SpaceX is Developing a Reusable VTVL Rocket

SpaceX's test site in McGregor, Texas. (Credit: SpaceX)

Via my friend Clark Lindsey over at HobbySpace comes some rather startling news:

SpaceX is developing an 106-foot tall reusable vertical takeoff and vertical landing (VTVL) rocket called Grasshopper based upon the first stage of the Falcon 9 rocket.  It has applied for an experimental permit to conduct a series of flights up to 11,500 feet at its engine testing facility in McGregor, Texas.

Here’s the description of the vehicle and its flight profile from a draft environmental impact assessment released by the FAA earlier this week:

The Grasshopper RLV consists of a Falcon 9 Stage 1 tank, a Merlin-1D engine, four steel landing legs, and a steel support structure. Carbon overwrapped pressure vessels (COPVs), which are filled with either nitrogen or helium, are attached to the support structure. The Merlin-1D engine has a maximum thrust of 122,000 pounds. The overall height of the Grasshopper RLV is 106 feet, and the tank height is 85 feet.

The propellants used in the Grasshopper RLV include a highly refined kerosene fuel, called RP-1, and liquid oxygen (LOX) as the oxidizer. The Grasshopper RLV has a maximum operational propellant load of approximately 6,900 gallons; however, the propellant loads for any one test would often be lower than the maximum propellant load. Even when the maximum propellant load is used, the majority of the propellant would remain unburned and would serve as ballast to keep the thrust-to-weight ratio low.

Flight Profile (Takeoff, Flight, and Landing)

The Grasshopper test program expected to be conducted under an experimental permit would consist of three phases of test launches, which would be performed in the sequence detailed below. SpaceX would repeat tests under each phase as necessary until SpaceX is ready to proceed to the next phase. Multiple test launches could occur each day during daytime hours only, and would be consistent with SpaceX’s lease with the City of McGregor. For example, SpaceX is prohibited from conducting engine tests between the hours of 12:00 a.m. and 7:00 a.m. per SpaceX’s lease with the City of McGregor.

Launch Phases 1 and 2: Below-controlled-airspace VTVL

The goal of Phase 1 is to verify the Grasshopper RLV’s overall ability to perform a VTVL mission. During a Phase 1 test, the Grasshopper RLV would be launched and ascend to 240 feet AGL and then throttle down in order to descend, landing back on the pad approximately 45 seconds after liftoff. The Grasshopper RLV would stay below Class E Airspace (700 feet AGL). In Phase 2, there would be slightly less propellant loaded, a different thrust profile, and the maximum altitude would be increased to 670 feet, still below Class E Airspace. The mission duration during Phase 2 is again approximately 45 seconds.

Launch Phase 3: Controlled-airspace VTVL (maximum altitude)

The goal of Phase 3 is to verify the Grasshopper RLV’s ability to perform a VTVL mission at higher altitudes and higher ascent speeds and descent speeds. To achieve this, the maximum mission altitude would be increased from 670 feet incrementally up to 11,500 feet. The altitude test sequence likely would be 1,200 feet; 2,500 feet; 5,000 feet; 7,500 feet; and 11,500 feet. The maximum test duration would be approximately 160 seconds. The Grasshopper RLV would land back on the launch pad.

One of SpaceX’s key goals is to be able to reuse the first stage of the Falcon 9, an aim that is considered crucial for its long-range business plan. Being able to fly a first stage back and land it intact would help the company accomplish its goal. On the initial two Falcon 9 launches, the first stages fell into the sea and were not in good enough shape to reuse.

Another intriguing possibility is SpaceX could enter the suborbital launch market. Masten Space Systems, Armadillo Aerospace and Blue Origin are all developing VTLV vehicles. XCOR and Virgin Galactic are building horizontal takeoff and horizontal landing vehicles for the same market.

SpaceX needs an experimental permit because McGregor is not a launch site and the rocket’s thrust is too high to be approved under a streamlined process. If the permit is approved, SpaceX is expected to take about three years to develop the Grasshopper with the number of flights possibly exceeding more than once per week:

The experimental permit would be valid for one year and would authorize an unlimited number of launches. The FAA/AST could renew the experimental permit if requested, in writing, by SpaceX at least 60 days before the permit expires. SpaceX anticipates that the Grasshopper RLV program would require up to 3 years to complete. Therefore, the Proposed Action considers one new permit and two potential permit renewals…

Although an experimental permit would authorize an unlimited number of launches, the FAA/AST must estimate the number of launches in order to analyze potential environmental impacts. In conjunction with SpaceX, the FAA/AST developed a conservative set of assumptions regarding the possible number of launches that could be conducted under any one experimental permit for the Grasshopper RLV at the McGregor test site. The FAA/AST has assumed that SpaceX would conduct up to 70 annual suborbital launches of the Grasshopper RLV under an experimental permit at the McGregor test site. This estimation is a conservative number and considers potential multiple launches per day and potential launch failures. To support the Grasshopper RLV operations, SpaceX proposes to construct a launch pad and additional support infrastructure at the McGregor test site.

And here’s some interesting information about engine testing at the Texas site:

As mentioned in Section 2.2, SpaceX currently conducts engine tests at the McGregor test site. SpaceX averages approximately five Merlin-1D tests per week as well as six Falcon 9 Stage 1 tests per year.