Multiple space agencies are now investigating cutting-edge propulsion ideas that could enable rapid travel to other bodies in the solar system.
These include NASA’s Nuclear Thermal or Nuclear Electric Propulsion (NTP/NEP) concept, which allows transit times to Mars in 100 days (or 45 days), and Neptune and its largest moon, Triton, which can be explored. Includes Chinese nuclear spacecraft.
While these and other ideas could enable interplanetary exploration, there are some major challenges beyond our solar system.
As we have seen in previous articles, it takes a spacecraft using conventional propulsion 19,000 to 81,000 years to reach its nearest star, Proxima Centauri (4.25 light years from Earth). To this end, engineers have been studying proposals for unmanned spacecraft. The spacecraft relies on beams of directed energy (lasers) to accelerate light sails to a fraction of the speed of light.
A new idea proposed by UCLA researchers is a twist on the beam sail idea. A pellet beam concept that could accelerate a 1-ton spacecraft to the edge of the solar system within 20 years.
Entitled Pellet Beam Propulsion for Breakthrough Space Exploration, the concept was proposed by Artur Davoyan, Assistant Professor of Mechanical and Aerospace Engineering at the University of California, Los Angeles (UCLA).
This proposal was one of 14 proposals selected by NASA’s Innovative Advanced Concepts (NIAC) program as part of the 2023 selection, awarding a total of US$175,000 in grants to further develop the technology. bottom. Davoyan’s proposal builds on recent work using directed energy propulsion (DEP) and light sail technology to achieve solar gravitational lensing.
As Professor Davoyan told Universe Today in an email, the problem with spacecraft is that they rely on the rocket equation.
“All modern spacecraft and rockets fly on expanded fuel. The speed of a ship is determined by this fundamental limit of the rocket equation, which leads to relatively slow and expensive space exploration.Mission such as solar gravitational lensing is not possible with current spacecraft. cannot run.”
Solar gravitational lensing (SGL) is an innovative proposal that will be the most powerful telescope ever conceived. An example is the solar gravitational lens, which in 2020 he was selected for NIAC Phase III development.
This concept relies on a phenomenon predicted by Einstein’s general theory of relativity known as gravitational lensing. In this phenomenon, a massive object changes the curvature of spacetime, amplifying light from background objects. This technology allows astronomers to study distant objects with greater resolution and precision.
Placing the spacecraft at the heliopause (about 500 astronomical units from the Sun) will allow astronomers to study exoplanets and distant objects at the resolution of the primary mirror, which is about 100 kilometers (62 miles) in diameter. The challenge is to develop a propulsion system that can get the spacecraft to this distance in a reasonable amount of time.
To date, the only spacecraft to reach interstellar space are the Voyager 1 and 2 probes, launched in 1977 and currently about 159 and 132 AU from the Sun.
When it left the solar system, Voyager 1 was traveling at a record-breaking speed of about 17 km/s (38,028 mph), or 3.6 astronomical units per year. Nevertheless, it took the spacecraft 35 years to reach the boundary between the Sun’s solar wind and the interstellar medium (the heliopause).
At its current speed, it would take Voyager 1 over 40,000 years to pass another star system (the obscure star AC+79 3888 in the constellation Ursa Major). For this reason, scientists are studying directed energy (DE) propulsion to accelerate lightsails that could reach another star system in decades.
As Professor Davoyan explained, this method has some distinct advantages, but it also has its drawbacks.
“Laser sailing, unlike conventional spacecraft and rockets, does not require on-board fuel to accelerate, where acceleration results from lasers pushing the spacecraft through radiation pressure. This method can reach velocities close to the speed of light, but the laser beam diverges over long distances, which limits the distance the spacecraft can accelerate. High laser powers, gigawatts, some proposals would require terawatts, or impose constraints on the mass of the spacecraft.”
Examples of laser beam concepts include Project Dragonfly, a mission feasibility study that could reach a nearby star system within a century.
Then there is Breakthrough Starshot, which proposes a 100 gigawatt (Gw) laser array to accelerate gram-scale nanocraft (Starchips).
Starshot can reach Alpha Centauri in about 20 years at a maximum speed of 161 million km (100 million miles) or 20% of the speed of light. Inspired by these concepts, Professor D’Avoyan and his colleagues propose a novel twist on this idea: the pellet beam concept.
This mission concept could serve as a precursor to fast-transport interstellar missions like Starshot and Dragonfly.
But to their end, D’Avoyan and his team looked at a pellet beam system that would propel a 900 kg (1-tonne) payload to a distance of 500 AU within 20 years. Davoyan says:
“In our case, the beam that pushes the spacecraft is made up of small pellets, [we call it] pellet beam. Each pellet is accelerated to a very high speed by laser ablation, after which it maintains its momentum and pushes the spacecraft.
Unlike laser beams, pellets do not diverge rapidly, allowing them to accelerate heavier spacecraft. Pellets, which are much heavier than photons, carry more momentum and can transmit more force to the spacecraft. ”
In addition, the pellet’s small size and low mass means that it can be propelled by relatively low-power laser beams. Overall, Davoyan and his colleagues estimate that a 10-megawatt (Mw) laser beam could be used to accelerate a 1-ton spacecraft to velocities of up to 30 astronomical units per year.
Phase I efforts will demonstrate the feasibility of the pellet beam concept through detailed modeling of various subsystems and proof-of-concept experiments. They also explore the usefulness of pellet beam systems for interstellar missions that can explore nearby stars in our lifetime.
“Pellet Beam aims to change the way deep space is explored by enabling high-speed transport missions to far-flung destinations,” said Davoyan. “With pellet beams, we can reach the exoplanets in less than a year, reach 100 AU in about three years, and solar gravitational lensing at 500 AU in about 15 years. The pellet beam is capable of propelling heavy spacecraft, unlike ” (~1 tons), greatly expanding the range of possible missions. ”
The SGL spacecraft, if realized, will allow astronomers to directly image neighboring exoplanets (such as Proxima b) at multi-pixel resolution and acquire spectra from their atmospheres. These observations provide direct evidence of atmospheric, biosignatures and even technosignatures.
Thus, the same techniques that allow astronomers to directly image exoplanets and study them in extensive detail will also allow interstellar missions to explore them directly.
This article was originally published by Universe Today. Please read the original article.