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Nuclear Reactors in Space: For or Against?


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Personally, I believe that application of nuclear power in space would be very much in our interest. Not only do nuclear thermal rockets offer a major improvement over existing propulsion technologies, but the use of nuclear reactors as power sources for satellites, space probes, and the like could allow for much greater scientific return or utility. However, I realize that nuclear power does have associated risks, and there are others who may feel different. Whether you are for or against the usage of nuclear power in space, I am curious to hear your opinions.

 

For reference, here's an interesting paper discussing the topic.

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Nuclear reactors for space use have some pretty hairy engineering problems.

 

Since you're lobbing this sucker into orbit, it needs to have a good power to mass ratio.  Nuclear reactors are amazing at a lot of things, having high power to mass ratios ain't one of 'em, so you're going to be looking at something at least as complex as a naval nuclear reactor.  Those are usually fast neutron designs, which is a lot harder to design and operate than a thermal type.

 

If it's being used for an NTR the propellant will double as coolant, taking heat away from the core and keeping it at a stable temperature.  If you're using it for electrical power generation... things get exciting.  You need some means of rejecting waste heat, and since convection and conduction don't work in space, that leaves radiation.

 

If you want your radiators to be mass-efficient, the waste heat rejection needs to occur at a high temperature.  If you want to reject waste heat at a high temperature, you end up using really weird, really dangerous working fluids for your turbine... things like mercury.  Also, if you want good carnot efficiency your core temperature has to be super-high since your rejection temperature is so high...

 

Nuclear space power generation is just all kinds of fucked up and weird.  Not saying it's a bad idea overall, but it's considerably more involved than just taking a typical terrestrial nuclear reactor (most of which are absurdly reliable) and flinging it into the sky.

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Parking a satellite on the Earth-Sun L2 with a nuclear reactor onboard might be fun.  You'd always be in shadow, so your radiators would work better.  You could use the reactor to power some sort of electrical rocket (ion, hall thruster, VASMIR, plasma, take your pick) for station-keeping.

 

I can't immediately think of any reason to have a satellite hovering at L2 all the time, but doubtless there is one.

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  • 4 years later...

https://spacenews.com/final-fiscal-year-2019-budget-bill-secures-21-5-billion-for-nasa/

 



Of that total, $180 million will go to Restore-L, a satellite servicing mission also previously threatened with cancellation, and $100 million to nuclear thermal propulsion research, including planning for a flight demonstration mission by 2024.

 

Hype for potential of NERVA returning (plus probably some Timberwind DNA)

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  • 2 weeks later...

 

TOPAZ reactor, this international program was a bit too naive.

 

https://www.researchgate.net/publication/266516447_US-Russian_Cooperation_in_Science_and_Technology_A_Case_Study_of_the_TOPAZ_Space-Based_Nuclear_Reactor_International_Program

 

A powerpoint presentation in the post '91 mood, not primarily on space reactors but more on the dangers of the nuclear field.  

https://permalink.lanl.gov/object/tr?what=info:lanl-repo/lareport/LA-UR-09-00906

The 23 page reminds me of the story of FOGBANK.

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  • 11 months later...

https://breakingdefense.com/2020/02/darpa-doubles-dough-for-nuclear-powered-cislunar-rocket/

Demonstration Rocket for Agile Cislunar Operations (DRACO), formerly known as “Reactor on a Rocket (ROAR)” — $21 million, up from an initial $10 million in 2020. DRACO “will develop and demonstrate a High-Assay LowEnriched Uranium (HALEU) nuclear thermal propulsion (NTP) system.” NASA is working on similar nuclear thermal propulsion rockets, which use low-enriched — between 5 and 20 percent — uranium-235 (U-235). U-235 is the basic nuclear fuel for commercial light-water reactors when enriched to between 3 and 5 percent; the Navy’s nuclear reactors use U-235 fuel enriched to 90 percent. The new rocket would allow the US military to operate spacecraft in cislunar space, which DARPA’s budget documents call the “new high-ground” that is “in danger of being defined by the adversary.” DARPA budget documents say the Air Force is the targeted customer for DRACO. As Breaking D readers know, senior Air Force and DoD officials are increasingly speaking publicly about the need for the United States to expand its military space activities to cislunar space to counter China — which has a robust civil lunar exploration program that many in the US national security community suspect is a cover for military ambitions. Indeed, SDA’s planned space architecture includes sensors in cislunar space. DARPA’s funding boost for the project reflects its intentions to move from feasibility studies this year to an actual demonstration in a testing environment in 2021.

