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Outbox
Date: Fri, 28 Sep 2001 12:41:01
To: Mentor: Todd B. Harland-White
Subject A Rather Late Response from Atlantis II Team 6 Members
Dear Mr. Harland-White,
My name is Waseem Bakr, and I am writing on behalf of Team 6 (of MIT's Atlantis II Mission). We are very sorry for the long delay in our reply and hope that you accept our most sincere apologies.
As a start, we would like to introduce you to ourselves. The team consists of four members (Andy Lin, Kabir Mukaddam, Flora Amwayi and myself) and a UTF (undergraduate teaching fellow), Justin Schmidt. As you know, the team members are all freshmen, and Justin is a graduate studying Computer Science. Although we all come from different backgrounds and are probably going to major in different fields, we are united by a deep interest in the problem Mission 2005 presents, building an underwater research base at the Edmond Hydrothermal Vent Field. Probably, Professor Kip introduced you to all this and gave you the Mission's website, web.mit.edu/12.000/www/m2005/home2005.html .
We have started building our own website (which can be accessed at the following address: web.mit.edu/12.000/www/m2005/a2/6 . So far, we are still in the process of collecting information about the task that our team has undertaken, namely building one or more manned underwater vehicles for use by the researchers. We are having some difficulty in gathering enough sources. Most of the books as MIT's engineering libraries, as well as the greater part of sources on the Internet, are about UUVs.
After reading your resume, we were especially interested in your work from 1992 to 1994 on the design of manned submersibles (actually we were very impressed by the resume as a whole!). We hope that your experience in that field will help us a lot in our design. We recognize the fact that many of our suggestions for the submersible's design may be impractical or simply absurd since we are basing our design solely on the theoretical information we gather. For example, the powering method we suggested on the website may be very impractical, and therefore you are very welcome to criticize our 'amateurish' work. We would also be very grateful if you could guide us to more information sources.
As a final note, you have mentioned in your e-mail that you may visit Boston soon. If you do, please contact us, because we can't wait to meet you in person!
Sincerely,
Waseem Bakr
Team 6
Atlantis II
Mission 2005
Date: Mon, 01 Oct 2001 17:56:01
To: Mentor: Todd B. Harland-White
Subject: Pressure
Hi,
I am from the vent 6 team. Our team is debating whether to have a spherical or a cylindrical pressure hull. We know that the sphere is inherently stronger for a constant diameter, but we don't know how much stronger. Could you provide us with equations for the sphere and the cylinder that would tell us the pressure each shape could take based on a constant material, the thickness, and the radius. Putting it simply, we would like to know how much thicker and smaller we would need to make the cylinder to withstand the same pressure as the sphere.
Thanks, Kabir Mukaddam
Date: Thu, 04 Oct 2001 03:18:47
To: Vent 4
Subject: Energy
Hey guys, Our team, Vent 6, manned vehicle, was wondering what kind of power you will have on the habitat. We need a large source of power to recharge our vehicle between trips. If you could give us a rough idea that would be great.
Kabir
Date: Thu, 04 Oct 2001 03:21:39
To: Vent 10
Subject: Range
Hey guys, Our team, Vent 6, manned vehicle, was wondering what range will you have on your communications systems, because that may limit the range of our vehicle. If you could give us a rough idea that would be great.
Thanks, Kabir
Date: Thu, 04 Oct 2001 05:16:04
To: Mentor: Todd B. Harland-White
Subject: Models
I have a model of the dock and the corresponding hatch on the sub, but I am not sure if you have a cad program that can handle solidworks files. If you do I can send them to you for you to take a look at.
Kabir
Date: Wed, 10 Oct 2001 02:54:48
To: Mentor: Todd B. Harland White
Subject: Shaft and Other Questions
Hey Todd,
We had three questions we wanted to ask you. The first is that there will be an unmanned robot team in addition to our manned operations team. The unmanned robots would be much smaller than our submarine. Which would have a longer range assuming similar battery types and similar propulsion (scaled down, of course)?
The next question is we were wondering how a shaft, like the propeller shaft, goes from the inside to the outside without allowing any water to come in. We could not find out how this was done in other submarines.
The last is a question of feasibility. Our team has come up with a unique docking design. If you could critique it, we would appreciate it. Attached are the two files. The first is the hatch that will be on the sub. The second is its corresponding dock, which will be on the habitat. The cone of the hatch will fit into the inside cone of the dock (both doors will be closed because they are exposed to the water pressure). Once the sub is in position, the space between the doors will be vented into the habitat, thus creating a pressure difference that will push the sub into the dock with many tons of force to keep the seal. Both doors can now be opened. When the sub is ready to leave the dock, the outside water will be vented into the cavity, equalizing the pressure and allowing the sub to pull away. Is this a reliable option?
