MOL discussion

[tankmodeler]

I believe that it didn't need to be airtight. The tunnel was merely a passage way to the MOL. The Gemini was depressurized and the floated in their suits through the tunnel to the MOL and sealed and pressurized the MOL..

No, I don't buy that. The hatch isn't large enough to exit with a sealed suit, under pressure, and with some sort of self contained life support system. Even the small emergency chest packs were too large to mange through the heat shield hatch & tunnel and, if you've seen the spacecraft films footage of the 0G tests of the hatch/tunnel arrangement, getting throught here in a pressurised suit would have been a real problem, if possible at all.

There must have been a seal and the seal would have had to have been at least good enough to support hours of operation even if it bled down over time.

Now, none of the images I have seen shows a hatch at the aft end of the tunnel. If that is true, then the tunnel must remain perfectly sealed for the whole mission, implying a really good seal.

I wonder if you could adjust the fit of the tunnel to the shield well enough to permit a grease type sealing compound to act as the final seal? That would eliminate the need for a line charge, but you'd need both some sort of actuator (probably springs) to force the separation and a really viscous goop to make the seal. Certainly the surface of the Gemini B shield around the hatch shows signs of precision machining and this is probably to prepare the surface forwhatever the seal was supposed to be.

Bloody good question, Jim. I wonder if the answer to this is still buried out there in "Classified Document Land". MOL was pretty far along by the time it was killed, so there must have been a really advanced design for this seal by then.

Paul

[Hoonte]

The internal tunnel structure was not the only possibility

here is a progress report on a expandable gemini to mol crew tranfer tunnel.

[Jim]

The internal tunnel structure was not the only possibility

The internal tunnel was the final design.

[Danderman]

I would imagine that a redesign of Gemini to allow for transfers through the nose/top would eventually have been cheaper and easier than all these through the heat shield design ideas.

Huh?   No way.  Though the nose would be impossible with keeping within a Gemini design.   The diameter is less than the tunnel width.  Where would the RCS and parachutes go?  Add a docking mechanism, rendezvous equipment, 3 axis ACS, translation engines, etc. It would be a whole new spacecraft.

The MOL Gemini just required a hatch and tunnel interface and it had many unnecessary systems removed. 

MOL without a Gemini still required a T-IIIM and adding a docking system  would add back some weight.

Again, the trade on the table is a single redesign of Gemini to allow nose-first docking with a solo launched MOL vs the actual baseline. Biting the bullet on "fixing" Gemini to convert it into a real ferry spacecraft would have been cheaper in the long run, and IMHO saved the program.

Of course, had the USAF done that, we wouldn't have SLC-6 today.

As for a solo-launched MOL requiring development of Titan IIIM, that implies that the difference in capability between Titan IIIM and Titan IIIC was more than the mass of a Gemini.

So, the trade is:

Baseline:

1) redesign Gemini for rear docking, including development of a pressurized section in the rear for a tunnel, docking, rear crew station, heat shield hatch, access hatch in the re-entry capsule between the ejection seats;

2) Develop Titan IIIM to loft Gemini + MOL for initial habitation. Required construction of SLC-6.

or

Alternate:

1) Redesign Gemini for nose docking and crew transfer, requires different shell, but same subsystems as original Gemini. Fly MOL without Gemini for all MOL launches.

2) Fly MOL from existing Titan IIIC launch pads on Titan IIIC launcher.

I suspect that the alternate would have been flying in 1967, at a much lower cost to the government.

[simonbp]

A heat-shield hatch sure seems scary, but I wonder whether it's really as risky as it looks.

I dunno; just how many doors does Shuttle have in its headshield? Off the top of my head, I can think of seven, at least thee of which (the ET attach points) are closed after the orbiter is on in space...

[Jim]

Again, the trade on the table is a single redesign of Gemini to allow nose-first docking with a solo launched MOL vs the actual baseline. Biting the bullet on "fixing" Gemini to convert it into a real ferry spacecraft would have been cheaper in the long run, and IMHO saved the program.

Of course, had the USAF done that, we wouldn't have SLC-6 today.

As for a solo-launched MOL requiring development of Titan IIIM, that implies that the difference in capability between Titan IIIM and Titan IIIC was more than the mass of a Gemini.

So, the trade is:

Baseline:

1) redesign Gemini for rear docking, including development of a pressurized section in the rear for a tunnel, docking, rear crew station, heat shield hatch, access hatch in the re-entry capsule between the ejection seats;

2) Develop Titan IIIM to loft Gemini + MOL for initial habitation. Required construction of SLC-6.

or

Alternate:

1) Redesign Gemini for nose docking and crew transfer, requires different shell, but same subsystems as original Gemini. Fly MOL without Gemini for all MOL launches.

2) Fly MOL from existing Titan IIIC launch pads on Titan IIIC launcher.

I suspect that the alternate would have been flying in 1967, at a much lower cost to the government.

No,  two launches per mission is going to cost more in the long run especially with a new spacecraft. 

Titan IIIC launch pads did not exist on the west coast.

The difference in capability between Titan IIIM and Titan IIIC WAS more than the mass of a Gemini

Redesign Gemini would be more than the actual Gemini in cost. 


SLC-6 is require in any case and it did not cost that much.

New pad costs are cheaper than new spacecraft.

[Jim Davis]

Again, the trade on the table is a single redesign of Gemini to allow nose-first docking with a solo launched MOL vs the actual baseline.

