Motherships and Rocketships

Satellites today are launched via booster rocket from a limited number of ground facilities, which can involve a month or longer of preparation for a small payload and significant cost for each mission. Launch costs are driven in part today by fixed site infrastructure, integration, checkout and flight rules. Fixed launch sites can be rendered idle by something as innocuous as rain, and they also limit the direction and timing of orbits satellites can achieve.

__ Airborne Launch Assist

Burt Rutan's Stratolaunch

The Stratolaunch system, which is currently in development, is a collaboration between billionaire Paul Allen, aerospace legend Burt Rutan and former NASA Administrator Mike Griffin. The company is constructing a massive new carrier aircraft to hoist heavier payloads into orbit on air launched rockets.

An air launch, where the rocket is dropped from an air-breathing mothership that’s borne aloft by wings and aerodynamic principles instead of pure thrust, tends to be vastly cheaper than a ground launch.

By using the lowest and thickest part of the atmosphere to lift the wings of the mothership, instead of forcing the sheer power of the rocket to push through it itself, you can save on a lot of fuel (and thus, money). And by cutting out the first and hardest 40,000 feet of the atmosphere using an air-breathing-mothership-and-drop approach, you can cut potentially millions from you budget…

… if you’ve only got something small that needs to go into space, it’s hard to beat the mothership approach. Air launch systems have other advantages too, such as the ability to launch from practically any runway, thereby avoiding weather that could delay a ground launch, as well as launching the rocket in any direction. Perhaps most importantly, the mothership itself is reusable, meaning a big portion of the launch system’s architecture doesn’t have to be built from scratch every time. For smaller payloads, motherships represent the future of space travel.

__ Motherships Proliferate

Burt Rutan has some ideas about making motherships much larger, in order to launch ever larger payloads into virtually any type of orbit possible from Earth.

DARPA is developing a more modest and versatile form of airlaunch spacecraft that can be launched from an F-15E fighter jet.

The goal of ALASA is to develop a significantly less expensive approach for routinely launching small satellites, with a goal of at least threefold reduction in costs compared to current military and US commercial launch costs. Currently, small satellite payloads cost more than $30,000 per pound to launch, and must share a launcher with other satellites. ALASA seeks to launch satellites on the order of 100 pounds for less than $1M total, including range support costs, to orbits that are selected specifically for each 100 pound payload.

Several entities are developing airlaunch assist vehicles, including Virgin Galactic, Stratolaunch, Orbital, the US Air Force, and several more.

NASA is also interested in developing private contractors for launching multiple small payloads via ground launch:

NASA has awarded a total of $17.1 million to three companies to launch miniscule cubesats, which to date have had to tag along as secondary payloads on big rockets.

The space agency gave $6.9 million to Los Angeles-based Rocket Lab USA; $5.5 million to Firefly Space Systems of Cedar Park, Texas; and $4.7 million to Virgin Galactic LLC of Long Beach, California, in three separate, fixed-price “Venture Class Launch Services” (VCLS) contracts. [Cubesats: Tiny, Versatile Spacecraft Explained (Infographic)]


Elon Musk’s SpaceX is attempting a comeback from a disastrous launch explosion earlier this year:

Jeff Bezos’ company Blue Origin is still perfecting its launch system:

The “Dream Chaser” is proceeding with its novel approach:

United Launch Alliance is becoming a reliable go-to contractor for critical larger payload launches

Heavy Launchers are on the way. NASA, SpaceX, ESA, Russia, and others are developing heavy lifters in preparation for larger scale development in space.

Upcoming space conference:

The permanent development of cis-lunar space makes more sense as a launchpad to other planets beyond the Earth – Moon system . First learn to crawl, then walk, then run, then fly. Space is a dangerous and alien environment. Long-distance manned missions beyond cis-lunar space seems a bit premature at this time. Logistics and supply lines . . .

Cis-lunar fueling stations for Mars missions

The Lunar Space Elevator

Space Radiation Counter-Measures

More space topics and links from Selenian Boondocks

Hibernation via cryonic sleep for deep space missions

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2 Responses to Motherships and Rocketships

  1. Bob Wallace says:

    Too bad we didn’t do with Project Orion right at the beginning.

