Recent geopolitical events have seen a shift in emphasis on the part of the US Navy with regards to the reloading of missiles at sea. While this was a significant concern in the Cold War, the end of that conflict saw the capability abandoned, with the cranes installed on many early VLS ships being landed in the late 90s and 2000s. But the growing understanding that a war with China could involve massive expenditure of munitions without the ability to retreat and reload has made the issue once again salient. While the main plan is to use a transportable crane system on the deck of a receiving ship, this has competition from a far more ambitious system tested in secret last year.
The transportable crane system is tested aboard Chosin
By far the easiest way to transfer cargo between ships is vertical replenishment or VERTREP, where a helicopter moves the load. No need to come alongside or string lines, with all of the tactical implications that brings. But missiles are big and heavy enough that a VERTREP solution would only fit one or two at a time, and there would still be the problem of moving the missile canisters from the VERTREP area into the cells themselves. The new solution, developed under the codename Dipole Pyton, bypasses all of these problems by transferring the missiles directly, using a revolutionary upgrade to the rocket booster already needed to launch from a VLS cell. By replacing the traditional solid-fuel boost motor with a thrust vector controlled liquid rocket system, the munition can be flown to and landed vertically inside a specially-modified VLS canister on the receiving ship. This modified canister is expected to receive and fire up to 17 missiles before requiring maintenance ashore.
The idea originated at NSWC Hastings, who quickly sought help from the world leader in landing rockets vertically, SpaceX. The system, which has been tested with Tomahawk and SM-6 so far, replaces the standard solid booster used to launch the missile with a throttleable JP-5/Peroxide engine that both moves it from the ammunition ship to the destroyer's VLS and serves as the first stage when the missile is actually launched. The engine is an updated derivative of the De Havilland Super Sprite, which had a perfect safety record in RAF and British Airways service in the 1950s. On landing, the engine transitions to peroxide-only operation, and the resulting low-temperature exhaust is easily handled by the flame-handling system built into the VLS. The crew then merely has to refuel the booster using JP-5 already provided for the ship's helicopter and 85% hydrogen peroxide from a tank added for the purpose, then attach the connectors for power and data and run a brief self-test.1 On launch, the main difference is that the HTP/JP-5 mix burns somewhat cleaner than existing solid rockets. There has apparently been some discussion on the part of SpaceX of trying to fly the booster back to the ship for reuse, but the Navy does not appear particularly interested in this concept.
A De Havilland Super Sprite
The first tests were carried out ashore at NSWC Hastings, and then on a barge at the same facility, and appeared to confirm the viability of the system. SpaceX agreed to do most of the technical development, and an at-sea test was run late last year to transfer missiles from the test barge Carlos del Toro (YSR-1) to the destroyer William D Porter. Details of the results are still extremely sketchy, but it appears that the system worked well enough in very calm seas, but when tested in rougher water, things went less well, with a booster colliding with the VLS as it descended, causing a spill and fire that was put out without too much trouble. Fortunately, nobody was hurt, the occasional tendency of peroxide-jet fuel fires to violently explode didn't show up, and the missile was a test unit without a live motor, but this failure looks to have doomed Dipole Python. Things were made worse once engineers at other organizations began to look into it, and pointed out that hydrogen peroxide is rather unstable, and becomes corrosive to aluminum if contaminated by chlorides, which are difficult to avoid in the maritime environment. Also, the proposal to use the Mk 41's water deluge system to deal with any exothermic decomposition problems or fires would make it impossible to rearm ships equipped with the newer Mk 57 VLS, which lacks any sort of active cooling for the missiles onboard. Despite these problems, recent reports suggest that Dipole Python might have been resurrected for political reasons, although nobody expects it to actually bear fruit.
1 Thanks to John Schilling for helping me run down details of the rocket system. ⇑
Comments
It seems like extra strike capacity could be gained by repurposing SpaceX drone landing ships, at least if having the missiles land in the VLS tubes proves to be a problem.
Bean, you have overlooked the even more revolutionary Monopole Anaconda proposal. As I understand it, this was to remove the 8x8 VLS cluster entirely, leaving a large hole with sockets for connecting the electrical and fire control cables. The VLS cells themselves would be replace the upper stages and payload for a SpaceX Falcon 9 first stage, which would take off but instead of launching the upper stage just land within the deck cavity, delivering 64 ready to fire missiles in one go. With the lower trajectory and speed requirements there would even be enough residual fuel for an empty cluster to launch itself back to the mainland for reloading.
Two initial hurdles were the first cluster being launched into LEO orbit, the SpaceX engineers moving so fast they hadn't read past the first two pages of the requirements; and the USN demand that the fairing of the Falcon first stage be made square cross-section instead of round so that it fitted neatly into the cavity without rebuilding the ships.
Sadly the project was abandoned after ship captains complained that they "couldn't see a god-damn thing" from the bridge due to the first stage being in the way, although there just might have been some top-weight concerns as well.