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Space Forum / Shuttle / November 2003Interesting concept
http://www.spaceref.com/news/viewpr.html?pid=13103 > http://www.spaceref.com/news/viewpr.html?pid=13103 The Space Tug concept itself is nothing new. A Space Tug was included in early Space Shuttle planning. The concept goes back much farther than that and has even been considered for a Hubble servicing mission, IIRC. Like many other good ideas the Shuttle Space Tug was not well thought out. The Inertial Upper Stage (IUS) was initially called the "Interim" Upper Stage due in part because it was to be "Interim" in the sense it would be replaced by the Space Tug and then later by the Shuttle Centaur Upper Stage (CUS). The Tug concept died early on in the Shuttle development. The CUS died after it was shown to be too dangerous from a launch and Range Safety perspective when it was determined that Shuttle Centaur payloads involving plutonium driven Radioisotope Thermal Generators (RTGs) would likely be released in a massive payload explosion in a Challenger-like disaster scenario. The results of a plutonium release even a small one, would be a public relations nightmare for NASA. The RTG can survive an unmanned spacelaunch vehicle explosion. Good late concept on Space Tug. http://www.astronautix.com/craft/spacetug.htm Really good brief Shuttle History written before STS 107 apparently. http://www.astronautix.com/lvfam/shuttle.htm  SignatureDaniel http://www.challengerdisaster.info Mount Charleston, not Charleston, SC Actually, the big problem with the shuttle Centaur (the Centaur-G') involved the changing perception of the hazards associated with venting the boiloff from the Centaur liquid hydrogen and liquid oxygen tanks while it was inside the orbiter payload bay. NASA apparently had this problem figured out and was in the process of retrofitting the necessary plumbing into one of the orbiters when the Challenger explosion occurred (Jan 1986). That disaster and the demands of the Rogers Commission forced NASA to reassess the entire Critical Items List and shuttle safety in general. One of the things to go was the shuttle Centaur which, due the heightened safety concerns in the post-Challenger period, was deemed too risky to fly in the payload bay. I don't think that there was a strong linkage between NASA junking the Centaur-G' and the supposed hazards of RTGs and plutonium. Remember that the Galileo spacecraft contained more than 50 pounds of plutonium and was launched together with it's IUS on Atlantis (STS-34, the 31st shuttle flight that lifted off on 18 Oct 1989). Regardless of which upper stage was used, NASA still had to complete an extensive environmental impact evaluation before the Galileo launch was allowed to proceed. You can find more info on this interesting topic in Chapter 36 of my 2002 book on U.S. manned spaceflight in the 20th century. Later Ray Schmitt > > http://www.spaceref.com/news/viewpr.html?pid=13103 > [quoted text clipped - 28 lines] > > Mount Charleston, not Charleston, SC > Actually, the big problem with the shuttle Centaur (the Centaur-G') involved > the changing perception of the hazards associated with venting the boiloff [quoted text clipped - 6 lines] > was the shuttle Centaur which, due the heightened safety concerns in the > post-Challenger period, was deemed too risky to fly in the payload bay. I believe you are referring to how do you vent those propellants safely in an abort scenario as well, due to payload weight landing issues. My understanding from having read the Range Safety reports generated in the wake of the Challenger Disaster is that the entire issue of Shuttle Centaur was also extensively reviewed as *part* of a major update to the Webb/McNamara 1963 agreement on use of the Eastern Test Range as it pertains to Range Safety Officer (RSO) activities and NASA manned space launch vehicles. There was an extensive amount of work done on the Launch Abort Safety Panel and much of it pertains to range safety hazards. A big issue in that regard as I understand it is the important role the Flight Director and Flight Dynamics Officer (FDO) play in identifying the controllablity of the shuttle. During the first 30 seconds of flight there were questions about how well the FDO could actually determine three sigma dispersions both laterally and vertically IIRC. Anyway my point is that the concerns for RSO action were very real when it came to having a Shuttle Centaur with an RTG powered deep space probe. It might make an RSO think twice about Arm and Fire commands if he is worried about blowing a chunk of SRB through one of those Centaur fuel tanks next to an Irridum clad RTG. Also back then the External Tank (ET) had Range Safety linear shaped charges (LSCs) which might