Apollo 10 contingency plans

[Bob B.]

We are of course discussing a hypothetical landing that would not be by the book.  So there is no reason to assume that the engine would be safed after landing, by the book.  Anything physically possible, even though well beyond normal procedures remains viable.  That said, the method by which they could have landed without the guidance of the computer during the final stage is unclear to me.  Particularity if Stafford and Cernan had not trained for it.  Perhaps if the goal was just to land, rather than to land is a specific spot, it was possible.

Apollo 10's LM had a total mass of 30,735 lbm, with 18,218.7 lbm of decent stage propellant.  The ascent stage at staging had a mass of 8,273 lbm, with 2,631 lbm propellant.  Both the descent and ascent engines had a specific impulse of 311 s.  Therefore the Δv of both stages was,

Δv (descent) = 311 * 32.174 * LN[ 30735 / (30735 - 18218.7) ] = 8,989 ft/s
Δv (ascent) = 311 * 32.174 * LN[ 8273 / (8273 - 2631) ] = 3,830 ft/s
---------------------------------------------------------------------------------------
Δv (total) = 12,819 ft/s

For the six Apollo landings, the median Δv for powered descent and ascent are as follows (the variance from mission to mission was small):

Δv (descent) = 6,696 ft/s
Δv (ascent) = 6,063 ft/s
-----------------------------
Δv (total) = 12,759 ft/s

So, theoretically, it looks like Apollo 10 did have enough total Δv to just barely match that needed to land and takeoff again.  Of course that doesn't mean it was possible; the LM wasn't designed to takeoff using the descent stage.  I also can't conceive of any emergency that would compel them to land.  They were already in orbit, so why land just to takeoff and get back to where they already were. 
 
 

[VQ]

Therefore the Δv of both stages was...

Δv (total) = 12,819 ft/s

For the six Apollo landings, the median Δv for powered descent and ascent are...
Δv (total) = 12,759 ft/s

So, theoretically, it looks like Apollo 10 did have enough total Δv to just barely match that needed to land and takeoff again.  Of course that doesn't mean it was possible; the LM wasn't designed to takeoff using the descent stage.  I also can't conceive of any emergency that would compel them to land.  They were already in orbit, so why land just to takeoff and get back to where they already were.

I think there are the makings of a decent historical fiction in here:

During the A10 mission's LM test, an unforeseen and massive solar flare erupts. Stafford and Cernan, just having entered the moon's shadow, recognize that they will promptly receive a fatal radiation dose in the thinly-walled LM as they come across to sunrise so they perform an impromptu manual landing in the dark and out of radio contact with earth, expending too much fuel from the descent stage and dinging the DPS engine bell in a hard landing in the process. Mission control directs Young to return to earth alone, as he is getting dangerous doses of radiation on each orbit despite the shielding of the oriented CSM stack. Young declines to leave while there is a chance of rescue. Stafford and Cernan race against the clock of resource depletion and DPS helium rupture disc while attempting radical field modifications: reducing ascent stage mass by removing windows, hatches, backup equipment, and sections of the pressure hull and pounding the DPS engine bell back into a functional shape. Young, progressively sickened from radiation exposure, relays technical guidance to the astronauts on the moon with each pass and positions the CSM in an optimal orbit for rendezvous with the LM. Young eventually slips into a coma, and the CSM systems degrade as mission control struggles to keep the CSM (and Young) alive remotely and with intermittent radio contact. Stafford and Cernan, struggling with exhaustion after their two day (and counting) long spacewalk, complete repairs and attempt orbital rendezvous, staging the DPS to the APS in flight.

[Obviousman]

I like that!

[ka9q]

I don't doubt for an instant that there are non-scientists and non-engineers who have been exposed to metric units their whole life who would get confused by some uses of SI units.  For instance, a layman probably doesn't know what a Newton is or how it's used.

Because they don't understand that force and mass are two different things...

[ka9q]

During the A10 mission's LM test, an unforeseen and massive solar flare erupts.

For which the best response would be an immediate rendezvous and docking with the CSM, not a landing...

[Echnaton]

During the A10 mission's LM test, an unforeseen and massive solar flare erupts.

For which the best response would be an immediate rendezvous and docking with the CSM, not a landing...

Ya, but this is the Hollywood version.  I've had similar Hollywood speculations, too and wondered about how to present a plausible rescue. The real problem in gaining even Hollywood correspondence to the real world is the fact that the CSM is traveling in excess of 3000 miles an hour. Hollywood plausibility says that you could do a sub-orbital LM launch that would, in a one in a million chance, cross paths with the CSM but overcoming the speed differential for astronaut transfer strains my imagination to produce a plausible scenario.  It's not like Young could have thrown out a line for them to jump into space and grab on to.

[Dalhousie]

I don't doubt for an instant that there are non-scientists and non-engineers who have been exposed to metric units their whole life who would get confused by some uses of SI units.  For instance, a layman probably doesn't know what a Newton is or how it's used.

