In part 1 of Fricken Rockets Getting Boosted by Fricken Lasers we got some background on the concept of laser enhanced rockets. (If you haven't read it yet, I would suggest clicking here first)
Powering our Saturn 5's electric turbopumps is incredibly energy-intensive, requiring almost as much energy as the propellers on a nuclear carrier.* The variable that most directly impacts our turbopump's energy demand is the flow rate of the engines, the flow rate for the engines is dependent on the mass of the spacecraft. The bigger our spaceship, the more flow rate we need to keep the engines fed. The Saturn 5 was capable of transporting 140,000 kg to Low Earth Orbit for sake of comparison a SpaceX Falcon 9 Full Thrust is capable of transporting 22,800 kg to the same orbit**. The Falcon 9 Full Thrust uses its 9 Merlin Engines to achieve about 16.3% of the payload capacity of the Saturn 5. Each Merlin Engine has a massive turbopump supplying 7.5 MW of pumping capacity, meaning that the Falcon 9 FT needs about 67.5 MW of total pumping capacity. Observant readers, with probably insane levels of recall, might note that the Saturn 5's first stage pump requirements totaled 205 MW when we compare this to the Falcon 9 FT's 67.5 MW turbopump power we see that the Falcon has about 32.9% the total pump capacity of the Saturn 5. What the Falcon 9 has over the Saturn 5 in our energy concerns is that there is relatively more surface area for our lasers.
For our Saturn 5 calculations, we assumed that about half of the area of the first stage would be devoted to our power receivers, giving the lasers about 200 square meters of effective area to target. A Falcon 9 first stage is 42.6 meters tall and 3.6 meters in diameter, that means that if we covered the body of the first stage with collectors our lasers could reasonably expect an effective target area of about 75 square meters. This surface area is fantastic news laser boosted rockets while 75 meters is only about 38% of the area of the Saturn 5, the energy demand for the Falcon's pumps is only 32.9% of what the Saturn 5 needed. Using our 40% conversion efficiency, we can estimate that the rocket will need to receive 168.75 MW of energy from the lasers (67.5MW/0.4). The average peak flux of energy on the rocket would be 2.25 MW/m^2, or about 12% less than what the Saturn 5's receivers would need to handle.
Scaling down to the Electron rocket the math gets even more interesting. At 17 meters in total height and 1.2 meters in diameter, we can conservatively estimate the ability to have 6 square meters of receivers. These 6 square meters will need to supply up to 1 MW of power to the pumps, giving us 2.5 MW of laser energy needing to get to the rocket (1MW/0/4). For the Electron rocket the panels would only need to handle 416 kW/m^2 of flux (2.5MW/6m^2). While this isn't a small amount of energy, it is way more manageable than what would be needed for larger rocket launches.
By modeling three different sizes of rockets we can see that the smaller the rocket the smaller the energy overall needed to power the turbopumps. A combination of needing less energy for the turbopumps in tandem with increases with relative surface area gives an exciting opening for developing laser enhanced rockets, start small and build bigger as technology improves.*(3)
Developing laser Enhanced Rockets might follow a timeline something like this
Step 1
Wireless power transfer testing. Create a competition where teams are challenged on their ability to have a combination system capable of transferring Energy densities of over 400 kW/m^2 without exceeding design envelope for first stage rocket body simulant
Step 2
Wireless power transfer testing with moving targets
Winners of Step 1 and additional applicants will compete to wireless beam energy at sample liquid fuel rockets. These rockets will still use traditional turbo-pumps, teams are judged on their ability to continuously supply a set energy intensity to the rocket.
Step 3
Small Scale Pump testing
Competing institutions will be challenged to build liquid fuel powered sounding rockets with electric turbopumps. Scoring parameters might include factoring what percentage of power for the turbopump came from wireless energy sources.
