Early this week, SpaceX held a conference call to announce that two private individuals have paid their firm a “significant deposit” to be flown around the Moon next year. Although details are sketchy to nonexistent, it would appear that the mission profile is to circumnavigate the Moon before coming back to Earth in a free-return trajectory. The as-yet-unknown crew would fly in the as-yet-unflown Dragon 2 spacecraft – launched to the Moon by the as-yet-unflown Falcon Heavy launch vehicle. One thing portrayed as certain was the date – “late next year,” meaning presumably November or December of 2018 – by sheer coincidence no doubt, the 50th anniversary of the flight of Apollo 8, the first human mission to circumnavigate the Moon.
Although accustomed to hearing periodic, grand pronouncements by various New Space companies, skepticism continues to grow over their follow-through, as actual accomplishment is sporadic and less certain. What we do know for certain is that SpaceX’s one operational launch vehicle (Falcon 9) has had a few issues, the most troubling being an explosion of the vehicle on the pad last September. Although the Falcon 9 successfully sent a Dragon cargo shipment to the ISS this past week, questions about the basic design of the vehicle (e.g., the immersion of a carbon composite-wrapped helium tank in the vehicle’s LOX tank) and preparation procedures (e.g., filling the LOX tank with “slush” oxygen during late stages of the countdown with crew aboard) remain unanswered.
Though promoted continuously over the last five years, we’ve yet to see even a structural test article of the Falcon Heavy launch vehicle. Still, many speak of this rocket as if it has already been in service for a decade or more. Falcon Heavy – a rocket design requiring the simultaneous and balanced operation of 27 engines during its boost phase, surely constitutes a challenging operational objective. The N-1 Soviet rocket had 30 engines in its first stage; it launched four times and exploded each time. Such a record does not automatically portend a similar outcome for the Falcon Heavy, but it does constitute food for thought. Additionally, SpaceX’s booster landing and recovery system is built into each segment of the FH first stage, complicating operations and reducing its total payload capacity.
A LEO-configured Dragon 2 would tip the scales at about 7-8 metric tones; one destined for the Moon will be at least this massive, possibly a bit more given the need for maneuvering fuel to assure putting the spacecraft on the correct return trajectory, and necessary extra consumables for the week-long journey. The Saturn V was able to put 48 metric tons in translunar injection (TLI), about 2/5 of its 120 metric ton LEO capacity. The Falcon Heavy, using lower specific impulse kerosene-LOX, should be able to send about 7-10 metric tones TLI, probably adequate for a “heavy” Dragon 2 manned circumlunar flyby.
Still, a few misleading claims have been made for the Falcon Heavy. The SpaceX web site claims that Falcon Heavy is the largest launch vehicle since Saturn V, but the Soviet Energia of the 1980s could place 100 metric tones into LEO, almost twice the capacity of Falcon Heavy. The press release announcing the lunar flyby makes the point that “At 5 million pounds of liftoff thrust, Falcon Heavy is two-thirds the thrust of Saturn V,” but this is an irrelevant metric. The measure of launch vehicle performance is the amount of mass that can be delivered to orbit. For Falcon Heavy, this figure is 54 tones, a bit less than one-half the quantity of the Saturn V (120 tones).
PR exaggeration and lingering questions about the reality of Falcon Heavy aside, there are several other serious issues about the feasibility of this mission. The Dragon 2 has never flown in space, let alone transported people there. The milestone of the first human flight on Dragon 2 has been pushed back multiple times; it is currently scheduled for sometime in 2018, close to the circumlunar tourist mission. Of course, paying passengers are assumed to have given informed consent, but would the FAA approve such a flight, given the short time and small experience base between initial LEO flights and a lunar one? A flight to the Moon occurs outside of the Earth’s Van Allen radiation belts, so solar activity must be carefully monitored to avoid flight during periods of active Sun – a large coronal mass ejection during translunar flight would mean instant death for the crew.
SpaceX has no experience in tracking, flying and operating vehicles at lunar distances. Global tracking facilities probably can be leased to monitor and control the flight, but it is unclear that the SpaceX flight teams have the knowledge and experience to conduct such a flight. A Dragon 2 on its way to the Moon has no hope of rescue, so its life support and flight control systems must function perfectly.
Perhaps the greatest challenge comes at the end of the mission. A spacecraft returning from the Moon approaches the Earth at near escape velocity, about 11 km/second, half again as fast as a LEO entry. Fifty years ago, the returning Soviet Zond spacecraft used a “skip” technique, whereby the vehicle enters Earth’s atmosphere to dissipate some energy (slow down), flies back out into space to lose excess heat (cool off), and then re-enters the atmosphere again before landing. In September 1968, the Zond 5 spacecraft lost its navigation and guidance system just before Earth return. The spacecraft landed safely, but experienced 15-20 times the force of gravity during the ballistic re-entry. The onboard crew of two turtles survived this torture, but it is not clear that a human would have.
Given all these questions and unknowns, how real is this circumlunar flight? I suggest that as with many other New Space public relations extravaganzas, this “mission” should be taken with a very large grain of salt. Like its big brother NASA and their imaginary “Journey to Mars,” New Space effectively uses the media to shape perceptions. In today’s society, press releases are covered as real accomplishments. You don’t actually have to do anything in space – you simply have to announce that you are going to do it. Increasingly, space has become the realm of the pseudo-event – a space theater reminiscent of P.T. Barnum.
Meanwhile, China continues its systematic and continuous progress toward the Moon and dominance of cislunar space.