The key to Spacex reusable rockets, at least for the first stage, is the difference in speed. “It really comes down to what the staging Mach number would be,” Musk says, referencing the speed the rocket would be traveling at separation. “For an expendable Falcon 9 rocket, that is around Mach 10. For a reusable Falcon 9, it is around Mach 6, depending on the mission.” For the reusable version, the rocket must be traveling at a slower speed at separation because the burn must end early, preserving enough propellant to let the rocket fly back and land vertically. This also makes recovery easier because entry velocities are slower. However, the slower speed also means that the upper stage of the Falcon rocket must supply more of the velocity needed to get to orbit, and that significantly reduces how much payload the rocket can lift into orbit. “The payload penalty for full and fast reusability versus an expendable version is roughly 40 percent,” Musk says. “[But] propellant cost is less than 0.4 percent of the total flight cost. Even taking into account the payload reduction for reusability, the improvement is therefore theoretically over a hundred times.” A hundred times is an incredible gain. It would drop cost for Musk’s Falcon Heavy rocket—a scaled-up version of the Falcon 9 that’s currently rated at $1000 per pound to orbit—to just $10. “That, however, requires a very high flight rate, just like aircraft,” Musk says. “At a low flight rate, the improvement is still probably around 50 percent. For Falcon Heavy, that would mean a price per pound to orbit of less than $500.”
water-electrolysis propulsion system for 3U CubeSats is proposed that could fill the gap in the available propulsion systems at this scale. Combining the advantages of electric propulsion with those of chemical rockets, the system is safe both to handle and to launch; it is lightweight, and it is capable of providing roughly 1000 meter per second, enough delta V to reach lunar orbit from GTO. The efficiency of the proposed technology is at least 75% for Cornell’s prototype system, consisting of Ni electrodes and 0.5 M KOH as electrolyte. With over 1 km/s of ΔV from 1 kg of water as propellant, sample missions include compensating for drag, orbit raising and lunar exploration. Cubesats could go all around the EArth-moon system (cislunar) and over to near earth asteroids. and through gravitation manifolds perhaps around the solar system.
NASA has a nuclear-propulsion project with a budget of US$3 million. Nuclear power and propulsion came high on the list of recommended technologies in an NRC report. This could mean bigger future budgets for nuclear propulsion
The Lithium Lorentz Force Accelerator (LiLFA) as one of the most promising candidates for planetary exploration and heavy payload orbit raising missions. It can have an exhaust velocity of 50 km/second and a thrust density of 100,000 newtons per square meter
In an interview with Sander Olson, fission propulsion advocate Tabitha Smith argues that fission rockets could be rapidly developed and become the enabling technology for opening up the solar system for human exploration. Tabitha is in charge of the Bifrost project
Brian Wang is a Futurist Thought Leader and a popular Science blogger with 1 million readers per month. His blog Nextbigfuture.com is ranked #1 Science News Blog. It covers many disruptive technology and trends including Space, Robotics, Artificial Intelligence, Medicine, Anti-aging Biotechnology, and Nanotechnology.
Known for identifying cutting edge technologies, he is currently a Co-Founder of a startup and fundraiser for high potential early-stage companies. He is the Head of Research for Allocations for deep technology investments and an Angel Investor at Space Angels.
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