''Interstellar Express'' or ''Interstellar Heliosphere Probe'' (), is the current name for a proposed Chinese National Space Administration program designed to explore the

heliosphere The heliosphere is the magnetosphere, astrosphere and outermost atmospheric layer of the Sun. It takes the shape of a vast, bubble-like region of space. In plasma physics terms, it is the cavity formed by the Sun in the surrounding interstell ...

and

interstellar space Outer space, commonly shortened to space, is the expanse that exists beyond Earth and its atmosphere and between celestial bodies. Outer space is not completely empty—it is a near-perfect vacuum containing a low density of particles, predo ...

. The program will feature two

space probes Space is the boundless three-dimensional extent in which objects and events have relative position and direction. In classical physics, physical space is often conceived in three linear dimensions, although modern physicists usually conside ...

that will purportedly be launched in 2024 and follow differing trajectories to encounter

Jupiter Jupiter is the fifth planet from the Sun and the largest in the Solar System. It is a gas giant with a mass more than two and a half times that of all the other planets in the Solar System combined, but slightly less than one-thousandth t ...

to assist them out of the Solar System. The first probe, ''IHP-1'', will travel toward the nose of the heliosphere, while the second probe, ''IHP-2'', will fly near to the tail, skimming by Neptune and

Triton Triton commonly refers to: * Triton (mythology), a Greek god * Triton (moon), a satellite of Neptune Triton may also refer to: Biology * Triton cockatoo, a parrot * Triton (gastropod), a group of sea snails * ''Triton'', a synonym of ''Triturus' ...

in January 2038. There may be another probe—tentatively ''IHP-3''—which would launch in 2030 to explore to the northern half of the heliosphere. ''IHP-1'' and ''IHP-2'' would be the sixth and seventh spacecraft to leave the Solar System, as well as first non-

NASA The National Aeronautics and Space Administration (NASA ) is an independent agencies of the United States government, independent agency of the US federal government responsible for the civil List of government space agencies, space program ...

probes to achieve this status.

History

The heliosphere and the interstellar medium have so far been explored by only three NASA probes: ''

Voyager 1 ''Voyager 1'' is a space probe launched by NASA on September 5, 1977, as part of the Voyager program to study the outer Solar System and interstellar space beyond the Sun's heliosphere. Launched 16 days after its twin ''Voyager 2'', ''Voya ...

'', ''

Voyager 2 ''Voyager 2'' is a space probe launched by NASA on August 20, 1977, to study the outer planets and interstellar space beyond the Sun's heliosphere. As a part of the Voyager program, it was launched 16 days before its twin, '' Voyager 1'', o ...

'', and '' New Horizons''. Both ''Voyagers'' used gravity assists to take them out of the plane of the ecliptic: ''Voyager 1'' to the north with Saturn in 1980, and ''Voyager 2'' to the south with Neptune in 1989; '' New Horizons'' designed to stay within the plane to allow for exploration of other

Kuiper belt objects The Kuiper belt () is a circumstellar disc in the outer Solar System, extending from the orbit of Neptune at 30 astronomical units (AU) to approximately 50 AU from the Sun. It is similar to the asteroid belt, but is far larger—20 times ...

. However, none of these probes are exploring the tail of the heliosphere; ''

Pioneer 10 ''Pioneer 10'' (originally designated Pioneer F) is an American space probe, launched in 1972 and weighing , that completed the first mission to the planet Jupiter. Thereafter, ''Pioneer 10'' became the first of five artificial objects to ach ...

'', which was headed toward the tail after its Jupiter flyby in 1973, lost contact with Earth in 2003. Later spacecraft which would remain within the

Solar System The Solar System Capitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Solar ...

, such as '' Cassini–Huygens'', have gathered valuable data on the heliosphere and how it interacts with the interstellar medium, suggesting that the heliosphere is not shaped like a comet but is rather spherical.

Overview

Each probe is to weigh about 200 kilograms, to use

radioisotope thermoelectric generators A radioisotope thermoelectric generator (RTG, RITEG), sometimes referred to as a radioisotope power system (RPS), is a type of nuclear battery that uses an array of thermocouples to convert the heat released by the decay of a suitable radioact ...

for power, and to carry 50 kilograms or more of scientific instruments such as optical cameras, magnetometers, dust detectors, and neutral atom and particle payloads. They will also study anomalous

cosmic rays Cosmic rays are high-energy particles or clusters of particles (primarily represented by protons or atomic nuclei) that move through space at nearly the speed of light. They originate from the Sun, from outside of the Solar System in our ow ...

, interplanetary dust, and the interstellar medium. Depending on whether monopropellant or ion propulsion is used, the probes would be launched using either

Long March 3B The Long March 3B (, ''Chang Zheng 3B''), also known as the CZ-3B and LM-3B, is a Chinese orbital launch vehicle. Introduced in 1996, it is launched from Launch Area 2 and 3 at the Xichang Satellite Launch Center in Sichuan. A three-stage rock ...

