Engineering topics

Lester, Daniel

Publications and source records attributed to Lester, Daniel.

8 records

NASA NTRS2011

Low-Latency Lunar Surface Telerobotics from Earth-Moon Libration Points

Concepts for a long-duration habitat at Earth-Moon LI or L2 have been advanced for a number of purposes. We propose here that such a facility could also have an important role for low-latency telerobotic control of lunar surface equipment, both for lunar science and development. With distances of about 60,000 km from the lunar surface, such sites offer light-time limited two-way control latencies of order 400 ms, making telerobotic control for those sites close to real time as perceived by a human operator. We point out that even for transcontinental teleoperated surgical procedures, which require operational precision and highly dexterous manipulation, control latencies of this order are considered adequate. Terrestrial telerobots that are used routinely for mining and manufacturing also involve control latencies of order several hundred milliseconds. For this reason, an Earth-Moon LI or L2 control node could build on the technology and experience base of commercially proven terrestrial ventures. A lunar libration-point telerobotic node could demonstrate exploration strategies that would eventually be used on Mars, and many other less hospitable destinations in the solar system. Libration-point telepresence for the Moon contrasts with lunar telerobotic control from the Earth, for which two-way control latencies are at least six times longer. For control latencies that long, telerobotic control efforts are of the "move-and-wait" variety, which is cognitively inferior to near real-time control.

Lester, Daniel↗

NASA NTRS2011

Long-Duration Human Habitation Beyond Low-Earth Orbit: Why is the Near Future Critical?

For more than a decade, habitation systems capable of comfortable human occupation and effective operations beyond low-Earth orbit (LEO) for more than a few weeks have been a priority recommendation to NASA. This capability is a lynch pin for human exploration beyond the Earth-Moon system. Here we describe briefly some relevant concepts and discuss justifications in the current political and financial environment for why near-term human habitation systems beyond LEO is an imperative.

Thronson, Harley A.↗

NASA NTRS2010

Human Exploration Beyond LEO by the End of the Decade: Designs for Long-Duration "Gateway" Habitats

For the past few years, designs have been developed that are intended to demonstrate that a long-duration habitation system beyond LEO is plausible within several years. Here we summarize a pair of designs with the overriding goal of development and operation beyond LEO before the end of the decade that also build upon experiments and lessons learned from ISS. Both concepts here have the goal of an expandable long-duration habitat at Earth- Moon L1 and/or L2. Both options require subsequent launches for the astronauts. If a heavy-lift launch vehicle is available this decade, an expandable 30.5 mt habitat and departure-stage propulsion system may be launched to E-M L1,2 in a single launch and will offer 575 cubic meter (roughly half the habitable volume of ISS) If existing (or near-future) EELVs are the available launch vehicles this decade, a 16 mt, 170 cubic meter design that uses a pair of launches of Delta IV H and LEO rendezvous/fuel transfer to reach E-M L1,2.

Thronson, Harley↗

NASA NTRS2009

Potential Science Missions Enabled by NASA's Planned Ares V

NASA s planned Ares V cargo vehicle with its 10 meter diameter fairing and ~60,000 kg payload mass to L2 offers the potential to launch entirely new classes of space science missions such as 8-meter monolithic aperture telescopes, 12-meter aperture x-ray telescopes, 16 to 24 meter segmented telescopes and highly capable outer planet missions. The paper will summarize the current Ares V baseline performance capabilities and review potential mission concepts enabled by these capabilities.

Stahl, H. Philip↗

NASA NTRS2009

Potential Astrophysics Science Missions Enabled by NASA's Planned Ares V

NASA s planned Ares V cargo vehicle with its 10 meter diameter fairing and ~60,000 kg payload mass to L2 offers the potential to launch entirely new classes of space science missions such as 8-meter monolithic aperture telescopes, 12- meter aperture x-ray telescopes, 16 to 24 meter segmented telescopes and highly capable outer planet missions. The paper will summarize the current Ares V baseline performance capabilities and review potential mission concepts enabled by these capabilities.

