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Apollo 13

Day 6, part 5: Service Module Separation

Corrected Transcript and Commentary Copyright ©2020 by W. David Woods, Johannes Kemppanen, Alexander Turhanov and Lennox J. Waugh. All rights reserved.

Last updated 2020-04-21

The pace of crucial events is ramping up aboard the still-docked stack of Apollo 13. The LM's RCS jets were used to perform a final nudge on their trajectory to ensure safe return. Command Module Pilot Jack Swigert has applied electric power to the RCS jets in the Command Module Odyssey in what is one of the first duties he has to perform in the newly awakening spacecraft. As long as everything works according to the plan, they should have as good a chance of returning home safely as any Apollo crew so far. However, to get there, they will have to accomplish many unusual milestones, the first of which is coming very soon in the form of separating the Command Module (and docked Lunar Module) from the damaged Service Module while still a considerable way away from reentry.

137:40:49 Haise: Okay. If you're happy, can we maneuver to Service Module Sep attitude now?

137:40:57 Kerwin: That's affirmative, Aquarius. [Long pause.]

That was Fred Haise requesting that 13 maneuver to Service Module separation attitude following this - this burn which went right on the money. We're at 137 hours, 41 minutes.

137:41:19 Lovell: And I'm pitching up to the proper attitude.

137:41:23 Kerwin: Okay. We're looking at it.

137:41:26 Lovell: And it's again necessary to use the TTCA to pitch.

137:41:30 Kerwin: Okay. Affirmative.

Long comm break.

For the Service Module separation, Apollo 13 will pitch about 90 degrees along the radial axis. That's 90 degrees off the flight path angle. We show 13 at the present time at a distance of 37,581 nautical miles away with a velocity of 10,138 feet per second. We're now at 137 hours, 42 minutes into the mission. This is Apollo Control Houston.

Distance, 18,776 km, velocity 3,090 m/s.

137:43:55 Kerwin: Aquarius, Houston.

137:43:58 Lovell: Go ahead, Houston.

137:43:59 Kerwin: Okay. Recommend you terminate P41. [Pause.]

137:44:08 Lovell: Okay.

Long comm break.

Program 41 is used to calculate and control RCS maneuvers, such as the one just performed. Since the crew opted to use AGS for controlling the burn, it served only as a display for the maneuver.

137:47:38 Slayton: Hey, Jim, have you broken into the medical kit per my recommendation a few hours ago?

137:47:46 Lovell: Yes. Everything is taken care of Deke.

137:47:49 Slayton: Okay, fine. You might hit it again in about 2 hours.

137:47:55 Lovell: Okay.

Long comm break.

Deke is reminding the crew of his earlier suggestion that they should pep themselves up with the dextroamphetamines. The Crew Technical Debriefing had some crew comments on this and their other medication use.

Lovell, from 1970 Technical debrief: "The medical kits were adequate. We used aspirin."

Swigert, from 1970 Technical debrief: "I used two Lomotils ad one Dexedrine."

Lovell, from 1970 Technical debrief: "I used Dexedrine and we also used quite a bit of aspirin and one Darvon."

Haise, from 1970 Technical debrief: "You used two Lomotils?"

Swigert, from 1970 Technical debrief: "They didn't do any good."

Haise, from 1970 Technical debrief: "Are you sure you got the right compartment?"

Swigert, from 1970 Technical debrief: "I think so."

Haise, from 1970 Technical debrief: "And we used seasickness pills."

Lovell, from 1970 Technical debrief: "No you didn't."

Swigert, from 1970 Technical debrief: "I took the Marezine."

Lovell, from 1970 Technical debrief: "Dexedrine."

Swigert, from 1970 Technical debrief: "I took a Dexedrine."

Lovell, from 1970 Technical debrief: "I just took one Dexedrine."

Haise, from 1970 Technical debrief: "I didn't take any because the seasickness pills had that in it."

