Tencent technology news on August 21, SpaceX, a space exploration technology company under Elon Musk, submitted a document to the Federal Communications Commission (FCC) on Thursday local time, disclosing new details about its plan to design and deploy next-generation satellites in its “Starlink” Internet system, Including plans to use its interstellar spacecraft as the main vehicle for putting nearly 30000 satellites into orbit.
SpaceX submitted a revised plan for the star chain project to the FCC, including a description of the plan known as the star chain “Gen2 system”. SpaceX wrote in the document: “the second generation system is designed to supplement the first generation star chain system currently deployed by SpaceX. Although the original plan provided unprecedented capacity for the satellite system, the demand for more broadband continues to grow, and the demand for user connections has never been so important. ”
SpaceX is ready to launch the star chain satellite
Star chain is a capital intensive project of SpaceX, which aims to establish a space-based Internet with thousands of satellites in order to provide high-speed Internet services to consumers anywhere in the world. SpaceX first launched a beta service for specific consumers, charging $99 a month. Over the past year, the company began to seek network support for aviation services and expand the service to large mobile vehicles, such as ships and trucks.
Although the star chain Internet service is still in the testing stage, SpaceX recently said that at present, the network has about 90000 users in 12 countries, and more than 500000 potential customers place orders or pay refundable deposits. So far, SpaceX has launched 1740 satellite chain satellites, and its first generation system will be launched in November 2019. The second generation plans to launch nearly 30000 satellites in total.
The second generation satellite chain is larger and heavier
SpaceX said that the second-generation satellite chain is heavier and “will be larger than the original design and generate more power”. At present, the deployed satellite chain weighs about 260 kg each, generates about 3 kW of solar energy, and the maximum bandwidth is about 18 Gbps. The second generation satellite weighs about 850-1250kg, and the maximum bandwidth will be three times that of the existing satellites. This will enable these satellites to “support the expansion of the SpaceX network” and “accommodate additional payloads in the future”, which means that satellite chains may be able to host sensors or antennas for other companies.
The “preferred configuration” of the second generation system will include 29988 orbiting satellites, which will be deployed at 9 altitudes ranging from 340 km to 614 km above sea level. Previously, SpaceX had proposed that 30000 satellites would be deployed at eight altitudes between 328 km and 614 km. The company said in the document: “SpaceX will distribute capacity more evenly by latitude for multiple dip angles to ensure better and more consistent global coverage.”
In addition, SpaceX’s revised plan will “nearly double the number of satellites deployed in solar synchronous orbit”, which will enable the company to “provide better services to polar regions such as Alaska”.
SpaceX also pointed out: “SpaceX has invested in advanced propulsion capabilities for its satellites. Therefore, when the satellite can move, the risk of collision with large objects is reduced to zero. ” When the satellite chain fails, SpaceX can operate it to re-enter the earth’s atmosphere, burn it and disintegrate it. SpaceX stressed that if the satellite chain loses control, the relatively low altitude of the satellite in orbit means that it will operate in orbit for “less than four years” and then re-enter the atmosphere and burn down.
Space debris is another major threat faced by satellite chain satellites. SpaceX plans to further deal with this threat through the second generation system. The company wrote: “SpaceX is also aware that under unlikely circumstances such as collision with small debris or meteoroids, the satellite itself may become a source of debris, which may form a parabola or cause the satellite to lose control, and prevent the processing of the satellite after the end of the mission. SpaceX has been exploring ways to make its satellites less vulnerable to this threat. Although the design of these protection functions is still being finalized, SpaceX has improved the redundancy of power and propulsion systems. ”
On August 6, 2021, the Starship prototype S20 was integrated into the top of the super heavy booster B4
SpaceX has previously said that the Starship will bring additional capabilities to the deployment of its star chain network, but the latest submitted document outlines that the company plans to use the Starship as the main delivery system of the second generation system. The company’s leadership had previously touted the enhanced deployment capabilities that starships would bring. Gwynne shotwell, President of SpaceX, said in 2019 that the Falcon 9 rocket could launch 60 satellite chains at a time, but the Starship would be able to “launch 400 satellites at a time”.
