The Space Launch System (SLS) is the latest heavy-duty launch vehicle developed by the United States, and one of its uses is to return to the moon. The rocket is divided into Three Types: Block 1, Block 2 and Block 2A. Among them, the SLS block1 launch vehicle is the rocket that the United States recently launched, but has been postponed many times due to failures. It is said that the SLS block 1 carrier rocket has been postponed 17 times, which can be described as a series of twists and turns. In this regard, many netizens are schadenfreude, feeling that the US technology is not working, and even suspect that the US "Apollo" moon landing plan was fake. However, the skinny camel is bigger than the horse, and the technical strength of the United States is still very strong, not to the point that the SLS lunar rocket cannot be built.
SLS block 1 launch vehicle
Although the SLS rocket is the latest rocket developed by the United States, it is essentially a technical transplant of the American space shuttle.
It is understood that the SLS rocket is a heavy disposable launch vehicle derived from the US space shuttle. It is part of NASA's Deep Space Exploration Program, which includes manned missions to Mars and manned moons.
SLS rocket Block 1, Block 2 and Block 2A three models of core first-stage main engines are 4 RS-25 hydrogen-oxygen engines, directly transplanted from the main engine of the US space shuttle; The two boosters are solid rocket engines, and the technology comes from the boosters of the U.S. Space Shuttle. Among them, SLS Block 1 is 98.3 meters high, is a manned carrier rocket, take-off weight of 2603 tons, take-off thrust of about 3752 tons, low-Earth orbit capacity of 70 tons, earth-moon transfer orbit capacity of 27 tons; SLS Block 2 type is 111.25 meters high, take-off weight of about 3000 tons, take-off thrust of 4750 tons, near-Earth payload of 130 tons, Earth-moon transfer orbit payload of 45 tons, the first launch date is expected to be 2029; Block 2A capacity increase model The near-Earth payload of 143 tons, which may even be increased to 160 tons, is still in the planning period and there are many variables.
1. Introduction to boosters.
The boosters of the SLS rocket are divided into Block 1 and Block 2, both of which are parachute recovery and can be reused.
The block 1 type booster directly uses the shuttle's SRB booster, the basic components include the engine (including housing, propellant, igniter and nozzle), the main structure, the separation system, the flight control instrument, the fireworks equipment, the deceleration system, the thrust vector controller, the recovery system, the safety self-destruct system.
SRB Booster
The SRB boosters are 45.46 m high, 3.71 m in diameter, weigh 589,550 kg and charge 498,850 kg, producing approximately 1,270 tons (2,800,000 pounds) of thrust per booster at launch, which then quickly increases to 1,406 tons (3,100,000 pounds) of thrust. The propellant consists of ammonium perchlorate (oxidant, 69.6% mass), aluminum (fuel, 16%), iron oxide (catalyst, 0.4%), polymer (such as PBAN and HPPB, as binder, secondary fuel, 12.04%), epoxy resin (curing agent, 1.96%). This propellant, also known as ammonium perchlorate combination propellant (APCP), has a sea level specific impulse of 242 seconds and a vacuum specific impulse of 268 seconds.
The Block 2 booster borrowed from the Shuttle's SRB booster design to improve and upgrade to 1632.9 tons (3600,000 pounds of force), also adopted a five-stage design and parachute recovery design, with reusable functions, 53.9 meters long, 3.66 meters in diameter, using polybutadiene-acrylonitrile as propellant, dry weight 725.7 tons.
2. Introduction to the core level.
The Space Launch System (SLS) stage is the world's tallest and most powerful rocket core stage, reaching a height of 64.6 meters and a diameter of 8.4 meters. The main engines of the core stage of the Block 1, Block 2 and Block 2A models are all four RS-25D/E hydrogen-oxygen engines, and the technology is derived from the main engine of the Us Space Shuttle.
Four SLS core stages of four RS-25D/E engines are being installed
The RS-25D/E graded combustion hydrogen-oxygen engine has a sea-level thrust of 189.6 tons (1858 kN) and a vacuum thrust of 232.5 tons (2279 kN), producing a maximum thrust of 109%, a specific impulse of 4432.5 m/s (452.3 s) and a weight of 3.527 tons. The first stage is also equipped with flight computers and many of the avionics needed to control rocket flight. The first stage is designed to have a working time of approximately 500 seconds, a separation speed of nearly Mach 23 and an altitude of more than 161.5 km.
