APOD and General Astronomy Discussion Forum
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The shuttles are old, both physically and in terms of their underlying technology. It is increasingly difficult to fly them safely, but simply building new ones using old technology doesn't make much sense. The primary value of the shuttles was their ability to carry a heavy payload, which was important in constructing the ISS. Now that the ISS is finished, however, that heavy lift capacity is no longer needed. It is massively uneconomical to use shuttles for nothing more than carrying people up and down from low Earth orbit. A Soyuz can do that for less than 1/10 the cost. So what all this means is that there is very little need for the shuttles anymore, and no existing programs that would justify replacing them.Phil Sayre wrote:Is there a good reason why this is the last shuttle, when we don't have anything else to fly up there? I'm sorry, but it makes no sense to me.
Yes.Chris Peterson wrote:The shuttles are old, both physically and in terms of their underlying technology. It is increasingly difficult to fly them safely, but simply building new ones using old technology doesn't make much sense. The primary value of the shuttles was their ability to carry a heavy payload, which was important in constructing the ISS. Now that the ISS is finished, however, that heavy lift capacity is no longer needed. It is massively uneconomical to use shuttles for nothing more than carrying people up and down from low Earth orbit. A Soyuz can do that for less than 1/10 the cost. So what all this means is that there is very little need for the shuttles anymore, and no existing programs that would justify replacing them.Phil Sayre wrote:Is there a good reason why this is the last shuttle, when we don't have anything else to fly up there? I'm sorry, but it makes no sense to me.
bystander wrote:
Abstruse Goose
http://www.planetary.org/blog/article/00003099/ wrote:
House Committee Votes the Wrong Way – JWST to be Canceled
by Charlene Anderson,Jul. 14, 2011
<<Yesterday, the U.S. House of Representative's Appropriations Committee marked up the bill covering NASA's budget that was sent to it by the Commerce, Justice, and Science (CJS) Subcommittee, and the results will not make Planetary Society supporters happy.
For example:
-- An amendment to overturn the cancellation of the James Webb Space Telescope (JWST) was defeated.
-- An amendment to add money to commercial crew development also failed.
-- The budget request for NASA's Space Technology program remains cut by 60 percent.
The big winner in today's House committee action was again the Space Launch System, the rocket legislated by Senate committee, which was given even more money than requested in NASA's proposed budget.
The appropriations bill now goes to the floor of the House of Representative for a vote by all 435 members, possibly next week, or possibly after the annual August recess. It is probable that another amendment to save JWST will be offered from the floor, but prospects for its passage are not good.>>
http://en.wikipedia.org/wiki/Space_Launch_System wrote: <<The Space Launch System, or SLS, is a Shuttle-Derived heavy launch vehicle being designed by NASA, following the cancellation of the Constellation Program, to replace the Space Shuttle after its retirement. The NASA Authorization Act of 2010 envisions the transformation of the Ares I and Ares V vehicle designs into a single launch vehicle usable for both crew and cargo. It is to be upgraded over time with more powerful versions.
The Space Launch System is to be a Shuttle-Derived heavy launch vehicle and is to be upgraded over time. The initial capability of the core elements, without an upper stage, should be for between 70 tons and 100 tons into low-Earth orbit (LEO) in preparation for transit for missions beyond low-Earth orbit. With the addition of integrated upper Earth Departure Stage the total lift capability of the Space Launch System should be 130 tons or more.
Preliminary designs indicate that the current Space Shuttle Main Engines (RS-25) and Space Shuttle Solid Rocket Boosters would be utilized, and much of the External Tank design would remain the same. This design would require dramatically less development time than the Ares V heavy lift launch vehicle.
On May 24, 2011, NASA announced that development of the Orion from the Constellation program will continue under the name Multi-Purpose Crew Vehicle (MPCV). NASA was expected to make an announcement on July 8 about the SLS's Shuttle-based configuration. For early flights it has an 8.4-meter diameter core with RS-25 engines, 8.4-meter upper stage with J-2X engine, and 4 to 5 segment solid rocket boosters. However, further evaluations have delayed NASA's decision on SLS until late July or August 2011. On June 17, 2011, Aerojet announced a strategic partnership with Teledyne Brown to develop and produce a domestic version of the NK-33 engine, with its thrust increased to 500,000 lbf at sea level. This booster is to compete against Shuttle-derived solid rocket boosters for the SLS launch vehicle.>>
Cooling - there are large radiators attached to the inner sides of the doors, and if for some reason they cannot be opened, the mission must be terminated quickly (within hours, IIRC). The Shuttle cooling design also assumes a one-orbit day-night cycle. The ISS orbit is at high enough inclination to be in continuous sunlight for brief periods around the solstices, and shuttle visits have not been possible during these times.rwb wrote:One serious question: Why have they almost always opened the bay doors early in the mission? Is there a cooling issue, or is there some other reason, such as making a shuttle more visible to observers?
Thanks, Davico & alter-ego. I had a feeling someone here would know the answer to my question!alter-ego wrote:As Davico said, the LCM is located at the engine end of the cargo bay, supporting the MPLM. The picture here shows the LMC (aka Lightweight Multi-Purpose Equipment Support Structure Carrier) carrying an ammonia tank assembly. You can see this same framework in the APOD.nGuinn wrote:Does anyone know where the LCM (Lightweight Multi-Purpose Carrier) is in this photo?