The company said that modifying the height and design of the satellite chain will also allow SpaceX to launch the satellite directly into the predetermined orbit with a starship. “The revised plan will enable launch activities to use the capabilities of starships to deploy satellites at a faster speed without having to wait for a period of time in berthing orbit before maneuvering,” the document said. SpaceX can deploy the satellite into orbit within weeks rather than months after launch. ”
SpaceX also mentioned the backup plan to continue to use the Falcon 9 rocket to deploy the second generation system, in case the Starship cannot be put into use when the new star chain system starts to launch. In the past year, the company has completed many test flights of starship prototypes, and is getting closer and closer to its first orbital flight attempt. SpaceX recently integrated the Starship prototype S20 into a super heavy rocket booster for the first time. Musk said over the weekend: “it should be ready to fly in a few weeks. Now it is waiting for regulatory approval.”
Starship and star chain are projects worth billions of dollars, which are crucial to the growth of SpaceX, driving the company’s valuation to $74 billion.
Redesign of starship flaps
If we want to use the Starship to launch the star chain satellite, we must improve its design. Musk said that there is a “small mistake” in the design of the front flap of the starship, which requires minor but obvious changes to the future prototype. The starship is 9 meters in diameter and about 50 meters from the top to the tail. It is the superior of the two-stage fully reusable aircraft. SpaceX hopes that the Starship and its super heavy booster will become the easiest and fastest reusable aviation system in history, and even realize the same day reuse of the two.
The Starship flaps will be redesigned
In addition to the shuttle style thermal insulation layer composed of thermal insulation blanket and thermal insulation tile, the goal of interstellar spacecraft is to achieve this reusability by descending in the atmosphere and recovering land, which is different from any other spacecraft, space shuttle or rocket. Before landing, the Starship will fall freely when it is tens of kilometers away from the ground, and then turn violently into a vertical direction at the last moment, and land with its tail instead of gliding.
Now, according to musk, this largely requires a small but significant redesign of two of the Starship’s four flaps.
During the five suborbital test flights of starship prototypes completed from December 2020 to may 2021, SpaceX turned this strange landing concept from design to reality. Although four of the five tests ended in spacecraft explosions, they actually failed in the last 15 to 30 seconds of the test flight of more than 6 minutes.
After reaching the highest point of 10km in about four and a half minutes, all five starship prototypes successfully shut down the Raptor engine, realized abdominal turnover, and then landed stably on the ground using a combination of small pressurized gas thrusters and four large flaps. Just as skydivers can adjust their bodies, arms and legs to control their direction and posture, starships use two pairs of front and rear flaps to achieve a similar level of control.
Due to the huge surface area and relatively low mass before landing, the unprecedented free fall descent naturally reduces its speed to 160-320 kilometers per hour (about 50-100 meters per second). At the same time, SpaceX avoids great complexity and increases the mass of structural wings or tail wings similar to those on aircraft. In addition, the space shuttle uses wings to taxi and land on a very long runway, while the starship is designed to flip to the vertical and land using three of its six Raptor engines, just like SpaceX’s Falcon booster.
In the actual re-entry process, the interstellar spacecraft uses a thermal shield made of about 15000 thermal insulation tiles to decelerate from orbital speed to subsonic speed. These flaps also help to control the angle of attack of the aircraft, so as to control the extreme heating experienced by it. According to musk, in order to improve the moment arm (i.e. lever or other equivalent torque) of the Starship flap and reduce or remove the undesirable aerodynamic characteristics, SpaceX will further shrink these flaps, bring them closer to the nose cone of the starship, and point them towards the leeward side of the Starship.
Obviously, these relatively small changes mean that part of the front flap of the Starship will no longer be directly affected by reentry heating, which may allow SpaceX to completely remove the static “air cover” wrapped on the spacecraft flap to prevent overheated plasma and gas from contacting the sensitive parts. However, SpaceX’s thermal protection team completed the installation of a heat shield on one of the front flap covers for the first time a few days ago.
However, at present, it seems that S20 will try to use the existing flaps for the first orbital launch of the Starship prototype. However, its next prototype may adopt a new flap design（ Tencent Technology (reviser / Jinlu)