Zubrin's take on Elon's Mars plans

Elon Musk has revealed his true nature over the last year.  I used to admire him, believing that he wished to make the world a better place.   I no longer think that.  Nevertheless,  I am going to continue to report news and opinions about SpaceX's Starship,  as I have been a keen follower since it was first announced nearly ten years ago, and because I believe that mankind should go to Mars.

Starship remains far ahead of any competitor.  There's the DreamChaser, but it's been in development for 20 years, and its first lauch has just been postponed again.  Jeff Bezos's New Glen reusable booster has only just had one launch, which wasn't completely successful.  Unlike SpaceX, which has landed its booster, and will soon land Starship, New Glen has yet to return safely to base.

Starship had its first successful flight two days ago, after several failures.  SpaceX's development method is to test its rockets in action, see what's wrong, fix the issues, and then test again.  It's taken 10 Starship launches to get its first success, and there is still a long way to go.  Reusable rockets are essential, to cut costs, and for Starship, that means getting the heatshield tiles to work.  Perhaps another 10 launches will be needed for the technical problems with the heatshield to be solved.  A first step will be to launch Starship and let it land at Starbase, rather than into the sea, so that the engineers can see what's wrong by inspecting the damage to the tiles, the hull and the fins.

Despite the technical difficulties, I have no doubt that Starship will over the next couple of years become as reliable a workhorse as the Falcon 9.  But will it be the foundation for a Mars city?  Well, probably not.  

I've talked before about Zubrin's plans.  He points out that there are no great grasslands or oceans on Mars, and that we can't colonise it in the same way the New World was colonised.  We will have to grow all our food inside domes or caverns.  The initial populations on Mars will be limited by this.  He also argues that a "Starboat" (a rendering is shown below), about 1/5th the size of the Starship, would be much more practical, because the energy needs to produce propellant for Starship for the return journey to Earth would require 60,000 square metres of solar panels, which by themselves would need 3 Starships, and therefore another +-20 launches of refuelling tankers.  A Starboat would require only 1/5 of that.  In addition, a "Starboat" could be lifted  fully fuelled from Earth into orbit by a Starship, ready to head to Mars, and would not require in-orbit propellant transfer.

Musk is fixated on having just one workhorse: Starship.  Yet it has already morphed into 4 distinct variants:  the passenger Starship; the fuel tanker; the cargo version with its huge bay door; and the Moon landing vehicle.  One more wouldn't make much difference.

A concept for "Starboat"

Here is a video about Robert Zubrin's take on Musk' Mars plan.

Will we get to Mars?  Yes.  Will Mars have a million inhabitants by 2060?  I doubt it.  

But the first scientific bases will expand, and eventually there will be small towns with a few thousand inhabitants living in domes and caverns.  It will take decades to reach a Martian population of a million.

Meanwhile, the need to make it all work will be powerful technological driver, providing incentives to develop the technology needed for a space civilisation, all of which will be good for Earth.  Think for example of the need for vat meat and fish, for air and water purification systems, for workable, safe, small nuclear reactors, for plant varieties which can flourish in very different conditions from on Earth, and for more efficient, cheaper and faster transportation between Mars and Earth.  Just as space has already led to incredibly useful new technologies on Earth--solar panels being just one--so will Mars lead to improvements in Earth-based technology and science.

How to get to Mars

Another excerpt from Robert Zubrin's The Mars Dream is Back

The SpaceX Plan

While there should be fair competition for all mission hardware used by the human Mars exploration program, it is a foregone conclusion at this time that the best launch system for the effort will be the SpaceX Starship. This soon-to-be operational system will offer comparable lift capacity to the SLS but with at least twenty times the launch rate and two orders of magnitude lower cost. We therefore assume that Starship will be selected as the program launch booster.

