Ocean-based launch:
extending a successful approach
to new applications
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by Andrew E. Turner
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The forgiving water launch infrastructure permits conscious relaxation of launcher reliability as a path to even lower launch cost for payloads that are easily replaceable and thus can tolerate some launch failures. This thinking gave rise to the Aquarius launch vehicle concept previously discussed here (See “The myth of heavy lift”, The Space Review, May 17, 2004, and “Low-cost launch and orbital depots: the Aquarius system”, The Space Review, January 30, 2006). Aquarius will ferry low-cost, replaceable supplies of water, air, food, and propellant to the International Space Station and propellant to other satellites, permitting higher-cost launchers to carry large spacecraft to orbit with nearly empty propellant tanks that will be topped off in space. This large, novel low-cost vehicle can also ferry low-cost small spacecraft to orbit economically, which can easily be produced in excess quantities to make up for losses due to the significant Aquarius launch failure rate. Three R’s: recovery, retrieval and reuseFor sounding and test rocket missions, floating launch
and recovery is attractive. Retrieval of the vehicle, sensor, and test
article payloads for analysis and re-launch is relatively easy, with no
obstacles and terrain problems between the mission crew and the recovery
site. The rockets are far smaller than the multi-stage Sea Launch Zenit-3SL
booster, facilitating handling of the vehicles using small ships and cranes.
The forgiving water launch infrastructure permits conscious relaxation of launcher reliability as a path to even lower launch cost for payloads that are easily replaceable and thus can tolerate some launch failures. Launching the recoverable, easily refueled, reusable liquid-fuel sounding rocket from a floating condition avoids the need for a specialized, durable launch platform, provided payloads are low-cost. This eliminates a potential need for payload removal in the event of a launch scrub, which was a safety showstopper for the US Navy’s Sea Launch and Recovery (SEALAR) program in the 1990s, which involved floating launch and water landing. With proper design, “landing” in the water at modest velocities is benign, and supports rapid recovery and reuse with no need for refurbishment due to ground impacts. This could enable multiple flights per day for research rockets. The use of floating launch and water recovery would have prevented the loss of Armadillo Aerospace’s Pixel vehicle on October 21, 2006 and the loss of the DC-X ten years earlier. Both of these craft tipped over when flying at low altitude and suffered hard impacts with the ground that caused irreparable damage. On the other hand, the US Navy’s Hydra 1 vehicle was permitted to fall from a significant height into the lagoon at Pt. Mugu, California after a successful floating launch on March 18, 1960 and was subsequently retrieved and re-flown. Hydra 1’s straight up and down flight was enabled by floating launch: if it had been launched from a platform, it would have a suffered a catastrophic collision with the platform following descent. Pelican: resuming floating launch researchSpace Systems/Loral (SS/L), in cooperation with its partners
Interorbital Systems, Microcosm, Professor Robert Twiggs and his laboratory
at Stanford University, and Capt. John E. Draim, USN (Ret.), has submitted
a proposal for US Government funding for the development of Pelican, a
small liquid-fueled reusable floating launch sounding rocket. Unlike nearly
all of today’s sounding rockets, Pelican will be easily refueled and re-launched
within a short span of time without replacing any part of its structure
or requiring extensive servicing. While Pelican would initially demonstrate
the flight stabilization concept that enables large floating launch vehicles
like Aquarius, it could become a useful research and operational vehicle
in its own right.
Unlike nearly all of today’s sounding rockets, Pelican will be easily refueled and re-launched within a short span of time without replacing any part of its structure or requiring extensive servicing. Interorbital Systems would build and fly this vehicle; it holds an FAA license to perform floating launches from the Pacific and has flown a number of land-based sounding rockets from the Mojave Desert. The new problem of maintaining guidance and control of a vehicle which is sufficiently “tail-heavy” to float stably when it is upright in the water and yet must fly in this aerodynamically unstable orientation through the atmosphere will be addressed by SS/L and Prof. Twiggs’ team. SS/L holds a US patent on the forward-and-aft controller that will be used to actively stabilize Pelican during flight. Microcosm has extensive sounding rocket experience from its Project Scorpius, including vehicle structure from its composite materials development program. Pelican paves the way to responsive launch of re-usable sounding rockets, which can achieve altitudes in near-Earth space far more rapidly than balloons or aircraft, returning samples or test articles to the ground in a matter of minutes. ConclusionWe have discussed several ways forward involving ocean-based
launch in this article, from the proven platform-launched high-end Sea
Launch Zenit-3SL, capable of carrying top-of-the-line commercial telecommunications
satellites, down to low-cost reusable sounding rockets and low-cost launch
of supplies and other replaceable payloads. Sea Launch’s previous success
in launching five large geosynchronous spacecraft in 2006 rivals the success
rate of all other commercial launchers. Pelican and Aquarius pave the way
to platform-less floating launch of low-end payloads for atmospheric research,
reusable sounding rockets, and the eventual economical launch of supplies
and low-cost microsats. Launch rates for these new vehicles will be far
higher and schedules more flexible and responsive than any launcher in
place today, supporting broader and more beneficial use of space.
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