2. Introduction to the core level 2.
The engine of the second stage of the SLS rocket core is also not newly developed, the Block 1 type adopts 1 RL10B-2, the Block 2 type uses 4 RL10B-2, and the Block 2A type uses 1 J2X, of which the RL10B-2 expansion cycle hydrogen-oxygen rocket engine directly copies the "Delta III" rocket secondary engine, and the J2X open-type circulating hydrogen-oxygen rocket engine is directly copied from the "Ares One" secondary engine. The RL10B-2 engine has a vacuum thrust of 11.2 tons (110.1 kN), a dry weight of 301 kg, and a specific impulse of 462 seconds. The J2X engine has a vacuum thrust of 133.356 tons (110.1 kN), a dry weight of 2472 kg, and a specific impulse of 448 seconds.
SLS rockets apply a large number of existing mature technologies, the technical difficulty is very small, but still many delays, indicating that the US space sector is not a small problem.
The overall design idea of the SLS rocket is "simple and reliable", the booster provides most of the thrust, and the core stage adopts the hydrogen-oxygen engine design with the highest specific impulse to ensure that the capacity coefficient is not too bad. In order to ensure reliability, the core level also installs only 4 engines that have been developed decades ago, but further improvements are made to appropriately increase thrust, reduce the number of parts, and improve fault points that are prone to problems, and generally still adhere to the principle of "simple and reliable". The core second stage also follows the principle of "simple and reliable", and is also based on the comprehensive improvement and upgrading of the old engine.
SLS block 1 and SLS block 2 launch vehicles
For the United States, the most difficult engines in the launch vehicle are improved by using mature and old models, and have been successfully developed, and the development of a new model is very difficult, and it is only a matter of time before the development is successful. At present, in the field of space, the gap between us and the United States is still very large, and before the successful launch of the Long March 9 series of carrier rockets, we still did not mock the capital of the United States.
Overall, the overall design idea of the SLS rocket reflects the idea of "reliability is king" everywhere, and on the whole, it can be seen as a patchwork of the combination of the US space shuttle booster and the main engine, only the core-level arrow body needs to be redesigned, the change workload is much smaller than the new development, and the development difficulty is also much smaller than the new development.
However, even with such a small amount of change, the SLS blpck1 rocket is still plagued by the problem of liquid hydrogen leakage at the core level many times. To some extent, this confirms the previous report: NASA (Boeing Manufacturing) has a serious brain drain, and there are many problems in internal management.
Of course, from the perspective of the general environment, the hollowing out of the industry in the United States is the culprit, and a large number of low-end industries have been transferred abroad, resulting in an incomplete domestic industrial chain in the United States. The hollowing out of the industry has also led to the need for a small number of products required by many spacecraft to be customized around the world, and the cost is naturally high. At the same time, it has also led to a large number of scientific and technological brain drain in the United States, and if you pay attention to observation, you will find that most of the members of NASA are not young. The average age of U.S. space technicians is said to be in their 50s, compared with the average continental space technicians in their 30s.
Most of the mainland space researchers are very young
Although it is not smooth, the small liquid hydrogen leakage problem is not difficult for the United States, but the cost is the big trouble.
Media reports say it is estimated that NASA will spend $93 billion on the Artemis program from fiscal year 2012 to fiscal year 2025; From fiscal 2021 to fiscal year 2025, it will cost $53 billion. In particular, the cost of a single launch of the SLS rocket is more than $4 billion, which is unbearable even for the deep-pocketed United States, and the Office of the Inspector General of the United States, which audits NASA's project, described the SLS project as "unsustainable" in its report.
In contrast, the continental Long March 9 carrier rocket costs much less. The Mainland Space Administration revealed that the Long March 9 was successful in the first battle, and the development of the rocket's key technology research and program deepening stage was successfully completed in 2019, costing 1.5 billion yuan, and more than 800 specific research and development projects were completed within the total amount of funds stipulated and within the specified time.
It is understood that the single launch cost of the Long March 5 series of carrier rockets is about 630 million to 700 million yuan (about 150 million US dollars), even if the cost increases by 4 times, the single launch cost of the Long March 9 series of carrier rockets is only 3.15 to 35 billion yuan (about 750 million US dollars), far lower than the SLS series rockets in the United States.
Schematic diagram of the launch of the Long March 9 carrier rocket
The economic strength gap between China and the United States is far from 5 times, according to this cost comparison, the development cost of the US SLS series of heavy carrier rockets is too expensive, which is not conducive to future Sino-US space competition. However, for the United States, the SLS series of heavy carrier rocket program has been as simplified as possible, as far as possible the use of mature technology, the cost has been difficult to continue to reduce, if the long march 9 from scratch to develop, its research and development costs must be higher, more unfeasible. If the United States is still unable to reduce the development and launch costs of the SLS series of heavy carrier rockets in the future, the continental space technology is likely to surpass the United States in the end!