New Mars Forums

Well! That was another ** very ** interesting meeting (from my perspective)

kbd512 was in fine form, and we were off to the races with a rapid series of deep dives.

I'm attempting to recall the highlights ....

We opened with a review of GW Johnson's work on the second/third stage rocket for the SpinLaunch system.

GW had run a series of studies that reached a solution that (I gather) convinced him that the SpinLaunch idea could actually work in the Real Universe, with a couple of caveats .... he set the mass of the projectile at 1500 kg (approximately) and the launch velocity at 5500 mph.

With those two adjustments, he was able to compute a fling that would put the projectile where it needs to be for his design for a second/third stage system to complete delivery of the 200 kg payload to an orbital refueling station at 150 km.

kbd512 and I discussed alternative sites for a launcher, and that part of the discussion was certainly wide ranging.  However, there would appear to be sufficient reasons for the orbital plane of the fuel station to remain right where it is.  A consequence of the current design for the orbital plane of the fuel station is that a SpinLaunch system would have two opportunities to toss fuel/oxidizer/supplies up to the station. This is because the orbital plane passes over McGregor, Texas twice a day.

The launcher can toss a payload once an hour, so it could (theoretically) toss payloads into 24 orbital planes if there would be customers in orbit to receive the materials.  As the space economy grows, such a situation seems highly likely.

However, for a first orbital refueling station, there is only going to be one for quite a while, so a SpinLaunch system can only toss payloads to the station twice a day.

In order to provide 100 tons of propellant, at the rate of 200 Kg per toss, the company would need multiple launchers. 

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After we had considered GW's recent work, we went on to an extended discussion of the solar panel installation there in Houston, and the Real Universe on-the-ground observed performance.  kbd512 indicated he might be able to contact the engineer who designed his system, to ask why the performance dropped off when clouds obscured the Sun.  kbd512 reminded me that the electronics that controls the system is set to handle both over voltage and under voltage situations.  The clouds may well have caused an under voltage condition to cause the controller to stop energy flow into the batteries.  That is something the engineer might be able to address, if kbd512 can reach him.

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After ** that ** we took a dive into thermodynamics, with a focus on my question about how much of energy invested in a compressed air store can be recovered, after the temperature of the compressed gas has been allowed to fall to ambient temperature, as is normal for compressed air systems such as pneumatic tool compressors.

kbd512 found a Wikipedia article that has an impressive calculus graph, showing an area under a curve that (I assume) represents stored energy, but I was unable to deduce the percentage of the energy invested in the store that can be recovered after the temperature reaches ambient conditions. 

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Finally we spent a few minutes considering a compressed energy store for home power backup, and kbd512 reminded me that he has published quite a bit of information about a compressed air system for a car.  I asked if that system could be adapted for a home energy backup, and with some hesitation, kbd512 seemed to think the basic mechanism might work.

There is some (or maybe a lot of) uncertainty about how far an automobile sized compressed air system could hold up if asked to power a refrigerator for a week.

I hope that someone in the forum is interested in this question and is willing to take a look at finding the answer.

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All in all, despite technical difficulties that occurred from time to time due to improvised nature of my hardware, I thought this was an interesting and productive session.

We'll try again next week.

As a reminder if any of our European members read down this far... I am willing to work with you if you would like to set up a Google Meeting or a Zoom session at a time that works better for you.  Mars Society very kindly allows us to continue using the Zoom facility we set up when they were using Zoom. The Society no longer pays for Zoom, so the sessions are limited to 40 minutes or so, but that is usually enough time for folks to make some progress, or just to socialize.

(th)

Setting up for tonight's Google meeting.... so far no issues... (th)

We are underway...

kbd512 is here.

(th)

GW Johnson sent a PDF file of his latest round of work on the SpinLaunch venture....

In the PDF at the link below, GW shows that if the launch is upgraded to 5500 mph, and the device adheres to the mass, cross section and length that he has chosen, the vehicle will cross over the 37 mile altitude and still have some momentum for the second stage to work with. The mass GW has chosen is 3500 lbm, which is substantially less than the mass ChatGPT4o estimated would be required to put a 200 kg payload into orbit.

Despite the smaller mass, GW's design does achieve the altitude needed for the second stage to take over.

For readers (like me) who might not be familiar with "lbm", here is a Google definition:\

That means GW's estimate of 3500 lbm would be 1585 kg, well below the 2000 that ChatGPT4o "thought" would be needed.

That 1585 kg needs to include the payload of 200 kg, the propellant and casing, the auxiliary hardware to allow the rocket to function after dealing with 10,000 G, the carrier for the package, and the control electronics to manage the rocket burns and navigate the vehicle to a docking with the destination.

