On Orbit fuel depot

tahanson43206 · 2021-09-01 08:09:20

For Void on phone so brief thanks for reminder

For Callinam time for drawing - suspect good idea _ timely need sketch

Void · 2021-09-01 09:13:17

Thanks (th), you are quite reasonable.

I agree that Calliban's concepts are well worth consideration, and then even more.
Thanks for your contributions Calliban.

I don't view this as a socker match where we must sink to low bahaviors, as bad fans.
I really do enjoy your product, and feel that indeed sometimes and often what I
produce is not the best. However, I do like a review before dismissal.

As for GW Johnson, almost always I will get out of the way, as I think he is the
real thing.

Done.

tahanson43206 · 2021-09-01 09:32:51

For Void Still on phone Have request
Can Will you create drarwing for Calliban?
Please show Callinam what his words look like after your render
I think his idea may be opportunity for Large Ship
(th)

Void · 2021-09-01 09:55:15

Well, I would have to retrieve my account. That is how I am. Quite a lot of chaos.

I think I could better answer specific questions on portions of my posts, or at this point I am quite content to step out of the way. I made you and Calliban aware I had some notions. I don't proclaim that they have no faults, or that no-one can do better.

I am very interested in other thinking(s)

Done.

tahanson43206 · 2021-09-01 10:57:15

For void Thanks for considering request.

For Callinam

Try your idea in contest of Large Ship

Set receiving. Starship below source tanker

Need design for docking

Need design for escalator to move tanker down to receiver

(th)

tahanson43206 · 2021-09-01 13:28:32

That was interesting ... while visiting a remote site, my laptop refused to "see" the local WiFi connection, but the cell phone saw it just fine. I can now better appreciate the devotion of SpaceNut, who keeps the forum running despite having only a cell phone to work with at times!

***
For Calliban ... following up on your idea of rotation .... your original post omitted the counterweight. I'm glad to know you were not thinking of rotating the tanker and receiving vessel around a common Center of Gravity. That misunderstanding is possible when only words are available to try to convey a complex idea.

***
For RobertDyck ... the idea of Calliban may present a totally unexpected and immediate opportunity for the Large Ship initiative ...

Can you think of a way to dock tankers at the nose of the Large Ship (as you described in large Ship recently) and then (somehow) employ Canada Arm (squared) to move the Starship to a point just above a Starship mounted in the rim of the Large Ship to receive fuel.

The concept I have in mind would run ** outside ** the habitat rim.... The spokes you have described could provide a framework for movement of Starships from the nose to the rim where they would secure to receive fuel. The tankers could then dock and transfer to a point just above the waiting receiving vessel.

This concept would increase the value of the Large Ship idea to first priority status if you can think of a way to make this work.

The refueled Starship would "cast off" by releasing the clamps holding it to the Large Ship.

Momentum management would require some thought.

Since you are starting to develop 3D models, perhaps Calliban's idea can slip into your workflow.

Update at 15;29 local time .... Because momentum must be carefully managed in this system, I would propose you extend the central shaft an equal distance fore and aft, so that two Starships can move simultaneously from docking ports to refueling ports.

Release of refueled vessels would then occur simultaneously, so that momentum of the Large Ship is conserved.

The vessels would receive momentum away from the Large Ship, so timing of release would be coordinated with local conditions to insure safety.

Update at 16:36

A fuel depot based upon the Large Ship framework would be extremely important at Mars.

The problem of risking return based upon whether or not the in situ production system works can be eliminated by sending a copy of the Fuel Depot Large Ship variant to Mars, and sending as many tankers along with the fleet as are required.

In addition, fuel created on Mars can be lifted to orbit to refuel vessels that do not land, such as the Large Ship itself.

(th)

tahanson43206 · 2021-09-02 10:52:48

As a follow up to mailings to NewMars Admins ...

The binder I put together (for word-by-word study later today) includes:

1) CV of GW Johnson dated 4-19-20.
2) Draft 2 letter to Dr. Zubrin (5 pages)
3) Image of design of lander version 2

Please let me know if you are missing any of these items.

Dr. Johnson has requested the materials be kept private for the time being.

Feedback should be provided to Dr. Johnson at his email address on record.

