Essay PreviewMore ↓
This report will focus on the most popular ideas and projects being tested today which include some already well-established technologies as well some that have only just entered the laboratory.
There will also be some focus on the power plants that will provide the energy necessary to cross the interspatial void between the planets.
Nuclear Thermal Rocket (NTR)
The NTR presents a great advantage over traditional chemical propulsion systems. NTR uses fission reactions to generate thermal power, which in turn heats a liquid propellant to produce thrust.
How to Cite this Page
"Propulsion Systems for Manned Mars Missions." 123HelpMe.com. 20 Feb 2020
Need Writing Help?
Get feedback on grammar, clarity, concision and logic instantly.Check your paper »
- Crew mission to mars Science and Engineering A crewed mission to Mars would be the pinnacle of one of the breathtaking engineering endeavors of mankind in its entire history. This would require technological capability, engineering ingenious, and organizational infrastructure of the kind that must be refined through decades of drudgery and experience in operating space systems. Crewed missions to Mars would require to tackle unique challenges in logistics, operations, resources and environments at scales that have not been encountered before.... [tags: International Space Station, Human spaceflight]
1348 words (3.9 pages)
- Terraforming Mars is the process of purposely changing the known properties of Mars to satisfy safe human habitation. In order to do this, we would have to use a 1000-year timeline. A thousand year timeline is best because it would give humans the time needed to change the atmosphere of Mars, change the temperature of Mars, grow food, and more. In order for the terraforming process to work, humans must permanently live on Mars for. For humans to permanently live on Mars, a fuel source must be used.... [tags: mars, human habitation, co2 atmosphere]
1154 words (3.3 pages)
- “The United States is justified in spending billions of dollars on NASA space missions to Mars.” Throughout the course of history, man has dreamed of stepping foot on another planet. The advances in technology in the 20th century have allowed man to do what at one time was considered unthinkable for millenniums before. With the advent of the modern space program in the early 1950’s, NASA has performed many inconceivable feats. They have sent and returned men to space. They’ve set up space stations orbiting the earth.... [tags: essays research papers]
1475 words (4.2 pages)
- For decades, humans have wanted to see more of the planet we call Mars, the red planet. There have been many successful attempts to get a glimpse of the interesting planet, and scientists are still working on a better solution to get there. The first rover to explore Mars was "Mariner 4", which arrived on November 28, 1964. It was a spacecraft designated to orbit the planet of Mars, but not to land. It lasted for about 8 months, and was not able to survive much longer than that due to the conditions on and around Mars.... [tags: Mars Rover Design]
2782 words (7.9 pages)
- Mars Buzz Aldrin once said, “By refocusing our space program on Mars for America’s future, we can restore the sense of wonder and adventure in space exploration that we knew in the summer of 1969. We won the moon race; now it’s time for us to live and work on Mars, first on its moons and then on its surface.” The possibilities and questions about if life on Mars, the red planet in the solar system, have been around for years. With new research, this possibility is becoming a more of a reality everyday.... [tags: Mars, Water, Colonization of Mars, Life]
1812 words (5.2 pages)
- The idea to colonize Mars is thought to be a long shot but researchers believe it is possible. It’s crazy to think that one day there could be another planet like Earth. However, the researchers for the Mars-one program have been figuring out ways to do it. Mars is about 35 million miles away from the earth so one of the hardest parts of it all will be getting there (UCSB). To successfully colonize Mars you need to know; how to get there, who would go, and how to survive once you’re there. A lot of people think since Mars is much farther than the Moon that is would take a bigger spaceship to get there but this is not true.... [tags: colonize mars, mars one, red planet]
1000 words (2.9 pages)
- Nuclear Propulsion The true proposition of a possibility that we could use a nuclear device to allow us to easily travel to mars and back might seem absurd, but the fact of the matter it is an all posable realty. Due to the basic concept of a rocket 's propulsion system is a controlled series of bombs destined to be detonated at certain times creating an uplift of thrust that eventually launches the craft fast enough to break through the atmosphere. The bombs that we use today make up most of the weight of our spacecraft in the form of liquid hydrogen and liquid oxygen.... [tags: Nuclear weapon, Cold War, Nuclear fallout]
1231 words (3.5 pages)