Stahl, H. Philip↗

NASA NTRS2008

Ares V and Future Very Large Launch Vehicles to Enable Major Astronomical Missions

The current NASA architecture planned to return humans to the lunar surface includes the Ares V heavy lift launch vehicle designed primarily to carry the Altair lunar lander and to be available before about 2020. However. the capabilities of this system (and its variants) are such that adapting the vehicle to launch very large optical systems could achieve major scientific goals that are not otherwise possible. For example, an 8-m monolith UV/visual/IR telescope appears able to be launched to the Sun-Earth L2 location by an Ares V with a 10-m fairing. Even larger apertures that are deployed or assembled in space seem possible, which may take advantage of other elements of NASA's future human spaceflight architecture. Alternatively. multiple elements of a spatial array or two or three astronomical observatories might he launched simultaneously. That is, Ares V appears to offer the astronomy communities an opportunity to put into orbit extremely capable observatories, in addition to being a key element of NASA's current architecture for human spaceflight. For the past year, a number of scientists and engineers have been eva1uating concepts for astronomical observatories that take advantage of future large launch vehicles, including the science goals of such missions and design modifications to the vehicle to enable the observatories. In parallel, members of the Solar System science communities have likewise been considering what major science goals can be achieved if new, extremely capable launch systems become available.

Thronson, Harley↗

NASA NTRS2008

Does the NASA Constellation Architecture Offer Opportunities to Achieve Multiple Additional Goals in Space?

Every major NASA human spaceflight program in the last four decades has been modified to achieve goals in space not incorporated within the original design goals: the Apollo Applications Program, Skylab, Space Shuttle, and International Space Station. Several groups in the U.S. have been identifying major future science goals, the science facilities necessary to investigate them, as well as possible roles for augmented versions of elements of NASA's Constellation program. Specifically, teams in the astronomy community have been developing concepts for very capable missions to follow the James Webb Space Telescope that could take advantage of - or require - free-space operations by astronauts and/or robots. Taking as one example, the Single-Aperture Far-InfraRed (SAFIR) telescope with a 10+ m aperture proposed for operation in the 2020 timeframe. According to current NASA plans, the Ares V launch vehicle (or a variant) will be available about the same time, as will the capability to transport astronauts to the vicinity of the Moon via the Orion Crew Exploration Vehicle and associated systems. [As the lunar surface offers no advantages - and major disadvantages - for most major optical systems, the expensive system for landing and operating on the lunar surface is not required.] Although as currently conceived, SAFIR and other astronomical missions will operate at the Sun-Earth L2 location, it appears trivial to travel for servicing to the more accessible Earth-Moon L1,2 locations. Moreover, as the recent Orbital Express and Automated Transfer Vehicle Missions have demonstrated, future robotic capabilities should offer capabilities that would (remotely) extend human presence far beyond the vicinity of the Earth.

Thronson, Harley↗

NASA NTRS1994

Pushing the limits of spatial resolution with the Kuiper Airborne observatory

The study of astronomical objects at high spatial resolution in the far-IR is one of the most serious limitations to our work at these wavelengths, which carry information about the luminosity of dusty and obscured sources. At IR wavelengths shorter than 30 microns, ground based telescopes with large apertures at superb sites achieve diffraction-limited performance close to the seeing limit in the optical. At millimeter wavelengths, ground based interferometers achieve resolution that is close to this. The inaccessibility of the far-IR from the ground makes it difficult, however, to achieve complementary resolution in the far-IR. The 1983 IRAS survey, while extraordinarily sensitive, provides us with a sky map at a spatial resolution that is limited by detector size on a spatial scale that is far larger than that available in other wavelengths on the ground. The survey resolution is of order 4 min in the 100 micron bandpass, and 2 min at 60 microns (IRAS Explanatory Supplement, 1988). Information on a scale of 1' is available on some sources from the CPC. Deconvolution and image resolution using this database is one of the subjects of this workshop.

Lester, Daniel↗