Skip to content
FastestThings

Vehicles

Helios 2

NASA prints 150,000 mph at perihelion on 17 April 1976. Two histories quote that figure. A 70 km/s account is a real disagreement and is not the rank.

Also known as Helios-B, Helios B
Post on X (opens in a new tab)

Velocity

Published as 150,000 mph

Heliocentric speed at perihelion, 17 April 1976. NASA's 150,000 mph is the rank. A published 70 km/s is a different figure and is not stored.

OfficialNASA (opens source in a new tab)

In context

  • 6.0 laps of Earth an hourConstant · Earth's equator, 40,075 km (WGS 84)
  • London to New York in 1 minConstant · London to New York, 5,570 km great-circle
  • 2.3× Earth's speed around the SunSourced · Earth, 29.8 km/s. NASA planetary fact sheet, mean orbital speed

Worked out from the sourced figure above, which stays the ranked number.

Mechanism

Why it's so fast

Helios 2 is fast in a frame you have to name. A rocket does not need to breathe the air, and a spacecraft's big speeds come from burns and from falling in a gravity field.

  1. Say what the speed is relative to

    Speed relative to the Sun, to Earth, or to the air are different measurements. The entry keeps the frame in the conditions. Mixing them would invent a comparison.

  2. Gravity or a burn

    Helios 2 gets its ranked speed from the burn or the fall the sources describe. This note does not add a delta-v the papers did not print.

Nearby on this list: Parker Solar Probe.

Provenance

Every measurement

Claimed, measured and official figures side by side, each with its source. The ranked figure is marked.

  1. 67.06km/s150,000mphRanked figure

    Heliocentric speed at perihelion, 17 April 1976. NASA's 150,000 mph is the rank. A published 70 km/s is a different figure and is not stored.

    Wikipedia prints 70 km/s (about 160,000 mph) for the same perihelion. That disagreement is noted. Aerospaceweb's 241,350 km/h is 150,000 mph converted.

    Official
    NASA (opens source in a new tab)

Reference

Specs

Frame
Heliocentric
Event
Perihelion, 17 April 1976
Speed
150,000 mph
Operators
NASA and DFVLR

Context

Background

NASA's 2024 account of the Helios missions says Helios 2 traveled at a new record of 150,000 mph on 17 April, at about 27 million miles from the Sun. Aerospaceweb quotes about 150,000 mph (241,350 km/h) for the perihelion of 0.29 AU on 17 April 1976. A Honeysuckle Creek history quotes about 241,350 km/h for that same day. The ranked figure is NASA's 150,000 mph.

Wikipedia prints 70 km/s, written there as about 250,000 km/h and 160,000 mph. That is several thousand miles per hour away from 150,000 mph, so it is a real disagreement, not a rounding. The NASA history is the rank. Helios 1's 148,000 mph appears in the same NASA article and was not repeated by the two histories, so it is not a row.

Spot a wrong number?

Every report is read by a person, and corrections are dated on the page.