Thanks, Kabir
Attachment 1
Attachment 2
Date: Thu, 11 Oct 2001 00:17:59
To: Mentor: Todd B. Harland-White
Subject: Cooling
Hey Todd,
We have a few more questions that we would like your opinion on. The first is cooling. We know that we will have to have a heater on board to keep the sub at a comfortable temperature, but we would like to know if a cooling system is also necessary. We will be working around the hot vents, but they are relatively small, so it might not be necessary. If we did have it, how would we vent the heat if we are surrounded by heat?
The second is cracking. If we are over a vent, it is likely that half of our sub will be very hot and the other half will be cold. Would the expansion cause cracks to form in the titanium pressure hull?
The last is about a distillation. There will be two people with missions of about 10 hours. We were originally just going to give them water bottles, but distilling the seawater is an interesting concept. If the distiller is small enough then it would be a good idea, in case there is an emergency and the people are trapped in the sub for long periods of time. It might also be useful for making moonshine if the crew gets bored.
Thanks, kabir
Date: Sun, 14 Oct 2001 00:37:00
To: Mentor: Todd B. Harland-White
Subject: Docking
Hi Todd,
We know that the docking issue is not our top priority now, but it seems that Team 4, the team responsible for designing the habitat finds it a pressing issue. Let me give you an idea about what design they have in mind for the habitat. They are thinking of building the habitat from 4 spheres packed together with connecting passages between them. Their argument for designing it using 4 spheres as opposed to one, is that it will be much easier to manufacture 4 small spheres instead of one big one, and that the modular design enables them to expand the habitat later. The spheres will have a radius of about 5.5m to 6m and will be attached by cables to the sea floor. I don't want to go into more details, but I just want to mention the important fact. The spheres are each for a specific purpose. One is for living, another is a command sphere, the third is a lab and finally the fourth is for docking. Our concern is the last sphere.
During the last interteam meeting, we told Team 4 that the docking mechanism we designed is going to keep the submarine attached to the outside of the habitat, and therefore the large docking sphere would simply be a waste of space and money. Our submarine can be attached to any of the other spheres if we make the necessary modifications to that sphere's walls. Of course, we only speak for ourselves; we do not know if the docking sphere would be necessary for the AUVs and ROVs of Team 7.
Then, they brought up an important point. What would we do if we need to fix the submarine? Take it up to the surface? Too costly. Use ROVs to repair it? Almost impossible. So maybe the docking sphere is necessary after all! We would like to have your opinion on this matter. Is it better to use a docking sphere or stick to our old plan of attaching the submarine to the outside?
Thanks, Waseem
Date Wed, 17 Oct 2001 18:50:34
To: Vent 7
Subject: Core Sampling
Hi,
Our team, manned operations, has talked to one of your team members (Tawanda) about the e-mail both of our teams got from Vent 2, concerning core sampling. Tawanda said he'd prefer that we be responsible for this task, since it will require heavy machinery for drilling ten meters into the seafloor. We'd like an 'official' statement from your team as to who will be reponsible for this job (you, us or both teams?) so that we can respond to Vent 2 soon.
Thanks,
Waseem
Date: Thu, 18 Oct 2001 15:11:00
To: Mentor: Todd B. Harland-White
Subject: Hull design
Dear Todd,
I have just realized that the way our team is working will lead us nowhere. Unfortunately, we haven't found much reading material about submarine design. This lead us to inventing our own designs. A natural consequence of this 'inventing' is that our designs are totally impractical (in the case of some designs, I would even say silly.) Let me tell you about the incident that has suddenly brought be into touch with this grim reality.
Since the start of the project, our team has argued on the shape our pressure hull should be: spherical or cylindrical. Finally, a few days ago, I've decided to take a firm decision to stop all this arguing. I decided the hull should use multiple intersecting spheres (a design I've seen in a book), which gives us the advantages of both spheres and cylinders. I started writing a lengthy page on our website to explain why I came up with this design. All the arguments I used in my page were derived from mere common sense and occasionally from equations that applied to simple physical objects but probably won't apply to something as complex as a submarine. I stopped halfway through the page design and decided to continue on the next day. After that, I went back to reading from the book and ass I read, I realized that all my arguments were wrong, simply due to the fact that so far our team did not even have the slightest notion of something called exostructure or the outside hull!