Step 4
Moving into commercial development of electric turbopumps
Step 5 Launch a spacecraft where some of the power needed for launch comes from wireless energy
Step N
Next-generation laser enhanced competition, as energy densities of long range wireless power transfer increase to certain pre-determined values, organizations like NASA and DARPA have competitions where teams compete on their ability to propel rockets where some amount of direct thrust comes from heat provided by lasers.
(at this point I ramble a bit, feel free to keep reading, but I won't judge if your eyes just glaze over and you just decide to read something else)
Developing a laser enhanced rocket system will not be an easy undertaking, while the abstract principle is straightforward there are many risks to commercialization.
Cost of developing the laser platform will be the biggest challenge, our world is rife with innovations that came too late after market forces chose a solution.*(4) Theoretically, a laser enhanced rocket should be cheaper than a more conventional design in the real world this is not a guarantee. Getting laser enhanced rockets to the point where they can compete on cost will not be easy.
A best-case development scenario for laser enhanced rockets would come from a partnership of multiple space launch companies agreeing to implement the technologies mentioned above. Each partner organization would share the cost of the laser power base stations maintenance and upkeep.
Realistically for laser enhanced rockets to become a mainstream innovation the number of launches will need to increase drastically. Frustratingly for futurists, we need a large volume of launches from the same general geographic vicinity and for those launches to have a fairly similar first stage flight path. The more variation in launches the less useful our laser platforms would be (or more expensive as the lasers would need to cover more area). These realizations should not be treated as an absolute negative. For much of the commercial sector flexibility in space-craft orbits is incredibly useful, but for projects like sending missions beyond the Earth-Moon system, a standardized orbit isn't necessarily a bad thing. A standardized orbit and rendezvous location would allow for the development of an orbital dry dock facility. At this drydock fuel and materials could be stockpiled for future missions. Refueling and assembling in orbit could allow for much more flexible deep space missions, instead of requiring the first missions to Mars to produce all of their return fuel on Mars mission planners could take advantage of fuel stockpiles that built up as secondary payloads for other launches.
Another approach to improve the utility of laser enhanced rockets in the early stages is by creating an open standard booster stage and docking mechanism. These open standard boosters could supply additional early-stage power with a more narrowly defined flight path than a full first stage.
I hope you found this idea interesting, I know its a complicated topic, feedback and questions are welcomed.
*according to the Wikipedia article linked above, a Nimitz carrier's nuclear powerplant supplies about 260 MW of power to the propellers, vs our 205 MW of pumping power (some might say 78.8% isn't almost but I'm gonna, because finding analogous power requirements was wasting way too much time)
**okay so not like perfectly exact, this is because the Saturn 5 article lists its lift capacity for getting to an orbit of 170 km with an inclination of 30 degrees, on the flip side the Falcon 9 Full Thrust just lists low earth orbit and an inclination of 28.5 degrees (where low earth orbit isn't well-bounded) for those who want to crunch the numbers in greater detail to minimize the confusion on the comparison please feel free to let me know. That being said these numbers probably get us in the ballpark.
*(3) we shouldn't ignore the fact that turbopumps do in fact get more power-efficient as they get bigger. The Electron can only get about 200 kg into orbit less than 1% of what a Falcon 9 FT can get into orbit, at the same time, the Electron's pumps need about 1.48% of the power than the Falcon 9 does. Basically, Falcon 9's can move 48% more cargo per unit of pumping power (not a useful actual rubric but interesting)
*(4) this is along the lines of BetaMax vs VHS or BluRay vs HDDVD, not some kind of conspiracy
*(5) we are going to assume these panels are designed to be readily added to a rocket and have the appropriate mass properties
The best-case scenario for a country like the United States would be something like this.
The US Airforce in a continuing desire to increase launch cadence declares that launches must meet certain cost performance goals, to that end they offer affordable access to an Air Force owned power transfer station and a partnering business would supply the necessary panels*(5) to capture the energy required for launching. The added weight of these panels and the associated electrical sub-systems is offset by the improved fuel efficiency as more rocket fuel can be used to actually propel the spacecraft.