Long March 5 Long March 5 (LM-5; zh, s=长征五号 , p=Chángzhēng wǔ hào), or Changzheng 5 (CZ-5), and also by its nickname "''Pang-Wu''" (胖五, "''Fat-Five''"), is a Chinese heavy-lift launch vehicle developed by the China Academy of Launch Vehic ...

rockets. While ''IHP-1'' and ''IHP-2'' will use RTGs for power, ''IHP-3'', if approved, would use a nuclear reactor.

50000 Quaoar Quaoar (50000 Quaoar), provisional designation , is a dwarf planet in the Kuiper belt, a region of icy planetesimals beyond Neptune. A non-resonant object (cubewano), it measures approximately in diameter, about half the diameter of Pluto. T ...

and its moon

Weywot Weywot, officially (50000) Quaoar I Weywot, is the only known moon of the trans-Neptunian planetoid 50000 Quaoar. Discovered by Michael Brown and T.A. Suer using images acquired by the Hubble Space Telescope on 14 February 2006, its existence wa ...

are currently being considered as potential flyby targets for ''IHP-1''. Centaur exploration has also been considered for both probes. While a 2024 launch date was targeted, the

COVID-19 pandemic The COVID-19 pandemic, also known as the coronavirus pandemic, is an ongoing global pandemic of coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The novel virus was first identi ...

has caused some delays, which may render it to launch at a later date. Future dates of May 2025 and 2026 launches have already been considered for ''IHP-2'', and it is possible that ''IHP-1'' could be moved to those as well.

Scientific payload

The probes are proposed to carry the following suite of instruments:

Trajectory

The goal of the spacecraft is to have travelled a total of 100 astronomical units by 2049, which is the centennial celebration of the

People's Republic of China China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's most populous country, with a population exceeding 1.4 billion, slightly ahead of India. China spans the equivalent of five time zones and ...

's founding. ''IHP-1'' will launch in May 2024. In October 2025 it will return to Earth for a

gravity assist In orbital mechanics and aerospace engineering, a gravitational slingshot, gravity assist maneuver, or swing-by is the use of the relative movement (e.g. orbit around the Sun) and gravity of a planet or other astronomical object to alter the p ...

, then loop back in December 2027 for yet another gravity assist. In March 2029 the probe will fly by Jupiter to send it on a trajectory toward the nose of the heliosphere and potentially make observations of

centaurs A centaur ( ; grc, κένταυρος, kéntauros; ), or occasionally hippocentaur, is a creature from Greek mythology with the upper body of a human and the lower body and legs of a horse. Centaurs are thought of in many Greek myths as being ...

or Kuiper belt objects, including the flyby of Quaoar, along the way. By 2049 the probe will be 85 AU away from the Sun. ''IHP-2'' will launch between May 2024 and May 2026, but it will likewise receive two gravity assists from Earth in May 2027 and March 2032 respectively. The flyby of Jupiter in May 2033 will send it on a path to fly by Neptune in January 2038 at only 1,000 kilometers above its cloud tops. The probe may also release an atmospheric impactor prior to the flyby. After the flybys, the probe will visit a Kuiper belt object, and by 2049 the probe will have traveled 83 AU away from the Sun, heading toward the yet-unexplored tail of the heliosphere. If launched with ''Tianwen-4'', there may be very well a chance for comparative planetology in some form. After ''IHP-2'''s flyby of Neptune and Triton is performed in 2038, ''Tianwen-4'''s Uranus flyby and probe would occur in 2039, and ''IHP-1s Quaoar flyby would occur in 2040, allowing for comparisons of similar planetary cohorts within a short span of only a few years.

Flyby targets

IHP-1

File:The Earth seen from Apollo 17.jpg, alt=The Blue Marble, from Apollo 17, Earth (2x gravity assist) File:Jupiter and its shrunken Great Red Spot.jpg, alt=Jupiter and its shrunken Great Red Spot, Jupiter (flyby) File:Quaoar-weywot_hst.jpg, alt=Quaoar and its moon Weywot (Hubble), Quaoar and Weywot (flyby)

IHP-2

File:The Earth seen from Apollo 17.jpg, alt=The Blue Marble, from Apollo 17, Earth (2x gravity assist) File:Jupiter and its shrunken Great Red Spot.jpg, alt=Jupiter and its shrunken Great Red Spot, Jupiter (flyby) File:Neptune - Voyager 2 (29347980845) flatten crop.jpg, alt=Neptune from Voyager 2, Neptune (flyby) File:Triton_moon_mosaic_Voyager_2_(large).jpg, alt=Triton mosaic from Voyager 2, Triton (flyby)

References

External links

{{Asteroid spacecraft Chinese space probes Proposed space probes Missions to Jupiter Missions to Neptune Missions to minor planets