- The notion to colonize Mars is believed to be a long shot but researchers believe it is possible. It’s crazy to think that one day there could be another planet like Earth. However, the researchers have been figuring out ways to do it. Mars is about 35 million miles away from the earth so one of the hardest parts of it all will be getting there. If life was constantly evolved on any of the other planets, Mars is the probable contender. Other than Earth, Mars is the planet with the most welcoming climate in the solar structure.... [tags: Mars, Earth, Planet, Sun]
1070 words (3.1 pages)
- National Aeronautics and Space Administration (NASA) launched two similar twin robotic rovers, which were Spirit and Opportunity toward Mars on 10 June and 7 July 2003 (NASA 2012). Spirit and Opportunity landed in Gusev Crater on 4 January 2004 and in Meridiani Planum on 25 January 2004 respectively (NASA 2012). Opportunity is still operating and roving after 10 years on the Martian surface while final communication of Spirit to the Earth took place on 22 March 2010, which is around six years into its mission (NASA 2012).... [tags: nasa, spirit and opportunity]
1060 words (3 pages)
- Mars Mars is the fourth planet from the sun and the last of the solid, non-gas planets in our solar system. Mars is the seventh largest planet in our solar system. The diameter is about 4,220 miles. The equatorial circumference is about 13,259 miles. Earth’s equatorial circumference is about 24,901 miles so Mars’ equatorial circumference is approximately 53.2% that of Earth. The radius of Mars’ core is 1,056 miles. The surface area is 55,742,106 square miles, which is about 28% that of Earth. Mars’ volume is 163,115,609,799 cubic kilometers.... [tags: Fourth Planet, Sun, Solid, Non Gas, Solar System]
1249 words (3.6 pages)
- Civil Rights Historical Investigation
- Integrated Marketing Communication
- The Importance of New Zealand’s Forestry Industry
- Value Relevance of Accounting Information during IFRS Convergence Process and Indonesia
- Three Philosophies of Human Rights
- Reverse Logistics Network Design for the Collection of End-of-Life Vehicles
Comparison of propulsion types for mars mission. 
Open cycle Gas-Core Nuclear Rockets (GCNR) is the most efficient NTR concept with potential to Isp range of 3000-5000 seconds. 
The open cycle GCNR design has never been fully tested due to the complexity of the fluid dynamics involved. The core is essentially comprised of a sphere of nuclear plasma suspended by liquid hydrogen (LH2) in a reaction chamber with direct contact between the fission source and the propellant. The design has the advantage of being able to theoretically increase the exhaust temperature of the propellant to 10’s of thousands of Kelvins (turning the propellant in to a plasma), hence dramatically increasing the Isp, but this then raises an issue of nozzle cooling. Most designs state that the use of a magnetic nozzle would be the solution to this problem. The complexity of GCNR arises due to the issue of containment of the fissile material that generates the thermal power. The design is unlikely to be developed due to the intense radioactivity of the exhaust gas.
Schematic of the Open-Cycle GCNR design. 
Another GCNC concept is the ‘nuclear light bulb’ design, which does not allow contact of the radioactive plasma core with the propellant. The fissile material (typically an isotope of uranium) is encased in a transparent fused silica containment vessel, which transfers energy into a flow of LH2, which is then expanded through a de Laval nozzle to produce thrust. The Isp of the GCNR is typically around 2000 seconds with potential to reach much higher Isp with containment, maximum working temperature and nozzle limitations (cooling etc.) being the limiting factors. This concept has yet to be developed experimentally. 
Schematic of the Nuclear Light bulb design. 
Solid core NTR designs are the most common and researched of NTR. They employ a traditional solid fusion reactor design and the process of operation is well understood and has a high controllability and simplicity when compared with its contemporaries.
The ROVER/NERVA program (1955 -1972) successfully demonstrated 20 compact solid-core reactor designs for space application. These tests provided proof of concept and proof of design that NTR technology is a feasible option for interplanetary travel. 
Solid core NTR’s can attain specific impulses (Isp) upwards of 900s, more than twice the Isp of chemical rockets and achieving high levels of thrust (10’s-100’s of Klbf). In the Mars Design Reference Architecture (DRA) 5.0 study conducted by NASA in 2009 concluded that solid core NTP was the optimal choice to carry crews and cargo in Earth to Mars transit. The DRA 5.0 based their calculations on the 25 Klbf engine design from the Rover-NERVA project, a configuration of 3 “Pewee” engines (diagram can be found in appendix), the highest performing engine from the Rover Program, to be used in parallel. The Pewee-1 engine design was successfully test at a peak thermal power output operating at ~507MWt for 40 minutes. 
The design itself is relatively simple and has the ability to; self-start, stop, restart, has demonstrated sustained engine operation and can operate at a wide range of thrust levels.
