtained from the Fung disk model for aspen. Implications for spacecraft SAR (e.g., SIR-C) systems and their ability to determine biophysical characteristics of forest canopies are discussed. The precision of SAR data is insufficient to provide consistent tests of the relationship of LAI to the scattering coefficient for single polarizations alone. Backscatter models only provide a simulation of part of the canopy, and more attention needs to be placed on collecting field data which support tests of the microwave scattering models.

Pitts, D. E.↗
NASA NTRS1990

Radar detection of flooding beneath the forest canopy - A review

Synthetic aperture radar remote sensing is a promising tool for detection of flooding on forested floodplains. The brigtht appearance of flooded forests on radar images results from double-bounce reflections between smooth water surfaces and tree trunks or branches. Enhanced backscattering at L-band has been shown to occur in a wide variety of forest types, including cypress-tupelo swamps, temperate bottomland hardwoods, spruce bogs, mangroves and tropical floodplain forests. Lack of enhancement is a function of both stand density and branching structure. According to models and measurements, the magnitude of the enhancement is about 3 to 10 dB. Steep incidence angles (20-30 deg) are optimal for detection of flooding, since some forest types exhibit bright returns only at steeper angles. P-band should prove useful for floodwater mapping in dense stands, and multifrequency polarimetric analysis should allow flooded forests to be distinguished from marshes.

Hess, Laura L.↗
NASA NTRS1990

A methane flux transect along the trans-Alaska pipeline haul road

This paper reports and analyzes methane flux measurements made during the summer of 1987 at 10 km intervals along a north-south direction from Prudhoe Bay to the Arctic Circle in Alaska. Mean CH4 flux from the arctic tundra was 52 mg/sq m/d while that from high-latitude taiga was 11 mg/sq m/d. Fluxes in mg/sq m/d for various plant communities were: wet tundra, 90; low brush-muskeg bog, 45; moist tundra, 31; freshwater ponds, 21; spruce forest, 4.6; and alpine tundra, 0.6. Annual CH4 emission from global tundra and taiga environments is estimated at 38 Tg and 15 Tg, respectively. This is about 46 percent of the wetland emission term of 10 percent of the global atmospheric input.

Whalen, S. C.↗
NASA NTRS1991

Kappa Group: The initial guess. A proposal in response to a commercial air transportation study

Kappa Aerospace presents their Aeroworld Aircraft, the Initial Guess (IG). This aircraft is designed to generate profit in the market which is currently controlled by the train and boat industry. The main priority of the design team was to develop an extremely efficient aircraft that could be sold at a reasonable price. The IG offers a quick and safe alternative to the existing means of transportation at a competitive price. The cruise velocity of 28 ft/sec. allows all flights to be between 20 and 45 minutes, which is a remarkable savings in time compared to travel by boat or train. The IG is propelled by a single Astro-05 engine with a Zinger 10-6 propeller. The Astro-05 is not an extremely powerful engine; however, it provides enough thrust to meet the design and safety requirements. The major advantage of the Astro-05 is that it is the most efficient engine available. The fuel efficiency of the Astro-05 is what puts the aircraft ahead of the competition. The money saved on an efficient engine can be passed on as lower ticket prices or increased revenue. The IG has a payload of 56 passengers and a wingspan of 7 ft. The 7 ft. wingspan allows the aircraft to fit into the gates of all of the cities that are targeted. Future endeavors of Kappa Aerospace will include fitting a stretch version of the IG with a larger propulsion system. This derivative aircraft will be able to carry more passengers and will be placed on the routes which have the greatest demand for travel. The fuselage and empennage are made of a wooden truss configuration, while the wing is made of a rib/spare configuration. The stress carrying elements are made of spruce, the nonstress carrying elements are made of balsa. The wing is removable for easy access into the fuselage. The easy access to the batteries will keep maintenance costs down.

