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#51 Today 07:13:50
- Void
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- Registered: 2011-12-29
- Posts: 9,558
Re: Data Centers (Including Off World)
I decided to ask a strange question of my phones search engine this morning, and got an answer that I liked.
Query: "If falcon 9 second stage would be refilled in orbit, how much delta v would it have?"
Well even my search engine on my computer had something to say that looks useful, instead of it telliing me I asked a stupid question. Quote:
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Delta‑V for a Refilled Falcon 9 Second Stage
If the Falcon 9 second stage were to be refilled in orbit (e.g., with propellant from a tanker or in‑orbit refueling system), the total ΔV budget would be the sum of the stage’s original ΔV and the ΔV from the added propellant.Current Falcon 9 Second Stage ΔV
For a typical Falcon 9 Block 1.2 (Full Thrust) mission to a low Earth orbit (LEO) with nominal payload, the second stage’s ΔV is about ~4,500–4,600m/s launchercalculator.com+1. This is the velocity change it can provide from its initial propellant load.Adding Refill Propellant
The Tsiolkovsky rocket equation shows that ΔV scales logarithmically with mass ratio:is the effective exhaust velocity (≈3,400m/s for Merlin‑1D in vacuum) and
m
initial
is the total mass after refill.If you add a significant amount of propellant (e.g., 10–20tonnes), the ΔV gain is not linear — it’s the logarithm of the mass ratio. For example:
Adding 10tonnes to a 17tonne stage could add ~100–150m/s ΔV.
Adding 20tonnes could add ~150–200m/s ΔV.
Larger refills (50–100tonnes) could add 300–500m/s or more, but practical limits apply due to structural, thermal, and mission constraints.
Total ΔV Example
If the original second stage ΔV is 4,500m/s and you add 20tonnes of propellant:Total ΔV ≈ 4,650–4,700m/s (small gain, but enough for some mission flexibility).
With 50tonnes added, Total ΔV ≈ 4,800–4,900m/s — still below the ~9.4km/s needed for ISS, but could enable higher orbits or more maneuvering.
Practical Considerations
Structural limits: The stage’s tanks and structure have a maximum propellant capacity.Thermal management: Refilling in orbit adds complexity for heat rejection.
Mission profile: Extra ΔV must be used efficiently; excess propellant in LEO is costly to return.
Propellant type: If using a different propellant (e.g., methane/LOX),
v
e
changes, affecting ΔV.Bottom line: A Falcon 9 second stage with a 20tonne refill might gain ~150m/s ΔV, bringing total ΔV to ~4,650m/s, while a 50tonne refill could push it to ~4,800–4,900m/s launchercalculator.com+1. The exact number depends on the refill mass and the stage’s initial mass ratio.
My phone said: "If the Falcon 9 second stage were refilled in orbit, it would have approximately 10 to 11 km/s of delta v. available with an empty payload fairing.
"
Now, I am wondering about water in orbit and Hydrogen electric thrusters.
Query: "Hydrogen electric space thrusters?"
Quote:
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Hydrogen-Based Electric Space Thrusters
Hydrogen-based electric thrusters are a class of spacecraft propulsion systems that use hydrogen as a propellant, but instead of burning it chemically, they electrify and accelerate it using electric or electromagnetic fields. This approach combines the high specific impulse of electric propulsion with the high energy density of hydrogen.How They Work
In electric propulsion, an electric or magnetic field accelerates charged particles (ions or plasma) to produce thrust. Hydrogen thrusters can be:Ion thrusters: Ionize hydrogen gas and accelerate the ions using electrostatic grids or electromagnetic fields Wikipedia.
Hall-effect thrusters (HETs): Use a magnetic field to confine electrons, which ionize hydrogen and accelerate the ions through a cross-field electric field www.urathrusters.com+1.
Pulsed plasma thrusters: Use short bursts of plasma to generate thrust, sometimes with hydrogen as the working gas Wikipedia.