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A consideration with using nuclear generated electricity on a telescope is that the radiative surfaces to cool the scope would have to be large, which would necessitate a wider radius to increase the surface area without overlapping the radiative vectors, which would increase the moment of inertia. This might not be that big of a problem, considering a lot of telescopes just look at one location for long periods of time, but would pose a problem when trying to turn 180 if there is an urgent requirement (asteroids and such). Also, launching such a large  satellite will cause problems, unless we work on our microgravity construction techniques. 
 

Though, on advantage of it being so far out (the Earth-Sun L2), you could indeed use volatile coolants like NaK, not that big of an environmental risk cause space is already inhospitable, though Earth’s gravity might render this point moot if coolant leaves the L2 area at certain vectors. 

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  • 2 weeks later...

Ok, did some research, and it turns out that the Earth-Sun L2 point is ~1.5 million km from Earth, give or take, and the umbra that Earth casts is only ~1.4 million km in length... which means this point is never in full shadow, and you cannot use the Earth or any vector within the vicinity of the Earth to radiate a spacecraft’s heat.  
 

On a side note, I feel incredibly inconvenienced by these facts. 

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  • 6 months later...

   TEM is a Russian project of Transport module with nuclear reactor as source of energy for 4 ion engines, planned to be used as a space towing vehicle.

 

   Reactor is located on a tip of this space vehicle, solar panels-looking parts in the middle are cooling system and in the end there is engine module.

 

  And looks like this is not just project that exist in CGI, recent photos are showing parts of the TEM being assembled. Although it is likely that this is not a vehicle that will fly to space, but a testing rig.

14732743

   TEM's "spine"

 

Spoiler

14732745

   Frontal part, AFAIK with mounting panels around it for cooling system.

 

14732746

   Cooling system panels.

 

14732747

   Engine module.

 

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  • 1 month later...
On 2/19/2020 at 10:28 AM, Lord_James said:

A consideration with using nuclear generated electricity on a telescope is that the radiative surfaces to cool the scope would have to be large, which would necessitate a wider radius to increase the surface area without overlapping the radiative vectors, which would increase the moment of inertia. This might not be that big of a problem, considering a lot of telescopes just look at one location for long periods of time, but would pose a problem when trying to turn 180 if there is an urgent requirement (asteroids and such). Also, launching such a large  satellite will cause problems, unless we work on our microgravity construction techniques. 
 

Though, on advantage of it being so far out (the Earth-Sun L2), you could indeed use volatile coolants like NaK, not that big of an environmental risk cause space is already inhospitable, though Earth’s gravity might render this point moot if coolant leaves the L2 area at certain vectors. 

 

 

As I understand it, this is part of why a lot of proposed nuclear space reactors have used exotic working fluids like mercury vapors to spin the turbines.  Mercury can be used with a very high heat rejection temperature, which helps keep the radiators smaller.

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  • 3 weeks later...

   More about nuclear-powered planetolyots.

Quote

   Roscosmos has signed a contract worth 4.2 billion rubles for the development of a preliminary design of the nuclear space tug "Nuclon" for flights to the Moon, Jupiter and Venus, follows from the materials of the state corporation posted on the public procurement website.

 

   Few random pics

image

 

WRIFv7-Xt-F0-M

   Nuclear reactor. Yellow and Blue are protection of rest of vehicle behind reactor from radiation.

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  • 5 months later...

   More information released about TEM (nuclear-powered spacecraft) planned first mission. TEM was named Zevs (Zeus), looks like.

https://tass.ru/kosmos/11446501

Quote

   MOSCOW, May 22. / TASS /. The first mission of the Zeus transport and energy module (TEM) will take 50 months. This is stated in the presentation of the executive director of Roscosmos for promising programs and science Alexander Bloshenko, presented in the framework of the educational marathon "New Knowledge".

 

   "50 months is the total duration of the mission," the presentation says. Bloshenko said that the first flight is scheduled for 2030. "We have designed it now. Together with the Russian Academy of Sciences, we are calculating the ballistics of this flight, payloads," the executive director explained. According to Bloshenko, the mission will begin on Earth, then it is planned to fly to the Moon, where the spacecraft will separate, then there will be a gravitational maneuver near Venus, where the spacecraft will also separate, then it will fly towards Jupiter and its satellites.

 

   In December last year it became known that Roskosmos and KB Arsenal signed a contract for the development of a preliminary design of the nuclear tug Nuclon, which will be used for flights into deep space. The contract value is over 4.17 billion rubles. It was concluded on December 10. The end date of the contract is July 28, 2024.

 

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   Video quotes from the speech of the executive director of Roscosmos A. Bloshenko on promising programs at the "New Knowledge" marathon on May 22, 2021. 