(th)

tahanson43206 · 2021-09-02 17:13:21

From recent comments in Large Ship topic, it appears that RobertDyck believes that bladders can handle cryogenic liquids for transfer from tanker to receiving vessel. This opinion indicates that RobertDyck has not had time (perfectly understandable) to read this topic.

for those readers of the forum who might be interested in an alternative point of view and recommendation, select messages posted by GW Johnson in this topic.

Update at 19:21 local time ...

A quick search for posts by GW Johnson with the word "bladder" came back with 9 citations.

Of these, I thought this one is most useful for anyone who thinks that a bladder system would work with cryogenic liquids:

I am not sure what the depot storage tank approach should be with these cryogenic materials. One option is the same free-surface tank technology as the vehicles that use it. The other might be some sort of "syringe"-like system, but probably not a bladder system, because venting is incompatible with bladders.
Re: Interplanetary transportation » On Orbit fuel depot » 2021-08-22 09:30:33

No one has time to read every message posted on this site, so it is easy to understand how members miss the wisdom posted by other members. Incorrect beliefs persist on this forum, as they do in all of human experience.

Update at 20:35 local time ... I went back and read this topic from the beginning ... I note that every so often GW Johnson tried to bring the topic back into focus after it went veering off as so often happens.

He has been consistent over the entire period.

Since SpaceX is using cryogenic propellants and will continue to do so, discussion of bladders seems unlikely to fit the reality that SpaceX engineers are dealing with right now.

GW Johnson has suggested ullage (chemical or ion) to provide artificial gravity for cryogenic propellants, and Calliban has added rotation as an option.

It seems reasonable to me to suppose that a vessel designed in a manner similar (but obviously different from) RobertDyck's Large Ship would have the ability to create as much artificial gravity as is needed.

Details of how to put arriving vessels into position to either offload propellant, or to accept it, remain to be worked out.

(th)

GW Johnson · 2021-09-02 21:23:00

Just to be clear, RobertDyck is probably correct about his materials surviving at mild cryogenic temperatures. I worry about it because to the best of my knowledge, bladdered cryogenics have never yet been flown on anything.

That may have less to do with properties at cryogenic temperatures, and more to do with an incompatibility of any and all bladder designs, with the venting the boiloff vapors of cryogens. Finding a practical place to put the vent, and separating the vapors from the liquids at the vent, may well be impossible in zero-gee.

GW

RobertDyck · 2021-09-02 22:35:39

I haven't read this topic. Just the last 2 posts. If the concern is technology that hasn't flown before, that's a problem that has plagued NASA in recent decades, preventing progress. The NACA was created in 1915 because commercial companies refused to invest in new technology. They wanted reliable return on investment, so would only build aircraft using technology that had already been proven. That resulted in extremely slow technological development. The NACA was created specifically to develop high risk / high payoff technologies. The "risk" did not mean risking human lives, it meant risking money. New technology may or may not work. If it doesn't work, then you've invested money that cannot be recovered. But NACA was funded by federal government money. The result was NACA ensured rapid development of aircraft technology. After Sputnik was put in orbit, NACA was changed into NASA. Part of NASA's mandate today is still development of new aircraft technology.

Another example. Years ago there were proposals for a robotic sample return mission to Mars. But the cost was too high, government wouldn't fund it. Someone would realize that ISPP would dramatically reduce mission cost, so mission cost was something government was willing to fund. The mission would be approved and proceed. During development, someone would say they don't want new technology on "my" mission, so ISPP would be removed. That caused mission cost to skyrocket. The extreme cost caused government to cancel the same thing. So no robotic sample return, the idea remained dead for years. Until someone new realized ISPP would reduce the cost to something affordable, and the whole cycle started again. This occurred 3 times that I'm aware of, and probably more.

Of course eventually they excuse of sample return was used to get Perseverance rover approved. The guy who headed the Curiosity rover program wanted a second rover. The Mars Exploration rovers, Spirit and Opportunity, were two rovers. He wanted a second big rover. So excuses were made, Perseverance was approved. Even though there's no possible way to get those samples back to Earth. It just won't happen.