After payload delivery to low Earth orbit (LEO), however, there are a number of ways that the mission could proceed. SpaceX’s own proposed mission plan would be to fly the Starship to LEO along with 100 tons of cargo, and then refuel it with 600 tons of methane/oxygen bipropellant delivered to orbit by six tanker Starships. This would provide it with sufficient propellant to fly to Mars on a six-month Conjunction-class trajectory, aerobrake into Mars orbit, and then land on Mars. After unloading its cargo, the Starship could serve as the home for a very substantial crew for a year and a half, during which time it would be refueled with some 600 tons of methane/oxygen bipropellant produced from Martian carbon dioxide and water. This would be enough to fly back to Earth on a six-month trajectory carrying the crew and ten tons of cargo.

This mission plan offers a number of advantages. First and foremost, it requires use of only a single flight system that is already in an advanced stage of development and scheduled for use as part of the Artemis Moon program as well. Thus, the same team and infrastructure used to operate Artemis could support the Mars program simultaneously, offering both programs large cost savings. Second, the payload delivered to the surface of Mars is enormous relative to competing approaches, and so is the potential crew size. Elon Musk advertises Starship as a transport capable of delivering 100 colonists to Mars at a time. Such a large number would neither be necessary nor desirable for an exploration mission, but a crew of twenty or so might be readily accommodated. This would be around four times the size of the crew proposed in most other credible Mars mission plans. Moreover, the entire crew would be landed on Mars, where they all would be available to support the field exploration effort, and where they all could avail themselves of natural gravity and substantial radiation protection offered by the Martian environment. Unlike typical NASA mission designs, no one would be left on an orbiting mothership doing nothing useful except for minding the store, while undergoing extensive deconditioning from extended exposure to zero gravity and soaking up cosmic rays. Furthermore, there would be no mission-critical Mars orbit rendezvous on the return leg of the mission.

There are difficulties with this plan, however, which stem from the same source as the problem with SpaceX’s lunar mission architecture: the Starship is way too heavy to serve as an optimal ascent vehicle. By a rough estimate, to make the 600 metric tons of propellant required to refuel the Starship once on Mars within a year and a half would require a power source with an average round-the-clock output of 600 kilowatts. A solar array that could do that would cover 60,000 square meters — that’s over 13 football fields in size — and weigh about 240 metric tons. It would require three Starship flights just to deliver such a solar array to Mars, and it would then be a major burden to deploy and maintain. A more practical alternative would be to use nuclear power. We could imagine a plausible reactor design at this power level with a mass of about ten tons. (See Endnote 2.)

From a technical point of view, nuclear is the far superior alternative to supply the required surface power. However, to achieve the necessary compact size and weight, space nuclear reactors require the use of either plutonium or highly enriched uranium, which are both controlled substances. Thus the government will need to be involved. This poses issues, because the Department of Energy is afflicted by all the same bureaucratic pathologies as NASA, if not more so. A reactor development program done in-house at the modern DOE would never produce a working system on the timeline required for a human Mars mission program. Instead, it would have to be a commercially-led effort with the DOE playing a supporting role.

 

The Starboat Plan

There is another way to mitigate the energy production problem. We could achieve a very large reduction in the amount of propellant needed by introducing an additional flight element, which I call a Starboat. This could be a vehicle of similar type to the current SpaceX Starship but scaled down by about a factor of five in mass. This could play numerous roles that would correct the weaknesses in the SpaceX plan. For example, it could do a direct return from the Mars surface to Earth using 120 tons of propellant or perform a low-Mars-orbit rendezvous using just 50 tons of propellent, with a single tanker in low Mars orbit being able to support five such return flights. It could also be lifted to Earth orbit fully fueled by a single Starship and sent directly to Mars with five tons of cargo without any Earth-orbit refueling, or 25 tons of cargo with a single tanker refueling. This would eliminate the problem of needing to launch seven Starships (the mission vehicle plus six tankers) within a single launch window as is required by the SpaceX plan. If, as assumed in these examples, the Starboat is used as the interplanetary flight vehicle, the crew size would have to be reduced from twenty to four or five, but that might well be appropriate for initial missions that will need to be conducted before all the base infrastructure is up and running.

