Continuing from the previous article, this article estimates the structure, launch capability, etc. of the solid-fuel rocket KAIROS (Kai-based Advanced & Instant Rocket System), which Space One plans to launch from Kushimoto-cho, Wakayama Prefecture, based on published data.
[Reference] Video of a previously held symposium (November 08, 2020)
The following additional information about the KAIROS launch vehicle was disclosed at the symposium. The following is a summary of the capability estimation for the KAIROS launch vehicle, taking into account such additional information.
2．Estimation of dimensions and structure of the KAIROS rocket
More detailed information is now available as a 2D model and a decomposition model. This information is used to estimate dimensions and structure.
Kairos rocket estimation
Kairos Rocket Outline Drawing
The Kairos rocket is a 3-stage + 4th stage PBS rocket structure, and the overall impression is that composite materials are used extensively, and judging from the CG coloring alone, the 3rd stage uses a composite rocket motor case to reduce structural weight. The ISA 3/PBS (3/PBS interstage structure), which connects the fourth and third stages, is also likely to be made of carbon-based composite material, which has been thinned from the outside.
3．KAIROS Rocket motor and propulsion system information
From the images obtained, we determined the dimensions and estimated the rocket motor specifications.
Kairos rocket estimation
Kairos rocket Rocket motor comparison image
From the appearance of the Kairos rocket, as shown in the image, the rocket motor has a TVC that is operated entirely by a 2-axis linear actuator. The nozzle appears to be equipped with a movable nozzle made of a composite material such as C/C composite with a metal liner at the connection. It is reasonable to assume that the second stage rocket motor and the first stage rocket motor are also made of composite material.
However, if the production cost is to be reduced, metal rocket motors are cheaper, so it is possible that a hybrid configuration is used as a trade-off, such as using metal rocket motors only for the first stage to reduce costs while focusing on the upper stage. The first stage may be a metal rocket motor to reduce cost.
[1st stage rocket motor] B-1 motor
Length : approx. 8.34m (estimated dimensions)
Diameter : 1.35m
Thrust : ?
Burning time : ?
[Second stage rocket motor] B-2 motor
Length : approx. 3.14m (estimated dimensions)
Diameter : 1.35m
Thrust : ?
Burning time : ?
[3rd stage rocket motor] B-3 motor
Length : approx. 1.8m (based on press information),
The fourth stage PBS is equipped with a unit called "KAIROS PAM" (PAM stands for "Payload Assist Module"), which is a single-component thruster unless the tank interior is divided. There are three thrusters mounted at every 120 degrees of the PBS maneuver, which are supposed to control the pitch, roll, and yaw of the rocket.
For reference, a comparison with the Epsilon launch vehicle PBS (hydrazine one-component type) is shown below.
Comparison of KAIROS PAM and Epsilon rocket PBS
As for the thruster, from the image information, it appears that IHI is using a green propellant thruster similar to the one shown below, as it utilizes a long and narrow thruster.
Space Oneのロケット内部構造等について推定した結果から、最終的にロケット全体の能力値を推定した表を以下に示す。推定の前提として、衛星質量を150kgとし、PBSを100kgとした。ここで、低軌道への打ち上げ能力は250kg、太陽同期軌道への打ち上げ能力は150kgと公開されているが、後者の想定で、PBS込みの重量とした。
なお、1.35mの固体ロケットモータは、M-3ロケットからも少し外れた外径となる。このクラスと同等の打ち上げロケットとしては、イスラエルが初の人工衛星を打ち上げた、「シャヴィト」（Shavit）から発展した、Shavit1 (LK-A)）がある。Shavit1は、固体3段式，質量 30000 kg，外径 1.35m, 全長17.2 m, LEO 225kgであり、Shavit1は、Shavitの増強型である。
This article estimates the launch capability of the solid-fuel rocket: KAIROS (Kii-based Advanced & Instant ROcket System), which Space One plans to launch from Kushimoto-cho, Wakayama Prefecture, based on external views and published data.