Lovell, from 1970 Technical debrief: "Yes. I was a bit concerned about taking too much Dexedrine. I was afraid it might wear off before I got down."

Apollo Command Module medical kit.

Fred wondering about whether Jack found the right tablets is a genuine worry. The medical kit was extremely compact and sometimes it was hard to find the correct medication. It is recorded that Gene Cernan accidentally took one of the anti-motion sickness dextroamphetamine/scopolamine tablets while trying to take an anti-flatulence tablet during Apollo 17.

All the crewmembers would be familiar with the effects of the stimulants. Pre-mission medical testing included the crew taking all the drugs carried onboard to see if any adverse effects would develop.

Apollo Control Houston, 137 hours, 48 minutes. That was Donald K. Slayton on the line talking to Jim Lovell; the recommendation he referred to was the recommendation he made earlier in the morning that the Apollo 13 crew take Dexedrine tablets. We now show Apollo 13 in an altitude of 36,969 nautical miles.

Distance to go, 68,467 km and closing in fast.

Apollo Control, Houston. The Guidance and Control Officer for the Lunar Module here in Mission Control confirms they are moving in an attitude now for separation.

137:50:37 Kerwin: Aquarius, Houston. Aft Omni.

137:50:41 Lovell: I beat you to it, Houston.

137:50:43 Kerwin: Yes. I thought you did, but I thought I'd say it anyway.

Very long comm break.

Our countdown clock shows that we are 19 minutes away now from time of separation; Service Module jettison; for this, Jack Swigert is in the Command Module; Jim Lovell and Fred Haise in the Lunar Module; Commander Lovell will fire the thruster, or fire the thrust, LM thrust to push the Service Module at one half foot per second; Swigert activates the Pyros with a switch in the Command Module. After separation, 13 will back off with the Lunar Module RCS at one half foot per second, providing the separation delta velocity of one foot per second. We are 137 hours, 52 minutes into the flight and Apollo 13 now 36,616 nautical miles away. This is Apollo Control, Houston.

Distance to go, 67,813 km. They have traveled over 600 km in four minutes or so.

137:55:52 Kerwin: Okay, Aquarius; Houston. That attitude looks pretty good. How's Jack getting along?

137:55:58 Lovell: He's getting along, all set to go. And I'm going to go into PGNS Att Hold.

137:56:02 Kerwin: Roger.

Comm break.

137:57:06 Kerwin: Aquarius, Houston.

137:57:10 Lovell: Go ahead.

137:57:11 Kerwin: Roger. Again for fuel-consumption reasons, we'd like you to go back to the AGS mode you were in rather than PGNS Att Hold. Over.

The LM RCS fuel supply is approaching a point where they are no longer able to measure the amount left accurately, and want to be sure that they have enough for the final stretch.

137:57:20 Lovell: Okay. I'm in PGNS Minimum Impulse right now while we're firing. And I'll go back to the AGS mode.

137:57:31 Kerwin: Okay, Jim. PGNS Min Impulse is okay; AGS is okay too. It's your choice.

137:57:37 Lovell: Soon as we get rid of the Service Module, Joe, I think I'll be able to maneuver a lot better.

137:57:42 Kerwin: Sure thing.

137:57:48 Lovell: Okay, Jack just reported that all thrusters fired on both rings.

137:57:53 Kerwin: Real fine. Real fine. [Long pause.]

That was the test of the thrusters on the Command Module, and as you heard, they all fired - we are at 137 hours, 58 minutes into the flight; and this is Apollo Control, Houston.

137:58:32 Lovell: And SM Jett at 138:12. [Pause.]

137:58:43 Kerwin: Roger. Understand; that's SM Jett, 138:12. It's not that time critical, Jim.

137:58:52 Lovell: Can we do it at any time, Joe?

137:58:55 Kerwin: I think so, but let me check. Aquarius, Houston. That's affirmative. You can jettison the Service Module when you are ready; no big rush, but any time.

137:59:14 Lovell: Okay. Sounds good.

Comm break.

