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A big problem of NTRs, exposed by GWJ in a precedent topic, is the long duration of start-up and cool-down, which makes them unfit for low delta-V short burns like course correction maneuvers. For that reason the designed-but-never-built NTR spaceship Copernicus was forced to store tons of NTO-MMH for RCS and course corrections.
A potential solution of this problem is the NTR-based OMS system exposed in this study:
chrome-extension://efaidnbmnnnibpcajpcglclefindmkaj/viewer.html?pdfurl=https%3A%2F%2Fntrs.nasa.gov%2Fapi%2Fcitations%2F20180006734%2Fdownloads%2F20180006734.pdf&clen=1873598
The NTR is a low enriched uranium NTR derived from the old NERVA. The orbital maneuvering system is tied to the nuclear rocket and uses the same hydrogen propellant, which enters into the core via an auxiliary circuit and is expelled through a secondary nozzle (in a bimodal NTR the core is maintained hot for all the mission to produce electric power, so the OMS system is always ready for use).
This kind of OMS thermal rocket has an exhaust velocity of 5000 m/s, less than the main rocket, which is about 9000 m/s, but far above a NTO-MMH OMS like that of the Space Shuttle, and also has the advantage to use the same propellant of the main engines.
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This post is a follow up to #1 by Quaoar, posted in January of the current year, and languishing ever since.
I read the post by Quaoar, and thought about it a bit, and decided the topic is worth supporting.
However, for SpaceNut ... for the record, here is a list of all the topics that contain "thermal" in the title, as of 2022/08/21:
Index» Search» Topics with posts containing '*thermal*'
Pages: 1
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Topic Forum Replies Last postPlanetary Cores and potentials for geothermal power. by Void
Science, Technology, and Astronomy 17 2022-08-15 13:44:36 by tahanson43206Thermal Energy Storage by tahanson43206 [ 1 2 3 ]
Science, Technology, and Astronomy 68 2022-08-13 21:22:06 by tahanson43206Nuclear Thermal rockets and an update. by Oldfart1939
Human missions 6 2022-05-06 15:59:49 by Mars_B4_MoonNuclear Thermal Propulsion Module by Oldfart1939
Interplanetary transportation 4 2022-04-14 23:36:44 by SpaceNutThermal heat storage by SpaceNut [ 1 2 ]
Science, Technology, and Astronomy 36 2022-01-16 13:53:35 by SpaceNutOMS for nuclear thermal rocket by Quaoar
Interplanetary transportation 0 2022-01-07 14:40:50 by QuaoarA revival of interest in Nuclear Thermal Propulsion? by Oldfart1939 [ 1 2 3 ]
Interplanetary transportation 57 2021-12-18 09:34:39 by Mars_B4_MoonSolar thermal power by Decimator
Life support systems 11 2021-12-05 19:13:51 by SpaceNutElectricity from Thermal Activity in Magnets by tahanson43206
Science, Technology, and Astronomy 3 2021-03-13 11:52:24 by SpaceNutUltra Safe Nuclear Technologies Delivers Advanced Nuclear Thermal Prop by RobertDyck
Science, Technology, and Astronomy 4 2020-12-15 11:27:56 by SpaceNutNuclear Thermal Rocket by tahanson43206
Interplanetary transportation 12 2020-11-08 23:54:08 by SpaceNutThermally manipulating the Martian upper atmosphere. by Void
Terraformation 6 2020-07-15 21:46:57 by VoidSodium Vapour Thermal Propulsion by Terraformer
Interplanetary transportation 6 2014-05-03 16:16:57 by JoshNH4HSolar Thermal for Ground Launch by eliaslor
Interplanetary transportation 6 2014-03-10 18:20:50 by GW JohnsonPages: 1
Index» Search» Topics with posts containing '*thermal*'
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For Quaoar ....
The NTR is a low enriched uranium NTR derived from the old NERVA. The orbital maneuvering system is tied to the nuclear rocket and uses the same hydrogen propellant, which enters into the core via an auxiliary circuit and is expelled through a secondary nozzle (in a bimodal NTR the core is maintained hot for all the mission to produce electric power, so the OMS system is always ready for use).
In another topic, far away, kbd512 and others are discussing what I gather is an improved way of converting thermal energy to mechanical energy.
Setting ** that ** aside for the moment, and taking a cue from your mention of a reactor kept hot to provide electricity for a vessel, it occurred to me that at ** least ** 50% of the fission generated heat is lost to the environment on Earth.
However, in space, such a reactor ** could ** (theoretically and subject to correction) be cooled by passing hydrogen gas over the cooling fins.