Without a government backing laser enhanced rockets, we are unlikely to see this technology hitting mainstream uses. The aerospace industry has sunk billions of dollars developing the rocket technology they use
Powering our Saturn 5's electric turbopumps is incredibly energy-intensive, requiring almost as much energy as the propellers on a nuclear carrier.* The variable that most directly impacts our turbopump's energy demand is the flow rate of the engines, the flow rate for the engines is dependent on the mass of the spacecraft. The bigger our spaceship, the more flow rate we need to keep the engines fed. The Saturn 5 was capable of transporting 140,000 kg to Low Earth Orbit for sake of comparison a SpaceX Falcon 9 Full Thrust is capable of transporting 22,800 kg to the same orbit**. The Falcon 9 Full Thrust uses its 9 Merlin Engines to achieve about 16.3% of the payload capacity of the Saturn 5. Each Merlin Engine has a massive turbopump supplying 7.5 MW of pumping capacity, meaning that the Falcon 9 FT needs about 67.5 MW of total pumping capacity. Observant readers, with probably insane levels of recall, might note that the Saturn 5's first stage pump requirements totaled 205 MW when we compare this to the Falcon 9 FT's 67.5 MW turbopump power we see that the Falcon has about 32.9% the total pump capacity of the Saturn 5. What the Falcon 9 has over the Saturn 5 in our energy concerns is that there is relatively more surface area for our lasers.
For our Saturn 5 calculations, we assumed that about half of the area of the first stage would be devoted to our power receivers, giving the lasers about 200 square meters of effective area to target. A Falcon 9 first stage is 42.6 meters tall and 3.6 meters in diameter, that means that if we covered the body of the first stage with collectors our lasers could reasonably expect an effective target area of about 75 square meters. This surface area is fantastic news laser boosted rockets while 75 meters is only about 38% of the area of the Saturn 5, the energy demand for the Falcon's pumps is only 32.9% of what the Saturn 5 needed. Using our 40% conversion efficiency, we can estimate that the rocket will need to receive 168.75 MW of energy from the lasers (67.5MW/0.4). The average peak flux of energy on the rocket would be 2.25 MW/m^2, or about 12% less than what the Saturn 5's receivers would need to handle.
Scaling down to the Electron rocket the math gets even more interesting. At 17 meters in total height and 1.2 meters in diameter, we can conservatively estimate the ability to have 6 square meters of receivers. These 6 square meters will need to supply up to 1 MW of power to the pumps, giving us 2.5 MW of laser energy needing to get to the rocket (1MW/0/4). For the Electron rocket the panels would only need to handle 416 kW/m^2 of flux (2.5MW/6m^2). While this isn't a small amount of energy, it is way more manageable than what would be needed for larger rocket launches.
By modeling three different sizes of rockets we can see that the smaller the rocket the smaller the energy overall needed to power the turbopumps. A combination of needing less energy for the turbopumps in tandem with increases with relative surface area gives an exciting opening for developing laser enhanced rockets, start small and build bigger as technology improves.*(3)
Developing laser Enhanced Rockets might follow a timeline something like this
Step 1
Wireless power transfer testing. Create a competition where teams are challenged on their ability to have a combination system capable of transferring Energy densities of over 400 kW/m^2 without exceeding design envelope for first stage rocket body simulant
Step 2
Wireless power transfer testing with moving targets
Winners of Step 1 and additional applicants will compete to wireless beam energy at sample liquid fuel rockets. These rockets will still use traditional turbo-pumps, teams are judged on their ability to continuously supply a set energy intensity to the rocket.
Step 3
Small Scale Pump testing
Competing institutions will be challenged to build liquid fuel powered sounding rockets with electric turbopumps. Scoring parameters might include factoring what percentage of power for the turbopump came from wireless energy sources.
Step 4
Moving into commercial development of electric turbopumps
Step 5 Launch a spacecraft where some of the power needed for launch comes from wireless energy
Step N
Next-generation laser enhanced competition, as energy densities of long range wireless power transfer increase to certain pre-determined values, organizations like NASA and DARPA have competitions where teams compete on their ability to propel rockets where some amount of direct thrust comes from heat provided by lasers.