138:00:41 Kerwin: Aquarius, Houston.

138:00:44 Lovell: Go ahead.

138:00:45 Kerwin: Roger. We recommend that you use the AGS for the separation maneuver, because we'd like to get the proper weight in for the DAP before we use the PGNS again.

138:00:59 Lovell: Roger. We will. Stand by.

Comm break.

Jettisoning the Service Module will drop their mass considerably, hence the Digital Autopilot will have to be reprogrammed to take this into account.

Apollo Control, Houston; 138 hours, 1 minutes into the flight. As you heard earlier, Joe Kerwin told Apollo 13 that they could separate at their convenience, that followed a time identified by Jim Lovell, which would be some 2 minutes after what we had earlier carried on the ground, we now show Apollo 13 at a distance of 35,729 nautical miles away from Earth, traveling at a speed of 10,400 feet per second. At 138 hours, 2 minutes into the flight; this is Apollo Control, Houston.

Distance, 66,107 km velocity is 3,170 m/s and rising.

138:02:06 Lovell: SM Sep.

138:02:09 Kerwin: Copy that.

Comm break.

Pyrotechnic separation control switches on the bottom of Panel 2 on the MDC. Original scan via heroicrelics.org.

To jettison the Service Module, they've opened the guards on CM/SM Sep 1 and 2 switches and energized them.

Diagram of the Service Module separation.

Lovell, from 1970 Technical debrief: "When we got to the point to jettison the SM, I thrusted up. Then, Fred went to verify that Jack was going to throw the right switch."

Swigert, from 1970 Technical debrief: "I wanted Fred there to make sure that I raised the CM/SM Sep switch and not the CM/LM Sep switches."

Haise, from 1970 Technical debrief: "I did go, but he had gray tape over the LM Sep switches. I figured that was enough of a safeguard and the way Jim thrusted, I needed to be there to control the pitch again with the TTCA."

Swigert, from 1970 Technical debrief: "You should have seen Fred when we got back there. I was all ready to go; I had the logic up and I was ready for pyro arm. Fred said he would get a Go from MSFN. Then I reminded him that we didn't have any telemetry and MSFN couldn't give us a Go. When I asked if he was ready, he looked at me with a wistful sigh, as if, 'Well, go ahead.' I put power up, and I could hear the relays clicking."

Lovell, from 1970 Technical debrief: "We debated putting the hatches on, but we thought we might as well go all the way."

We copied that report from Jim Lovell, that Service Module separation at 138 hours, 2 minutes, 8 seconds. And as you heard, that was ahead of schedule. We presently show Apollo 13 at 35,611 nautical miles [65,952 km] away from Earth.

Command Module/Service Module electric interrupter.

Hitting the CSM Sep switches energizes the sequential systems, and the automatic separation procedure begins. To safely remove the two spacecraft from one another, the electric cabling is cut with a pyrotechnic guillotine device. A small explosive charge is used to power the guillotine that deadfaces the connections and locks into place to stop them from accidentally reconnecting.

Service Module Umbilical

Once the electric connections are cut, another explosive guillotine separates the Service Module Umbilical from the Command Module.

Command/Service Module tension ties.

Finally, three shaped charges cut the tension ties that hold the Service and Command Modules together, and create a spring action that pushes the Command Module away. In a normal separation sequence, electronics boxes inside the Service Module command the Service Module RCS jets to fire until fuel depletion, to put as much distance between the two modules as possible. With the special situation of Apollo 13, the Service Module is completely inert, and the LM RCS jets are used for a manual maneuver to first separate them, then to turn around in a manner that allows them to observe the Service Module.

138:03:53 Lovell: Do you see it, Jack? [Long pause.]

138:04:26 Kerwin: Okay, Aquarius; Houston. I recommend you terminate Average G. Over.

Average G is a computer routine that calculates their acceleration during powered flight, i.e. when a thrust maneuver is performed. To terminate it, they have to key in Verb 37 Enter 00 Enter to put the computer to idle or Program 00, 'P00' mode.