 

   Bloshenko covered nuclear-powered spacecraft TEM in second part of this video. In short - this is promising tech, partially based on Soviet experience. Nuclear reactor is much more powerfull compared to Soviet designs, they are aiming for ~500 kW. Rear section is swappable.

   He sees this type of spacecraft as better alternative for flying to other planets, (including Mars, compared to Mask's Spaceship) because of effects of space on human body (not counting on radiation, just no gravitation alone creates situation when after 0.5 years human body needs 2 years to restore, bones loosing calcium and potassium, problems with coordination and reaction). Missions should take less time, which those types of spacecrafts can provide. 

 

image

   Looks like TEM design programm is called "Nuklon", spacevehicle+"cargo" that will fly is named "Zevs". According to Bloshenko part of design problems are solved, some are still in the process.

   Picture shows 2 versions, one with ion engines (Variant 2) and one with rotary magnetoplasma engine.

 

   Stats:

  • Mass (dry/fueled, t) - 20.6/22.0
  • Mass of load bearing trusses - 10.6
  • Mass of energy block - 7.0
  • Mass of engine module (dry) - 1.4
  • Mass of support systems - 3.0
  • Mass of fueld components DUOS [don't know what is it, for reactor maybe] - 0.44
  • Mass of Xenon (fuel for ion engines) - 1.0
  • Sizes in transport configuration (L, D, meters) - 24.9/5.0 
  • Sizes in ready config - (L, D of SOTR*, D of BF) - 56.7 / 10.6 / 20.9
  • Moment of inertia (X/Y/Z) t*m2 - 72/7400/8400

Angara 5V will be used to launch sections of TEM, using Fregat block

*SOTR - radiators for reactor, total area is 696 m2.

Power of reactor is 470kW.

 

image

   This pic shows orbital station using TEM and parts of TEM as well. Front section is reactor and necessary systems, after it SOTR-N, load bearing trusses, SOTR-V, support systems module, orbital station modules.

 

image

   Planned first mission of TEM as part of Zevs complex, in 2030. Moon, Venus and Jupiter in 50 months. Mission is currently undergoing planning phase.

 

 

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  • 2 months later...

https://iz.ru/1315347/olga-kolentcova/zevs-pomozhet-otvetit-na-vopros-est-li-zhizn-na-sputnikakh-iupitera

 

Quote

The first mission of the nuclear tug "Zeus" will include a search for life on the moons of Jupiter. Alexander Bloshenko, executive director of Roscosmos for advanced programs and science, spoke about this in an interview with Izvestia. According to him, the tug will fly around the Moon, head towards Venus, leave several satellites there, and finally begin its journey to Jupiter. There, "Zeus" will check the planet's satellites for biomarkers and conditions potentially suitable for the existence of life. The device is planned to be made in such a way that its power can be changed depending on the flight range and assigned mission.

Looking for life

- Alexander Vitalyevich, will it be possible to launch the Zeus nuclear tug into space?

- Experimental confirmation of key technologies and development of the conceptual part of the project documentation should be completed in 2024. Further, the tug project can begin to be implemented - first in the design bureaus, and then in iron in the shops. The first mission will take place in 2030. Now its parameters are calculated by scientists and specialists of various profiles. First, Zeus and the payload module, each on its own launch vehicle, will be launched into low-Earth orbit from the Vostochny cosmodrome. Further, their orbital docking will be carried out and a flight around the Moon and return to the Earth will be carried out. Then the docking with another payload module will be tested. Next, "Zeus" will fly towards Venus, perform a gravitational maneuver there and head towards the satellites of Jupiter. The duration of the mission will be 50 months, it will end around 2034. - Will the re-docking take place automatically? - Of course, since the presence of a nuclear reactor on Zeus does not imply the involvement of people on it today. And in general, the expediency of direct participation in human space missions at the current level of technological development is an open question that is being discussed all over the world. Life forms new current trends, and they are directed towards robotization, automation and the widespread use of artificial intelligence.

— How are you planning to load Zeus to solve the scientific problems of the first mission? “Our space scientists are planning to use the unique transport and energy capabilities of the Zeus to solve a wide range of scientific problems at all stages of the mission. At the first stage, the nuclear tug should provide radiophysical research of the Earth-Moon satellite. A powerful onboard radar complex, which includes several radars, will have to scan the lunar rocks under the regolith for lava tubes, cavities, accumulations of useful resources, including ice. Detailed maps of the surface and near-surface layer will be created, important properties and features of the soil will be studied - this will be useful for the implementation of the future lunar program. In the next stages, "Zeus" will go into deep space. A number of scientific satellites - probes are supposed to be delivered to Venus, as well as Jupiter and its satellites. I would like to explore the atmosphere, magnetosphere and internal energy sources of Jupiter, explore the subglacial oceans of Europa and Ganymede. In addition, we will check the moons of Jupiter for the presence of life there. More specifically, we plan to test the moons of Jupiter for the presence of so-called biomarkers and conditions potentially suitable for the existence of life.