  2. gbaikie says:

    —An air launch, where the rocket is dropped from an air-breathing mothership that’s borne aloft by wings and aerodynamic principles instead of pure thrust, tends to be vastly cheaper than a ground launch.

    By using the lowest and thickest part of the atmosphere to lift the wings of the mothership, instead of forcing the sheer power of the rocket to push through it itself, you can save on a lot of fuel (and thus, money). And by cutting out the first and hardest 40,000 feet of the atmosphere using an air-breathing-mothership-and-drop approach, you can cut potentially millions from you budget…—

    I generally like the idea of using motherships, but I think there alternative ways of getting spacecraft out of the the atmosphere.
    A problem with mothership is the practical limitation of it’s payload [the rocket and it’s payload that the Mothership is lifting]. If 20 tons or less it’s doable but if it’s say 50 tons it’s quite problematic.
    With a conventional chemical rocket, the first stage is designed to get the rest of the rocket into orbit- achieves velocity of around Mach 6 and passes thru Q max [maximum dynamic pressure] which generally above 40,00 feet.
    Most of the mass of these rockets in in the first stage. A Falcon 9’s first stage is about 400 tons, and payload and second stage is close to 100 tons and first stage achieves about 2 km/sec and rest of rocket does the remaining 6 km/sec. Falcon-9 has 9 engines in first stage, and 1 rocket engine of same size powering the second stage.
    Most of the mass of the first stage is the oxygen part of of the rocket fuel [LOX- liquid oxygen] and with a mothership instead lifting LOX, it gets the oxygen from the atmosphere- so mothership doesn’t have to takeoff with 300 tons of LOX.
    It should be noted that LOX is fairly cheap- about $50 per ton. So first stage might use about $15,000 of LOX, whereas the engines might be about 1 million dollars for each- though the aspect of cost of large amount of rocket fuel use, is one using more engine power- half the rocket fuel mass is roughly half the amount engine power
    needed, and how large the tanks are and it’s plumbing is not significant cost.
    And mothership reuse their engine, and rockets have not done this, yet [well, some engines of the Shuttle were refurnished and reused- but most of rocket power of the shuttle’s “first stage” was it’s solid boosters].
    Anyhow, my idea of getting rocket out of the atmosphere is accelerate rocket by a modest amount- say to 100 mph, and having rocket accelerated vertically.
    And to have a launchpad in the ocean.
    And this way of launching a rocket can boost any size rocket.
    So rough comparison, mothership launches from 50,000 ft, launches at say 500 mph and at say 45 degree angle and rocket launched is about 20 tons vs launching from about 500 to 1000 feet
    and 100 to 200 mph, starts vertical and it can be 50 to 1000 tons [or is Sea dragon or whatever].
    Now I call it a pipelauncher because it’s a pipe- a large and tall pipe. It works by using buoyancy of water- it’s sort of a boat- if you call something which travels vertically in the water rather across the water as a boat. Such a boat has been made- sort of. It travels horizontally, and parks vertically. It’s called Flip. Video:

