近日，日本一項科技創舉再次引起外界關注：一家日本航太新創公司計劃將牛糞轉化成生物甲烷作為火箭燃料，並提出「一小時從東京飛往紐約」的超高速太空運輸概念，單程票價預估約為一億日圓（約合 65.7 萬美元）。這個計劃將環保、農業廢棄物利用與商業太空旅行結合，雖令人耳目一新，但也引發技術可行性與安全性的廣泛討論。

事件起源於日本多家新創公司和研究團隊的研發工作。以Interstellar Technologies等公司為代表，他們將牛糞經過發酵、提純，生成以甲烷為主的生物氣體，進一步液化成可用於火箭燃燒室的液態生物甲烷。在實驗台上完成的靜態點火測試顯示，該燃料在短時間內能產生可燃火焰與推力，證明其作為推進燃料的潛力。

該技術的商業構想主打「次軌道或亞軌道點對點運輸」，利用火箭繞行高空飛行，將地表長距離航程大幅縮短，理論上能將東京至紐約的行程壓縮至約一小時。推廣方還強調，使用國內可取得的生物甲烷燃料，不僅能降低能源對外依賴，還具有環保與循環經濟的優勢。

然而，從工程和商業可行性角度看，從實驗室測試到實際載人運輸仍存在巨大挑戰。首先，生物甲烷的能量密度、重量比和燃燒特性與傳統火箭燃料（如液態氫或煤油）不同，直接影響推力和比衝表現；其次，火箭發動機的可靠性、長時間運作、熱管理、振動及材料耐久性等問題仍需大量測試驗證；再者，點對點太空交通涉及發射場布局、空域協調、乘客加速承受能力、緊急救生系統及國際法規等複雜問題，僅靠新燃料並不足以解決。多位專家提醒，媒體報導的時間表與票價多帶有宣傳性質，公眾應保持理性。

關於票價與商業模式，雖有宣稱「每次一億日圓、一小時到紐約」，但實際成本會受到發射次數、基礎設施、乘務與保險、監管合規、燃料供應鏈及安全測試等多重因素影響。即使技術突破，要將票價降低到大眾可承受的水平，也需要長期努力與規模化運作。

這一事件帶來兩個值得關注的層面：一是科技與可再生資源的創新結合，將農業廢棄物用於能源，展現創意與環保潛力；二是媒體敘事與公眾期望的差距，企業為吸引目光與投資，常以理想化時間表與票價包裝研發進度，容易引發過度樂觀的預期。對一般公眾而言，這既是一個令人興奮的科技故事，也提醒大家在面對新奇技術宣示時，保持理性判斷與問責意識。

Recently, a seemingly bizarre yet real technological endeavor in Japan has captured public attention: a Japanese aerospace startup is developing a method to convert cow manure into biomethane as rocket fuel, with a commercial concept of “one-hour travel from Tokyo to New York” via high-speed point-to-point space transport. The proposed single-trip ticket is estimated at 100 million yen (approximately $657,000 USD). This initiative combines environmental sustainability, agricultural waste utilization, and commercial space travel, generating both excitement and widespread debate over technical feasibility and safety.

The project originates from the efforts of several Japanese startups and research teams. Companies such as Interstellar Technologies have been experimenting with processing cow manure through fermentation and purification to produce methane-rich biogas, which is then further liquefied into liquid biomethane suitable for rocket combustion. Static fire tests on test stands have demonstrated that this fuel can generate thrust and flames over short durations, showing potential as a rocket propellant.

The commercial concept focuses on suborbital or near-suborbital point-to-point transportation, where rockets would fly at high altitudes to bypass the long distances of ground travel, theoretically reducing a journey like Tokyo to New York to about one hour. Proponents emphasize that using domestically sourced biomethane reduces reliance on external energy sources while also offering environmental and circular economy benefits, positioning cow manure fuel as a policy and marketing highlight.

However, from an engineering and commercial perspective, transitioning from laboratory or test-stand experiments to actual manned transport faces significant challenges. First, the energy density, mass ratio, and combustion characteristics of biomethane differ from conventional rocket fuels like liquid hydrogen or RP-1, directly affecting thrust and specific impulse. Additionally, issues such as engine reliability, long-duration operation, thermal management, vibration, and material durability require extensive testing. Furthermore, point-to-point space travel involves complex factors such as launch site layout, airspace coordination, passenger acceleration tolerance, emergency rescue systems, and international regulations—challenges that cannot be solved by a new fuel alone. Experts caution that media-reported timelines and ticket prices are often promotional, and the public should maintain realistic expectations.

Regarding ticket pricing and commercial viability, claims of “100 million yen per trip” or “one-hour flights to New York” are largely visionary statements used for early-stage fundraising or market positioning. Actual costs would be influenced by launch frequency, infrastructure, crew and insurance, regulatory compliance, fuel supply chains, and safety testing. Even with technological breakthroughs, reducing ticket prices to levels accessible to the general public will require extensive long-term efforts and scaled operations.

This initiative highlights two noteworthy aspects: first, the innovative linkage between technology and renewable resources, demonstrating creative use of agricultural waste as energy; and second, the gap between media narratives and public expectations, as companies often package their R&D progress with appealing schedules and pricing to attract attention and investment, which can lead to overly optimistic interpretations. For the general public, this story is both an exciting technological development and a reminder to approach bold technological claims with rational scrutiny and accountability.