Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Space Shuttle Main Engines

  1. Dec 6, 2004 #1

    RE: Watters and Enigma

    In light of the latest shutdown thread - Nerva - "what the hell"
    Firstly neither of you have ever posted any replies on that thread. Secondly, i doubt it that you Enigma, are an aerospace engineer. I have been looking at your posts and am amazed at what little seems to be understood by you in the fields of space flight dynamics. Also, i doubt it that even if you are an aerospace engineer, that you would have much understanding in nuclear physics, in specific relevance to nuclear engineering. General practice in aerospace engineering is related to the fields of petrochemical (fossil fuel) based rocket designs, microgravity installations, orbital mechanics and basic astrophysics. A leading aerospace engineer at the NASA Glenn Research Centre (Cleveland), Stanley Borowski, has both degrees in aerospace as well as nuclear engineering, neither amalgamated, so this highlights my point clearly.

    Thirdly, i doubt it that you would understand the lengthy debate posted on this thread about prospects of nuclear engineering, which was primarily conversed between myself and Astronuc, not you. If you can't understand simple logic, a simple hypothesis i put forward, some theoretical calculation in nuclear energy output expressed all in laymen terms within basic English, which was mostly without math than I doubt it you know much about anything to do with nuclear engineering or even space.

    Your arbitrary views on nuclear reactor based space exploration should not allow you the legality to close my thread down.
    No one's opinions should be enough to stop public thread's from being written. Yes I grant you that i am only sixteen, but what is the big deal, are you jealous. I doubt it that, either you, have any access to top secret nuclear schematics. By the way, that's preposterous, nuclear engineering is far from ''the secret of secrets.'' I have many schematics ranging from the SSME's, OMS, RCS to NERVA based design schematics on my computer, none needing clearance of any kind. (judging if your really are an engineer, than you should know all of those acronyms)

    The fall of the NERVA program, and the eminent fate of all nuclear engines harnessing reactor based designs;

    The recent demise of the NERVA program is due to final conclusions laid in 1972 (or possibly 73, reports are many, and sketchy on this). The overall energy output of all 20 tried, tested and recorded NTR (Nuclear Thermal Rockets) most harnessing reactor based designs, where existent between 50,000 to 250,000 pounds of thrust.

    The SSME (Space Shuttle Main Engines) harnesses about 412,000pt inside earths atmosphere, about 512,000pt (pounds of thrust) in vacuum, and the combined take off of a 747 commercial airliner is about 220,000pt.

    This led to costly engine manufacturing, extreme environmental-health risks and wasted engineers, developers and companies time and money. The project cost about 1.5 billion dollars to be exact, that's about 7 billion dollars today that was spent on the NERVA project. The process of such designs, is a direct port of technology from nuclear reactors used in today's commercial power plants, nuclear subs and other energy manufacturing installations. The idea of using elements such as Hydrogen in today’s NTR (which contain nuclear reactors) clearly illustrates the complete and utter un-understanding for nuclear technology which has lead to teams of engineers, specifically those inside NASA's Glenn Research Center, to depict future concepts to be in equivalent of about 15,000pt due to cost cutting and resizing issues for premium t\w ratio (thrust to weight) requirements.

    This 15,000pt bench mark for a new NTR is being worked on at this very point in time in both the NASA Glenn and NASA Marshall Space Flight Centers in the U.S for purposes to create the 'Next Gen' launch systems for planetary missions. These missions are the future for astronaut manned space flights. The orbiter's OMS (which is a secondary propulsion system, Orbiter Maneuvering System) produces in total of two engines, 12,000pt.

