On Orbit Refueling Techniques and Depot

tahanson43206 · 2021-10-20 12:17:18

For SpaceNut ... we did not appear to have a topic dedicated to this topic.

Since GW Johnson has been working on this specific technology, I am hoping this topic will be helpful for collecting knowledge and insights.

GW Johnson has published at least one article in ExRocketman, and I expect there will be more articles or posts in future.

(th)

tahanson43206 · 2021-10-20 12:18:52

For GW Johnson re Article in Review

Thanks for providing the draft of your work-in-progress!

I am taking a break after reaching page 3.

(th)

SpaceNut · 2021-10-20 16:59:34

https://exrocketman.blogspot.com/2021/0 … tions.html

Propellant Ullage Problem and Solutions

kbd512 · 2021-10-20 17:12:51

GW,

Why no mention of capillary action to control the movement of propellant within the tanks?

SpaceNut · 2022-04-20 17:34:47

repost if we are making a tank on orbit system

We know that the James watt shield aids in the keeping of liquid Helium cold to control the boil-off with 50 Kelvin shield The Sunshield Webb/NASA

The sunshield will allow the telescope to cool down to a temperature below 50 Kelvin (-370°F, or -223°C) by passively radiating its heat into space. The near-infrared instruments (NIRCam, NIRSpec, FGS/NIRISS) will work at about 39 K (-389°F, -234°C) through a passive cooling system. The mid-infrared instrument (MIRI) will work at a temperature of 7 K (-447°F, -266°C), using a helium refrigerator, or cryocooler system.
Of course the Starship is refueled in Earth orbit, the fuel can be sub-cooled, but not below -182 °C since that's the freezing point of Methane. So not as much shielding will be required....I did do a boiloff run and found if we fill it to slowly that we would loss a starship or 2 fillings to get it full due to the boil off.
https://www.reddit.com/r/SpaceXLounge/c … ions_uses/
of course liquid hydrogen can be liquefied by cooling to approximately 20 K (−253 °C) at atmospheric pressure [5,6,7].
https://iopscience.iop.org/article/10.1 … 012012/pdf
Zero boil-off methods for large-scale liquid hydrogen tanks using integrated refrigeration and storage

Remember that the tanks for the large ship are even larger than that of several starships....
5 layers to the shield
Kapton. Each layer is coated with aluminum, and the sun-facing side of the two hottest layers (designated Layer 1 and Layer 2) also have a "doped-silicon" (or treated silicon) coating to reflect the sun's heat back into space.
Each layer of the sunshield is incredibly thin. Layer 1 will face the sun and is only 0.05 millimeters (0.002 inches) thick, while the other four layers are 0.025 mm (0.001 inches). The thickness of the aluminum and silicon coatings are even smaller. The silicon coating is ~50 nanometers (nm) (1.9 microinches) thick, while the aluminum coating is ~100 nm (3.93 microinches) thick.

tahanson43206 · 2022-04-20 17:41:34

For SpaceNut re #5

Thanks for this helpful addition to the topic!

On a related note ... Dr. Johnson just sent a copy of his Lunar Propellant study to several members of the North Houston chapter of the NSS.

In the correspondence was a reminder of our plan to send the link to his presentation to Executive Director James Burk.

I have received no confirmation that the link arrived safely.

It may well have !!! I am simply unable to confirm safe arrival.

The intention here is to try to build a higher level connection between the Mars Society and the NSS.

(th)_

tahanson43206 · 2024-05-10 20:06:27

For GW Johnson (in particular and all welcome)...

https://www.youtube.com/watch?v=Uju2g-yUDFE

At about 10 minutes into this video about SpaceX plans, a NASA representative is interviewed. The subject is on-orbit refueling and the key concept is that ullage is assumed. Details about how the ullage will be achieved are not provided, or at least, ** I ** did not hear any.

I didn't watch most of the video... there is some nice animation.

There ** was ** a report that the on orbit refueling test in flight #3 was successful.

(th)

GW Johnson · 2024-05-11 12:57:06

Tom:

I heard no ullage solutions either.

All I know is that when you first go into free fall, the propellant in a tank breaks up into free-floating globules, but eventually these form a film all over all of the inside surface. If the volume is large, that film is significantly thick.

