Spacecraft need to move faster to safely explore the solar system and beyond – nuclear rockets may be the answer

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<p>With the dream of Mars in my heart <a href=Of both NASA And Elon Musk, A long-range manned mission through space is coming. But you may be surprised to find that modern rockets do not travel much faster than past rockets.

There are many reasons why faster spacecraft are better, and nuclear rockets are the way to do it. They offer many advantages over traditional fuel-burning rockets and modern solar-powered electric rockets. 8 U.S. Space Launches We have carried nuclear reactors in the last 40 years.

However, in 2019 Laws regulating nuclear space flight have changed And the work on this next-generation rocket has already begun.

Why do you need speed?

The first step in space travel is to use a launch vehicle to get the ship into orbit. These are the large fuel-burning engines people imagine when they hear the launch of a rocket, and due to gravity constraints, they are unlikely to disappear in the near future.

Interesting things happen when the spacecraft arrives in space. The ship needs to accelerate further to escape the Earth’s gravity and reach its destination in deep space. This is where the nuclear system comes into play. If an astronaut wants to explore the moon or perhaps more than Mars, he needs to fly very fast.Space is large-scale, And Everything is far..

There are two reasons why high-speed rockets are suitable for long-distance space travel. It’s safety and time.

Astronauts traveling to Mars Exposed to very high levels of radiation May cause serious problems Long-term health problems such as cancer and infertilityRadiation shielding is useful, but it is very heavy and the longer the mission, the more shielding is needed. A better way to reduce radiation exposure is simply to reach your destination faster.

But human safety is not the only advantage. As space agencies explore farther into space, it is important to get data from unmanned missions as soon as took Voyager 2 has 12 years to reach Neptune, I took an incredible photo on the way. If Voyager 2 had a faster propulsion system, astronomers might have been able to get those pictures and their information many years ago.

The speed is good. But why are nuclear systems so fast?

Today’s system

When a ship escapes the Earth’s gravity, there are three important aspects to consider when comparing propulsion systems.

  • Thrust – The speed at which the system can accelerate the ship

  • Mass Efficiency – How much thrust the system can produce for a certain amount of fuel

  • Energy Density – How much energy a given amount of fuel can produce

The most common propulsion systems in use today are chemical propulsion (normal fuel-burning rockets) and solar-powered electric propulsion systems.

Chemical propulsion system Although it provides a lot of thrust, chemical rockets are not particularly efficient and rocket fuels are not very energy dense.Produced by Saturn V rocket that launched an astronaut on the moon The power of 35 million newtons At lift-off Carried 950,000 gallons of fuelMost of the fuel was used to put the rocket into orbit, but it is clear that there are limits. It takes a lot of heavy fuel to reach anywhere.

Electric propulsion systems use the power generated by solar panels to generate thrust. The most common way to do this is to use an electric field to accelerate the ions. Hall thrusterThese devices Commonly used to power satellites It can also have mass efficiency that is more than five times higher than chemical systems. But they produce much less thrust – About 3 newtons, Or just enough to accelerate the car to 0-60 mph in about two and a half hours. The energy source, the sun, is essentially infinite, but it is not as useful as the ship moves away from the sun.

One of the promising reasons for nuclear rockets is that they provide incredible energy densities.The energy density of uranium fuel used in nuclear reactors 4 million times Than hydrazine, a typical chemical rocket propellant. It’s much easier to bring a small amount of uranium into space than to carry hundreds of thousands of gallons of fuel.

But what about thrust and mass efficiency?

Two nuclear options

Engineers have designed two major types of nuclear systems for space travel.

First called Nuclear heat propulsionThese systems are very powerful and reasonably efficient. They use a small fission reactor similar to that found on nuclear submarines to heat a gas, such as hydrogen, which is accelerated by a rocket nozzle to provide thrust. NASA engineers say the mission to Mars with nuclear thermal propulsion 20% -25% shorter than traveling on a fossil fuel rocket..

Nuclear heat propulsion system Twice as efficient as a chemical propulsion system – That is, using the same amount of propellant mass, it produces twice the thrust, Thrust of 100,000 NewtonThis is enough force to accelerate the car to 0-60 mph in about 1/4 second.

The second nuclear-based rocket system is called nuclear electric propulsion. Nuclear power system has not been built yetBut the idea is to use a high-power fission reactor to generate electricity and power an electric propulsion system such as a Hall thruster. This is very efficient.about 3 times better than nuclear heat propulsion systemSince the reactor can produce a large amount of power, it was possible to operate many individual electric thrusters at the same time to generate sufficient thrust.

Nuclear power systems are ideal for very long-distance missions because they do not require solar energy, are extremely efficient, and can provide relatively high thrust.However, while nuclear electric rockets are very promising, there are still many. Technical problems to be solved Before using.

Why are there no nuclear rockets yet?

Nuclear thermal propulsion systems have been studied since the 1960s, but have not yet reached space flight.

Rules The system, first imposed in the United States in the 1970s, basically required case-by-case review and approval of nuclear space projects from multiple government agencies, as well as explicit approval from the president. ..along with Lack of funding for nuclear rocket system researchThis environment has prevented further improvements in the reactor for use in space.

Everything changed when the Trump administration issued an executive order. Presidential memorandum While supporting the need to keep nuclear launches as safe as possible, the new directive will reduce the amount of nuclear material and enable nuclear missions. Skip the multi-institutional approval processFor example, only sponsoring agencies such as NASA need to prove that the mission meets safety recommendations. Large-scale nuclear missions go through the same process as before.

With the revision of this regulation NASA received US 10 million in 2019 budget Develop nuclear heat propulsion. DARPA also Space nuclear heat propulsion system Enable national security operations beyond the Earth’s orbit.

After 60 years of stagnation, nuclear fuel rockets could go into space within 10 years. This exciting achievement heralds the arrival of a new era of space exploration. People will go to Mars and scientific experiments will make new discoveries throughout the solar system and even more.

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This article is reprinted from the following conversationIs a non-profit news site that aims to share ideas from academic experts. It was written by: Ian Boyd, University of Colorado at Boulder..

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Iain Boyd is funded by the following sources, none of which are related to space propulsion: Office of Naval Research Lockheed-Martin Northrop-Grumman L3-Harris

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