However, 1385 kg is a lot to work with, so we can stay tuned to see if GW can put the package together.

Here is the link to the PDF:

link goes here: https://www.dropbox.com/scl/fi/p8t4m1cj … okgyf&dl=0

(th)

The link to the Cycloid animation at Imgur.com appears to have been discontinued.

This is an attempt to see if a new copy of the link will work:

https://i.imgur.com/VPFn7ip.mp4

The link appears to work if a visitor clicks on it, but the automatic display no longer activates the animation.

As a reminder, this animation shows a conceptual display of what a system to deliver payloads from orbit to the surface of Mars might look like.

Imgur.com showed 208 views of the animation to date.  A few of those are just the author checking to see if the link still works.

(th)

For all ....

The email below arrived today... I had applied for a membership in a new service that Executive Director James Burk had recommended.

The application was entered some time ago, but it would have been shortly after our Google meeting with Mr. Burk. In any case, after a bit of delay, here is the response:

Something in the text I attempted to post caused the dreaded AISE, so I'll try reducing the post to just the key concept...

OK... whatever text was causing the problem is gone, and the essence of the email is preserved.

(th)

Place holder for today's Calendar update...

RA 03h 53m 45.7s Dec +19° 31' 51.3" Appar J2000
Mag: 0.94 (Estimated: JPL)  Const: Taurus
Sun Dist: 212,232,047 km [25.9 km/s]
Earth Dist: 246,553,944 km [35.4 km/s]

Martian Year:   
37
Martian Month:   
10
Solar longitude Ls:   
296.9
Sol number:   
558

I found a laptop that had Python installed, and ran the program developed by ChatGPT4o as reported above.

The program produced a graph which is definitely encouraging. It shows that when the mass of the projectile is increased, while everything else remains the same, the apogee is much higher.

I will attempt to deliver the image via imgur.com

(th)

For GW Johnson.... I asked ChatGPT4o to write a little Python program to show the performance of a SpinLaunch projectile if the mass is increased while the cross section is held constant...

I'm not in a position to run the program right now, but if there is a NewMars member who can run Python, please download the little program and publish the results.

GW is currently looking at 300 Kg mass for the projectile,l and I am recommending a mass of 2000 kg, which is the mass of payload, third stage and second stage.

(th)

Energy store numbers:

Two kilowatts for 24 hours is 48 kilowatt hours.

48 kwh for 7 days is 336 kwh

How large would an energy store have to be to hold 336 kwh for emergency use?

In charging the energy store, the thermal energy would be lost to the environment, leaving only the spring energy.

How much energy has to be invested in the store, to be able to secure 336 kwh when the energy is needed?

The efficiency of the equipment to translate stored spring energy into electric current is a factor. 

(th)

For Terraformer and SpaceNut ... thank for your observations and questions!

This new initiative by Calliban seems (to me at least) well worth developing further.

My reason is a that I am hoping it will turn out that using a liquid as the working fluid for storing energy and retrieving it is more efficient than using a gas.  I recognize that the performance of a fluid based system vs a gas based one is dependent upon the quality of manufacturing.

Fortunately, this is one of Calliban's areas of expertise.

If we think of the system as a mechanical battery (like a hydraulic dam energy storage and retrieval system) then we might be able to envision a sturdy, long lived and highly efficient energy storage system.

Questions that our members might address include:

1) what combination of liquid and gas is best for this application?

Calliban mentioned oil, and Terraformer asked about water ... there must be advantages and disadvantages to each.

2) Air is readily available, but it is a mixture.  Is it better to use just one gas? If so, which one is best for this application?

3) Container.... Calliban opened with iron/steel (not sure) but whatever it was, it had an upper temperature limitl.

Since temperature rise is a necessary byproduct (or characteristic) of this design, are there superior materials for this purpose?

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We have members who are ** very ** good with numbers.

I'm thinking here of kbd512, in addition to Calliban who launched the current inquiry.

kbd512 recently experienced a power outage that lasted an extended period of time.

He reported to us in another topic that the system that he had hoped would provide power for a refrigerator to keep medicine secure was unable to perform that needed service, because (it turned out) that Hurricane Beryl's remnants absorbed sunlight before it could reach the solar panels at his home.

A mechanical battery might be able to provide 2 kw of power for a week

What would be physical characteristics of such a system?

Could Calliban's suggestion serve for this purpose?

(th)

Thanks to RobertDyck for Post #3, with the image of the actual navigation instrument used in the Apollo missions and links to relevant information.

(th)

For GW Johnson!

Regarding "Weekly Reader" (which I remember from elementary school)...

(th)