We ** do ** have Calliban in the forum membership, and if the question is of interest, we might be lucky enough to win a few minutes of his time to estimate the thrust that such a cooling system might produce.
From what I can gather from the ongoing discussion in another topic, it is to the advantage of that system to run the reactor hot. Thus, I presume that the exhaust of heated hydrogen gas would have some vigor, but I don't have any way of quantifying the thrust that might be achieved.
In contrast to the Nuclear Thermal Rocket, which was thoroughly studied and tested in the late 1960's, this would be a small thrust that would last a long time.
The comparison that seems reasonable to make is with electric propulsion.
How much thrust might a reactor employed in this service achieve?
Would it make sense to combine the technologies?
If 50% of the thermal energy can be converted to mechanical rotation of a generator shaft, then (presumably) some of the resulting energy could be enlisted to accelerate ions for a traditional ion drive.
However, the thermal energy NOT converted to mechanical motion might ??? be available to accelerate hydrogen gas used as a coolant.
If this post reaches you, I'd be interested in your assessment of the potential of combining these technologies.
(th)
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The last reference mission was number 5 and it covers the use of nuclear thermal rockets. in the human folder
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To answer the original post, this paper is directly from NASA's technical report server: Engineering of the Magnetized Target Fusion Propulsion System
Abstract. Engineering details are presented for a magnetized target fusion (MTF) propulsion system designed to support crewed missions to the outer solar system. Structural, thermal and radiation-management design details are presented. Propellant storage and supply options are also discussed and a propulsion system mass estimate is given.
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For RobertDyck re #5
Thank you for finding the original article and making it available once again. The publication date appears to be 2003.
I scraped this text from the first page of the 24 page pdf...
Engineering of the Magnetized Target Fusion Propulsion System
G. Statham 172,
S. Whitel 72,
R.B. Adams l,
Y.C.F. Thio 3,
J. Santarius 4,
R. Alexander l,
J. Chapman l,
S. Fincher l,
A. Philips l and
T. Polsgrove l
NASA Marshall Space Flight Center,
Advanced Concepts Department,
Huntsville, AL 3.5812, USA.ERC Inc., 555 Sparkman Drive,
Executive Plaza, Suite 1622,
Huntsville, AL 35816, USA.US. Department of Energy,
Office of Fusion Energy Sciences,
19901 Germantown Road,
Germantown, MD 20874, USA.Institute of Fusion Technology,
University of Wisconsin,
Madison, WI 20874, USA.Abstract. Engineering details are presented for a magnetized target fusion (MTF) propulsion system designed to support crewed missions to the outer solar system. Basic operation of an MTF propulsion system is introduced. Structural, thermal, radiation-management and electrical design details are presented. The propellant storage and supply system design is also presented. A propulsion system mass estimate and associated performance figures are given. The advantages of helium-3 as a fusion fuel for an advanced MTF system are discussed.
INTRODUCTION
Magnetized Target Fusion (MTF) is a propulsion technique that combines features from both inertial and magnetic confinement fusion approaches and capitalizes on research results in both areas (Thio, 1999).
The MTF technique offers the promise of both high specific impulse and low dry mass; as such it is well suited to the demands of high delta-v travel to the outer solar system, including human exploration missions.
The work reported in this paper was carried out as part of the Human Outer Planet Exploration (HOPE) study, part of the Revolutionary Aerospace Concepts (RASC) program.
The HOPE objective was to design a vehicle capable of conducting a human exploration mission of the Jovian moon Callisto.
The MTF propulsion system design, as reported here, was developed to satisfy the requirements of this mission.
Details of the mission and vehicle are reported separately (Adam, 2003).
This paper is organized as follows.
First a brief overview is presented, addressing the basic processes involved in MTF operation. For the purposes of this description, the main fusion fuel is assumed to be deuterium.
The subsequent sections are devoted to engineering descriptions of the major MTF components.
Finally, the more advanced MTF system, using a mixture of deuterium and helium-3 as the main fusion fuel, is introduced.
BASIC MTF OPERATION
In outline the MTF system operates as follows.
A small plasma target comprised of an easily-ignitable fuel (a 50% deuterium - 50% tritium molar mixture) is compressed to fusion conditions by converging streams of high-speed plasma, produced by an array of magnetoplasmadynamic (MPD) accelerators, also known as plasma guns.
Energy released from the deuterium-tritium reactions initiates deuterium-deuterium fusion reactions within a deuterium layer immediately surrounding the target.
The use of a deuterium-tritium target, with its relatively low ignition temperature, makes the initial fusion burn relatively easy to initiate, but the main energy + 1 of24+ (continued in the free downloadable pdf)
(th)
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