*Since this estimate was made in June 2020, the rocket diameter was estimated to be φ1.4m. Later information, φ1.35m, was revealed by a newspaper article in July 2021.
*This blog will write a new article or add more information later, Because of additional information.
Canon's SLR cameras are the best. Let's all buy one.
1．Space One's new solid-fuel rocket: KAIROS, whose appearance has been released.
Canon Electronics announced in 2018 that it has established SPACE ONE, a joint venture to promote the small rocket launch business. Space One, established by Canon Electronics, IHI Aerospace, Shimizu Corporation, and the Development Bank of Japan, aims to achieve the world's shortest contract-to-launch period and the world's highest launch frequency by providing a dedicated small launch vehicle and launch site, with the goal of commercialization in 2021.
The actual status of the rocket development has been shrouded in mystery so far, and it is believed that IHI Aerospace will be in charge of the propulsion system, but only the following information has been released as specifications.
The appearance of the rocket was included in a presentation given at a briefing session in Kushimoto Town, Wakayama Prefecture, in August 2019, but the images of the slides were not made available to the public via the Internet. However, at a presentation held at the Ministry of Education, Culture, Sports, Science and Technology on Wednesday, January 15, 2020
This article estimates the launch capacity of the Kairos rocket that Space One is planning to launch from Kushimoto-cho, Wakayama Prefecture, based on its external view and published data.
2．Space One KAIROS Rocket Structure Understanding and Structure Estimation
External view of Space One's KAIROS rocket, released via the Ministry of Education, Culture, Sports, Science and Technology
To estimate the structure of the launch vehicle, we estimated the interior of the launch vehicle from the information on the dimensions of the satellite payload in the public "Launch Vehicle Overview" and the official website.
2-1．Dimensions of the satellite payload space
Payload space dimensions from Space One official website and
and the image with the correct scale and aspect ratio
First, we grasped the dimensions of the satellite payload space. We used the "Space One Official Website Payload Launch Capability Document" posted on the official Space One website as a reference. The dimensions, scale, and aspect ratio of the payload space in this document were wrong when I measured them, so I corrected them as shown in the figure above.
The image on the right is from the official website, and the image on the left is from the author's corrected image with the correct scale ratio. I don't know if it is intentional or just a matter of randomness that the dimensions in the external documents are wrong. In fact, as long as the dimensions are given, there is no problem, but as a satellite launch company, I think it would be better to make sure that the documents are in line with the actual situation.
2-2．Estimation of Space One KAIROS rocket structure dimensions
Assuming that the published data was correct, we traced the images to get an idea of the external and internal dimensions of the rocket.
To begin with, there is only one picture of the aircraft that has been released to the public, and the accuracy of the details is unknown. In addition, the published specifications are sketchy: the weight is "about" 23 tons, and the total length is 18 meters.
The outline drawing of the rocket is a CG outline drawing, and the observation point of view seems to be the view of the rocket body from the center side. (If you look closely, you can see that the nozzles and fairings are angled.) Therefore, it is not an accurate representation of the side projection of the vehicle, and the further away from the center, the larger the error becomes. The further away from the center, the larger the error. Therefore, please understand in advance that what I am going to describe is a rough estimation to some extent.
From the outline drawing, I assumed the size of the rocket to be just 18 meters in length, which is the size disclosed by Space One. The figures are probably rounded off, so there is an error of about 18m → 18m ± 0.5m. On top of that, I estimated the structure as follows, taking into account the CG intervals and other factors.
It should be a 3-stage + PBS (post-boost stage) configuration with a diameter of about 1.4 meters.
In July 2021, it was announced in a newspaper article that it would be 1.35m in diameter, and this estimation seems to have been largely correct.
Estimated KAIROS rocket structure dimensions
Size and structure comparison with M-V No. 4 and Enhanced Epsilon launch vehicle
3．The diameter of the rocket is about 1.4 meters, and it follows the know-how of the M-3 rocket?