    So a pipelauncher would be bigger than FLIP, though close to it’s tonnage of 700 tons.
    And whole idea is to lift a rocket upwards rather than stay in the water vertically. Pipelauncher
    would be towed location, horizontally, and then deploy to be vertically and mostly just a pipe, which has way to add air to inside the pipe. So has open pipe at it’s bottom and it’s capped at
    the top, and to rocket is put on top of it. Add a lot of air, and pipe and rocket on top of it goes up.
    And best way to add enough air is to use liquid air. The water inside the pipe would vaporize the the liquid nitrogen and oxygen, but to use less air, one also heats the air. Sort like using a flame thrower pointed downward into the pipe. So roughly use 100 gallon of fuel [kerosene, natural gas, or whatever] and tens of tons of liquid air. And the temperature of air inside pipe could be say, -100 C to 100 C. And this range of temperature of the air is over a time period of 10 seconds
    or more [or not enough time to warm or cool the pipe itself by much- one could also spray water on the pipe to prevent colder than 0 C or warmer than 100 C, but such a need if required would only be limited to small portion of the pipe].
    Now pipelauncher would limited in terms of how fast one could accelerate a rocket. One aspect related to this is few things travel at supersonic speeds in water. And other aspect is that larger speeds require more length or pipe and/or faster acceleration.
    So the distance involved [and pipe length must be in the water accelerate] is for example:
    5 m/s/s in 10 seconds is 250 meter distance and 50 m/s [111.6 mph]
    10 m/s/s in 5 seconds is 125 meter distance and 50 m/s
    10 m/s/s in 10 seconds is 500 meter distance and 100 m/s.
    So 1 gee acceleration is 9.8 m/s/s and it doubles the weight of pipelauncher and rocket it’s lifting.
    And 19.6 m/s/s triples the weight. But lifting a lot weight is not much of problem.
    A typical rocket blast off with less than 9.8 m/s/s, even less than 5 m/s/s of acceleration and how acceleration a rocket can withstand is a bit of an issue, but the acceleration from a pipelauncher can be constant. Or if one wanted exactly 10 m/s/s for 5 seconds, you could operate it to achieve such constant and uniform acceleration. unlike rocket launches which can be bumpy with vibration- particularly true with solid rockets, and such a bump ride would be added spikes of positive and negative acceleration.
    Another issue is do you want the pipelauncher to leave the water- or it’s train going upward, do want to stop before it’s speed carries it out of the water- if so one needs the pipe longer than whatever distance is need for the vertical acceleration.
    And finally do want to design pipelauncher to lift any kind of rocket, or design it for specific rocket or class of rockets.
    But roughly speaking if one want modest acceleration attain about 100 mph and say rocket which weighs more than 500 tons, the pipe going to be about 200 meters long and 15 to 20 meters in diameter, and using say marine aluminum and pipe wall thickness of 1/4 to 1/2″ thick.
    And/or it going to weigh about 500 or more tons.
    As for costs, steel would be about $+1000 per ton, marine aluminum is about $+3000 per ton
    so cost to make pipelauncher should less than 5 million. And one is not going to get a mothership for less than 50 million. And you probably can’t build launch pad on land for less than 5 million dollars. Or NASA spends somewhere more than 100 million for each of it’s launch pads.
    So in terms of costs of big pipes [made in shipyard] if less than say 500 meter long, it’s fairly cheap. Or shipyards are designed to make big things and it has labor force nearby which does this type of construction. So one is essentially making an unusual hull of a boat and infrastructure
    to do this all over the world. Or South Korea is largest shipbuilder in the world, and could get it
    built in South Korea.
    So question is how does a 500 tons rocket launched at [50 m/s/] 100 mph say 100 meter above the water compare to mothership which launches 20 tons at 250 m/s 500 mph and at 15000 meter.
    In terms of energy KE = 1/2 mass times velocity square. So it’s 645 million joules vs 645 million joules of KE. Hmm I thought mothership would be more. Anyway mothership is less massive, the biggest is Stratolaunch:
    “This would make it the largest airplane, by wingspan, to ever fly. It will weigh in at over 540,000 kg (1,200,000 lb) including the fully fueled launch vehicle and will require a runway at least 12,000 feet long.”
    Again more similar than I thought
    So mothership can fly anywhere in the world [though I imagine it needs launch range like any rocket launch]. And pipelauncher probably launch from the equator- though it also could launched anywhere in the oceans of the world, though require a few weeks to drag it someplace, rather than hours to fly there.
    Now a rocket blasting off from a land launch pad requires more than 10 second to reach 100 mph.
    A falcon 9’s first stage burns it’s engines for 170 seconds going thru about 340 tons, or 2 tons
    per second, 20 tons in 10 second. about 2/3 LOX and 1/3 kerosene. Or:
    LOX Mass 276,600kg
    RP-1 Mass 119,100kg
    A mothership would burn about 10 tons of fuel
    Pipelauncher would use about 40 tons liquid nitrogen and 10 tons of LOX [liquid air] and around 200 kg of some kind of fuel, say natural gas/propane.

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