138:04:33 Lovell: Okay, I've got her, Houston.

138:04:36 Kerwin: Beautiful, beautiful. And for you information, Jim, you'll be coming up on an RCS caution light for helium. No sweat. Over.

138:04:46 Lovell: And there's one whole side of that spacecraft missing.

The newly separated Service Module floating away. This color image shows the missing panel and the now released SM/CM umbilical, on the top.

138:04:50 Kerwin: Is that right? [Pause.]

138:04:57 Lovell: Right by the - Look out there, will you? Right by the high gain antenna, the whole panel is blown out, almost from the base to the engine.

138:05:09 Kerwin: Copy that. [Long pause.]

138:05:22 Haise: Yes, it looks like it got to the SPS bell, too, Houston.

138:05:28 Kerwin: Think it zinged the SPS engine bell, huh?

138:05:31 Haise: That's the way it looks; unless that's just a dark brown streak. It's really a mess. [Long pause.]

The damage inside sector 4 is evident. The hull panel is almost entirely gone, and although the fuel cells can be seen on their installed positions, the section with the cryogenics tanks and their support equipment is a jumble of jagged metal and broken insulation.

While the crew was only able to take a glimpse and describe what they saw, the photographs they took were used to analyse the total extent of the damage. The place of the O₂ Tank 2 is empty. Damage is visible to the High Gain Antenna and the SPS engine nozzle as well.

You heard that report from Jim Lovell, as Aquarius is moving away from the Service Module at the present time.

138:05:51 Kerwin: Okay, Jim. We'd like you to get some pictures, but we want you to conserve RCS. Don't make unnecessary maneuvers. [Long pause.]

138:06:08 Kerwin: And, Jim; Houston. In particular, of course, we don't want any translation maneuvers.

138:06:16 Lovell: Right on that. Joe, you realize that when I went up to the SM Sep attitude, I had to use TTCA to do it.

138:06:25 Kerwin: That's affirm. We know that. That's okay. [Long pause.]

Fred Haise followed Jim's remark with the comment that it got through the Service Propulsion System bell too. That it was really a mess. We're at 138 hours, 7 minutes into the flight. Apollo 13 now 35,200 nautical miles...

Distance to go, 65,190 km.

138:06:50 Lovell: All right. She's drifting right down in front of our windows now, Houston.

138:06:55 Kerwin: Okay.

Comm break.

138:08:12 Haise: Okay, Joe, I'm now looking down the SPS bell, and it looks - looks okay on the inside; maybe it is just a streak.

138:08:19 Kerwin: Okay. Copy that, Fred. Was the bell deformed on the outside or just nicked or what?

138:08:33 Lovell: I think the explosion, from what I could see, Joe, had - had stained it. I don't know whether it did any actual deformation or not.

138:08:41 Kerwin: Okay. [Long pause.]

138:09:09 Haise: Man, that's unbelievable! [Long pause.]

The skin of the Command Module and the Service Module shine in sunlight, betraying the fogged-up windows of the LM. The now distant Moon is also seen as a bright spot.

138:09:38 Lovell: And, Joe, looks like a lot of - a lot of debris is just hanging out the side near the S-band antenna.

138:09:47 Kerwin: Roger, Jim. [Long pause.]

Drawing of the Service Module based on the photographs. From the Investigation Report. Electric cables and pieces of insulation spew out of the damaged Service Module. While the fuel cells can be identified, the space that should be occupied by the number 2 oxygen tank is empty. The damage to the high gain antenna is very much evident too, with one of the horns visibly twisted from the bay 4 panel hitting it.

138:10:43 Kerwin: Aquarius, Houston.

138:10:46 Lovell: Go ahead.

138:10:47 Kerwin: I know you're busy, but when Jack gets a chance, we'd like Bat C current and Main A voltage in the Command Module.

Their moment of shocked reflection is soon gone, interrupted by the need to get back to business.

Comm break.


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