Laser cooling of silicon could provide a new technique to manipulate individual Si isotopes. We perform laser spectroscopy on a Si atomic beam at 252 nm to measure the isotope shifts between 28 − 30Si. This article has been approved for public release: distribution unlimited (USAFA-DF-2023-61).

This work is aimed to introduce a strategy that may help reach the conclusion that using lasers in space is one of the most promising methods to reduce the risk of collisions between active satellites and middle-size LEO debris.The strategy accounts for the implementation of the post-Newtonian (p-N) corrections that are decisive to reach the accuracy required by some Just-in-Time Collision Avoidance (JCA) space-based methods.In fact, we show how and why all JCA methods similar to the one introduced here, which involves simple formations of trackers in Sun-synchronous orbits (SSO), would be within the most efficient to throw middle size debris objects into the Atmosphere by laser ablation, as long as the trackers can implement these corrections while the objects are targeted.

In this paper, we review practical limitations to laser space propulsion that have been discussed in the literature. These are as follows: (1) thermal coupling to the propelled payload, which might melt it; (2) a decrease in mechanical coupling with number of pulses, which has been observed in some cases; and (3) destruction of solar panels in debris removal proposals that might create more debris rather than less. Previously, lack of data prevented definite assessments. Now, new data on multipulse vacuum laser impulse coupling coefficient Cm on several materials at 1064 nm, at 1030 nm, and at 532 nm are available. We are now able to compare the results for single and multiple pulses on materials that have been considered for laser ablation space propulsion (LASP), or that are likely space debris constituents, and decide whether LASP is a practical idea. Laser space propulsion and debris removal concepts depend on thousands or hundreds of thousands of repetitive pulses. Repetitive pulse mechanical coupling as well as thermal coupling (which can melt the target rather than propel it) are both important considerations. Materials studied were 6061T6 aluminum, carbon-doped polyoxymethylene (POM), undoped POM, a yellow POM copolymer, and a mixture of Al and POM microparticles combined and pressed, containing a 50%/50% mixture of the two materials by mass. We address 6 and 70 ps pulses because of the availability of data at these pulse durations. We also briefly consider continuous wave (CW) laser propulsion. Finally, we consider a recent paper concerning solar panel destruction from a positive perspective.

The Photonics Project is a set of web based calculation tools for educational and analytical use. The tools are primarily Python based notebooks that execute as Web based Apps to the user, not requiring any programming knowledge or installation of any software. There will also be some tools showing full mathematical notation that are MathCad based and require the free MathCad plug in. The calculations primarily follow from equations as presented in the Infrared and Electro-Optical Systems textbook by Ron Driggers et al (second edition). They encompass a suite of Radiometric, Optical, and other photonic functionality. Further efforts are ongoing including an active imaging and photonics devices pages. Like Python itself, the site is open to suggestions and collaboration from users and submission of further tools and functionalities. And totally free of charge to all users.

We measured the impulse coupling coefficient Cm (target momentum per joule of the incident laser light) and ejecta velocity vE with glass-covered Si solar (photovoltaic) cells following the irradiation by repetitive 71 ps, 1064 nm laser pulses at fluence of order 10 J/cm2 in vacuum. We measured high Cm values up to 600 N/MW, but very low specific impulse Isp = vE/go of order 10 s. Thousands of glass particles 20–1500 μm in size were ejected and found on the floor of the vacuum chamber close to the target. At lower fluences, larger pieces were ejected. While pulsed laser coupling data exist on typical metals used for satellite construction, to our knowledge, this is the first data on solar arrays which comprise a large fraction of the total area exposed to a laser pulse intended to nudge or re-enter a satellite. On bare Si, Cm was about two orders of magnitude lower, and no large pieces were dislodged. The consequence of these data are that lasers for nudging or re-entering defunct satellites should be focused carefully on the metal parts, avoiding solar arrays, to avoid creating a cloud of microscopic debris, enhancing rather than ameliorating the space debris problem. Further, data on MLI (multi-layer insulation) and other complex layered structures should be obtained to guarantee against other unintended consequences.

The ever increasing number of orbital objects since 1957 raises numerous questions concerning future sustainability of space. Among the 34,000 objects larger than 10 cm in orbit, 20,000 only are cataloged. These cataloged objects include roughly 2000 active satellite, among which less than 1500 are maneuverable. All the rest are orbital debris, large satellites of launcher upper stages, mission related objects, inert pieces from fragmentations or collisions, with no maneuvering capabilities.Collision Avoidance is a common practice when at least one maneuvering satellite is involved, even though it requires a very significant effort to do so.But it is today not possible to avoid collisions among two debris, which represent by far the most frequent collision scenario. It appears necessary to find solutions to avoid such collisions as they have the potential to generate thousands of new orbital pieces and feed to so-called Kessler syndrome; indeed, numerous publications underline the frequent near-misses among very large derelict, and the consequences such collisions would have.Several solutions for such “Just in time Collision Avoidance (JCA)” have been proposed and are recalled in the paper. Three of them have recently been studied in order to assess their feasibility, and appear promising.The use of an orbital laser system can first drastically improve our the accuracy of the ephemerids, second impart a very small ΔV to a passive debris early enough to enable a significant increase in distance between the two objects.Another solution which appears very promising considers the launch on a small sounding rocket of a system releasing a cloud of particle and gas in front of one of the debris; the associated drag, even very small, is enough to lower the probability of an announced collision.Swarms of nano-tugs could also be attached to the most hazardous derelicts, de-tumble them, and slightly modify their trajectory in order to prevent collisions.

Transferring small payloads from Earth to low Earth orbit (LEO) and to interplanetary space using laser ablation propulsion is a new application of pulsed laser ablation propulsion, which offers parameters not available with chemical propulsion. In earlier work, we showed how to use a 1 MW average power pulsed laser to launch a 25 kg satellite from LEO to a Mars Hohmann transfer orbit in 18 minutes. Here, we discuss a lower-power application that can achieve the same result, and also cheaply and rapidly launch swarms of microsatellites into geosynchronous orbit (GEO) for communication, Earth observation, and observation of assets in GEO. The result will be a network of satellites with different functions that is robust to failures. Laser propulsion offers orbit/launch mass ratio m/M impossible with chemical rockets as well as low launch cost/kg. The main purpose in this paper is to illustrate satellite launch with repetitive pulse lasers at realistic laser average power levels. The benchmark laser has 80 ps pulsewidth, 5 kJ pulse energy, 355 nm wavelength (third Nd harmonic), and 20 Hz pulse repetition rate, using the “L’ADROIT” laser station design. To minimize laser power, we employ eight loops of steadily increasing apogee, propelled at perigee by a L’ADROIT laser in LEO, followed by a circularization “burn” at apogee using a second L’ADROIT in GEO with similar laser power. We estimate the final mf/M ratio for these maneuvers to be 43%–53%, delivering 10.8 kg into a Mars Hofmann transfer orbit and 13.2 kg to GEO. The ablated mass is contained in a spherical shell surrounding the satellite payload composed of a mixture of metal powder and polyoxymethylene. The mixture is tailored to the mission to give a matched specific impulse Isp and momentum coupling coefficient Cm. For the GEO insertion, the ablation shell splits and is re-entered after one orbit by a final “burn” from the GEO laser.