The rocket diameter of Space One, estimated from the outline drawing, is about Φ1.35 to Φ1.4m, even taking into account the error. Here, we estimated the rocket diameter to be Φ1.4m.
This diameter is the same size of rocket motor diameter as the M-3 rocket with a diameter of Φ1.41m, which used to be operated by the Institute of Space and Astronautical Science (ISAS). If this estimate is correct, it means that Space One's rocket can use the previous manufacturing facility design and development know-how of the former Nissan Motor (now IHI Aerospace).
To compare the scale of the rockets, a comparison of the size of the M-3H rocket and the Space One rocket is shown in the figure below.
Comparison of M-3H rocket and Space One KAIROS rocket
Space One is a company established with investment from Canon Electronics and IHI Aerospace, but since solid fuel rocket technology is used for the propulsion system, it is not a rocket development from scratch. The technology of the current IHI Aerospace, which has supported ISAS space rocket development for many years since the days of the former Nissan Motor, is being used.
It is unclear whether the manufacturing facilities for the M-3 rocket, which has the same diameter, are still available or can be used. However, rather than adopting a completely new diameter rocket motor, it is a very rational choice to set the same diameter as that of the M-3 rocket, because it is possible to use some of the past rocket motor manufacturing technology and development know-how.
By using the same diameter, they can use the existing design of the grain manufacturing equipment, even if it is not a metal rocket motor of the same diameter. Test jigs and other equipment that have been used in the past can also be used.
The representative diameter is 1.35m, which is a new development. This is the same diameter as Israel's Shavit and China's Land space's ZhuQue-1 (ZQ-1, LandSpace-1, LS-1), which will be discussed later.
4．Same diameter as M-3S rocket, half the weight, half the launch capability
Payload weight ratio comparison between Space One and other rockets (low orbit)
The table above is a comparison of the payload weight ratio between Space One's launch vehicle and other launch vehicles (low orbit). In addition to solid-fuel rockets, liquid-fuel rockets are also shown on the right for reference.
Due to the structural weight and specific impulse, liquid-fueled rockets are basically more advantageous in terms of payload weight ratio per rocket weight. Also, the larger the rocket, the more advantageous the payload weight ratio.
I was not able to find a solid-fuel rocket that has already been put to practical use with an equivalent scale of 150 kg payload, but the M-3S rocket that was once operated by ISAS can be used as a reference. The manufacturer of the rocket is IHI Aerospace (formerly Nissan Motor), the same as the manufacturer of Space One's KAIROS rocket.
◆M-3S rocket
Launch capability: 300 kg (low orbit)
Length: 23.8 m
Diameter: Φ1.41 m
Weight: 48.7 t
As mentioned earlier, the diameter of Space One's rocket is about the same as that of the M-3 rocket (Φ1.4m), and interestingly, it is exactly half the weight of the M-3S rocket (48.7t → 23t), and has exactly half the launch capacity (0.3t → 0.15t).
5．CFRP rocket motors or metal rocket motors?
It is not possible to determine whether the Space One rocket uses a metal rocket motor or a CFRP rocket motor. The following options may be considered.
・Manufacture with all CFRP rocket motors.
・To reduce the cost, only the first stage is made with metal rocket motors, and the second and third stages are made with CFRP rocket motors.
If we want to achieve high performance, we should use CFRP rocket motors for all stages, but if we want to reduce the manufacturing cost, metal rocket motors are cheaper, so we can choose to use metal rocket motors for the first stage only to reduce the cost and focus on the upper stage. There is a possibility that a hybrid configuration is used as a trade-off.
6．Estimated performance of the Space One KAIROS rocket
The following table shows the final estimates of the overall capability of the rocket based on the results of estimating the internal structure of the Space One rocket and other factors.As an assumption for the estimation, the satellite mass was assumed to be 150 kg and PBS was assumed to be 100 kg. Here, the launch capability to low earth orbit and sun-synchronous orbit are disclosed as 250 kg and 150 kg, respectively, but we assumed the latter and assumed the weight including PBS.