Alternatively, instead of putting a tanker in low Mars orbit, a Starship fully fitted out for crew could be stationed there, and the Starboat only employed as a reusable shuttle between the surface and orbit. In that case, the plan could retain the ability to employ twenty-person crews, as they could ride out and land Mars along with 100 tons of freight on a standard Starship, only needing to accept the closer quarters on the smaller vehicle during a short Mars-to-orbit flight on the return leg.

The development of the Starboat would also fix the excessive launch problem with the SpaceX Artemis mission plan. The current plan requires 200 tons of propellant to be delivered to low lunar orbit to fuel the Starship on a roundtrip sortie to the lunar surface. At one fifth the size, a Starboat could make the same trip with only 40 tons of fuel. Similarly, the propellant requirement for a round trip from the Gateway to the lunar surface would be reduced from 400 tons to 80. And this could be further reduced by another factor of four when and if lunar oxygen production becomes operational. (See Endnote 3.)

The Starboat could also serve as the upper stage of a reusable first-stage booster in the same class as the Falcon-9, Neutron, and New Glenn boosters, thereby creating a fully reusable medium lift system capable of performing many important supporting mission roles. With a payload delivery capability to Mars of up to 25 tons, about twenty times as much as the landing system used to support the Curiosity and Perseverance missions, it could also deliver large scale robotic exploration missions to the Red Planet, as we shall discuss below.

Finally, and critically, the Starboat would endow the Mars base crew with global mobility. Mars is a planet with a surface area equal to all the continents of the Earth put together. It cannot be explored from a single base using slow moving ground vehicles with limited range. To explore Mars competently, we need worldwide access and the ability to travel rapidly across distances of continental scale. With 50, or better yet, 100 tons of propellant, the Starboat could give us this capability in spades. (See Endnote 4.)

Without Starboat, Mars base explorers would be limited to a region about the size of Brooklyn. With Starboat, they would have the freedom to roam over an expanse nearly double the size of the continental United States.

If additional Starships were landed to establish refueling bases scattered at long distances across the planet, more such explorable regions could be opened up. Nine such refueling stations would provide coverage of the entire world.

The Starboat would add enormously to both Artemis and Mars mission effectiveness, and make the two programs coherent with each other. It should therefore be developed as an essential program element. (See Endnote 5.)

Musk said when he first proposed Starship that it would be better to concentrate all development and research on Starship and its booster, because making a successful re-usable rocket would be so difficult.  But once SpaceX has made Starship work, there is no particular reason why "Starboat" can't be made. 

The last couple of months have however raised another issue.  Is Musk still capable of running any business?  He tweets all day; he's obsessed with spreading right-wing tropes and memes; he's obviously neglecting Tesla.  Gwynne Shotwell runs SpaceX, so it might be OK. 

One of the saddest things about Musk disappearing down his rabid-right rabbit-hole is that we may not get to Mars for another 30 years.  This would have been an extraordinary achievement for him.   Instead he will be remembered for the DODGY disaster.

DreamChaser, Sierra Nevada's re-usable "boat".

The Dream Chaser space plane

 Competition is good, because it cuts costs.  The Dream Chaser space plane by SNC is another way to get to and from Low Earth Orbit (LEO), competition to SpaceX's Starship.  Like the Space Shuttle, it can land like a plane on a runway.  

The Space Shuttle was supposedly reusable, to cut the costs of launching to LEO, but in practice, checking and replacing the heat shield tiles was so expensive that it still cost billions each launch.  It was also not very safe, with two shuttles blowing up, one during launch, and one during re-entry.  It was retired 13 years ago, and all astronauts had to use the Soviet/Russian Soyuz rocket system to get to and from the International Space Station (ISS) until SpaceX's Dragon Crew Capsule started work.  

Musk's Starship is intended to colonise Mars, though it will be essential to launching all the Starlink satellites that will be needed to set up a mass universal satellite internet/phone system.   So the Starship lands vertically using retro-propulsion (the atmosphere on Mars isn't thick enough for wings to work).  This is tricky, though I don't doubt that SpaceX will eventually make it work.   