Source record↗
NASA NTRS1991

Final design proposal: Zeta group-Valkyrie. A proposal in response to a commercial air transportation study

The Valkyrie flying wing concept is a remotely piloted technology demonstrator designed to serve as a high volume commuter transport in Aeroworld. The 5.02 lb Valkyrie has a planform area of 1440 sq in and a wingspan of 84 in, which results in an aspect ratio of 4.9. The Valkyrie uses the NACA 2R(2)12 airfoil section. A leading edge wing sweep of 13.2 deg and a 2 deg dihedral were incorporated to provide lateral stability. The Valkyrie is semi-monocoque structure manufactured from spruce and balsa wood covered in plastic Mylar skin. The AstroFlight Cobolt 25 electric engine will power the Valkyrie with a Tornado 10-6 propeller. The Valkyrie is designed to take off in less than 20 ft. To eliminate the difficulties associated with rotating the aircraft at takeoff, the wing is mounted on its landing gear at the take off angle of attack of 8 deg. The Valkyrie provides a greater payload to weight ratio than a conventionally configured aircraft of comparable weight. Considering the requirements, the Valkyrie is the most efficient design for the specified mission.

Source record↗
NASA NTRS1992

Biophysical, morphological, canopy optical property, and productivity data from the Superior National Forest

Described here are the results of a NASA field experiment conducted in the Superior National Forest near Ely, Minnesota, during the summers of 1983 and 1984. The purpose of the experiment was to examine the use of remote sensing to provide measurements of biophysical parameters in the boreal forests. Leaf area index, biomass, net primary productivity, canopy coverage, overstory and understory species composition data are reported for about 60 sites, representing a range of stand density and age for aspen and spruce. Leaf, needle, and bark high-resolution spectral reflectance and transmittance data are reported for the major boreal forest species. Canopy bidirectional reflectance measurements are provided from a helicopter-mounted Barnes Multiband Modular Radiometer (MMR) and the Thematic Mapper Simulator (TMS) on the NASA C-130 aircraft.

Hall, F. G.↗
NASA NTRS1992

JEFF: Air transport system design simulation

Jeff is a remotely piloted vehicle designed by the Blue Team, a division of AE441, Inc., to fulfill the mission proposed by G-Dome Enterprises: to build a cost efficient aircraft to service Aeroworld with overnight cargo delivery. The design of Jeff was most significantly influenced by the need to minimize costs. This objective was pursued by building fewer large planes as opposed to many small planes. Thus, by building an aircraft with a large payload capacity, G-Dome Enterprises will be able to minimize the large costs and the large number of cycles that are associated with a large fleet. Another factor which had a significant influence on our design was the constraint that our design had to fit into a 2'x2'x5' storage container. This constraint meant that unless we wanted to build foldable wings that Jeff's span would be limited to 10 feet. Since this was not enough lifting surface to suit our needs a canard configuration was chosen to get the needed lifting surface and avoid the structural dilemma of foldable wings. The aircraft is constructed mainly of balsa, with spruce wing and canard spars and a monokote covering. It was designed to support a maximum payload weight of 35 oz. (total aircraft weight of 108 oz.) and withstand a maximum load factor of 2.5.

Source record↗
NASA NTRS1922

Impact Tests for Woods

Although it is well known that the strength of wood depends greatly upon the time the wood is under the load, little consideration has been given to this fact in testing materials for airplanes. Here, results are given of impact tests on clear, straight grained spruce. Transverse tests were conducted for comparison. Both Izod and Charpy impact tests were conducted. Results are given primarily in tabular and graphical form.

Source record↗
NASA NTRS1926

A New De Havilland Commercial Airplane : the D.H. 66 with Three Bristol "jupiter" Engines

The D.H. 66, constructed at Stag Lane Works of the De Haviland Aircraft Company built for Imperial Airways, Ltd. The fuselage has an all steel construction while the wings are made with box spars of wood and spruce ribs. It has a biplane tail and encloses the stabilizer trimming gear in a casing which serves to streamline the rear portion of the fuselage, but which is not part of the main structure. It weighs 9060 lbs. empty and 2500 lbs. after fueling with a total loaded weight of 14,700 lbs.

AIRPLANES - DES↗
NASA NTRS1995

Remote sensing of hydrologic variables in boreal areas, phase 2

During Phase 2 airborne Gamma Radiation measurements were conducted over 48 BOREAS (boreal ecosystem atmosphere study) flight lines. Ground measurements of the soil moisture (SM) of the mineral soil and the depth and water content (WC) of the moss/humus layer were collected for calibration of the flight lines. Special attention has been given to the flight lines over, and near, the primary tower sites in the southern study area (SSA); Old Black Spruce (OBS), Old Jack Pine, Old Aspen, and Young Aspen. Multiple ground surveys (September 1993, July, August, and September 1994) show the variation of the water content of the moss/humus layers and changes in the amount of standing water near the SSA OBS tower during the period September 1993 to September 1994. All ground data, airborne estimates and locations of flight lines and ground sampling points have been submitted to BORIS (BOREAS Information System). On 8-10 September 1994 exceptionally high values of cosmic radiation were observed by the airborne gamma radiation system over the SSA. Follow up investigation has not determined the source of, or what caused, the high cosmic count rates.

