Circular deck hatches

[RandyT0001]

During the development of the lunar module for NASA's moon landings the astronauts discovered that the original circular hatch mounted on the side of the module intended for the astronauts to use to egress from the ship to the surface proved to be a PITA to use. Though built in a diameter "technically" big enough for the astronaut and his PLSS backpack to pass through the backpack almost always caught on the hatch. The solution Grumman made was to redesign the hatch into a square/retangular shape. Once incorporated into the LM the astronauts had very few episodes of catching the backpack on the hatch. On the top of the LM where it docks with the capsule that hatch remained circular since the astronauts were not wearing their excursion suits while transferring from capsule to the LM.

So what does this have to do with Traveller? In the deckplans that I've seen the hatches that are depiected for interdeck transit (ie going 'up' or 'down') are circular hatches. Since the PLSS in Traveller is shown to be retangular in shape then in all probablility the interdeck hatches in Traveller need to be square/retangular just like the lunar module was for the same reasons. And they need to be depiected on deckplans that way also so that new fans can see them. I'm not going to redo all the deckplans I've already posted on the internet but I will make the change in my drawing symbol catalogue for future deckplans.

Opinions, comments?

 

[Andrew Boulton]

Traveller hatches are almost certainly quite a bit bigger, and PLSS backpacks much smaller (and used less often).

 

[Rover]

I always assumed (I know what happens when you do that) the hatches were circular for reasons of strength. Much like a porthole on a ship.

 

[aramis]

1) Grumman's issue was with a hatch on a wall, not a floor
2) the PLSS on a TL 10+ suit is considerably smaller than on the TL7 NASA suit
3) the Gruman hatch was about a meter in diameter; the traveller ones are usually shown at about 1.2-1.4m diameter.
4) the TL10+ suit is itself more flexible and comfortable than the TL7 NASA suit.

 

[Tekrat04]

The shape of a hatch was never an issue for me. The location of said hatch is way more important.

Locating a downward hatch in the middle of a hallway or in front of a doorway is a very bad place for it. A hatch on the floor is an obstruction under the best of condition, a manual hatch will stick up from the floor and an iris valve will be sunk in. That make it a trip hazard at the best of time. When it opens it can be a death trap. Downward hatches should allways be located away from any travel path. The rule of tumbs should be that if you need to step over a hatch get to some place than the hatch is located in the wrong place.

The location of an upward hatch need to be also considered carefully. Ther is always a ladder assoiciatied with an up hatch. Otherwise how would you go from deck to deck? Jump and hope you have the reach and strenght to muscle your way up? That ladder cannot be located in front of a doorway nor can it block a passageway.

It's to bad that most deck plans in Traveller fail to abbide by these simple rules.

 

[far-trader]

I've generally treated the circular deck hatches as more iconic than representative. So where the deckplan shows a circular deck hatch in the middle of a corridor I tend to imagine it partly into an adjacent wall with a built in ladder. And the floor is made seamless and flat by a cover that slides or folds out of the way. Either manual for manual hatches or automatic for iris hatches (with a manual override of course). I don't even treat them as necessarily circular in every case. Square works fine too. But even if they were circular I'd think if there was an issue with PLSS getting caught up then the PLSS could be made rounded instead of square. And it might even look more futuristic.

 

[Tekrat04]

I've generally treated the circular deck hatches as more iconic than representative. So where the deckplan shows a circular deck hatch in the middle of a corridor I tend to imagine it partly into an adjacent wall with a built in ladder. And the floor is made seamless and flat by a cover that slides or folds out of the way. Either manual for manual hatches or automatic for iris hatches (with a manual override of course). I don't even treat them as necessarily circular in every case. Square works fine too. But even if they were circular I'd think if there was an issue with PLSS getting caught up then the PLSS could be made rounded instead of square. And it might even look more futuristic.

With all due respect I do not agree with you.

Even with a cover on a hatch that in hallway and/or in front of a door. The hatch is still in the way of people moving arround. How due you open the hatch when people are walking on it? How do you prevent people form walking on the hatch just before it opens? Or just after it opens?

Having the hatch off to the side also does not solve anything since the hatch will take up more than half of the hallway. The opening of the hatch need to be 70-100cm, the seal will take up another 5-10cm and the cover and ladder will also take up 5-15cm more. So at the minimum the hatch will take up 80 cm. That leave only 60-70cm, depending on the thickness of the walls, of passage way. Yes that is enough to walk arround an open hatch but that is the bare minimum and the hatch is still a hazard. The more likely senario is that the hatch will take up 90-120cm and that does not leave enough space to arround it safely.

What happens when the hatch is in the middle of an intersection? Or the ladder from the up hatch on the deck below blocks the trafic path?

The only way to avoid thes problems is to be better aware of the placement of up and down hatches. The past is the the past, we cannot change it. But lets stop repeating the same mistake over and over again.

 

[martletsquire]

Hatches

I always liked the round hatches in Traveller, until I toured several naval vessels (as an adult) and saw that all the nice, watertight hatches were rounded rectangles or oblongs, except for hatches in submarines.

Hmmmm.

And then, when I got all exited about SpaceX, I downloaded everything I could find on them and their Dragon capsule and... square access hatches.

Hmmmmm.

And then, in a fit of total stupidity, I started looking at all of the NASA documents available regarding the Saturn program (and Big Gemini) and found out we could have been in space big time without that worthless space plane, in a big way (look up the ideas for the next generation Saturn systems. 4 Saturn V lower sections in a square formation with another Saturn V lower mounted on top. OMG!. Well, to get to the point, rectangular hatches...