The fission of Uranium-235 within the composite fuel element generates thermal energy, which heats a liquid hydrogen propellant. The LH2 first moves from the storage tank through a duct wound about the exit nozzle for cooling (additional propellant heating) where it is then passed along the outside of the reactor to be heated further then through the cooling ducts in the super heated reactor core and subsequently expelled through a supersonic nozzle. Before being fed through the core some LH2 is syphoned off and channeled through turbines to drive turbo-pumps, which initially compresses the liquid fuel (shown in figure below). Hydrogen that has passed though the turbines is then routed back in to coolant channels surrounding the core.
Schematic of solid-core NTR design. 
Control of the engine output is through the matching of the LH2 flow to core cooling requirements. Reactor core output is controlled through the use of external control rods surrounding the outside of the fuel element vessel. These fuel rods are made from a combination of materials, typically half of the control absorbs neutrons (B4C) and the other half reflects them (BeO). The control rods are subsequently rotated to achieve a desired thermal output. Control face with neutron absorbing material facing the core for lower temperature output (less neutrons are reflected back into the core) and control face with neutron reflective material orientated towards the core for higher thermal output. 
Taking parameters from the Pewee 1 tests shown in table 1 calculations can be made for; specific impulse (Isp), throat and exit diameters exhaust exit velocity, thrust produced and the mass of fuel needed to reach the mission delta v.
Engine Performance characteristics outlined in Pewee 1 Tests. 
Tcore ~2556 K
Pcore ~6895 KPa
ε (exit to throat area ratio) ~300:1
LH2 flow rate ~18.6 Kg/s
Thrust to weight ratio ~3.5
Critical mass U-235 in core 36.4 kg
Nozzle chamber temperature ~1837 K
Nozzle chamber Pressure 4275 kPa
Mission delta V budget* 3.83 km/s
Total mass of Spacecraft* 139 t
*Taken from DRA 5.0 study. 
Assuming isentropic processes exhaust velocities (ue) can easily be calculated through the following equation. 
u_e=√(2γ(R_0/M)/(γ-1) T_02 [1-(P_e/P_02 )^((γ-1)/γ) ] )
Where R0 is the universal gas constant, T02 is the nozzle chamber temperature, p02 is the nozzle chamber pressure, γ is the ratio of specific heats, Pe is the nozzle exit pressure and M is the molecular weight of the propellant.
Given an exit to throat area ratio (A/A*) of 300 a nozzle chamber to exit pressure ratio (Pe/P02) can be evaluated through isentropic relations.
Using liquid hydrogen (LH2) as propellant yields (table of LH2 properties in appendix).
Force of thrust (F_T) can then be calculated through the basic thrust equation.
F_T=m ̇u_e+(P_e-P_a ) A_e
F_T=m ̇c^* C_F
c^*=√(((R_0/M) T_02)/γ ((γ+1)/2)^((γ+1)/(γ-1)) )
C_F=A_e/A^* (P_e-P_a)/P_02 +√((2γ^2)/(γ-1) (2/(γ-1))^((γ+1)/(γ-1)) [1-(P_e/P_02 )^((γ-1)/γ) ] )
Subbing in values gives
m ̇ Is the mass flow rate of propellant, P_a is the ambient pressure (assumed to be zero), Ae is the exit area of the nozzle, c* is the characteristic velocity and CF is the nozzle coefficient. 
The specific impulse can now be evaluated.
I_sp=(c^* C_F)/g_0 =725.862 s
g_0 Is the acceleration due to gravity at the Earth’s surface (~9.81 m/s2). The mass of LH2 propellant needed to achieve the mission delta v budget is found using a derivation of Tsiolkovsky’s rocket equation. 
m_propellant=m_initial (1-e^(-Δv/(I_sp g_0 )) )
Inserting values from table ## and result obtained from equation # gives.
m_propellant=57.825 tonnes of LH_2
Hence the burn time would be.
t=m_propellant/m ̇ =m_initial/m ̇ (1-e^(-Δv/(I_sp g_0 )) )
t=3108.88 s=51.815 minutes
This burn time is reasonable as the pewee design was tested at full power for over 40 minutes. 
The mass of propellant used is for a one-way acceleration of the craft. It states in the Rover test files that the Isp of the Pewee engine was not optimised as it was primarily used as a test bed for reactor core elements. However specific impulses of this magnitude still hold a huge advantage over bi-propellant chemical propulsion when considering inter planetary travel. 
If the Isp were improved to the purported values of 900s and above this would reduce the weight of propellant needed by approx. 10 tonnes, which in turn reduce the burn time and overall mass of the craft, hence the mass of propellant required.
Improvements in specific impulse can be achieved though increased core temperatures, which a fission reaction can produce easily, but the limitation lay with the material properties of the core.