Do you expect to find life there? - This, of course, would make a revolution in the consciousness of mankind, understanding of the role and place of us in the Universe. Today it is difficult to even imagine what a leap could take place in biochemistry, medicine, pharmacology, and in almost all areas of our activity. Therefore, we plan to at least look for it there. Today, Jupiter's moons - Io, Europa, Ganymede and Callisto - along with Saturn's moons Titan and Enceladus attract the closest attention of scientists around the world and are even considered as objects for colonization in the distant future. It has been established that some of them have oceans covered with ice, from under which steam sometimes comes out, some tectonic activity is observed, which indicates a hot core of a celestial body. Heat and water are the necessary conditions for the existence of life. Many missions are organized to the moons of Jupiter. However, in order to obtain reliable and complete information, it is necessary to deliver a large amount of high-tech equipment there - spectrometers, gas analyzers, multispectral cameras, and so on. It would be interesting to fly through the "exhaust" of steam, but this requires a separate special satellite, which Zeus can also bring as part of the payload module.

Difficult but possible - In the future, the range of tasks "Zeus" can expand significantly. Are you planning to make several tugs with different capacities? - You probably involuntarily asked two conceptual questions - about different missions using the Zeus and about different technical solutions of the Zeus itself. On the first question. I want to say right away that we are probably working with the best engineering staff. The designers of our design bureaus foresaw that in the future there would be a huge demand for Zeus as an interplanetary transport system. Therefore, its capabilities must be flexible in terms of scalability. A simple example. To minimize the flight time to the Moon and Jupiter, different engines are needed - because of the significantly different distances to these objects. Using the same engines to implement these tasks is simply inefficient. The same goes for fuel reserves and the design of fuel tanks, because they ultimately affect the mass of the delivered cargo. That is why the same Zeus will be used in flight to the Moon and Jupiter, but with different payload modules, which will include special main engines. - What about the second question? — Our country has been engaged in the development of space nuclear technologies quite a long time ago. In numerous publications you can find a lot of interesting things about this. The technology on which Zeus is based did not begin to develop and be mastered yesterday. Over the past decade, our enterprises have created a huge backlog that provides world leadership in this matter. We can create a tug with different capacities, but today we probably stopped at the golden mean - about 500 kW. From the point of view of the energy potential, this is enough to solve transport problems and provide energy for almost any payload. At the same time, from the point of view of design features, the solutions laid down are easily scaled on subsequent modifications of the tug up to 1 MW. In addition, to ensure maximum flexibility and durability of such a complex transport system, Zeus's maintenance capabilities are being preliminarily studied. For example, this can be done using a multifunctional reusable cruise ship capable of not only refueling the tug with expendable components, but also providing, if necessary, diagnostics and repair operations.

A matter of technology How does Zeus work? - If you do not go into details at all, then everything is simple - this is an ordinary heat engine and replaceable energy consumers. The nuclear reactor - the heart of Zeus - can simply release a huge amount of heat that needs to be converted into electricity. Next comes the "technical fork" of design options. We settled on machine energy conversion. The coolant, passing through the core of a nuclear reactor, heats up and sets the “machine” in motion, in our case it spins a turbine with its steam, which makes the electric power generator work. In this case, the efficiency can reach up to 30%. Further, the electric power is transmitted to consumers on the payload module - sustainer engines, target equipment and on-board support systems. It was this option - as the most promising and effective, but also the most technologically complex - that was chosen for Zeus. — What components are the most difficult to design and develop? — The most complex elements are a reactor plant and an energy conversion system based on a gas turbine generator. I will not touch on the complexity and innovativeness of the reactor plant, since it is the "eparchy" of another state corporation (Rosatom), but I will focus on the energy conversion system. Imagine a turbine and a generator rotating at a speed of 1 thousand revolutions per second at a temperature on the turbine blades of about 1.5 thousand degrees Kelvin (about 1.2 thousand degrees Celsius. - Izvestia). Moreover, this entire system should work without failures in outer space at a very large distance from the Earth for at least 10 years. But that's not all. A little earlier we said that only 30% of thermal energy is converted into electrical energy. The remaining 70% of the heat must be disposed of through a heat recovery system. This is a very difficult task in outer space, since this is possible only through thermal radiation, because there is no direct exchange of heat with the environment - vacuum -. For this purpose, spacecraft are equipped with special surfaces that effectively emit in the infrared range of the spectrum, but in our case, at our energies, these surfaces turn into very large fields, becoming the most difficult design task for development and testing in ground conditions.

