标题: Why It Took Hakuto-R months to Enter Moon Orbit [打印本页] 作者: choi 时间: 昨天 12:04 标题: Why It Took Hakuto-R months to Enter Moon Orbit 本帖最后由 choi 于 6-7-2025 12:06 编辑
Today's news first, out of a total two.
(1) Kenneth Chang, Second Ispace Lander Crashes to the Moon. New York Times, June 7, 2025, at page A8.
Quote:
(a) "the landing time of 3L17 pm Eastern on Thursday [June 5] * * * Its [ispace's] second spacecraft launched in January [2025] and has been taking a roundabout path to the moon, entering [moon] orbit last month. * * * Around the scheduled time [for landing] * * * contact was lost with the spacecraft. Soon, the looks of silent concern in the control room were eerily similar to what unfolded during ispace's first mission [for moon landing, which met the same fate]. During the news conference * * * 'At this point, we do not know clearly about the casuse [of gailure],' Takesji Hakamada, the chief executive of ispace, said in translated remarks.
(b) Ispace emerged from a Japanese team that had aimed to win the Google Lunar X Prize, which offered $20 million for the first privately financed venture to land on the moon. None of the X Prize teams got off the ground before the competition expired in 2018. Mr Hakamada, who was the leader of the Japanese X Prize team, raised private financing to push forward.
(c) ispace's lunar lander "Resilience shared a SpaceX Falcon 9 rocket with another lunar lander, Blue Ghost from Firefly Aerospace of Cedar Park, Texas [a city in suburban Austin].
"The Blue Ghost spacecraft, financed by NASA, took a quicker path to the moon, landing on March 2, and completed an almost flawless two-week mission.
"Another NASA-financed lander, by Intuitive Machines of Houston, landed on the moon a few days later, but toppled over. Although Intuitive Machines was able to communicate with the lander, named Athena, it ran out of energy a day later and most of the mission's objectives were not accomlished.
(a) "Resilience is on a path to the moon that's often referred to as a low-energy transfer. * * *
"On such a path, the Resilience lander travels for hundreds of thousands of miles, soaring into deep space and waiting for the moon's gravity to naturally capture the spacecraft into lunar orbit.
"In contrast, other vehicles such as Firefly Aerospace's Blue Ghost and the Nova-C [ie, Athena] lander, developed by Texas-based company Intuitive Machines, have used large engines to fire themselves on a much more direct path. Intuitive Machines’ latest Nova-C lander, for example, reached the moon about a week after takeoff.
"Compared with lunar landers developed by Ispace's competitors, Resilience is lightweight and relatively cheap with a smaller rocket engine.
(b) "But there are downsides [for the long route], too.
"And [ispace Chief Financial Officer 野﨑 順平 Jumpei] Nozaki said that, no matter the outcome of Resilience's trip, Ispace will abandon the low-energy transfer approach with its third mission.
* * *
" 'Reaching the moon quickly is also “really important for our customers,' Nozaki said.
"These clients include research groups, companies and governments that pay Ispace to fly cargo such as science instruments on board the lunar lander.
"Spending months in transit can put extra wear on instruments as they are exposed to the intense radiation environment and wild temperature swings of space before they begin operating on the lunar surface, according to Ispace.
(3) science:
(a) My May 28, 2025 posting titled "Firefly Aerospace's Blue Ghost" at (3)(a): "Here are two flight profiles of Hakuto-R Mission 2: early AND and latest (in the latter, Successes 8 through 10 are yet to happen). See M2 Status, ispace, undated (under the heading "Hakuto-R Missions"). https://ispace-inc.com/m2
, where the early (or top) illustration, which is no longer in ispace's Web page (but reproduced at the bottom) is low-energy transfer (we now learn from CNN).
(b)
(i) Both Firefly Aerospace's Blue Ghost and Intuitive Machines' Athena used Hohmann transfer https://en.wikipedia.org/wiki/Hohmann_transfer_orbit
(1925)
, (ii) whereas ispace's Resilience used low-energy transfer. https://en.wikipedia.org/wiki/Low-energy_transfer
(section 4 See also: • Gravity assist)
View the two animations, each for a spacecraft: namely
(A) GRAIL A (which was launched on Sept 10, 2011 and entered moon orbit on Dec 31, 2011 (more than a year later), and
(B) Smart Lander for Investigating Moon (SLIM; of Japan's equivalent of NASA; launched on Sept 6, 2024 and entered lunar orbit on Dec 25, 2023).
Wakter Hohhmann (1880 – 1945; German) proposed the Hohhmann transfer in 1925, and Edward Belbruno (1951- ; American; PhD from NYU in 1981) proposed low-energy transfer in 1987.
(c) BLT (Ballistic Lunar Transfer) Cheat Sheet. Advanced Space,LLC, January 2021 https://s3-us-west-2.amazonaws.com/advspace.publicshare/BLT+(Ballistic+Lunar+Transfer)+Cheat+Sheet.pdf
("A ballistic lunar transfer (BLT) is a type of 'low-energy' transfer from the Earth to the Moon that uses the gravity of the Earth, Moon, and Sun to reduce the required ΔV" or delta-v)
Disregard the jargon "ballistic transfer" and delta-v (they are too much of a diversion). View Figure 1, whose left panel is top view and right panel, an inclined view (not completely lateral, but somewhat at an angle above).
(d) Parrish NL et al, Ballistic Lunar Transfers to Near Rectilinear Halo Orbit: Operational Considerations. NASA, 2020 https://ntrs.nasa.gov/api/citati ... ads/20200011549.pdf
("Ballistic lunar transfers (BLTs) exist for a variety of 3-body orbits.13 In these transfer orbits, the Sun's gravity is used to raise perigee and adjust inclination. In order for the Sun's gravity to have a significant effect on the trajectory, the apogee must be approximately 1-2 million kilometers")
And in Note (2)(b)(ii) Wikipedia link, the apogees of more than 1 million km are what are shown in these two animations (of low energy transfer) -- with SLIM's flight profile (several rounds around Earth before the low energy transfer closely resembling that of Hakuto-R.