    Because of the technical parameters of today's NTR, the largest down-fault seems to emanate from reactors and their part in nuclear engineering today. Using a reactor, uranium micro-fissions, which can produce thermal and other pressure properties that act out on light-weight fuels (accelerants) such as hydrogen, causing the fuel itself to super-heat, expand and increase in velocity – thus in energy output, which is directed through the nozzle. The very purpose of nuclear physics, reasons why the nuclear bomb was first intended to be built, where to use the very energy from 'direct nuclear fission + fusion' (the expanding ionization energy derived from neutron bombardment and/or lighter nuclei fuse) which underlies the very properties and purposes of nuclear physics today. Nuclear physics for space exploration is specifically intended, from the very beginning to today, to be beneficial in primarily - gargantuan energy output. (massive energy outputs)

    These feeble attempts in reactor based NTR show no advancement and lead nuclear propulsion into strange and unfamiliar places; Take into account this new NTR. To get this engine to operate, massive alterations where made to its design. It is now 1/16th the size of a common bench mark solid core NERVA, with about 1\18th - 1\19th % in total energy output of the original design, still has extreme environmental risks but is cost effective, this design spawning into a small 15,000pt nuclear thermal rocket. With this new NTR all advancements that where once made are now lost. Actually no advancements where ever made, the energy output of the NERVA program rockets where less than a chemical rocket with higher thermal, cost, environmental and expendability factors. So what actual advancements have been made with NTR's? None...
    To even consider using NTR's in the future, costs have to be cut, weight and size has to be met (mainly for t\w ratio problems), environmental factors play a large part and the most elusive effort becomes lost in this equation - total energetic thrust output. So this is the truth about NTR's that use nuclear reactors as sources for power advancement.

    What the hell is the point of 15,000pt in space, hasn’t anyone heard of momentum? The latest mission to mars (MER, Mars Exploration Rovers) showcases momentum and its balance in orbital mechanics, astrophysics and spaceflight dynamics quite well. The MER launch vehicle consisted of a three staged rocket.
    - The first stage was in assistance for primarily placing the rover just inside of LEO (Low Earth Orbit).
    - The second stage was the primary propulsion stage. It consisted of a small Aerojet AJ10 - 118K engine (using A-50 and N204 for fuels) which launched the third stage (and rover) into LEO. The second stage engine is restartable and fired twice. Once in LEO the vehicle re-aligned with mars and then the final and second burn took place in LEO which sent the rover in the correct alignment-direction and sufficient velocity to reach mars. The third stage was a small attitude thruster engine, available to make six quick direction changes primarily to put the rover back on a correct flight path by changing axial alignments. The primary propulsion engine which supported the vehicle to reach mars at a high enough velocity was the small Aerojet engine, thus coupled with the first two burns was assisted only by gradual loss and gain of momentum.

    If we take this flight plan into account, we can reciprocate most of the results for NTR performance to other planets.
    What NTR's should and need to have in account, is using nuclear technology for large energy outputs instead of small outputs and continuity. Granted, an engine with a 15,000pt output is small, but the ISP for this NTR is still very high. The ISP meaning specific impulse or efficiency, is about 900 (or so) which seems to be a great deal over other chemical combinations such as LH2 which is 453 is vacuum, Aerozine 50 which is 320 in vacuum, and Hydrazine which is 300 in vacuum (all ISP ratings rounded). However, don't be fooled by this few hundred rating increase.

    An engine with less energy output must maintain a constant velocity for longer to circum gravity. Thus, the engine must be -on- for extended periods of time, which causes the NTR to become expendable due to irreplaceable loss of nuclear fuel, thermal damage inflicted on the reactor, combustion chamber and internal components, eventual loss of hydrogen propellant and all factors which develop into a completely useless engine structure. All NERVA designs so far are fully expendable.

