T O P I C R E V I E W |
Silent Sea | Having read about the S-IVB (and the Apollo 10 lunar module ascent stage "Snoopy") in orbit around the sun, my question is simple: Why place these in such an orbit? |
Jim Behling | Because it was an easy way of disposing them. |
Silent Sea | Okay, easy makes sense. But what exactly makes it easy? Why orbit the sun? Why orbit anything? If it was pushed away in some general direction away from the CSM/LM so that it just goes off into endless space... is that more difficult than putting it into heliocentric orbit? I'm genuinely curious.
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chet | From what I've gathered the mission plan was to burn to depletion the remaining fuel in Snoopy's ascent stage so as to obtain further engine performance data. |
tfrielin | quote: Originally posted by chet: ...to obtain further engine performance data.
Also to collect data on which subsystems failed first as the batteries died — information that was useful during Apollo 13. |
Headshot | There were several possibilities for discarding unwanted Apollo S-IVB hardware. - Crashing it into the Moon
- Causing it to re-enter the Earth's atmosphere and burn up after a lunar fly-around.
- Putting it into a heliocentric orbit.
- Sending it into deep space (exiting the solar system).
- Sending it into the sun.
There was not enough remaining fuel on board the S-IVBs to accomplish Nos. 4 and 5. No. 3 was the easiest to accomplish until engineers decided on No. 1 to gain scientific data after seismometers were placed on the lunar surface. Limited battery life and frozen fuel lines would have precluded No. 2 from succeeding.As it was, an Apollo 12 S-IVB malfunction during its last burn (long after TLI) caused it to enter a large orbit around the Earth instead of going into a heliocentric orbit. |
tfrielin | I don't think it was a burn (in the sense that the S-IVB's J-2 engine was re-ignited) but a propulsive vent of the residual propellants, that placed the Apollo S-IVB stages on their lunar impact trajectories. See also the deliberate re-entry of the four S-IVB stages that placed the three Skylab crews in orbit, plus ASTP. All those S-IVBs were de-orbited via propulsive vents of the stages' excessive propellants. |
SpaceAholic | quote: Originally posted by tfrielin: I don't think it was a burn (in the sense that the S-IVB's J-2 engine was re-ignited) but a propulsive vent of the residual propellants, that placed the Apollo S-IVB stages on their lunar impact trajectories.
APS engine burns after S-IVB separation provided the required impulse... |
Headshot | My bad. I always believed that the J-2 engine re-ignited to use up the remaining fuel. After nearly 45 years I am still learning. |
Silent Sea | The Apollo 10 LM makes sense. I was just reading about that in Go, Flight! so it sounded familiar. Headshot's and the following posts make things clearer for me. So (aside from ones crashed into the lunar surface) it's actually most efficient for the remaining fuel to send the S-IVB toward the sun to orbit than send them off into deep space. Am I understanding this correctly? |
Jim Behling | quote: Originally posted by Silent Sea: Why orbit the sun?
Because it is already orbiting the sun, even while on the launch pad. If it is not in Earth or lunar orbit, it is by default in a heliocentric orbit. quote: ...to send the S-IVB toward the sun
It wasn't toward or away from the sun or deep space, it was just away from the Earth and moon. It is in a orbit of the sun that is similar to the Earth's. |
Space Cadet Carl | Starting in 2011, a group of British astronomers and students began searching for Apollo 10 LM Snoopy. NASA and JPL were to assist in the effort. Forty-six years later, it is the only formerly manned U.S. spacecraft still in space. John Young jokes about how somebody in the future is going to rendezvous with Snoopy and find all of his and Cernan's frozen "DNA waste" and other garbage stored onboard the craft. |
SkyMan1958 | Here's the page from the Apollo 12 Flight Plan where they send the S-IV B on the so called sling shot maneuver. It occurred roughly 4:45 hours after launch. |
SpaceAholic | quote: Originally posted by Headshot: My bad. I always believed that the J-2 engine re-ignited to use up the remaining fuel. After nearly 45 years I am still learning.
Not re-ignited, but there was propulsive venting of propellant (in gaseous state) through the nozzle to supplement the APS. |
Silent Sea | quote: Originally posted by Jim Behling: If it is not in Earth or lunar orbit, it is by default in a heliocentric orbit.
Now that it's put that way, it really makes a lot of sense. |
Tykeanaut | quote: Originally posted by Space Cadet Carl: Starting in 2011, a group of British astronomers and students began searching for Apollo 10 LM Snoopy.
So do we know exactly where LM Snoopy is? |
Robert Pearlman | From what I understand, the 2011 efforts were unsuccessful and Snoopy's location remains unknown. |