The engine examined in the DRA 5.0 utilizes U-235 fuel in a graphite matrix fuel element (UC2). U-235 has an energy density of 1.68e+13 J/kg, while Liquid hydrogen (1.20e+8 J/kg) is used for propellant. 
The thermal core in the Pewee design is comprised of 402 hexagonal fuel elements with internal cooling channels for the LH2 to flow through. A typical core design developed in the Rover-NERVA programs is shown in figure ##.
The internal flow channels for the heat transfer to the LH2 is moderated by a coating of niobium carbide or zirconium carbide to prevent corrosion of the uranium-carbon matrix by the super heated LH2. Clusters of six fuel elements were place around a central tie rod to place the fuel elements under axial compression to minimize damage caused by flow vibrations. 
A fraction of the LH2 flow is syphoned in to coolant channels through the supporting structure to reduce excess heat damage.
Several fuel element designs were tested by both the US and Russian NTP Programs with several inquiries in to different fuel element compositions and a particular focus on CERMET (ceramic-metal composite) fuel elements.
Figure ## below demonstrates the effect that core operating temperature has on Isp and the difference in operating temperatures of different fuel matrixes.
Soviet efforts of developing fuel elements produced unique geometries, resembling a drill piece, to maximise heat transfer. The ternary carbide fuel in the ‘twisted ribbon’ configuration provided the highest performance characteristics reportedly operating at maximum core temperatures of 3200 K.
‘Twisted ribbon’ design. 
There is a multitude of support for nuclear thermal rocket designs and application and with available technology seems to be the best option compared to the competing propulsion systems such as chemical combustion or electric propulsion for long term space missions.
The prospect of sending humans to mars is of great interest to many in the scientific community and members of the general public and there are no international space treaties that explicitly prevent the use of nuclear reactor technology in space. One mission parameter designated in NASA’s Prometheus project that could be taken into consideration was that nuclear reactors could not be in operation until the time for the spacecraft’s orbit to decay is longer than the decay time of the fissile material. Generally speaking, at the point where the craft will remain in orbit indefinitely. 
Mission parameters and safety considerations will help to alleviate public and administerial concerns. NASA literature dictates that several design factors should be considered when employing the use of fission reactor systems in space.
“The ability [of the reactor] to operate reliably without continual actions from ground control, the ability to keep the reactor in a subcritical state prior to startup and under various accident scenarios, the ability to remove operational and decay heat during specified normal and off-normal operating conditions, and the ability to reliably perform all necessary control and safety functions.”
At a distance in excess of 10ft (3.048m) is proportional to 1/r^2 , where r is the distance from the reactor core. The data in the table states at 0 degree orientation from reactor core (where crew module would be located), at a distance of 6ft, 1.8*10^7 rads/hour is released.  Assuming that the radiation from 6-10 ft. is also proportional to distance as stated above,
Rads per hour=k 1/r^2 .
Where for this purpose k will be called the coefficient of radiation environment and will have the units, (rads.ft2)/hour. It is a relative measure of the strength of the radiation source. K can be calculated from the tabulated data.
Maximum allowable occupational radiation absorption standards give 5rems/year or 0.0005704 rems/hour. 
Assuming rads ≈ rems (approximate maximum possible dose).
Without shielding the crew would have to be situated in front of reactor 1.066 ×〖10〗^6 ft (approx. 325 Km). The shielding required reducing radiation to the maximum occupational exposure level at ~7ft from reactor core would be approx. 40cm of lead shielding. 
With further advancement of nuclear thermal technology, the reactor for the NTR can be augmented for ‘Bi-modal’ operation, producing both the propulsive power for the craft but also can be run to produce electrical power, generated through a Brayton cycle configuration. This electrical power generated is estimated at .1-1 MWe, which can be used to run the onboard systems such as communication, refrigeration and life support systems as well as the possibility of an electric thruster to increase the delta v capabilities of the craft as well as performing orbital maneuvers. 
Thrust augmentation through injecting liquid Oxygen (LOX) into the divergent, supersonic section of the nozzle can deliver additional propulsive force by adding chemical energy and mass to the exhaust gas. The addition thrust achieved would result in shorted burn times thus reducing the LH2 mass required. Due to the higher density of LOX smaller containment vessels can be used further reducing the overall mass of the system. The table ## shows the variation of Isp versus LOX/H2 mixture in the exhaust. 
LH2 Properties 
Ratio of specific heats, γ ~1.4
Gas constant, R 4.12 kJ/kg
Specific heat at constant pressure, cp 14.32 kJ/kg
Cross section of Pewee engine design 
Nuclear Engine for Rocket Vehicle Application (NERVA)
. Robbins, W. (1991). An Historical Perspective of the NERVA Nuclear Rocket Engine Technology Program. [PDF] NASA Technical Reports Server.
