India's "Chandrayaan-3" lunar probe was launched on the 14th and soon after, problems arose. Initially, India planned the perigee to be 170 kilometers, but it turned out to be only 132 kilometers. The Karman line is at 100 kilometers, meaning if the perigee drops below 100 kilometers, it could lead to a crash.
Fortunately, on the 15th, "Chandrayaan-3" successfully completed its first orbital change, raising the perigee to 173 kilometers. But this led to another issue. Each additional orbital change implies more fuel consumption. Due to the insufficient thrust of the Indian rocket, it requires five orbital changes and over a month to send the probe to the Earth-Moon transfer orbit. In comparison, Chinese and American lunar probes only require two orbital changes, reaching the moon in just four days.
After the first orbital change, Chandrayaan-3's perigee and apogee were raised to 173 kilometers and 41,762 kilometers respectively. However, after the second orbital change, the perigee rose to 226 kilometers, but the apogee fell to 41,603 kilometers! Yesterday, Chandrayaan-3 underwent its third orbital change, and the Indian Space Research Organisation only announced its success without providing specific data. Originally, due to Chandrayaan-3's weak rocket propulsion, it required five orbital changes to reach the lunar transfer orbit. But now it seems that Chandrayaan-3 might need at least six orbital changes. It's quite possible that when Chandrayaan-3 reaches the lunar orbit, it will have exhausted its fuel.
The most critical issue with "Chandrayaan-3" is its weak engine retro-thrust. The mass of "Chandrayaan-3" at landing is close to 1 ton, which, considering the lunar gravity is a sixth of Earth's, is equivalent to 166 kilograms. The total thrust of the four main retro-thrust engines is 3200 newtons, or approximately 330 kilograms of force. This gives a thrust-to-weight ratio of 2.
Meanwhile, the mass of China's Chang'e 3 at landing is 800 kilograms, equivalent to 133 kilograms on the lunar surface. The main retro-thrust engine generates 7500 newtons, roughly equivalent to nearly 800 kilograms of thrust, giving a thrust-to-weight ratio of 6!
The thrust-to-weight ratio of Chang'e 3 is three times that of Chandrayaan-3. It is this powerful retro-thrust that reduced Chang'e 3's speed from 1.7 kilometers per second to 0.6 kilometers per second, thus ensuring a soft landing.
Chang'e 3's thrust-to-weight ratio is 6, while Chandrayaan-3 uses the same retro-thrust engine as Chandrayaan-2, with a thrust-to-weight ratio of only 2. Chandrayaan-2 has already proven to be a failure. Furthermore, the budget for Chandrayaan-2 was $141 million, while Chandrayaan-3's budget is only $75 million. And, according to Indian practices, if half of this $75 million is used for practical work, it would be a display of India's conscience. Is it because Indians have become more efficient, or has the dollar become more valuable than a few years ago? Of course not, it's because the Indian Space Research Organisation has repeatedly failed, leading to the Indian government losing patience and significantly cutting funding.
I know you will ask, why launch knowing it will fail? India does not have the ability to manufacture retro-thrust engines and can only purchase from other countries. But no country is willing to sell the most advanced retro-thrust engines to India. If India were to develop them itself, given the pace at which it developed the Arjun tank, which is still not operational after 30 years of development, it would likely take the same amount of time. Chandrayaan-3's launch has already been postponed multiple times; the Indian Space Research Organisation surely can't wait for decades for India's retro-thrust engines to be manufactured.
So where does the Indian Space Research Organisation's budget come from? Without funds, the team will disband. To secure more funding, the Indian Space Research Organisation, despite knowing they can't achieve it, can only boast. Chandrayaan-3 is not about seeking breakthroughs, but to show the Indian government and the Indian people that the Indian Space Research Organisation is doing something.
In the past 20 years, among the human lunar exploration programs, only China has succeeded. Japan can fail, Israel can fail, so why not India? If Chandrayaan-3 fails, the Indian Space Research Organisation can simply find an excuse, and the Indian people can accept it. After all, failure is the mother of success.
印度的“Chandrayaan-3”月球探测器14日发射，没过多久，就出现了问题。
本来印度计划的近地点是170公里，而实际上只有132公里。卡门线是100公里，也就是说，如果近地点低于100公里，就要坠毁了。
好在15日，“Chandrayaan-3”第一次变轨成功，把轨道近地点抬升到了173公里。
但这样一来，又引发了另一个问题。
多一次变轨，就意味着消耗了更多的燃料。
由于印度火箭推力不足，需要5次变轨，花费1个多月时间才能把探测器送到地月转移轨道。
而中美的月球探测只需要两次变轨，只需要4天就可以奔月。
第一次变轨后，Chandrayaan-3的高度升至173千米、41762千米，但第二次变轨后，近地点抬高到226千米，远地点反而降至41603千米！
昨天，Chandrayaan-3又进行了第三交变轨，印度航天局只宣布了变轨成功，没有给出具体数据。
本来，Chandrayaan-3的火箭动力弱，需要5次变轨才能到达月球转移轨道。但是，目前看来Chandrayaan-3至少可能需要6次变轨。
很有可能，当Chandrayaan-3到达月球轨道时，已经没燃料了。
“Chandrayaan-3”最致命的问题是发动机反推力太弱。
“Chandrayaan-3”着陆时的质量接近1吨，按照月表引力为地球六分之一来计算，相当于166千克。而4台主反推发动机的总推力是3200牛顿，也就是大约330公斤力。这样算下来，实际推重比是2。
而嫦娥3号着陆时的质量为800千克，月球表面重量相当于133千克。主反推发动机是7500牛，基本等于近800公斤的推力，实际推重比是6！
嫦娥3号的推重比是Chandrayaan-3的3倍。
就是这么强大的反推力才把嫦娥3号的速度从1.7公里每秒快速降低到0.6公里每秒，从而保证了嫦娥3号的软着陆。
嫦娥3号反动力发动机的推重比是6，而Chandrayaan-3用了与Chandrayaan-2同样的反推力发动机，推重比只有2。
Chandrayaan-2已经证明失败了。
而且，Chandrayaan-2的经费是1.41亿美元，Chandrayaan-3的经费只有7500万美元。并且按印度人的尿性，这7500万美元能有一半用于干实事，就算是印度良心了。
难道是印度人的效率提高了，还是现在的美元比几年前更值钱了？
当然不是，因为印度宇航局接连失败，印度政府没耐心了，大幅度削减了经费。
我知道，你一定会问，为什么明知失败，还要发射呢？
印度没有能力制造反推力发动机，只能向其他国家购买。但是没有哪个国家愿意把最先进的反推力发动机卖给印度。
如果让印度自己研发，按照印度生产阿琼坦克那种研发30年依然无法服役的速度，估计30年都搞不定。
Chandrayaan-3已经多次推迟发射了，印度宇航局总不能等几十年后，印度的反推力发动机造出来再发射吧？
这样一来，印度宇航局的经费从哪来？
没有费用，队伍会散的。
为了要到更多的经费，印度宇航局明知做不了，也只能吹牛。
Chandrayaan-3并不是为了追求什么突破，而只是让印度政府，印度人民知道印度宇航局在做事情。
最近20年，人类的探月计划，只有中国成功了。
日本可以失败，以色列可以失败，印度为什么不可以？
Chandrayaan-3失败了，印度宇航局随便找个借口糊弄下，印度人民也可以接受。
毕竟失败是成功之母嘛。
economictimes.indiatimes.com