*This estimate is current as of June 2020 and should be revised based on new public information.
Estimated performance of the Space One KAIROS rocket
(assuming a diameter of 1.4 m)
7．Basis for Estimating Rocket Launch Capacity
The following is the basis for the estimation.
◆Satellite: 150 kg → Public Information
◆PBS section: 100 kg (N2O/ethanol, Isp 300 sec)
The mass of PBS is estimated to be about 50 to 100 kg, but here we estimated it to be 100 kg. The propellant mass ratio was set to 0.33, or 1/3, because PBS is equipped with communication equipment, avionics, and gas push tanks.
The propellant was estimated to be "N2O/ethanol". This was stated during the public opening of the JAXA Noshiro Rocket Testing Center in 2017, "Canon Electronics will conduct a ground burn test starting next week. The propellant is N2O/ethanol," an explanatory staff member is reported to have said. In fact, ISAS and IHI Aerospace have collaborated in the past to conduct experimental research on N2O/ethanol propulsion system for PBS. Based on this information, the specific impulse was estimated to be 300 seconds based on the paper, assuming that the PBS, the fourth stage, is an N2O/ethanol propulsion system.
N2O/ethanol propulsion system jointly researched by ISAS and IHI Aerospace
*This estimate is current as of June 2020 and should be revised based on new public information. New information suggests that PBS is likely to be a monopropellant system.
◆Fairing section: 112kg
The weight of the fairing is based on that of the M-V. It is made of CFRP and aluminum honeycomb structure. The Space One rocket is estimated to have a fairing diameter of 1.5 m in diameter and 4 m in length, so the scale ratio was estimated by the following calculations.
((2.5/2)^2)*9=((1.5/2)^2)*4 X, X=0.16, 700X = 112 kg
◆Interstage section (2nd stage to 3rd stage)：30kg
Since the structure is considered to be lightened by CFRP, we estimated the weight to be 30 kg including the separation mechanism.
◆Avionics section and separation mechanism: 30kg
The avionics part is estimated to weigh 30 kg, including the separation mechanism, because Canon Electronics has applied its consumer technology cultivated through the manufacture of camera parts.
8．Additional Information
This estimate was made in June 2020, but the following information came out later.
Private Company Successfully Conducts Combustion Test in Noshiro to Develop Small Rockets
On the 30th, a solid motor combustion test was conducted at the Noshiro Rocket Testing Center of the Japan Aerospace Exploration Agency (JAXA) in Asanai, Noshiro City, Akita Prefecture, with the aim of launching a small rocket by the end of this fiscal year. The test was a success. Space One is a private company funded by Shimizu Corporation, Canon Electronics, and others. It is the first private company to apply the solid rocket technology developed by JAXA.
Solid Motor Combustion Test at Noshiro Test Center to Develop New Generation Small Rockets
On the 30th, a vacuum ground firing test of the third stage solid motor of the "New Generation Small Launch Vehicle," a small satellite launch vehicle being developed by Space One (headquartered in Tokyo) for launch this fiscal year, was held at the JAXA (Japan Aerospace Exploration Agency) Noshiro Rocket Testing Center in Asanai, Noshiro City. The test was conducted jointly by JAXA's Institute of Space and Astronautical Science (ISAS), and the test was completed without any trouble. The test was conducted in cooperation with JAXA's Institute of Space and Astronautical Science (ISAS), and the test was completed without any trouble. There were no problems with the motor, and the data obtained will be utilized for launch. The new-generation small rocket, which is being developed by the company, is a three-stage rocket with a total length of 18 meters, a typical diameter of 1.35 meters, and a total mass of about 23 tons, to which a liquid stage has been added to improve orbit injection accuracy. It is capable of injecting a 150 kg small satellite into a sun-synchronous orbit. This is the first time that Japan's solid rocket system technology, which has been developed since the Pencil Rocket, has been applied to a commercial project. The combustion test was conducted jointly by the company and the Institute in order to share the results of the latest solid motor technology and contribute to the maintenance and development