Value chain · CLM-1365
In plain terms
The paper's biggest design is a laser array 10 km across that would push a sail a metre wide, carrying a chip of about a gram, to a fifth of light speed in ten minutes. It would then reach the nearest star in about 20 years.
The claim as recorded
A 2016 directed-energy roadmap states that its full-scale design, DE-STAR 4, would push a wafer-scale spacecraft of about 1 g on a 1 m laser sail to about 0.2 to 0.26 of light speed in about 10 minutes, reaching Alpha Centauri in about 20 years. The design is a laser phased array 10 km on a side at 50-70 GW (70 GW in the worked cases), at a wavelength of 1.06 um. The 1 m sail is 1 micron thick and adds 1.4 g, for 2.4 g in total.
Evidence behind this: T2, a peer-reviewed journal paper (JBIS 69) read as the author's arXiv v8 copy; it permits "the paper states Y" for a proposed design, not a demonstrated one.
Scope and limits
A proposed design, not a demonstration. The paper gives three speeds for the 1 g case: about 26% c (PDF p.8), 0.2 c (PDF p.32) and 0.20 (PDF p.50, vmax 6.10 x 10^7 m/s, which is 0.203 c by my arithmetic). Recheck: a 1 m square sail 1 micron thick at 1.4 g/cc is 1 cm3, or 1.4 g. A 0.85 m sail is about 1.01 g, so the PDF p.50 case sets sail mass equal to payload mass. At 0.2 c, 4.3 ly takes 21.5 years, ignoring the acceleration phase. The explorer's FB-24 labels (about 1 km array, about 100 GW, a sail of about 4 m) are not this paper's full-scale figures. PDF p.26 does mention a "10 km array laser case operating at 100 GW", but with a 10 km array, not 1 km. The paper sizes a 1 km array only as a ground or orbital step on the way (see CLM-1366).
What it assumes
That the explorer's figures are meant to stand for this design family; the paper is one proposal among several.
Where it comes from
PDF p.8: "a full scale DE-STAR 4 (50-70 GW) will propel a wafer scale spacecraft with a 1 m laser sail to about 26% the speed of light in about 10 minutes"; same page, "DE-STAR units are denoted by numbers referring to the log of the array size in meters", so DE-STAR 4 is 10^4 m = 10 km (my arithmetic). PDF p.30: DE-STAR 4 "emits about 50 GW at 1.06" um. PDF p.31 (Figure 22 caption): 70 GW, 10 km array, 1 m reflector 1 micron thick, "Wafer mass is 1 g", reflector 1.4 g, "Total mass is 2.4g", "Alpha Centauri (4.3 ly) is achieved in about 20 years". PDF p.32 (Figure 24 caption): "Craft achieves 0.2 c in about 10 minutes (assuming an extended illumination)". PDF p.50: "The laser array is assumed to be 10 km on a side"; "The laser power is assumed to be 70 GW."; the 1 g case with a 0.85 m reflector reaches beta 0.20 with continued illumination (paraphrase).
Basis: array side (km); laser power (GW); wavelength (um); spacecraft and sail mass (g); sail size (m); speed as a fraction of c; time (minutes, years)
Cite this
energyaperture.com/c/clm-1365
CLM-1365, Energy Aperture, as of 2022-01.
Connected records
Other published records linked to this one. A list, not a judgement.