Round hatches look cool on deck plans, and on WWII Sub movies, but rectangular and square hatches are most likely the true reality of the Traveller Universe. I mean, square box, round hole?

 

[FreeTrav]

I had pretty much this discussion with a submitter, recently; we didn't get into square-vs-round hatches, but placement was a big discussion. The end result was that vertical hatches were placed so that they were NOT in the line of traffic, but were off in corners, alcoves off corridors, et cetera.

Acknowledging the "Rule of Cool" for SF, I still don't believe that "iris valves" will actually be used for airtight doors, either.

 

[BlackBat242]

I always liked the round hatches in Traveller, until I toured several naval vessels (as an adult) and saw that all the nice, watertight hatches were rounded rectangles or oblongs, except for hatches in submarines.

On the other hand, I've served aboard a USN aircraft carrier built in the 1950s (USS Ranger), and while the large hatches certainly were rectangular, about half of the smaller hatches (and especially many of those set inside the larger ones) were circular.

Yes, there were hatches set inside hatches. The large ones were open during normal operations, but when General Quarters was called, they would be closed (condition Zebra). If you had to move around during GQ you would use the smaller hatch, closing it behind you.


Aboard the museum ships Texas (ex-BB-35) and Lexington (ex-CV-16) there were also circular hatches.

First, a deck hatch on Texas, near "Y" main turret barbette.

Then a hatch inside a passageway on Lexington.

 

[martletsquire]

Hatches

Thanks, Bat, cool photos. And excellent info from someone who served. I like the hatch within a hatch better than just a hatch. Makes much more sence.

Round hatch for minimal and emergency movement.

Large hatch for airflow and material movement.

I remember from some of David Drake's books where, after a ship lands, all the external hatches are opened so the ship can air out. Reminds me of some of the photos of diesel subs in port during WWII.

And I agree with the "iris valve" thought. Cool, very Sci-fi, but...

It's right up there with memory metal hatches and other weird stuff. Cool until it breaks down and then you still end up using that hatch that is basically TL4+ to get around.

 

[HG_B]

Acknowledging the "Rule of Cool" for SF, I still don't believe that "iris valves" will actually be used for airtight doors, either.

I don't use them for airtight doors either. Also they would have to have a lot of space around the entire "door" to recess into. Space that is at a premium on a Trav ship.

 

[Fritz_Brown]

HG_B, I use them for "airtight" doors - which isn't the same thing as "vacuum-tight" hatches. The doors seal up pretty good (we don't want to be smelling your ... fresher activity in the passageways), but they won't hold when there's a significant pressure differential. I use a sliding door normally, rather than iris valves, too - except if I use them between decks, where an iris valve is just too cool not to use.

 

[Nightwind1]

On the other hand, I've served aboard a USN aircraft carrier built in the 1950s (USS Ranger), and while the large hatches certainly were rectangular, about half of the smaller hatches (and especially many of those set inside the larger ones) were circular.

Yes, there were hatches set inside hatches. The large ones were open during normal operations, but when General Quarters was called, they would be closed (condition Zebra). If you had to move around during GQ you would use the smaller hatch, closing it behind you.


Aboard the museum ships Texas (ex-BB-35) and Lexington (ex-CV-16) there were also circular hatches.

First, a deck hatch on Texas, near "Y" main turret barbette.

Then a hatch inside a passageway on Lexington.

This is pretty much the way it was on my cutter in the Coast Guard.

Of course, she was originally built in 1946...

 

[Fritz_Brown]

They are still that way, Nightwind. And, for those who haven't had the pleasure of having to move about during a GQ: no, those round hatches-in-hatches are NOT easy to get through.

 

[JimMarn]

Thanks, Bat, cool photos. And excellent info from someone who served. I like the hatch within a hatch better than just a hatch. Makes much more sence.

The small round hatch is an escape scuttle. The Texas is an old Battleship, build around 1920-1930. The ship I was on was built in 1960. Early version of the DDG.

With the large in-the-floor hatches, they were open most of the time. They covered steps going down or up a deck. During drills, or actual combat, they would be closed. If someone needed to get through, like the corpsman. The escape scuttle could be opened, and quickly closed back. I remember those being about 28 inches inside diameter on the ship I was on.

Due to the design of the rectangular floor hatches, that set of bolts around it holds it in place, but is hard to open and close quickly. The escape scuttle is quick in movement.

The picture of the small hatch would be for an escape trunk from the fire rooms, boiler plants deep within the ship. The engine rooms would have the same. If the main hatch out of those areas was jammed, or a fire above it, the escape trunks would be the only way for them to get out.

Vertically mounted hatches would be to close off areas to make them water tight, or confine damage from a fire. They have a metal arm to close open them, that moves a set of metal dogs, moving closure bolts, all around the rim of the hatch. Making it quick closing. The floor and wall mounted rectangular hatches had test ports. Rescue teams can use the small, less than one inch, terst port to test the atmosphere on the other side of the hatch. To see if it has breathable air, on fire, gas, water in the space, etc.

Ventilation would also be shut off in case of an attack or drill.

 

[Nightwind1]

They are still that way, Nightwind. And, for those who haven't had the pleasure of having to move about during a GQ: no, those round hatches-in-hatches are NOT easy to get through.

Even more fun in fire gear and an OBA.