My point is new technology is what space exploration is all about. NASA was created for human exploration of space, and new technology to enable that. Since the Shuttle program, NASA has become risk averse. That fear of new technology has prevented NASA from doing what it exists for. The attitudes of commercial corporations have infested NASA, the attitudes that NACA was created to resolve. So don't fall into the same trap.

RobertDyck · 2021-09-02 23:36:47

If your concern is boil-off and how to deal with in in a bladder, the solution is prevent boil-off. Remember I didn't suggest a bladder for just any propellant tank. The idea is for a tanker, so the bladder facilitates propellant transfer. So this isn't to feed propellant into an engine, it's to transfer propellant to another craft. A SpaceX tanker will not store propellant for any significant length of time, just long enough to rendezvous with the craft to receive it. And space is very cold, not cold enough to keep liquid hydrogen cold/liquid, but enough for soft cryogens. The trick is to ensure the tank isn't heated by sunlight. Exposing the tank to the cold of space, allowing heat to radiate, while shading from sunlight, should keep it cold. This is how modern space telescopes work. Operating temperature of the James Webb Space Telescope is -380°F (-228.9°C). At 1 atmosphere hydrogen boils at -252.78°C, but methane boils at -161.48°C and oxygen -182.96°C. Propellant is normally moderately pressurized, to about 10 atmospheres, which raises boiling temperature. And densified propellant is super cooled, but it's still warmer than -228.9°C.

GW Johnson · 2021-09-03 14:34:53

RobertDyck:

I'm not as sure as you that there will be no vapor formation to vent from inside the bladder. Yes, the gas pressure between the bladder and the shell stops the violent boiling, if it exceeds the vapor pressure of the liquid at whatever its temperature is. But that does NOT stop slow evaporation!

What stops slow evaporation is when the partial pressure of the vapor phase in the atmosphere atop the liquid equals or exceeds the vapor pressure of the liquid at its temperature. It is an analog to relative humidity. The puddle cannot evaporate when the relative humidity is 100%.

Note the phrasing "atmosphere atop the liquid". What is inside the bladder CANNOT be all liquid to get this "humidity-like" effect! There will simply have to be vapor at sufficient partial pressure in contact with the liquid, or you cannot stop the slow evaporation.

In zero-gee, that initially takes the form of bubbles floating about inside the larger volume of liquid. If the vapor volume dominates, it takes the form of liquid globules floating about in the vapor. I don't know what the transition between those end states is, but I am quite sure that it won't be all-liquid.

Short term, what you say is true, we could carry the cryogen in a bladdered tank. And what you say about the sun shield is quite true. But longer term (a few to several hours?), you will inherently get slow evaporation unless there is atmosphere in direct contact with the liquid, whose vapor partial pressure equals or exceeds the vapor pressure of the liquid.

There is just no way around those phase-change physics. Unless you utterly freeze the stuff. And even then, there is still a very small but nonzero vapor partial pressure that is required to be exerted on the ice surface to stop its sublimation.

By the time you deal with vapor along with liquid in your bladder, and add venting to control its pressure, plus liquid-vapor separation to your vent line, I think you are just better off with a free surface tank and some sort of ullage thrust during transfers. It's far simpler for fewer failure modes, and well proven in flight for 6 decades now.

GW

Last edited by GW Johnson (2021-09-03 14:37:39)

tahanson43206 · 2021-09-03 15:02:45

For RobertDyck ... thanks for engaging with GW Johnson on this important (and timely) topic!

For both ... I'm wondering if there are two problems to address, and each of you may be right for one of the two.

For RobertDyck ... your preference for a bladder might be right for a tanker that will only be in service for a few hours at most.

This option would depend upon discovery and proof of a flexible material that contains LOX and other cryogenic liquids effectively, and hold together despite the rigors of the work it will be asked to do. You have published suggestions for materials that might serve, and (hopefully) work is being done to prove the effectiveness of each of them.

For GW Johnson .... the destination for a load from a tanker is a vessel in LEO. If I am interpreting the text of RobertDyck correctly, he is suggesting that ** this ** vessel should be designed to maintain an effective sun shield, and to manage such boil-off as does occur so that vapor is captured and saved (or used as might be the case if a small internal combustion engine is part of the package) (references exist at multiple locations in the NewMars archive).

