Kimbo-II

Highlights: Incorporated regulate pressure system.

The Kimbo-II flight team successfully launched the Kimbo-II vehicle on Saturday August 1st, 1998 at the Reaction Research Society's Mojave Test Area.

Click here to view more pictures of Kimbo-II.

More details below.

The Kimbo-II vehicle consisted of the refurbished Kimbo-I with several major modifications. The principal design change involved the addition of a regulated gaseous Helium pressurization system which maintained relatively constant propellant tank and engine chamber pressures. This in turn enabled more complete propellant loading and produced a stable thrust at near the design level of 500 lbf (by contrast, the K-I thrust decayed by nearly 50% as the ullage pressures in the propellant tanks decreased from 390 to 145 psi during the burn). Two other upgrades included the addition of three pressure sensors for monitoring conditions prior to launch and the change to an externally-activated main valve system. The overall impact was an increase in length to 19 feet (three more than the Kimbo-I) and a three to four improvement in total impulse.

Because most of the core Kimbo-I components survived the hard landing, the team was able to repair it and implement the Kimbo-II upgrades in the relatively short period of three months. It also felt confident enough to skip a static fire and proceed directly to a flight attem pt. Their efforts produced a successful launch of the Kimbo-II on 1 August 1998, using Vertical Test Stand-1 in place of the 60-ft launch rail employed for Kimbo-I.

In contrast to the K-1 flight, the winds at the MTA were dead calm under the hot (>100 F) August sun and the Kimbo-II flight straight up in a textbook launch. However, this time out the recovery system failed completely and the nosecone remained firmly attached to the front of the vehicle throughout the entire flight. The resulting ballistic trajectory ended in near transonic terminal velocity, with an impact point one mile southwest of the launch site. This time, most of the hardware was destroyed, including once again the data logger, so the best performance estimate is that the Kimbo-II approached its peak predicted altitude (close to 20,000 ft).

Despite the tremendous shock loads, the injector elements of the 500 lbf pintle engine survived and have subsequently been utilized in the Kimbo-III/IV projects. The 0.25 in stainless steel engine chamber wall did burn through - indicating a long burn and presenting a challenge to develop a more effective ablative liner for future vehicles.

Besides the obvious need for continued improvement in the recovery system, the Kimbo-II also highlighted the value of real-time data acquisition and computer-based remote control and monitoring. All of these issues (the ablative liner, recovery and instrumentation, as well as improved maintenance features) have been addressed in the follow-on Kimbo-III/IV vehicles.

One other noteworthy event at the MTA added to the already high level of excitement and drama on the Kimbo-II launch day. Shortly after the K-II flight, another amateur team attempted to simultaneously launch two zinc-sulfur "beta" rockets. In-flight failures led to burning pieces of rocket littering the ground several hundred yards outside of the launch compound. The extensive amount of dry grass on the desert floor (a product of the El Nino rains from earlier in the year) served as the ultimate kindling and a raging brush fire quickly got underway that ultimately burned several hundred acres of the desert. Fortunately, no one was hurt and property damages were minimal. Impacts included a delay of several hours in recovering the remnants of the Kimbo-II, as well as protracted legal discussions with local authorities. Between that and the K-II, it was quite a day.