add some significant explosion velocities to flying pieces of shrapnel. The Challenger disaster magnified these potential concerns making them quite real. For instance beginning with STS 41-C, NASA observed the actual detonation of the ET during reentry. It was a substantial event and NASA sought to understand it immediately. They even installed ET cable tray dams to prevent excessive aeroheating during ascent. Earlier ETs had simply disentegrated having already vented their gases in the vacuum of space. Up until STS 51-L, NASA feared that the linear shaped charges of the ET had autoignited from aeroheating during reentry. This is why NASA sought to recover the LSCs from the ET after the Challenger disaster. They were ultimately recoivered floating on the ocean undamaged and undetonated even though they were briefly exposed to about 4500 degrees F. This discounted the aeroheating during reentry theory as causing the occasional ET detonation but AFAIK NASA has not released the cause of those occasional ET detonations. > I don't think that there was a strong linkage between NASA junking the > Centaur-G' and the supposed hazards of RTGs and plutonium. Remember that the [quoted text clipped - 3 lines] > NASA still had to complete an extensive environmental impact evaluation > before the Galileo launch was allowed to proceed. I don't know how strong the linkage was compared to the points you make. Maybe together and with other factors like the LH2 bulkhead cracking issue on the Shuttle Centaur, NASA threw in the towel. I have not seen the actual decision document canning the Shuttle Centaur along with its rationale if given. > You can find more info on this interesting topic in Chapter 36 of my 2002 > book on U.S. manned spaceflight in the 20th century. What is the name of your book and where is it for sale? It sounds interesting. SignatureDaniel http://www.challengerdisaster.info Mount Charleston, not Charleston, SC Snip > > You can find more info on this interesting topic in Chapter 36 of my 2002 > > book on U.S. manned spaceflight in the 20th century. [quoted text clipped - 7 lines] > http://www.challengerdisaster.info > Mount Charleston, not Charleston, SC The CD-ROM edition (57 chapters, 1438 pages) of my book entitled "U.S. Manned Spaceflight in the 20th Century: The Successes. The Failures. The Options." is available at Amazon.com. No paper edition yet. It's based on my 32-year career at McDonnell Douglas (1965-97) during which I participated in some of our major manned spaceflight programs (Gemini, Apollo Applications, Skylab, shuttle, DC-X/XA, X-33) as well as a lot of other interesting stuff (military reentry vehicles, satellite laser hardening, early Galileo, magnetic and laser fusion energy, Star Wars neutral particle beam research, joint U.S.-Russian robotic lunar exploration programs). Later Ray Schmitt > > http://www.spaceref.com/news/viewpr.html?pid=13103 > [quoted text clipped - 6 lines] > by the Space Tug and then later by the Shuttle Centaur Upper Stage (CUS). > The Tug concept died early on in the Shuttle development. Actually, the Space Tug became OTV - the Orbital Transfer Vehicle, and it was still under active development until circa ~1991. The qual unit was fabricated and the teleoperation software was pretty much complete at that time when it was cancelled by Congress, another victim of poor budget management by Congress. The last time I saw the qual unit was in 1992 or so in Building 4755 at Marshall Space Flight Center in Huntsville. SignatureHerb Schaltegger, B.S., J.D. Reformed Aerospace Engineer Columbia Loss FAQ: <http://www.io.com/~o_m/columbia_loss_faq_x.html> > Actually, the Space Tug became OTV - the Orbital Transfer Vehicle, and > it was still under active development until circa ~1991. The qual [quoted text clipped - 3 lines] > qual unit was in 1992 or so in Building 4755 at Marshall Space Flight > Center in Huntsville. You may be confusing OTV with OMV. Space Tug/OTV was capable of reaching GEO, while the later and smaller OMV was LEO-only. SignatureJRF Reply-to address spam-proofed - to reply by E-mail, check "Organization" (I am not assimilated) and think one step ahead of IBM. > > Actually, the Space Tug became OTV - the Orbital Transfer Vehicle, and > > it was still under active development until circa ~1991. The qual [quoted text clipped - 6 lines] > You may be confusing OTV with OMV. Space Tug/OTV was capable of reaching > GEO, while the later and smaller OMV was LEO-only. You could very well be correct. It's been well over ten years since I saw the hardware and any of the spec's. SignatureHerb Schaltegger, B.S., J.D. Reformed Aerospace Engineer Columbia Loss FAQ: <http://www.io.com/~o_m/columbia_loss_faq_x.html> |
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