These systems operate in the vacuum of space, where they can run for months or years on relatively small propellant masses, making them ideal for long-duration missions.
Advantages
High specific impulse: Much more propellant-efficient than chemical rockets, enabling large velocity changes with small propellant mass Wikipedia.High energy density: Hydrogen offers the highest mass-to-energy ratio of common propellants, allowing long mission durations.
Flexibility: Can be used for station-keeping, orbit transfer, and deep-space navigation.
Sustainability: In hybrid systems, hydrogen can be generated on-demand via electrolysis, reducing the need to carry large pre-filled tanks www.urathrusters.com.
Examples and Applications
URA Thrusters’ HYDRA system: A hybrid propulsion system that electrolyzes water to produce hydrogen and oxygen, feeding them into a bi-propellant Hall-effect thruster (HET) for electric propulsion. This allows both high-thrust and high-specific-impulse modes, with propellant generated from water, making it adaptable for missions requiring rapid trajectory changes www.urathrusters.com.NASA and ESA missions: While most use xenon, hydrogen-based electric thrusters are being explored for future missions where hydrogen’s energy density is advantageous.
Game simulations: In Space Engineers, hydrogen thrusters are modeled as high-thrust, versatile engines that work in both space and atmosphere, often paired with ion thrusters for hybrid performance spaceengineers.fandom.com.
Challenges
Low thrust: Electric thrusters produce small thrust, so they are unsuitable for launch from Earth’s surface Wikipedia.Power requirements: High specific impulse comes at the cost of needing significant electrical power.
Complexity: Hydrogen handling requires careful storage, pressurization, and safety measures.
Outlook
Hydrogen electric thrusters are a promising technology for future deep-space missions, satellite station-keeping, and in-space refueling. Advances in electrolysis-based propellant generation and high-power spacecraft systems will likely expand their role in sustainable, flexible space propulsion www.urathrusters.com+1.
So, I conclude that if we were to build a new ISS in orbit of Earth the proper thing to do would be to bring water to it, and to crack the water and store the Oxygen and use the Hydrogen to maintain orbit against atmospheric drag.
While it existed the water would reduce radiation exposure inside the station and Oxygen would be easier to store as LOX in low Earth orbit than Hydrogen.
So, periodically you would have a batch of LOX that you would use to refill for deeper space missions.
But I believe that RP-1 is more storable than Hydrogen or Methane. And it would also provide radiation protections.
>>>>>>
We may be beyond the practices of the ISS. But what if we could build something like that an host Training Data centers in orbit?
I have read that Inference can go to orbit but that radiation exposure will make Training Data Centers not practical in orbits. But if you shielding them with Water and RP-1, then could it become practical?
With water then you could crack a stream of Hydrogen and use it for thrust immediately and also cook up LOX to store.
Stored RP-1 would provide additional radiation protections.
Query: "Why can space data centers do Inference and not training compute?"
Qkuote:
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Why Space Data Centers Focus on Inference, Not Training
Space-based data centers are currently more suited to AI inference than to model training because of the energy, cooling, and infrastructure constraints of operating in orbit.1. Energy demands differ between training and inference
Training requires massive, sustained power to update model weights through backpropagation. Modern large language models (LLMs) can consume gigawatts of compute and tens of terawatt-hours annually Forbes.
Inference is far less power-hungry per request — it’s about running a fixed model to produce outputs (e.g., chatbot responses). Scaling inference is more efficient than scaling model size, and workloads can be distributed across many small nodes Forbes.
In space, where solar power is six times more intense than Earth’s best deserts www.moduledge.com, inference workloads can be sustained with smaller, more numerous satellites, each powered by compact solar arrays.
2. Cooling and thermal management
On Earth, cooling is a major cost driver, requiring large HVAC systems and water. In space, the cold of the vacuum can be used for radiative cooling, but there’s no air to carry heat away www.moduledge.com.
Training GPUs generate heat that must be dissipated continuously, which is harder in microgravity and with limited space. Inference GPUs can run at lower sustained loads, making them easier to cool in orbit.