Peck, Eugene L.↗
NASA NTRS1995

Remote sensing of hydrologic variables in boreal areas

During Phase 2 airborne Gamma Radiation measurements were conducted over 48 BOREAS flight lines. Ground measurements of the soil moisture (SM) of the mineral soil and of the depth and water content (WC) of the moss/humus layer were collected for calibration of the flight lines. Special attention has been given to the flight lines over and near the primary tower sites in the southern study area (SSA): Old Black Spruce (OBS), Old Jack Pine, Old Aspen, and Young Aspen. Multiple ground surveys (September 1993; July, August, and September 1994) show the variation of the water content of the moss/humus layers and changes in the amount of standing water near the SSA, OBS tower during the period September 1993 to September 1994. All ground data, airborne estimates and locations of flight lines and ground sampling points have been submitted to BORIS (Boreas Information System). On 8-10 September 1994 exceptionally high values of cosmic radiation were observed by the airborne gamma radiation system over the SSA. Follow-up investigation has not determined the source of, or what caused, the high cosmic count rates.

Peck, Eugene L.↗
NASA NTRS1995

Development of an L-, C-, and X-band radar for backscattering studies over vegetation

With the recent surge of interest in global change, the impact of different ecosystems on the Earth's carbon budget has become the focus of many scientific studies. Studies have been launched by NASA and other agencies to address this issue. One such study is the Boreal Ecosystem-Atmosphere Study (BOREAS). BOREAS focuses on the boreal ecosystem in Northern Canada. As a part of the BOREAS study, we have developed a helicopter-borne three-band radar system for measuring the scattering coefficient of various stands within the boreal forest. During the summer of 1994 the radar was used at the southern study area (SSA) in Saskatchewan over the young jack pine (YJP), old jack pine (OJP), old black spruce (OBS) and old aspen (OA) sites. The data collected will be used to study the interaction of microwaves with forest canopy. By making use of three different frequency bands the contribution to the backscatter from each of the layers within the canopy can be determined. Using the knowledge gained from these studies, we will develop algorithms to enable more accurate interpretation of SAR images of the boreal region. This report describes in detail the development of the L-, C- and X-band radar system. The first section provides background information and explains the objectives of the boreal forest experiment. The second section describes the design and implementation of the radar system. All of the subsystems of the radar are explained in this section. Next, problems that were encountered during system testing and the summer experiments are discussed. System performance and results are then presented followed by a section on conclusions and further work.

Lockhart, G. Lance↗
NASA NTRS1994

Growing season boundary layer climate and surface exchanges in a subarctic lichen woodland

Between June and August 1990, observations were made at two surface micrometeorological towers near Schefferville Quebec (54 deg 52 min N, 66 deg 40.5 min W), one in a fen and one in the subarctic lichen woodland, and at four surface climatological stations. Data from these surface stations were supplemented by regular radiosonde launches. Supporting measurements of radiative components and soil temperatures allowed heat and moisture balances to be obtained at two sites. The overall surface meteorological experiment design and results of micrometeorological observations made on a 30-m tower in the lichen woodland are presented here. Seasonal variation in the heat and water vapor transport characteristics illustrate the marked effect of the late summer climatological shift in air mass type. During the first half of the summer, average valley sidewalls only 100 m high are sufficient to channel winds along the valley in the entire convective boundary layer. Channeling effects at the surface, known for some time at the long-term climate station in Schefferville, are observed both at ridge top and in the valley, possibly the response of the flow to the NW-SE orientation of valleys in the region. Diurnal surface temperature amplitude at ridge top (approximately equal to 10 C) was found to be half that observed in the valley. Relatively large differences in precipitation among these stations and the climatological station at Schefferville airport were observed and attributed to the local topography. Eddy correlation observations of the heat, moisture and momentum transports were obtained from a 30-m tower above a sparse (approximately equal to 616 stems/ha) black spruce lichen woodland. Properties of the turbulent surface boundary layer agree well with previous wind tunnel studies over idealized rough surfaces. Daytime Bowen ratios of 2.5-3 are larger than those reported in previous studies. Surface layer flux data quality was assessed by looking at the surface layer heat balance. Diurnal and seasonal scale heat budget imbalances were found. We suggest that unmeasured surface heat storage may be responsible for some of the observed imbalance. The presence of the unexplained residual in this and other studies of energy balance over forests casts a note of caution on the interpretation of energy balance components obtained using heat residual methods.

