2 Launched on 19 th Jan 2006 Orbits 39.5 AU from Sun (1 AU is average Earth-Sun distance) Journey of 3,463 days = 9.48 years 4,760,000,000 km journey (~3 billion miles) Pluto flyby on 14 th Jul 2015 at 12,500 km AU = 4.5 light-hours from Sun Where next?

3 Discovered 26 th Jun 2014 by HST Magnitude +26 Orbits 44.2 AU from Sun, Period 293 years Low inclination and eccentricity – classic KBO Estimated diameter km Flyby on either 31 st Dec 2018 or 1 st Jan AU from Sun at flyby Where Next?

4 Where would we like to go? – Nearest star! – ‘Interesting’ star!! – Earth-like exoplanet!!! – Across the galaxy!!!! – Another galaxy!!!!! Can we?

5 Speed of light, c = 1 ly/yr Destination Distance, d (ly)Time, t (yr)Speed, v (ly/yr) Pluto Proxima Centauri Vega Kepler-452b1, Across Galaxy100, Andromeda Galaxy2,500,0002, , Destination Distance, d (ly)Time, t (yr) Pluto Proxima Centauri Vega Kepler-452b1, Across Galaxy100, Andromeda Galaxy2,500,0002, Destination Distance, d (ly) Pluto Proxima Centauri4.24 Vega24.04 Kepler-452b1,400 Across Galaxy100,000 Andromeda Galaxy2,500,000 Let’s assume we can maintain a continuous acceleration of 1g = 9.81 m/s 2 = ly/yr 2

6 Special relativity becomes important!

7 Destination Distance, d (ly) Time on Earth, t (yr) Time on Rocket, T (yr) Speed at Destination, v (ly/yr) Pluto Proxima Centauri Vega Kepler-452b1,4001, Across Galaxy100,000100, Andromeda Galaxy2,500,0002,500, Special relativity becomes important very quickly! But… this for a fast flyby – no slowing down! Almost no time to view destination Radio signals back to Earth highly red-shifted

8 Destination Distance, d (ly) Time on Earth, t (yr) Time on Rocket, T (yr) Pluto Proxima Centauri Vega Kepler-452b1,4001, Across Galaxy100,000100, Andromeda Galaxy2,500,0002,500, Suppose we want to slow down to arrive at our destination at low speed? This is just ‘fiddling with numbers’ – what about the engine and fuel?

9 Consider our options… – Chemical fuel – Nuclear fuel – Matter/Anti-Matter Annihilation – Gamma-ray Lasers (Grazers) – Star-Trek Warp drives Wormholes Black-hole slingshots

10 Destination Distance, d (ly) Fuel Mass per kg of Payload Pluto kg Proxima Centauri kg Vega kg Kepler-452b1,4002, tonnes Across Galaxy100,00010,609, tonnes Andromeda Galaxy2,500,0006,630,635, tonnes Assume we can convert matter to energy with 100% efficiency! How much matter do we need?

11 Engine/Fuel not possible! – Wait for Star Trek solution? Slower travel possible (<1g) – Robotic Missions Only? – How many human generations? Shielding is an issue! – Interstellar dust – Cosmic Microwave Background Returning signals to Earth – Size of dish and power required – Delay between departure and signals returned!

Inspired by ‘The Relativistic Rocket’ Relativity/SR/Rocket/rocket.html