We simply thought that the pressure hull would be the only shell, and would not be surrounded by anything else. This ignorance is reflected in the picture you can see on our homepage. After the shock of learning about the existance of this element in the design, I began to question the validity of what we've done so far. Let me pose the questions I have so far (and probably many more will follow):
1- From what I've read and from the diagrams I've seen, I can imagine a simplified picture of the exostructure as a shell that encloses the inner shell where our scientists will reside. Is this picture right? (I'm not using shell to mean empty sphere, I just mean any hollow structure.) If it is, then why is the exostructure usually made from thin sheets of metal, while the pressure hull is much thicker? Doesn't the outer shell take much of the water pressure? If for example you have a strong metal sphere with another glass sphere inside it, and you put the spheres under very high pressure, won't the glass sphere be protected as long as the metal sphere does not collapse? If so, why should the pressure hull be stronger than the outer hull?
2- I've seen pressure hulls built usually to be spherical or some other strong shape. On the other hand, outer hulls are built in all kinds of fancy shapes to make them more streamlined. Doesn't this make them lose their strength? And does a streamlined outer hull eliminate the need for a streamlined pressure hull?
3-What is the buoyancy factor? The book refers to it as the weight of the hull over the weight of the water it displaces. This means that for a low buoyancy factor, the hull should be light and the weight of the water it displaces (which is proportional to its volume, right?) should be large. Then, in the next paragraph, it says that submarines operating in deep water should have a low buoyancy factor. I simply don't get that. Why should a submarine working in a deep environment be light? Shouldn't it be heavy so that it sinks down to deep water?
I would also appreciate it if you can also go the incomplete page I've written and tell me if the simplistic approach I'm using would work in practice(I personally think it won't.) The page is at: web.mit.edu/12.000/www/m2005/a2/6/hull.shtml
Thanks,
Deeply confused Waseem
Date: Mon, 29 Oct 2001 18:03:03
To: Vent 1
Subject: Things required of us
Hi guys,
This is a message from Vent 6. The information we got from you guys last time was ok but we need to know if you guys have come up with a more organized list of what you require us to do. So, please let us know as soon as possible and we'll appreciate it. Thanks.
Vent 6 members
Date: Mon, 29 Oct 2001 21:28:25
To: Vent 1 and Vent 2
Subject: Sensors
Vent 6 here again,
We need full information about the sensors you people need to carry out research. Could you please let us know by Wednesday if possible? We need to work on that during our next team meeting.
Date: Tues, 30 Oct 2001 19:22:43
To: Mentor: Todd B. Harland-White
Subject: Power and Propulsion
Dear Todd,
We're trying to get a figure for the power consumption of our submersible. We think the main consumers of the power will be the propellers, maybe followed by lighting and the ROV that will be attached to our sub. We've found out that the Alvin and other submersibles have a maximum speed of 2 knots or 3.4 km/hr. We think this is extremely slow. After studying lots of equations, we realized that the power varies with the cube of the velocity, which makes it hard to increase the speed without making the power consumption skyrocket. But one single submersible caught our attention: Deep Flight I. It's designed to go at a maximum speed of 12 knots! We couldn't find out how they did that. We would like you to give us a reasonable maximum speed we can state in our presentation that would be hopefully faster than the Alvin's, and at the same time won't make the panel of experts listening to us burst out in laughter. If you can help us find a way of attaining a speed similar to that of Deep Flight or even half of it at a reasonable power consumption, that would really be great.
Also, we were wondering about the number of thrusters we need. We think three is a good number for forward/backward motion and one for rotational motion. We plan to go up and down for large distances using the variable ballast. For shorter distances, we'll use the forward/backward thrusters along with two rudders to help the submersible pitch at an angle while it surges. Is that a reasonable configuration of thrusters?
Finally, how high does the power rating of thrusters go? We've found that most submersibles use 5hp or 10hp thrusters. Are thrusters with higher ratings available? How high should the total power consumption of the submersible go? We're probably going to use aluminium-seawater batteries. Is 150kW too much to ask from them?
Truly,
Waseem
Date: Sat, 03 Nov 2001 05:03:31
To: Vent 2
Subject: Drilling
Hello,
I am from the manned submersible team. We will be doing the drilling for you guys. You told us that we should be drilling down ten meters to get core samples. It would be much more convenient for us for the drilling depth to be eight meters. If ten meters was just an arbitrary number, then can we make it eight? The other question that we had was, do you want a large core sample for the whole depth of the drill or do you want a smaller sample at a certain depth. For example, this would mean a 0.1m long core sample from a depth of 8m rather than an 8m long sample.
Thanks,
Kabir