Technical Description of EcoRocket Heavy, World’s Biggest Rocket — AMi, Part VI
EcoRocket Heavy is probably the most unconventional rocket design ever considered.
The unconventional design was required by the need to create a vehicle that is ecological and unprecedentedly cost-effective, able to satisfy ARCA’s needs for a heavy rocket capable to perform competitive asteroid-mining operations, a program that is financed during the development phase through the company’s AMiE crypto.
The whole vehicle is built based on the Propulsion Modules (PM) that are 1.2 m diameter tanks and engine. At the top of the module there’s the pressurisation tank, followed by the propellant tank, holding 10 tons of water-based propellant, while at the bottom of the PM lies the engine.
The Propulsion Module is built entirely from composite materials based on S-type glass-fibre and epoxy resin. The fabrication technology for the tanks is proprietary.
First stage description
In the first stage, the PM is pressure-fed, fully reusable, with a sea-level thrust of 30,000 kgf and a sea level specific impulse of 78 s. What’s remarkable is that the tanks and the engine of the Propulsion Module are a unibody design, with no bolts assembly.
The Heavy’s first stage Propulsion Module’s propellant tank has a diameter of 1.2 m, a length of 7 m, while the pressurisation tank has the same 1.2 m diameter and a length of 2.6 m, both of them being built with composite materials.
The PM’s structure and engine are going to be submerged during the launch phase. The whole airframe, the engine and the avionics containers are waterproof and able to withstand an external pressure of 4 bar.
All PM’s are connected via metallic joints placed at three points along the airframe. Pneumatic locks connect the PMs groups belonging to each stage.
At separation, the locks are released, and the second and third stages are decoupled from the first one. The first stage has a larger frontal area and is lighter (when tanks are depleted) than the second and third ones. As the separation occurs at high dynamic pressure, the first stage will decelerate faster than the second one, allowing the latter to easily distance itself. Two seconds after separation, the second stage will start its engines and continue the ascent.
The first stage has an RCS system that is allowing the vehicle to keep a vertical trajectory.
On top of a few PM’s from the first stage there are drogue parachute containers that deploy at the apogee of the first stage’s trajectory. These keep the stage vertical during the descent. The first stage fires 12 PMs for around 6 seconds, allowing a soft landing in the water.
Also, on top of the PM’s there are avionics containers that house radio and satellite beacons, as well as the telemetry link and a video camera that will record the second stage separation and the deployment of the drogue parachutes.
The propellant tanks for the first stage are completely filled with propellant, while the pressurisation tanks are filled with air provided by external pressure sources.
Once the engine starts, the water level drops, increasing the tanks’ empty volume. Therefore, the pressure tends to decrease. However, based on the simulated flight profile, the increase of acceleration towards the end of the trajectory, successfully compensates for this pressure loss, as the acceleration increases the static pressure at the bottom of the tank. Also, the simulations show that a pressure drop in the tank is even desired, as it helps to prevent the engine reach a throttle level that would affect the airframe. To conclude, the pressure drop’s impact on vehicle performance is negligible. The simulations indicate a small speed loss of 5% and a small altitude increase of around 8%, compared to simulated tanks under a constant pressure.
The PM engine doesn’t use valves but burst disks that break when pressure in the propellant tank increases. This allows a significant cost reduction.
Taking into account the large number of Propulsion Modules and the necessity to maintain a uniform thrust across all of them, the engine chambers are interconnected to equalise pressure.
Each Propulsion Module for the first stage has a maximum propellant flow of 385 kg/s, delivering a maximum thrust of 30,000 kgf.
The first stage avionics are mounted in two containers placed on top of two Propulsion Modules. The avionics include: 0–5V type pressure sensors connected to an MCC board that is further connected to the flight computer through an I2C port; K-Type thermocouples also connected to an MCC board that is further connected to the flight computer through an I2C port; radio GPS beacon I based on Byonics GPS4 connected directly to the flight computer, able to replay data up to an altitude of 84 km; radio GPS beacon II; satellite GPS beacon that sends data (altitude, speed, heading) to the Flight Command and Control Center (FCCC) through an Iridium satellite connection; IMU connected to the flight computer; radio modem with a range of 20 km that sends flight data to the FCCC.
The data being sent to the FCCC through the flight computer includes: pressure and temperature data; radio GPS data (altitude, speed, heading); inertial navigation data from the IMU on all axes, i.e.acceleration, attitude (pitch, roll, yaw) and speed.
Commands sent to the vehicle are: RCS control based on the IMU data; second stage separation; parachutes deployment.
Commands received by the flight computer from the FCCC through the radio modems are: tank pressurisation followed by the engine start; emergency in-flight tanks venting, as a flight abort procedure; stage separation; parachute deployment.
The on-board 1 W modem has a high gain antenna, which is powerful enough for the first stage’s apogee (8 km) The modem is paired with an FCCC counterpart and connects to the centre’s computer.
The onboard video cameras can record the following steps: engine start, including while undersea; staging; and parachute deployment. The footage is recovered after each flight, after the stage has landed.