I think the problem with the recommendation of RobertDyck is that it is totally speculative and must be proven in orbit.

The recommendation of Calliban requires development of sophisticated hardware and control software. In my opinion, it would be well worth while for ** someone ** to study the rotating fuel depot concept thoroughly. That ought to be good for a Master's Degree, at minimum.

***
Side note to GW Johnson ... enjoyed reading the details in CV !!! Am starting detailed review of the letter.

I like your clarification this is an ** engineering ** probe, but wish you could move that clarification earlier in the letter.

I also question use of the term "pathfinder" .... That has baggage ... is there another term that better fits the engineering role?

(th)

RobertDyck · 2021-09-03 16:39:23

I posted details of densified liquid methane and oxygen in post #1203 in Starship is Go.... LCH4 at 10.41 bar pressure boils at -123.15°C. According to technical documents from the manufacturer, PCTFE becomes brittle at -240°C. Lots of room there. This is more than just "speculation".

I suggested a sunshade for the tanker ship. It would have to be built-in so the sunshade wouldn't impede launch or re-entry. Gemini 6A was able to make visual contact (see) Gemini 7 just 5 hours and 4 minutes after launch. That's quick compared to many Shuttle missions to ISS. Tanker sunshade has a few options, and I'm not advocating any specific one. One is a dewar flask, which is a tank within a tank. Basically a pressure tank to hold propellant, then an outer hull for the ship, with the vacuum of space between. The space could be filled with ambient air on the launch pad, and just not sealed so air flows out as the rocket gains altitude. Another option is something close to the hull that "springs out" in space, like the micrometeoroid shield of Skylab. The problem Skylab had was one of the solar panel "wings" ripped off during launch, due to aerodynamic force of supersonic flight. As it ripped off, it tore off a good chunk of the micrometeoroid shield. Dragon has flown with solar panels covered in a similar way as Skylab, but Dragon hasn't lost any solar panels during launch.

The depot would require a more elaborate sunshade. Something more like the James Webb Space Telescope.

SpaceNut · 2021-09-03 18:08:56

Rotating tanks would be placed into a shape of a W to allow for the fluid to go from the center tanks to empty to the outer units to receive the fuel. The tips of the V away from the center is the connection point for the fuel exchange when rotating.

tahanson43206 · 2021-09-03 18:34:24

For SpaceNut re #90

Your idea sounds interesting .... It would help if you were to create a little hand sketch to show what you have in mind.

You can make a sketch on a pad, take a picture of it with your Smart Phone, and upload that to imgur.com.

The words come across to me as having potential, but without a picture I am creating all sorts of images of what your idea might be.

(th)

SpaceNut · 2021-09-03 18:56:09

Starship refueling is connected at the bottom of the ship so all of the nose point in the same direction. The spinning ships at the center of the W would cause the fuel to want to flow towards the connecting point and then away in the receiving ship.

tahanson43206 · 2021-09-03 20:08:16

For SpaceNut .... a small sketch would really help to show your idea.

Words just aren't up to this particular challenge.

(th)

GW Johnson · 2021-09-04 09:13:18

TH:

Thanks for the editorial suggestions. They are good.

RobertDyck:

I quite agree about the sunshade thing. Such a think might be easy to construct on orbit about the facility. One might use lightweight tubing with insert-to-click joints to construct the frame, then hang aluminized mylar sheeting from it with zip ties.

Spacenut & Calliban:

There ought to be some way to get centrifugal force to settle the globules in a free-surface tank without spinning the whole cluster. Might we spin the individual tank about its axis and locate the liquid pickup tube along its periphery, perhaps? That way the facility does not spin, but the cylindrical tanks associated with it do.

That idea will be too heavy for the tankers and stages flying up to the facility, but it surely would make refueling with cryogenics from the facility easier.

GW

tahanson43206 · 2021-09-04 09:29:03

For GW Johnson re #94

Re editorial input ... thanks !!! I will send over the address for the letter shortly ... it is from the Mars Society announcements

Regarding your spin-the-tank idea ... Bravo! You're showing promise, in the company of creatives like Void!

I thought about that for a short while and realized it puts Elon back in the end to end refueling configuration, without the need for acceleration.