    Meanwhile the usage of LH2 (Liquid Hydrogen) for space flight will render the mission, vehicle, engine and the NTR specified project completely useless. I have previously worked with LH2 for theoretically planned interplanetary missions (primarily due to high ISP factors) and found that all efforts to use the fuel for spaceflight where in vein. LH2 cannot survive in liquidized form for an interplanetary mission. Liquid Hydrogen must be kept well below boil off point to remain in a liquid state, which is about - 200 degrees Celsius (- 400 degrees Fahrenheit). Even with a state of the art cooling system, this is not possible. Direct sunlight on a mission will cause the tank to overheat (maintaining axial changes away from direct sunlight for temperature drops is improbable for the duration of a mission.) LH2 has an extremely fine molecular structure, permitting it to breach the finest of cracks, holes and even most materials. The shuttle's ET (External Tank) must be 'topped up' continuously just until ignition (launch) to provide protection against boil-off from the Liquid Hydrogen forming into useless gas. LH2 stored for an extended period inside a tank will eventually boil-off into gas but before then it will reform into a solid state, more specifically forming large quantities of frozen ice sickles (a counter agent for this on the outside of the ET is polyisocyanurate foam.) Landing such a vehicle that contains an NTR (harnessing a reactor) on a planet, i.e. mars, would cause intolerable heat stress on the LH2 due to heat-trapping CO2 (Carbon Dioxide) found inside the atmosphere. The very fabric of space-time (referred to from general theory \ Einstein) - - (specifying in this instant, a geometrically defined area of space), say between mars and earth, pertains quiet low temperatures, substantially cold, however would still cause boil-off. LH2 is an extremely difficult fuel to work with in terms for space flight missions and should not, and probably will not, be implemented in future space flight designs for these reasons - even though now many engineers see it to be the way for NTR development.

    Taking all of these parameters into account, a mission using this future depicted NTR is believed (and calculated by NASA Glenn engineers) to reach mars in about 4 months - obviously on only a type -I interplanetary trajectory. Return mission to earth are calculated at about 8 months travel time. Threats are posed here for enviromental damage, physically to muscle and bone structures, and phycologically for astronauts. (Grav systems could be emplyed, however axial rotating modules are highly dubious)

    (P.S Astronuc, your having difficulty imagining the design we conversed earlier, only briefly in detail, because my hypothesis for 'direct fission (+) fusion propulsion uses -General Theory- on a -Quantum Mechanical- level) (I will explain my hypothesis in more detail whence I’m finished with my calculations - calculations currently at this time are only on a general scale - for probability / feasibility factors)
    Last edited: Dec 6, 2004
  2. jcsd
  3. Dec 6, 2004 #2


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    Do you honestly think that attacking the intelligence of those you're trying to persuade will get you anywhere?!?

    You can doubt all you want. I certainly don't have to prove myself to you. I have a BS in Aerospace Engineering, and am doing graduate research into smart materials for my MS in Aerospace Engineering. How much education have you had? ...that's what I thought.

    You know nothing about my views on space exploration. I didn't close the thread because I don't like nuclear propulsions systems. I closed the thread because you were spouting gibberish with horrendous grammar, incomplete analysis, and a condescending tone. Before the thread was closed I conferred both with the mentors on this site and with several colleages to ensure that I wasn't just "being dense" and missing something. Not a single person said that you were posting anything other than gibberish.

    And as for the "legality" issue:

    You agreed when you signed up to post on Physicsforums to abide by the forum rules. Included in those rules was this:

    More of this "nya-nya! I know stuff and you don't!" attitude which - in part - led me to the decision to close your thread. Yes, I know what the acronyms for Space Shuttle Main Engine, Orbital Maneuvering System, Reaction Control System, and Nuclear Engine for Rocket Vehicle Application are. I even have done preliminary designing and sizing of similar rockets and subsystems. The "Space System Design" classes are the culmination of three and a half years of study.

    You must realize, however, that the plans you have on your computer are between 20 to 30 years old at least, and have since been declassified. You do not have enough information to build one of your own from them. Looking at thirty year old plans _still_ does not give you any insight into what is being researched in the United States' top research facilities.

    All that being said, your thread was locked for a reason, and posting another one on the same topic will have the same result. If you persist down this road, you will simply be banned from the site.

    If you have a problem with my decision, you can bring it up with the forum administrator https://www.physicsforums.com/private.php?do=newpm&u=206 [Broken]. I can all but guarantee that they will come to the exact same conclusion I have.

    That being said, if anyone who was participating in the original thread feels that u235 had even the slightest idea what he was talking about, please send me a https://www.physicsforums.com/private.php?do=newpm&u=6 [Broken] and I will take it under consideration.

    Thread locked. Warning issued.
    Last edited by a moderator: May 1, 2017
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook