Spaceprobe




Spaceprobe is the name used by Breakthrough Initiatives for a very small, centimeter-sized, gram-scale, interstellar spacecraft envisioned for the Breakthrough Starshot program, a proposed mission to propel a fleet of a thousand Spaceprobes on a journey to the Alpha Centauri star system, the nearest extrasolar stars, about 4.37 light-years from Earth. The journey may include a flyby of Proxima Centauri b, an Earth-sized exoplanet that is in the habitable zone of its host star. The ultra-light Spaceprobe robotic nanocraft, fitted with light sails, are planned to travel at speeds of 20% and 15% of the speed of light, taking between 20 and 30 years to reach the star system, respectively, and about 4 years to notify Earth of a successful arrival. The conceptual principles to enable practical interstellar travel were described in "A Roadmap to Interstellar Flight", by Philip Lubin of UC Santa Barbara, who is an advisor to the Starshot project.

In July 2017, scientists announced that precursors to Spaceprobe, called Sprites, were successfully launched and flown through Polar Satellite Launch Vehicle by ISRO from Satish Dhawan Space Centre. Sprites were also to be flown on the KickSat-2 mission that was scheduled for November 2018.needs update

Componentsedit

Each Spaceprobe nanocraft is expected to carry miniaturized cameras, navigation gear, communication equipment, photon thrusters and a power supply. In addition, each nanocraft would be fitted with a meter-scale light sail, made of lightweight materials, with a gram-scale mass.

Camerasedit

Five sub-gram scale digital cameras, each with a minimum 2-megapixels resolution, are envisioned.

Processorsedit

Four sub-gram scale processors are planned.

Photon thrustersedit

Four sub-gram scale photon thrusters, each minimally capable of performing at a 1W diode laser level, are planned.

Batteryedit

A 150 mg atomic battery, powered by plutonium-238 or americium-240, is planned.

Protective coatingedit

A coating, possibly made of beryllium copper, is planned to protect the nanocraft from dust collisions and atomic particle erosion.

Light sailedit

The light sail is envisioned to be no larger than 4 by 4 meters (13 by 13 feet), possibly of composite graphene-based material. The material would have to be very thin and be able to reflect the laser beam while absorbing only a small fraction of the incident energy, or it will vaporize the sail. The light sail may also double as power source during cruise, because collisions with atoms of interstellar medium would deliver 60 watt/m2 of power.

Laser data transmitteredit

Laser communicator, utilizing light sail as the primary reflector, would be capable of data rates 2.6-15 baud per watt of transmitted power at distance to the Alpha Centauri, assuming 30m diameter receiving telescope on Earth.

Other potential destinationsedit

The table below lists possible target stars for similar photogravitational assist travel. The travel times are for the spacecraft to travel to the star and then enter orbit around the star (using photon pressure in maneuvers similar to aerobraking).

Name Travel time
(yr)		 Distance
(ly)		 Luminosity
(L☉)
Proxima Centauri 121 4.2 0.00005
α Centauri A 101.25 4.36 1.52
α Centauri B 147.58 4.36 0.50
Sirius A 68.90 8.58 24.20
Procyon A 154.06 11.44 6.94
Vega 167.39 25.02 50.05
Altair 176.67 16.69 10.70
Fomalhaut A 221.33 25.13 16.67
Denebola 325.56 35.78 14.66
Castor A 341.35 50.98 49.85
Epsilon Eridani 363.35 10.50 0.50
  • Successive assists at α Cen A and B could allow travel times to 75 yr to both stars.
  • The light sail has a nominal mass-to-surface ratio (σnom) of 8.6×10−4 gram m−2 for a nominal graphene-class sail.
  • Area of the light sail, about 105 m2 = (316 m)2
  • Velocity up to 37,300 km s−1 (12.5% c)

Other applicationsedit

The German physicist Claudius Gros has proposed that the technology of the Breakthrough Starshot initiative may be used in a second step to establish a biosphere of unicellular microbes on otherwise only transiently habitable exoplanets. A Genesis probe would travel at lower speeds, about 0.3% of the speed of light. It could hence be decelerated using a magnetic sail.

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