The liquids in the tanker will move to the outside of the tank, so a simple pump can collect them and shove them into the receiving vessel. The receiving vessel doesn't need any equipment to handle the liquids, other than the intelligent port to accept flow from the tanker.

The receiving vessel can continue to rotate between visits by tankers. My recollection is that Elon and Company proposed an on-orbit tanker to collect liquids from multiple tanker flights, before the manned (or mission) Starship arrives to collect all the booty.

(th)

SpaceNut · 2021-09-04 09:58:50

current starship utilage (thrusters) motion refueling.

starship tank with cargo hatch

this is the side by side
ru5h75qjw7g71.jpg?width=960&crop=smart&auto=webp&s=e8f66e477702ad84beafda67b61f595e20e67dd5

tahanson43206 · 2021-09-04 10:35:03

For SpaceNut ... thanks for the nice images in Post #96

Can you highlight where thrusters are at work?

They are not shown in the images.

My guess this is artwork showing concepts and NOT engineering.

(th)

tahanson43206 · 2021-09-04 11:57:12

For SpaceNut ....

Here is my drawing of your W, captured on Smart Phone, uploaded to gmail, and delivered to imgur.com

The hardest part was giving up on bluetooth. My laptop has bluetooth, and the smart phone can ** see ** the laptop, and two paired with each other, but after that nothing seemed to happen.

I ended up just sending the file to gmail, pulling it down on a desktop, and uploading it from there to imgur.com.

(th)

tahanson43206 · 2021-09-05 06:31:40

For SpaceNut ... Round 2 .... can you provide a similar diagram showing your concept of how the rotating system would work?

(th)

GW Johnson · 2021-09-05 11:24:56

TH:

I'm going to send you a sketch of my weird rotating-tank idea, to your email. I still have no clue about how to post such things for myself on these forums. I do not understand most of this computer stuff. No common dictionary.

The rotating-tank idea would require some symmetry in the disposition and masses of the tanks, but not as much as would be required if you spun the whole station. This idiotic notion might relieve us of the need for ullage thrust with free-surface tanks, for transfers FROM the facility. It's just stupid enough to possibly work good. Its Achilles heel is the rotating pipe joint. But that may well be solvable.

GW

New Mars Forums

Announcement

#76 2021-09-01 08:09:20

Re: On Orbit fuel depot

#77 2021-09-01 09:13:17

Re: On Orbit fuel depot

#78 2021-09-01 09:32:51

Re: On Orbit fuel depot

#79 2021-09-01 09:55:15

Re: On Orbit fuel depot

#80 2021-09-01 10:57:15

Re: On Orbit fuel depot

#81 2021-09-01 13:28:32

Re: On Orbit fuel depot

#82 2021-09-02 10:52:48

Re: On Orbit fuel depot

#83 2021-09-02 17:13:21

Re: On Orbit fuel depot

#84 2021-09-02 21:23:00

Re: On Orbit fuel depot

#85 2021-09-02 22:35:39

Re: On Orbit fuel depot

#86 2021-09-02 23:36:47

Re: On Orbit fuel depot

#87 2021-09-03 14:34:53

Re: On Orbit fuel depot

#88 2021-09-03 15:02:45

Re: On Orbit fuel depot

#89 2021-09-03 16:39:23

Re: On Orbit fuel depot

#90 2021-09-03 18:08:56

Re: On Orbit fuel depot

#91 2021-09-03 18:34:24

Re: On Orbit fuel depot

#92 2021-09-03 18:56:09

Re: On Orbit fuel depot

#93 2021-09-03 20:08:16

Re: On Orbit fuel depot

#94 2021-09-04 09:13:18

Re: On Orbit fuel depot

#95 2021-09-04 09:29:03

Re: On Orbit fuel depot

#96 2021-09-04 09:58:50

Re: On Orbit fuel depot

#97 2021-09-04 10:35:03

Re: On Orbit fuel depot

#98 2021-09-04 11:57:12

Re: On Orbit fuel depot

#99 2021-09-05 06:31:40

Re: On Orbit fuel depot

#100 2021-09-05 11:24:56

Re: On Orbit fuel depot

Board footer