. Ragsdale, R. (1991). Open cycle gas core nuclear rockets. [PDF] NASA Technical Reports Server.
. Latham, T. (1991). NUCLEAR LIGHT BULB. [PDF] NASA Technical Reports Server.
. Borowski, S., McCurdy, D. and Packard, T. (2009). NUCLEAR THERMAL ROCKET/VEHICLE CHARACTERISTICS AND SENSITIVITY TRADES FOR NASA’s MARS DESIGN REFERENCE ARCHITECTURE (DRA) 5.0 STUDY. [PDF] NASA Technical Report Server.
. Bret G. Drake, (2009), Advanced Propulsion [ONLINE]. Available at:http://www.nasa.gov/pdf/373665main_NASA-SP-2009-566.pdf [Accessed 17 April 14].
. Finseth, J. (2014). Rover nuclear rocket engine program: Overview of rover engine tests. [PDF] NASA Techical Reports Server.
. Borowski, S., McCurdy, D. and Packard, T. (2012). Nuclear Thermal Propulsion (NTP): A Proven Growth Technology for Human NEO / Mars Exploration Missions. [PDF] NASA Technical Report Server.
. University of Washington: School of Oceanography, (2005). Energy in Natural Processes and Human Consumption. [online] Available at: http://www.ocean.washington.edu/courses/envir215/energynumbers.pdf [Accessed 6 Apr. 2014].
. Borowski, S., McCurdy, D. and Packard, T. (2012). NUCLEAR THERMAL ROCKET (NTR) PROPULSION: A PROVEN GAME-CHANGING TECHNOLOGY FOR FUTURE HUMAN EXPLORATION MISSIONS. [PDF] NASA Technical Report Server.
. Bhattacharyya, S. K. An Assessment of Fuels for Nuclear Thermal Propulsion. Rep. no. ANL/TD/TM01-22. Argonne, IL: Argonne National Laboratory, 2001.
. Benensky, K. (2013). Summary of Historical Solid Core Nuclear Thermal Propulsion Fuels. [PDF] Penn State Scholar Sphere.
. Borowski, S., Corban, R., McGuire, M. and Beke, E. (1993). Nuclear Thennal RocketNehicle Design Options for Future NASA Missions to the Moon and Mars. In: Space Programs and Technologies Conference and Exhibit.
. Joseph J. MacAvoy, Nuclear Space and the Earth Environment: The Benefits, Dangers, and Legality of Nuclear Power and Propulsion in Outer Space, 29 Wm. & Mary Envtl. L. & Pol'y Rev. 191 (2004), http://scholarship.law.wm.edu/wmelpr/vol29/iss1/6
. NASA Space Science, Space Fission Reactor Power Systems: Their Use and Safety (Feb. 2003), at 2, available at http://spacescience.nasa.gov/missions/fissiontechsafety.pdf
. Stengel, R. (2014). Launch Vehicle Design: Propulsion. 1st ed. [PDF] Princeton University. Available at: http://www.princeton.edu/~stengel/MAE342Lecture2.pdf [Accessed 8 May. 2014].
. ANS / Public Information / Resources / Radiation Dose Chart. 2014. ANS / Public Information / Resources / Radiation Dose Chart. [ONLINE] Available at: http://www.ans.org/pi/resources/dosechart/?gclid=CKXnxcuYj74CFZcjvQod0KQAGQ. [Accessed 24 May 2014].
. NERVA. Performance/Design and Qualification Requirements. (1970). 1st ed. [ebook] Aerojet Nuclear Systems Company, p.74. Available at: http://www.fas.org/nuke/space/nerva-spec.pdf [Accessed 17 Apr. 2014]
. A Compass DeRose Guide by Steven J. DeRose. 2014. A Compass DeRose Guide by Steven J. DeRose. [ONLINE] Available at:http://www.derose.net/steve/guides/emergency/hardened.html. [Accessed 25 May 2014].
. Braeunig, R. (2012). Basics of Space Flight: Rocket Propulsion. [online] Braeunig.us. Available at: http://www.braeunig.us/space/propuls.htm [Accessed 3 May. 2014].
. Borowski, S. and Dudzinski, L. (2003). 2001: A Space Odyssey” Revisited—The Feasibility of 24 Hour Commuter Flights to the Moon Using NTR Propulsion with LUNOX Afterburners. Cleveland, OH, United States: NASA Glenn Research Center.
. Hill, P. and Peterson, C., Mechanics and Thermodynamics of Propulsion, 2ndEdition, Addison Wesley, Reading, Massachusetts, 1992.