Because they don't understand that force and mass are two different things...

I learned about Newtons in high school physics.  It's a safe bet that anyone who needs to understand the difference between force and mass will know whata Newton is.

[Peter B]

During the A10 mission's LM test, an unforeseen and massive solar flare erupts.

For which the best response would be an immediate rendezvous and docking with the CSM, not a landing...

Ya, but this is the Hollywood version.  I've had similar Hollywood speculations, too and wondered about how to present a plausible rescue. The real problem in gaining even Hollywood correspondence to the real world is the fact that the CSM is traveling in excess of 3000 miles an hour. Hollywood plausibility says that you could do a sub-orbital LM launch that would, in a one in a million chance, cross paths with the CSM but overcoming the speed differential for astronaut transfer strains my imagination to produce a plausible scenario.  It's not like Young could have thrown out a line for them to jump into space and grab on to.

Ironically, this is an issue discussed by the characters in "The Martian".

ETA: Would some variant of a Skyhook work? I'm not sure what equipment in a LM could be fashioned into a skyhook, but hey, Hollywood!

[Luther]

Ya, but this is the Hollywood version.  I've had similar Hollywood speculations, too and wondered about how to present a plausible rescue. The real problem in gaining even Hollywood correspondence to the real world is the fact that the CSM is traveling in excess of 3000 miles an hour. Hollywood plausibility says that you could do a sub-orbital LM launch that would, in a one in a million chance, cross paths with the CSM but overcoming the speed differential for astronaut transfer strains my imagination to produce a plausible scenario.  It's not like Young could have thrown out a line for them to jump into space and grab on to.

[cartoon]If you get the position and orientation just right, you could have the CSM come up behind them with the hatch open, and scoop them up.[/cartoon]

[Allan F]

....with a dV of 300 m/s which would make quite a mess.

[Zakalwe]

....with a dV of 300 m/s which would make quite a mess.

Ever seen those jet engine tests where they fire a chicken from an air cannon into a running engine to check for bird-strike damage?? 

[Allan F]

Yes. But two astronauts in EVA-gear is much bigger than a chicken. And the CSM is not designed for that kind of impact. It would not survive as a viable spacecraft.

[Echnaton]

ETA: Would some variant of a Skyhook work? I'm not sure what equipment in a LM could be fashioned into a skyhook, but hey, Hollywood!

The scenario goes pretty quickly to a "Space Shuttle to the moon" type of event. You have to make so many exceptions and modifications that the resulting spacecraft ceases to have any plausible fidelity to where you started.  Perhaps one could make a story out of a rescue from an errant landing of a damaged, hypothetically better equipped  LM, but Snoppy would not have had the resources. 

Maybe Apollo nostalgia will come aground to the point someone is willing to make a rescue movie about Apollo 21 or 25 or whatever would have been the start of building a lunar base.  A bad landing, or even better, perfidious sabotage,  causes damage to the helium pressurization system that prevents rendezvous and is still leaking pressure.  A rush against time to lift off while also needing to assemble a method of transfer through open space....

[Bob B.]

I don't doubt for an instant that there are non-scientists and non-engineers who have been exposed to metric units their whole life who would get confused by some uses of SI units.  For instance, a layman probably doesn't know what a Newton is or how it's used.

Because they don't understand that force and mass are two different things...

I learned about Newtons in high school physics.  It's a safe bet that anyone who needs to understand the difference between force and mass will know whata Newton is.

You guys are confirming the point I'm trying to make.  There is nothing instinctive about either system of units, they must be learned.  Most layman can use a tape measure, know how far it is to the next town, can measure out a portion of food, and know when it is time to loose weight because of what their bathroom scale tells them, but other than that they're largely ignorant of units of measure.  To know more than the basic everyday life stuff, it must be studied.  In one system a person learns that there are basic units of length (meter) and mass (kilogram), and there's a derived unit of force (Newton).  In the other  system a person learns that there are basic units of length (foot) and force (pound), and there's a derived unit of mass (slug).  Once those basics are learned, what's the problem?  It is no more difficult to solve a problem using English units than it is to solve a problem in SI units.  I just don't accept the argument that one system is intuitive while the other is some screwed up mess.  People who need to know do know, and those who don't know are going to be confused by some aspects of either system.

[Luke Pemberton]

It is no more difficult to solve a problem using English units than it is to solve a problem in SI units.  I just don't accept the argument that one system is intuitive while the other is some screwed up mess.  People who need to know do know, and those who don't know are going to be confused by some aspects of either system.

This reminds me of the untis in electostatics, I studied with SI units. My lecturer kept waffling on about other units but said we did not need to know them. As a physics student we were studying the subject from a purely esoteric perspective and learning other unit systems was never really critical, but the engineers learned CGS.