Vega C vs Vega
The two rockets look very much alike at a first glance; we have to dig deeply in the performances of Vega C to find the differences.
The first visual difference is that Vega C has a height of 34.8 meters, 5-meters taller than Vega. Differently from its predecessor, which was a small-lift launch vehicle with a capability of 1450 kg to a 700km SSO, Vega C is a medium-lift launch vehicle in the LV NASA classification. Vega C’s capability is 2200kg to a 700km SSO; that capability is more than 50% higher than that of Vega. This increase of capability is due to: the introduction of brand new first and second stages; the increase of the liquid propellant capability of AVUM that becomes AVUM+; and the greater payload volume. All these innovations will be explained in greater depth and illustrated with comparative tables in the next chapters.
Stages Innovations: the new first and second stages
First Stage
The new first stage, developed by AVIO, is P120C; it represents one of the largest monolithic and most powerful carbon-fibre, solid-propellant rockets ever built. With respect to the predecessor P80, P120C has a significant increase in thrust at liftoff.
Its powerful characteristics made P120C the perfect booster for Ariane 6, the Arianespace rocket still under development. In fact, the “C” in the name of the engine stands for “Common” as the engine is used both in Ariane 6 and Vega C.
| Vega C’s P120 C | Vega’s P80 | |
| Length | 11.7 m | 10.6 m |
| Diameter | 3.4 m | 3 m |
| Propellant mass | 143.6 t | 88 t |
| Motor dry mass | 11000 kg | 7330 kg |
| Motor case mass | 8300 kg | 3260 kg |
| Average thrust | 4500 kN | 3015 kN |
| Specific impulse | 278.5 s | 280 s |
| Combustion time | 132.8 s | 110 s |
Second Stage
Vega’s Zefiro 23 has been substituted with Vega C’s Zefiro 40, which has greater thrust and higher propellant capability. Zefiro 40 is expected to also be the second stage of Vega E, a rocket that is going to use “green” propellants. The inaugural launch of Vega E is scheduled for 2026.
The name Zefiro comes from the acronym ZEro FIrst stage ROcket.
| Vega C’s Zefiro 40 | Vega’s Zefiro 23 | |
| Lenght | 7.6 m | 7.5 m |
| Diameter | 2.3 m | 1.9 m |
| Propellant mass | 36.2 t | 24 t |
| Motor dry mass | 3006 kg | 1935 kg |
| Motor case mass | 2080 kg | 900 kg |
| Average thrust | 1304 kN | 1122 kN |
| Specific impulse | 293.5 s | 287.5 s |
| Combustion time | 92.9 s | 77 s |
The third stage, Zefiro 9, is exactly the same engine in Vega and Vega C.
AVUM+: the increase of liquid propellant capacity
The fourth stage is not a completely new engine, but it is a modification of the former AVUM; for this reason the updated engine is called AVUM+. The name AVUM stands form Altitude Vernier Upper Module, and its task is to ensure altitude control and precise orbital positioning. This module is designed for extended stays in space. AVUM+ needs the capability of re-ignition to reach a range of orbits and, after the separation of the payloads, it needs a final boost to de-orbit and burn up in Earth’s atmosphere over the ocean.
| Modified AVUM | AVUM | |
| Diameter | 1.5 m | 2 m |
| Propellant mass | 740 kg | 572 kg |
| Mass of inerts | 590 kg | 538.6 kg |
| Motor mass | 16 kg | 16 kg |
| Average thrust | 2.42 kN | 2.42 kN |
| Specific impulse | 314.6 s | 314.6 s |
| Combustion time | 940 s | 723 s |
Payload
Another important improvement among the rockets is the payload volume. In fact, Vega C has been developed to obtain a greater and more flexible payload capacity. For this reason AVIO has designed a bigger fairing which can store double the payload volume.
The flexibility and versatility of the rocket permits it to have the possibility to deliver payloads to multiple orbit, placing in orbit up to 90% of the satellites in the LEO market. The configuration of satellites in the fairing can be composed by two main large satellites, or various smaller satellites placed for rideshare missions.
Vega C Inaugural Launch
Vega C will lift off for the first time today, Wednesday July 13, with the LARES-2 and SSMS#4 missions on board. The LARES story is linked to the story of Vega, as, on February 13th 2012, ten years ago, LARES-1 was on board of the inaugural Vega flight, Vega C’s predecessor. Both Vega and LARES are Italian products, the first produced by AVIO, the second produced by ASI, the Italian Space Agency. The purpose of this mission is to measure the distortion of space-time caused by the rotation of a massive body. Einstein’s Theory of General Relativity predicted this phenomenon; we covered this effect in the Science Capsule “How Does Time Pass on Satellites?”.
Another six cubesats will be launched and boarded with the fourth Small Spacecraft Mission Service (SSMS #4): three of them are developed by Italian companies, one by a Slovenian one, and two by French ones.
- AstroBio, developed by Sapienza University of Rome, will detect biomolecules in space;
- GreenCube, also developed by Sapienza, will conduct experiments on the growth of plants in microgravity;
- ALPHA, developed by ARCA Dynamics, will understand phenomena related to Earth’s magnetosphere;
- TRISAT-R, by the University of Maribor in Slovenia, will investigate and map ionization radiation in MEO orbits;
- MT Cube-2 is a cubesat developed by the University of Montpellier;
- Celesta will test the effects of a harsh radiation environment on electronic systems.
The SSMS is developed to accomodate 1kg Cubesat to 400 kg minisat.