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Quaoar

Member

Registered: 2013-12-13

Posts: 665

OMS for nuclear thermal rocket

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.

tahanson43206

Moderator

Registered: 2018-04-27

Posts: 19,406

Re: OMS for nuclear thermal rocket

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
Search results
Topic    Forum    Replies    Last post

Planetary Cores and potentials for geothermal power. by Void
Science, Technology, and Astronomy    17    2022-08-15 13:44:36 by tahanson43206

Thermal Energy Storage by tahanson43206 [ 1 2 3 ]
Science, Technology, and Astronomy    68    2022-08-13 21:22:06 by tahanson43206

Nuclear Thermal rockets and an update. by Oldfart1939
Human missions    6    2022-05-06 15:59:49 by Mars_B4_Moon

Nuclear Thermal Propulsion Module by Oldfart1939
Interplanetary transportation    4    2022-04-14 23:36:44 by SpaceNut

Thermal heat storage by SpaceNut [ 1 2 ]
Science, Technology, and Astronomy    36    2022-01-16 13:53:35 by SpaceNut

OMS for nuclear thermal rocket by Quaoar
Interplanetary transportation    0    2022-01-07 14:40:50 by Quaoar

A revival of interest in Nuclear Thermal Propulsion? by Oldfart1939 [ 1 2 3 ]
Interplanetary transportation    57    2021-12-18 09:34:39 by Mars_B4_Moon

Solar thermal power by Decimator
Life support systems    11    2021-12-05 19:13:51 by SpaceNut

Electricity from Thermal Activity in Magnets by tahanson43206
Science, Technology, and Astronomy    3    2021-03-13 11:52:24 by SpaceNut

Ultra Safe Nuclear Technologies Delivers Advanced Nuclear Thermal Prop by RobertDyck
Science, Technology, and Astronomy    4    2020-12-15 11:27:56 by SpaceNut

Nuclear Thermal Rocket by tahanson43206
Interplanetary transportation    12    2020-11-08 23:54:08 by SpaceNut

Thermally manipulating the Martian upper atmosphere. by Void
Terraformation    6    2020-07-15 21:46:57 by Void

Sodium Vapour Thermal Propulsion by Terraformer
Interplanetary transportation    6    2014-05-03 16:16:57 by JoshNH4H

Solar Thermal for Ground Launch by eliaslor
Interplanetary transportation    6    2014-03-10 18:20:50 by GW Johnson

Pages: 1
Index» Search» Topics with posts containing '*thermal*'

(th)

tahanson43206

Moderator

Registered: 2018-04-27

Posts: 19,406

Re: OMS for nuclear thermal rocket

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)

SpaceNut

Administrator

From: New Hampshire

Registered: 2004-07-22

Posts: 29,431

Re: OMS for nuclear thermal rocket

The last reference mission was number 5 and it covers the use of nuclear thermal rockets. in the human folder

RobertDyck

Moderator

From: Winnipeg, Canada

Registered: 2002-08-20

Posts: 7,934

Website

Re: OMS for nuclear thermal rocket

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.

tahanson43206

Moderator

Registered: 2018-04-27

Posts: 19,406

Re: OMS for nuclear thermal rocket

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)