I don't think this works. Remember that MOL was to be launched into polar orbit. Gemini could not be placed into polar orbit by the Titan II. This would have meant launching the redesigned Gemini into orbit on a Titan IIIC or D.

So your scheme involves at a minimum:

1.) Massive redesign of Gemini.

2.) Two launches of Titan IIIC/D instead of 1 Titan IIIM.

3.) Manrating the Titan IIIC/D.

4.) Adding a rendezvous and docking procedure much of which would have to done independently of the ground due to polar orbit.

I think I would have gone the Titan IIIM 1 launch route.

 

[tankmodeler]

Again, the trade on the table is a single redesign of Gemini to allow nose-first docking with a solo launched MOL vs the actual baseline. Biting the bullet on "fixing" Gemini to convert it into a real ferry spacecraft would have been cheaper in the long run, and IMHO saved the program.

No, as Jim says, that level of redesign of the Gemini would have cost the same as a completely new vehicle, because that's what you would have needed. The front two subassemblies of the Gemini (the recovery module and the RCS system) filled up the entire volume. If you want to use that volume for a docking system and a passageway, where do the recovery system & RCS go? An expansion of the diameters of the nose means that the outer mould line of the basic capsule has to change to ensure that that the re-entry vehicle aerodynamics remain acceptable. As soon as you do that, you have an entirely new vehicle. Big bucks and even longer schedule.

No, a "redesigned" Gemini is not a cost effective solution and it wouldn't have mattered what was done, the program wouldn't have been saved because the Gemini wasn't the problem. Modern, robotic surveillance satellites killed off MOL.

Paul

[Blackstar]

As soon as you do that, you have an entirely new vehicle. Big bucks and even longer schedule.

They really designed themselves into a bind.  If MOL had flown earlier--say, by 1966--it might have had some utility.  But they essentially designed themselves a short-lived, non-reusable reconsat.  By 1969 this made little sense, and because it would have started flying in 1971, it made even less sense.  If Gemini was capable of multiple dockings (i.e. designed with a docking collar), they could have extended the lifetime of the MOL and so it might have made more sense.  But it really had a small window of opportunity and it missed that.  By the early 1970s, it was possible to extend the lifetime of robotic reconsats to several months.

[agman25]

Why didn't they just use Apollo?

[Arthur]

Why didn't they just use Apollo?

NIH?
Military vs NASA seems a common theme between Gemini-centric and Apollo-centric proposals.

[kevin-rf]

Why didn't they just use Apollo?

West coast Saturn?

This discussion does have me wondering, why was a new pad needed for MOL, why couldn't the Titan III C/D pad have been used. Did it not exist yet? If not, why then wasn't SLC-6 used when the Titan IIIC came to the west coast for the KH-9? Just curious...

[Jim]

Why didn't they just use Apollo?

West coast Saturn?

This discussion does have me wondering, why was a new pad needed for MOL, why couldn't the Titan III C/D pad have been used. Did it not exist yet? If not, why then wasn't SLC-6 used when the Titan IIIC came to the west coast for the KH-9? Just curious...

There wasn't a T-IIID pad at the time.  MOL and T-IIID would have been flying simultaneously.

BTW, T-IIIC never was used on the west coast.

[Jim]

Why didn't they just use Apollo?

Too big and expensive

[Blackstar]

Why didn't they just use Apollo?

Well, that's a good question.  I think the most simplistic answer is cost.  Apollo cost more than Gemini.  I don't know how much, but it was substantial.  Plus, Apollo had to be launched on a NASA rocket. 

But there were other programmatic issues too.  If USAF wanted to use Apollo, there was the risk of them getting in the way of the lunar program.  The great thing about Gemini was that NASA was going to stop using it, so USAF could essentially pick up the production run after NASA was finished and they would not interfere with Apollo or any other NASA mission in any way.

[kevin-rf]

There wasn't a T-IIID pad at the time.  MOL and T-IIID would have been flying simultaneously.

Was the thought at the time, that two pads where needed to keep the two programs from conflicting and each interfering with the other? Does this mean they had a good handle at how long Titan payloads would spend on the pad back then?

[Jim]

There wasn't a T-IIID pad at the time.  MOL and T-IIID would have been flying simultaneously.

Was the thought at the time, that two pads where needed to keep the two programs from conflicting and each interfering with the other? Does this mean they had a good handle at how long Titan payloads would spend on the pad back then?

T-IIID was for an CIA Hexagon and T-IIIM was for a USAF MOL.  Separate programs, one covert and one overt and very visible.

[John Charles]

Good discussion! Sorry I am joining late.

Note that there was one hole in the heat shield, but two plugs for that hole.  The heat shield plug was stowed in the transfer tunnel (as seen in the excellent Spacecraft Films video), and the pressure vessel hatch was stowed in the hatch holder on the aft bulkhead inside the cabin.

The pressurized transfer tunnel was sealed against the Gemini-B heat shield by a pliable pressurized ring with an internal spring forcing it against a special mounting ring on the heat shield.  (See the various photos of the Gemini-B heat shield available on the web.)  Something like this also formed the airtight seal between the Apollo CM and LM.

I can post images if desired (but it will take may some time to find them in my files).

John Charles
Houston, Texas

[John Charles]

The internal tunnel structure was not the only possibility

here is a progress report on a expandable gemini to mol crew tranfer tunnel.

Thanks very much for posting this document!  I have been looking for something like it.

John Charles
Houston, Texas

[Jim]

From the QUILL files.  Document 25. Semi-Annual Report to the PFIAB 1965-66, PDF page58m,

MOL camera layout