(at this point I ramble a bit, feel free to keep reading, but I won't judge if your eyes just glaze over and you just decide to read something else)
Developing a laser enhanced rocket system will not be an easy undertaking, while the abstract principle is straightforward there are many risks to commercialization.
Cost of developing the laser platform will be the biggest challenge, our world is rife with innovations that came too late after market forces chose a solution.*(4) Theoretically, a laser enhanced rocket should be cheaper than a more conventional design in the real world this is not a guarantee. Getting laser enhanced rockets to the point where they can compete on cost will not be easy.
A best-case development scenario for laser enhanced rockets would come from a partnership of multiple space launch companies agreeing to implement the technologies mentioned above. Each partner organization would share the cost of the laser power base stations maintenance and upkeep.
Realistically for laser enhanced rockets to become a mainstream innovation the number of launches will need to increase drastically. Frustratingly for futurists, we need a large volume of launches from the same general geographic vicinity and for those launches to have a fairly similar first stage flight path. The more variation in launches the less useful our laser platforms would be (or more expensive as the lasers would need to cover more area). These realizations should not be treated as an absolute negative. For much of the commercial sector flexibility in space-craft orbits is incredibly useful, but for projects like sending missions beyond the Earth-Moon system, a standardized orbit isn't necessarily a bad thing. A standardized orbit and rendezvous location would allow for the development of an orbital dry dock facility. At this drydock fuel and materials could be stockpiled for future missions. Refueling and assembling in orbit could allow for much more flexible deep space missions, instead of requiring the first missions to Mars to produce all of their return fuel on Mars mission planners could take advantage of fuel stockpiles that built up as secondary payloads for other launches.
Another approach to improve the utility of laser enhanced rockets in the early stages is by creating an open standard booster stage and docking mechanism. These open standard boosters could supply additional early-stage power with a more narrowly defined flight path than a full first stage.
I hope you found this idea interesting, I know its a complicated topic, feedback and questions are welcomed.
*according to the Wikipedia article linked above, a Nimitz carrier's nuclear powerplant supplies about 260 MW of power to the propellers, vs our 205 MW of pumping power (some might say 78.8% isn't almost but I'm gonna, because finding analogous power requirements was wasting way too much time)
**okay so not like perfectly exact, this is because the Saturn 5 article lists its lift capacity for getting to an orbit of 170 km with an inclination of 30 degrees, on the flip side the Falcon 9 Full Thrust just lists low earth orbit and an inclination of 28.5 degrees (where low earth orbit isn't well-bounded) for those who want to crunch the numbers in greater detail to minimize the confusion on the comparison please feel free to let me know. That being said these numbers probably get us in the ballpark.
*(3) we shouldn't ignore the fact that turbopumps do in fact get more power-efficient as they get bigger. The Electron can only get about 200 kg into orbit less than 1% of what a Falcon 9 FT can get into orbit, at the same time, the Electron's pumps need about 1.48% of the power than the Falcon 9 does. Basically, Falcon 9's can move 48% more cargo per unit of pumping power (not a useful actual rubric but interesting)
*(4) this is along the lines of BetaMax vs VHS or BluRay vs HDDVD, not some kind of conspiracy
*(5) we are going to assume these panels are designed to be readily added to a rocket and have the appropriate mass properties
The best-case scenario for a country like the United States would be something like this.
The US Airforce in a continuing desire to increase launch cadence declares that launches must meet certain cost performance goals, to that end they offer affordable access to an Air Force owned power transfer station and a partnering business would supply the necessary panels*(5) to capture the energy required for launching. The added weight of these panels and the associated electrical sub-systems is offset by the improved fuel efficiency as more rocket fuel can be used to actually propel the spacecraft.
Without a government backing laser enhanced rockets, we are unlikely to see this technology hitting mainstream uses. The aerospace industry has sunk billions of dollars developing the rocket technology they use
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