In terms of batteries, the flight computer, IMU, radio modem and the MCC board together use a Li-Po 22 V/1,5 A battery. The satellite GPS has an internal battery, while the video cameras use a 5 V/6 Ah battery each.
In total, the first stage has a number of 420 propulsion modules, has a diameter of 34.5 m and it stands 16 m tall. The empty weight is 145 t, while the launch weight is 4,200 t. The maximum thrust delivered is 12,600 tf.
Second stage description
The second stage is also made up of Propulsion Modules, with the engines’ divergent nozzles expanded to adapt to a 9 km staging altitude.
Each Propulsion Module for the second stage has a maximum propellant flow of 333 kg/s, delivering a maximum thrust of 30,000 kgf.
The Propulsion Modules propellant tanks have the same diameter and length as the first stage’s. The materials, fabrication technologies and RCS system are also identical.
The attachment elements between the second and third stage are identical to those between the first and second ones.
Taking into account that the separation between the second and third stage occurs at around 50 km, where the dynamic pressure is extremely low, the second stage will fire its top RCS’s to decelerate and allow the third stage to distance itself.
Some of the second stage PM’s have drogue parachutes in containers mounted on their top. These deploy at an altitude of 3,000 m, during descent. The second stage will reach apogee in space, at an altitude of 100 km. Both the first and second stages are using drogue parachutes designed to keep them vertical during descent. The cross-type parachutes were designed and manufactured by ARCA and tested over the Black Sea.
The second stage avionics are similar to the first stage ones with one exception: a 5 W radio modem is used, that can cover in excess of 100 km, which is more than double the second stage’s engine shut-down altitude.
The second stage flight computer, IMU, radio modem and MCC board will use a Li-Po 22 V/7 A battery, to compensate for the extra power drainage of the more powerful radio modem. All other batteries are identical to those used for the first stage.
In total, the second stage has a number of 90 propulsion modules, has a diameter of 16.3 m and it stands 18 m tall. The empty weight is 32 t, while the launch weight is 932 t. The maximum thrust delivered is 2,700 tf.
Third stage description
The third stage Propulsion Modules are different from the previous two stages. Although they use the same 1,2 m caliber, they are additionally housing a kerosene tank and the engine isn’t forming an unibody with the tanks section, but is bolted to the tanks structure through a transition.
Unlike the first two stages, the third one is expendable and does not have a recovery system. However, inside its core, the third stage carries the payload consisting of the AMi Cargo.
The third stage PM engine uses a composite, ablative, pressure-fed, bell-shaped nozzle engine that is expendable, with a thrust of 36,800 kgf and a specific impulse of 290 s at start altitude.
The engine is bolted directly to the PM structure through a composite flange with 32 M14 bolts.
Since cost and weight are our main concerns, the team decided not to use a regeneratively cooled nozzle for the third stage, opting instead for the use of film-cooled ablative composites.
Building on cases such as Fastrac and M-1, 10% of the total kerosene flow will act as a coolant barrier. The film is injected between the chamber and the engine cap, and the flow is adjustable.
The third stage tanks are completely full with propellant. The pressurisation tanks use helium to empty the propellant tanks.
Each engine uses one 100 mm stainless steel ball valve for the hydrogen peroxide line and a 50 mm ball valve for the kerosene line.
Each Propulsion Module for the third stage has a maximum propellant flow of 127 kg/s, delivering a maximum thrust of 36,800 kgf.
After the second stage has burned out, the third one detaches itself and starts the alignment procedure for orbit insertion with help from its own RCS thrusters.
After the alignment, the third stage starts the main PM engines to achieve orbit insertion.
The third stage avionics are mounted in two containers placed on top of two PMs. These are similar to the ones in the first and second stages in terms of sensors, DAQ and flight computer.
An even more powerful, 25 W radio modem is installed, with a high gain antenna that can cover a distance of up to 400 km (twice the third stage’s apogee). The modem is paired with the one located in the FCCC and connected to the centre’s computer.
Another difference compared to the first and second stages is the presence of a 1090 MHz transponder and encoder. The transponder responds to queries from the aviation radars, thus communicating the position of the rocket to the air control authority. The selected transponder is an A/C/S mode BXP6401–1-(01). The BXP6401–1-(01) is a compact and lightweight single block Mode-S transponder.
The third stage will use a Full HD live video transmitter.
The batteries will be similar to those used in stages one and two, with three exceptions: the battery used by the flight computer, IMU, radio modem and MCC board will be a Li-Po 22 V/16 Ah one; the transponder/encoder battery will yield a 22 V/4 Ah; the battery for the video transmission system will be defined based on the selected equipment.
In total, the third stage has a number of 30 propulsion modules, has a diameter of 8.8 m and it stands 20 m tall. The empty weight is 11 t, while the launch weight is 311 t. The maximum thrust delivered is 1,104 tf.
Due to its ecological first two stages and unprecedentedly cost-effective launch cost, EcoRocket trades performance in favor of the two previously mentioned features. In spite of this, the rocket will still be capable to deliver a payload of 24 t to LEO.
The EcoRocket Heavy’s thrust at start is 12,600 tf, while the launch weight is 5,443 t. This makes EcoRocket Heavy the heaviest rocket vehicle ever created by mankind.