of solid motor technology and testing technology in Japan. The full-scale motor (1.8 meters in length, 1.35 meters in diameter, and 9 tons in maximum thrust) was used to verify the combustion propulsion characteristics, the TVC function to change the direction of thrust and control the attitude by moving the nozzle with an actuator, and the measurement system. It has been five and a half years since the second stage motor of the enhanced Epsilon rocket was developed. About 70 people from the company and the institute participated in the test and prepared for the test. The work went smoothly, and with favorable conditions such as wind speed and direction, the motor was ignited at around 10 a.m. Flames and white smoke billowed out from the test building where the motor was installed, and a roaring sound echoed. According to Shinichiro Tokudome, associate professor at the institute and the chief of the experiment, the combustion time was about 70 seconds and the thrust was just under 9 metric tons, almost as planned. According to Shinichiro Tokudome, associate professor at the institute and head of the experiment, the test was almost on schedule, with a burn time of about 70 seconds and a thrust of just under 9 tons. He said that detailed test results would not be known until they are verified, but the test was a success, as good data was obtained, including normal operation of the TVC function. For ignition, a laser ignition system, which is not affected by static electricity or electromagnetic waves and which is a result of the institute's research, was used instead of an electric detonator, and it functioned properly. The data obtained will be analyzed and shared between the company and the institute. Associate Professor Tokudome said, "The spirit of challenge of the private sector is important for the market development of rockets, and JAXA will contribute to this by transferring the technology it has cultivated to companies, and will support the promotion of industry. In the future, JAXA plans to test the first-stage solid motor of a new-generation small rocket at the same test site.
The following information has been newly determined.
Representative diameter of 1.35m 【assumed in capacity estimation → slightly larger estimate of φ1.4m】
Conducted combustion test of 3rd stage rocket motor with TVC, burn time about 70 seconds, maximum thrust about 9 tons, laser ignition system used for ignition
As of July 2021, the first stage solid motor has not yet been tested.
Based on the scaling of thrust and burn time, the third stage estimated it have may propellant error of a few hundred kg.
The 1.35-meter solid rocket motor has an outer diameter that is slightly outside the M-3 rocket. An equivalent launch vehicle in this class is the Shavit1 (LK-A), which evolved from the Shavit, Israel's first satellite launch vehicle. the Shavit1 is a three-stage solid rocket with a mass of 30000 kg, an outer diameter of 1.35 m, a length of 17.2 m, and LEO 225 kg.
Shavit 1 is an augmented version of Shavit. Shavit1 is an enhanced version of Shavit. Shavit was a three-stage rocket with all solid fuel stages, and the first and second stages were based on the "Jericho 2" semi-medium range ballistic missile, and a spherical rocket motor manufactured by Rafael Advanced Defense Systems was added to the third stage of the missile to achieve satellite launch.
Israel's Shavit, with a diameter of 1.35 meters
Another rocket with a diameter of 1.35 m is the ZhuQue-1 (ZQ-1, LandSpace-1, LS-1), a three-stage solid rocket with a diameter of 1.35 m, developed by Land Space, a Chinese space venture, which was successfully launched in October 2018. ZhuQue-1 is slightly larger than the Kairos rocket, with all three stages 1.35 m in diameter, 19 m in length, 300 kg LEO, and 200 kg SSO. It has been pointed out that ZhuQue-1 may have been developed based on the rocket motor of the Dongfeng 26 (DF-26) medium-range ballistic missile, as well as Israel's Shavit.
ZhuQue-1, Shavit, KAIROSの比較
In addition, JAXA announced that IHI Aerospace has lent a jig to Space One. It is unclear what the jig means, but it is presumed to be a jig related to the manufacture of solid rocket motors.
"IHI Aerospace's dedicated tools for H-IIA, Epsilon, and H3 rockets were loaned to Space One Corporation for the purpose of "development and manufacturing operations of launch vehicles for nano-satellite launches."
