There are some of us that don’t see the business case as stated (millions of tons per year) for the SpaceX Starship. The size of the vehicle has led to a number of problem with permitting, ground support equipment, and complexity of the largest spaceflight vehicle to date. Short version is that development is longer, riskier, and more expensive than with a smaller vehicle using similar technology. It is well oversized for the missions claimed for Starlink as simple math gives under 800 total flights for the heavyweight Starlink2 constellation. Mars colonization doesn’t seem to have a visible investment strategy other than Elon impoverishing himself along with everything he can obtain from government and investors. The known Artemis and other missions are well under the capabilities claimed for Starship. The thousands of annual flights at 100-200 tons per flight need another market. Otherwise a much smaller, simpler vehicle with less development investment and risk could do the known projects, and could have been in revenue service years ago.
Assuming that there is an unstated market for the projected capabilities of the Starship/Superheavy combo that is being kept on the down low for the moment, what could it be? Orbital tourism will very likely expand considerably over the next decades. Many of us think it possible that the ramp up will be slow enough and safety/regulatory concerns high enough to extend that market beyond the nearer term profits necessary to get an appropriate ROI.
A recent discussion brought up another possibility that may fit the hardware development scenario currently unfolding. That is Solar Power Satellites in an orbit low enough to vastly reduce the financial barriers to entry compared to SPS in GEO. The orbit also needs to be high enough to avoid most of the orbital debris and working satellites in LEO. That orbit appears to be in the lower Van Allen belts. About 80% sunlight in most of these orbits of interest. Somewhere around 3,000-4,000 kilometers up, the radiation deters most responsible satellite operators in addition to the extra distance from the surface. The orbit being higher also degrades surface imaging to some degree. A bit of extra latency for communications is also unwanted.
If an SPS can operate at those altitudes, it has a serious effect on the assumptions normally associated with the concept. The primary effect is that beaming power from a maximum of 15% of the distance to GEO reduces minimum antenna and rectenna sizes to 2.25% (15%^2=2.25%) of the area of those in GEO. Minimum size of beaming antenna 100 meters diameter and minimum rectenna being under a kilometer in diameter. Also by being in a relatively low orbit suggests that components can be carried up from Earth without first building a Lunar and orbital industry.
There are serious objections to the concept starting with the radiation environment. There were two suggestions concerning this. One was that the units take the mass hit to be radiation hardened since Starship is going to carry hundreds of tons per flight for costs lower that of the Falcon9 or any other rocket in the world. The other suggestion was that Tethers Unlimited had a viable concept for draining the radiation from the Van Allen belts. In either case, the mass lift capabilities of the Starship come into play.
Second objection was that the solar collectors and beams would be moving all over the sky with variable distances and angles to the rectennas on the ground. Electronic steering of radar and communications antennas has apparently taken care of that issue. Starlink being quoted as case in point. Various satellites would shift beams during the orbit such that they always had a receiver available. For the limited time they didn’t, and the limited times that the rectennas weren’t receiving, there is the battery tech from Tesla.
Third was the millions of tons of CO2 produced by tens of thousands of annual launches by this huge system. The counter to that is that the clean electricity delivered would more than offset the launch CO2 in the near term and almost eliminate fossil fuel pollution in the long term.
Fourth was that this was a high risk vehicle for the foreseeable future. As in Starlink, mass produced components should be inexpensive enough to risk the occasional bad day. The SPS could create the demand for launch after Starlink2 is up and running in profitable service.
My reservations about Starship haven’t gone away. This is just trying to see what reasonable justification there could be for a launcher to be built by the thousands and each vehicle launching daily with a hundred or more tons of payload. This post is speculation. It is based on skepticism about the purported markets and an expectation that there is a rational reason for going this big this fast.