Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Relativistic Light Sails   One proposed method for spacecraft to reach nearby stars is by accelerating
sails using either solar radiation pressure or directed energy. This idea
constitutes the thesis behind the Breakthrough Starshot project, which aims to
accelerate a gram-mass spacecraft up to one-fifth the speed of light towards
Proxima Centauri. For such a case, the combination of the sail's low mass and
relativistic velocity render previous treatments formally incorrect, including
that of Einstein himself in his seminal 1905 paper introducing special
relativity. To address this, we present formulae for a sail's acceleration,
first in response to a single photon and then extended to an ensemble. We show
how the sail's motion in response to an ensemble of incident photons is
equivalent to that of a single photon of energy equal to that of the ensemble.
We use this 'principle of ensemble equivalence' for both perfect and imperfect
mirrors, enabling a simple analytic prediction of the sail's velocity curve.
Using our results and adopting putative parameters for Starshot, we estimate
that previous relativistic treatments underestimate the spacecraft's terminal
velocity by ~50m/s for the same incident energy, sufficient to miss a target by
several Earth radii. Additionally, we use a simple model to predict the sail's
temperature and diffraction beam losses during the laser firing period,
allowing us to estimate that for firing times of a few minutes and operating
temperatures below 300C (573K), Starshot will require a sail of which absorbs
less than 1 in 260,000 photons.

26
The categories of this paper are: bayes-an
25
The categories of this paper are: patt-sol
14
The categories of this paper are: math-ph
21
The categories of this paper are: adap-org
1
The categories of this paper are: cs
35
The categories of this paper are: mtrl-th
7
The categories of this paper are: hep-th
33
The categories of this paper are: plasm-ph
11
The categories of this paper are: hep-lat
8
The categories of this paper are: hep-ex
20
The categories of this paper are: acc-phys
29
The categories of this paper are: funct-an
10
The categories of this paper are: q-bio
22
The categories of this paper are: chao-dyn
36
The categories of this paper are: cmp-lg
5
The categories of this paper are: gr-qc