If the surface tension is also high, then you could suck quite slowly from that thick film, as long as you don't suck hard enough to cause a cavitation, meaning the surface tension cannot hold sway. The same would hold true for a pressure difference-driven transfer.

I prefer the ullage-thrust solution to settle the fluid into one pool somewhere in the tank. That is usually conceived as axial thrust settling fluid into the bottom ends of tanks, but that affects trajectory, too. I prefer spin gravity settling in one or another geometry. That requires more plumbing, but does not affect trajectory.

Almost nobody but me ever mentions spin gravity settling, though. I wonder why?

GW

tahanson43206 · 2024-05-11 13:34:47

For GW Johnson re #8

There is a window of opportunity for the spin-refuel solution you've described in your papers.

The ullage solution might make sense if the change in orbit is useful.

Clearly, both NASA and SpaceX are devoting their energies (and funds) to making the ullage solution viable.

In my opinion (based mostly on your work) the spin solution is ideal for a fuel depot.

***
For all ... this topic is available for analysis of the ullage generation orbital mechanics that NASA and SpaceX are obviously planning to manage. It would be interesting (to me for sure) to seen what an on-orbit ullage solution for a Starship sized vehicle would look like.

(th)

SpaceNut · 2024-05-11 14:30:53

The real issue for a fuel depot is the selection of the fuel types to be made use of once one build it.

Each fuel type has many requirements to keep the fuel from boiling.

This means temperature control whether by shade or by heating.

It's one of the reasons that the ISS has such a large power source and it's the same for the Artemis capsules solar design which gathers and uses more energy than a human needs on the planet's surface.

Calliban · 2024-05-14 03:04:29

I am a layman on the topic of rocketry. But for missions to the moon and Mars, orbital refuelling makes only limited sense to me. Most of the Starship upper stages sent from Earth to Mars or to the moon, will be canibalised on the surface of the respective bodies. Only a minority will be returning to Earth. Those that do return to Earth will benefit from orbital refuelling, as this then obviates the need to launch a fresh Starship from Earth surface for future trips to Mars. But for the majority of missions, a direct throw from Earth surface would appear to offer a superior mass ratio in terms of kg delivered to Mars per kg launched from Earth. For this task we would want a three stage, partially reusable rocket vehicle. The lower two stages would be reusable and would return to Earth. The upper stage would be designed to fly one way to its destination and would be parts upon reaching the surface.

On orbit refuelling only makes sense for the relatively brief period in which Starships are used to carry human beings between the two planets in both directions. It will very quickly become economically desirable to build an interplanetary ship equipped with high-ISP propulsion. At this point, orbital refuelling of Starships becomes obsolete, as these vehicles will only be used to ferry people and supplies between planetary surfaces and low orbits. But until the development of such a ship, orbital refuelling would appear to offer few advantages over a direct throw, three-stage rocket. Any thoughts?

Last edited by Calliban (2024-05-14 03:07:18)

SpaceNut · 2024-05-14 19:03:22

When refueling is an issue is when the payload is so low as compared to an empty ship waiting to be refilled. That makes little sense to use that ship as a lander at a destination since the amount of fuel is so huge.

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#1 2021-10-20 12:17:18

On Orbit Refueling Techniques and Depot

#2 2021-10-20 12:18:52

Re: On Orbit Refueling Techniques and Depot

#3 2021-10-20 16:59:34

Re: On Orbit Refueling Techniques and Depot

#4 2021-10-20 17:12:51

Re: On Orbit Refueling Techniques and Depot

#5 2022-04-20 17:34:47

Re: On Orbit Refueling Techniques and Depot

#6 2022-04-20 17:41:34

Re: On Orbit Refueling Techniques and Depot

#7 2024-05-10 20:06:27

Re: On Orbit Refueling Techniques and Depot

#8 2024-05-11 12:57:06

Re: On Orbit Refueling Techniques and Depot

#9 2024-05-11 13:34:47

Re: On Orbit Refueling Techniques and Depot

#10 2024-05-11 14:30:53

Re: On Orbit Refueling Techniques and Depot

#11 2024-05-14 03:04:29

Re: On Orbit Refueling Techniques and Depot

#12 2024-05-14 19:03:22

Re: On Orbit Refueling Techniques and Depot

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