— Why does space technology take so long to make and is expensive? - Our developers - engineers, testers, workers, technologists - all understand the cost of a mistake, they simply do not have the right to it. The error means an idle spacecraft in orbit. Unfortunately, while humanity does not have the technology for a full-fledged repair in orbit, this is why the price of a mistake is so high. Of course, our predecessors, we, our followers had and will have ups and downs, but we here on Earth, in the course of designing, designing, manufacturing, and experimental testing, strive to do everything to eliminate emergency situations as much as possible. To do this, at each stage of work, everything is repeatedly checked, each component of the spacecraft first undergoes autonomous tests that simulate its entire life cycle, from leaving the shop gate to the completion of the flight in space, then comprehensive tests as part of a larger system or unit, and so on. , before testing the fully assembled spacecraft on Earth. We can say that time and money in space technology is the price for the highest reliability. - Can external factors hinder the implementation of such an ambitious project? “We live in difficult times. We recently overcame the pandemic, and today we are forced to live under unprecedented sanctions pressure from foreign competitors. Conditions are unpredictable, and all sectors of the economy, including the financial sector, are affected by them. Despite this, in my opinion, priority projects, where our leadership is still obvious, should be supported at all levels of executive power, and we and our colleagues from the industry will not let us down.
 

 

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  • 2 weeks later...

https://ntrs.nasa.gov/citations/20210017131

Compass Final Report: Nuclear Electric Propulsion (NEP)-Chemical Vehicle 1.2

tK0ha4F.jpg

Quote

Many previous studies have examined sending crews to and from Mars. The most economical involved a
‘conjunction’ class whereby the crew spends around 500 days on Mars waiting for a ‘cheap’ return. The total
mission time results in over a 1000-day mission duration (about 3 years). Given the current experience level of only
one year on the International Space Station (ISS), it of interest to reduce that time to only two years, thus reducing
risk and minimizing required Mars surface infrastructure. The Phase 1.1 Study goal was stated as follows,
“Determine the feasibility of a two-year roundtrip class Mars mission concept of operation that enables boots on
Mars no later than 2036.” [1] While the Phase1 study did show feasibility for the NEP-Chemical option, the 2036
Opposition opportunity was found to stress the schedule due to proposed technology development schedules. A
2039 Opposition (which requires even more energy than the 2036 case) was chosen as representative for Phase 1.2.
Phase 1.2 also sought to further refine the concept, building on the feasibility, but addressing several challenges
brought by the red team and habitat team.

Given the date of 2039, nearer term technologies, primarily nuclear thermal and nuclear electric were deemed as the
most viable for these missions. As will be shown, the energy required to perform such a mission in only two years
(for the 2039 opportunity at least) is about three times that of the three-year conjunction mission. The rocket
equation (
Equation 1 below) shows that this mission would then require several times the propellant of the three-
year mission unless the specific impulse (ISP) of the propulsion system can be increased.

Based on lunar needs, a limit of five Space Launch System (SLS) launchers with 8.4 m fairings was imposed for the
piloted transportation portion of the mission, limiting the size of the system. When using nuclear electric propulsion,
the main limiting factor was packaging the required radiator area.

The higher I sp nuclear electric propulsion (NEP) system option is described herein but with a twist: in order to keep
the size of radiators packageable in one SLS and use proven reactor power system technology (~1200 K reactor
outlet temperature and superalloy-class Brayton) the NEP system had to be combined with a chemical propulsion
system. This combination of electric propulsion and high thrust chemical was found to be useful in previous design
studies combining solar electric propulsion (SEP) and chemical propulsion [2]. Such a combination allowed the low-
thrust system to provide significant change in velocity (∆V) during the interplanetary portions of the mission,
thereby notably reducing the ∆V required by the high thrust system to capture and depart from the Mars gravity
well. Here the high thrust ‘impulsive’ system is more efficient due to the Oberth Effect [3].

A plethora of trades, both at the mission and system level, as well as the subsystem level were performed to develop
these vehicle concepts. The most important will be described in each appropriate section in detail. A pictorial
summary showing the design evolution is shown in
Figure 2-1.
An entire family of NEP-Chemical transportation vehicles is described herein. The main driver and the primary
focus was the piloted vehicle, shown in
Figure 1-1, but additional concepts for cargo were performed using the same
‘building blocks’ in order to reduce costs and provide commonality. The cargo options are described in

APPENDIX B.

 

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