3. Infrastructure and deployment constraints
Training requires rack-scale, high-density hardware with extensive cabling, power distribution, and cooling infrastructure — all of which are difficult to fit into a satellite.
Inference can be run on smaller, modular GPU units that can be integrated into a mesh of satellites, forming a distributed cloud IEEE Spectrum.
Early space data center prototypes (e.g., Starcloud’s 1kW satellite with 5 GPUs) have already run inference workloads like Gemini McKinsey & Company, but not large-scale training.
4. Economic and operational trade-offs
Launch costs are extremely high — Falcon 9 is ~$1,400/kg Forbes. Training workloads are so power-intensive that the cost of moving them to space may not justify the savings.
Inference workloads can be distributed across many small satellites, reducing per-node cost and enabling rapid scaling Forbes.
In space, “real estate” is effectively limitless, so inference can be deployed in a constellation without land-use or permitting issues Forbes.
In short:
Space data centers can run inference because it’s less power-hungry, easier to cool, and more modular than training. Training’s extreme energy and cooling needs, plus the complexity of terrestrial-scale infrastructure, make it impractical for current space-based systems. Inference is the “lighter” workload that can leverage space’s abundant solar power and distributed architecture without breaking the physics or economics of orbital computing Forbes+1.
So, I feel that with heat pump technology you could turn a water filled tank into a radiator. The water tank as well as RP-1 would provide radiation protection for compute of either type.
A solar (Or nuclear) power supply would have two primary tasks. 1) Support Compute. 2) Crack H20, and produce thrust with H2, and make and store LOX.
If you have stored LOX, then you can refill any ship that uses Oxygen. RP-1, Methane, Hydrogen.
I feel that the process of using Water and RP-1 in association with data centers may have sufficient value that the byproduct "LOX" in orbit will be worth the trouble.
Water is relatively benign as a Cargo, and RP-1 has a long history of being managed successfully in the aircraft industry. It is not as exotic as is Hydrogen or Methane as a fuel.
Instead of dumping used Falcon 9 2nd stages into the atmosphere, I suggest their reuse in orbits. It may even make sense to bring fresh 2nd stages to orbit in Starship.
Further, if you could create a new version, where the engines could be changed our easily you could overcome the problem of coking and use them many times.
Yes the Merlin is less efficient than the Raptors, but it is not as much of a fussy baby.
Ending Pending 
Last edited by Void (Today 07:50:01)
Is it possible that the root of political science claims is to produce white collar jobs for people who paid for an education and do not want a real job?
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#52 Today 09:04:19
- Void
- Member
- Registered: 2011-12-29
- Posts: 9,558
Re: Data Centers (Including Off World)
I want to continue off of the just previous post I made today.
What if a logic could be established where you used a Merlin engine "X" number of times and then you melted it into propellants for a Neumann Driver or Magdrive propulsion system?
And then if you could plug a new Merlin engine on you do again.
So you would be reusing light weight Falcon 9 2nd stage tankage made primarily of a Aluminum/Lithium alloy?
You might daisy chain multiple instances of Falcon 9 2nd stages together to make a long ship.
The two ideas about how the Raptor is better than a Merilin are:
1) Raptors do not coke up as much.
2) Raptors are more efficient.
You can solve #1 by simply melting the engine into propellants for metal propellant drives.
You might be able to convert a Merlin to be full flow like a Raptor, since SpaceX already knows how to do that with Raptors.
So then you would have efficiency and relative reuse of the Falcon 9 2nd stages. (Just change out the engine periodically).
Materials like RP-1 and Water could be stockpiled in Lunar proximate situations such as "L1", "L4", "L5" and have a kitchen cool up LOX and then you would have a refilling station.
IF you used the Hydrogen from the water to move this setup it might be a very efficient way of providing for spacecraft interchanges.
Ending Pending
Last edited by Void (Today 09:12:36)
Is it possible that the root of political science claims is to produce white collar jobs for people who paid for an education and do not want a real job?
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