Fitzjarrald, David R.↗
NASA NTRS1994

Radon 222 tracing of soil and forest canopy trace gas exchange in an open canopy boreal forest

A set of continuous, high-resolution atmospheric radon (Rn-222) concentration time series and radon soil flux measurements were acquired during the summer of 1990 at a micrometeorological tower site 13 km northwest of Schefferville, Quebec, Canada. The tower was located in a dry upland, open-canopy lichen-spruce woodland. For the period July 23 to August 1, 1990, the mean radon soil flux was 41.1 +/- 4.8 Bq m(exp -2)/h. Radon surface flux from the two end-member forest floor cover types (lichen mat and bare soil) were 38.8 +/- 5.1 and 61.8 +/- 15.6 Bq m(exp -2)/h, respectively. Average total forest canopy resistances computed using a simple 'flux box' model for radon exchange between the forest canopy and the overlying atmosphere range from 0.47 +/- 0.24 s cm(exp -1) to 2.65 +/- 1.61 cm(exp -1) for daytime hours (0900-1700 LT) and from 3.44 +/- 0.91 s cm(exp -1) to 10.55 +/- 7.16 s cm(exp -1) for nighttime hours (2000-0600) for the period July 23 to August 6, 1990. Continuous radon profiling of canopy atmospheres is a suitable approach for determining rates of biosphere/atmosphere trace gas exchange for remote field sites where daily equipment maintenance is not possible. where daily equipment maintenance is not possible.

Ussler, William, III↗
NASA NTRS1998

Long-Term Arctic Peatland Dynamics, Vegetation and Climate History of the Pur-Taz Region, Western Siberia

Stratigraphic analyses of peat composition, LOI, pollen, spores, macrofossils, charcoal, and AMS ages are used to reconstruct the peatland, vegetation and climatic dynamics in the Pur-Taz region of western Siberia over 5000 years (9300 - 4500 BP). Section stratigraphy shows many changes from shallow lake sediment to different combinations of forested or open sedge, moss, and Equisetum fen and peatland environments. Macrofossil and pollen data indicate that Larix sibirica and Betula pubescens trees were first to arrive, followed by Picea obovata. The dominance of Picea macrofossils 6000-5000 BP in the Pur-Taz peatland along with regional Picea pollen maxima indicate warmer conditions and movement of the spruce treeline northward at this time. The decline of pollen and macrofossils from all of these tree species in uppermost peats suggests a change in the environment less favorable for their growth, perhaps cooler temperatures and/or less moisture. Of major significance is the evidence for old ages of the uppermost peats in this area of Siberia, suggesting a real lack of peat accumulation in recent millennia or recent oxidation of uppermost peat.

Peteet, Dorothy↗
NASA NTRS1999

Rapid Vegetational Change in Coastal North America: The Response to Climate Since the LGM

The late-glacial interval provided rapid shifts in climate which are mirrored by dramatic vegetational changes in North America. Through a transect of lake and mire sites from Connecticut to Virginia on the east coast and Kodiak Island on the western coast, we trace the warming following the LGM with the response of forests and tundra. A brief cold reversal in Virginia is seen from 12,260 to 12,200. The subsequent longer and extreme Younger Dryas event is marked in the southern New England - New Jersey region by dramatic boreal and deciduous forest changes. In the southeastern US, forests also change rapidly, with hemlock forest expansion suggesting increased moisture. In Kodiak Island, the warm, moist tundra of the Bolling/Allerod is replaced by colder, windswept Empetrum-dominated tundra during the Younger Dryas. The Pleistocene/Holocene shift in vegetation is remarkably pronounced in eastern North America as well as the Alaskan coastline. Response time of vegetation to climate change appears to be on the order of decades throughout these coastal locations, probably because of the proximity of sites to important ecotonal boundaries, and the magnitude of the events. Even in Virginia's Holocene record, a cold reversal inferred from increases in spruce and fir is noted at 7500 C14 yr BP. This response of the forests to a short-lived cooling shows the sensitivity of the biosphere to a rapid climate shifts.

Peteet, Dorothy↗