So, two alternate, competing technologies.  It --- at last! --- looks as if Dream Chaser will make its first test flight soon.  That is, if the rocket that is supposed to launch it is ready by then, which seems unlikely.  Perhaps SNC should have a chat with SpaceX, and use the Falcon 9 rocket to launch its Dream Chaser.

This video is a good explanation of Dream Chaser.

Astroclipper spaceplane

Earth's gravity well is too deep for single-stage-to-orbit spacecraft.  For example, though SpaceX's Starship would make it to orbit, it would have no fuel to return, let alone be able to carry a payload.  So we need two stages to lift a payload into orbit, and to make launches and space travel cheap (relatively), each stage needs to be re-usable.   SpaceX has done this already, with its Falcon 9 and Falcon Heavy, though Crew Dragon, the re-usable capsule to take crew to the ISS  (International Space Station) hasn't yet flown, and suffered a nasty setback when a previous prototype blew up during testing.  SpaceX's Starship/Super Heavy duo hasn't yet flown, though early tests have been promising.  If Starship/Super Heavy works it will be able to lift 100-150 tonnes into LEO (low Earth orbit) at 1000th the cost of existing launch systems.  But SpaceX's rockets lift off and land vertically, and that is on purpose—Starship is designed to work on celestial bodies where there is no atmosphere, such as the Moon.  Since the earliest days of space travel, the dream has been to have space vehicles which can take off from and land at airports just like planes.

Fraser Cain has done a good video about Astroclipper, a combined plane/rocket, which will do just that.

(All images from Fraser Cain's video)

The X-33, a single-stage-to orbit spaceship which was planned by NASA and then cancelled.  It would take off vertically then coast to a landing like an aircraft.  A 1/3rd size mockup was built, but the project was then cancelled.

But a winged spaceship (to assist re-entry and re-use) was first planned in 1957, and was called the Dynasoar.  It too was cancelled, for budgetary reasons.  This is the wind tunnel test model.

NASA toyed with this version of a re-usable booster, which would take off from an airport (instead of vertically) and then land at an airport.

Exodus Space Corp's solution is a two stage spaceplane.  It takes off from an airport like a jet, using conventional air-breathing jets.  At about 20 kilometres altitude, the rocket engines take over.  In an interesting wrinkle, the oxidiser isn't liquid oxygen (which means cryogenic fuel tanks with all their problems) but hydrogen peroxide.  At 75 to 110 k's, the two stages separate, and the first stage coasts back to land at an airport.

This is the timeline which Exodus Space Corp suggests.  The competitive advantages they point to seem plausible.  The timeline does not. 

The thing is, there is a ferment of new developments in space exploration right now.  SpaceX plans to have commercial launches of Starship by mid 2021, Blue Origin's New Glenn will have commercial launches in 2022, and Sierra Nevada Corporation's Dream Chaser in 2021.  By the mid 2030s, competing technologies will have gone through a couple of iterations.  Exodus Space Corp's offering will be competing against seasoned and familiar technology which will be hard to beat.  Given how rapidly SpaceX is developing its technologies, it's hard to see that they won't see off this competition.  If this two-stage spaceplane is cheap and convenient enough, SpaceX or Blue Origin or Virgin Space will easily be able to copy what Exodus Space Corporation is doing, because these ideas can't be patent-protected, and all the other players will be able to diversify from their existing technologies to produce something comparable.

Extremely interesting, all the same.

Dreamchaser

This is a space shuttle which looks like the former NASA Space Shuttle, except it's a lot smaller.  Unlike SpaceX's BFR/BFS/Starship/Super Heavy, it's designed purely to get to and from LEO.  Like the Shuttle, it will glide in to land at airport runways, whereas SpaceX's and Blue Origin's plans call for retro-propulsion (firing rockets to slow the booster or capsule for landing)

Initially, it'll just be for cargo, but later on, plans are that a crew version will be able to carry people (5, I think) to and from ISS.  NASA has approved its production, and has given Sierra Nevada Corporation, the company building DreamChaser (where did they get that name?) a contract for 6 missions to the ISS.

Competition is good.  It leads to lower costs and new ideas, especially where technology is developing rapidly.  The legacy space companies (ULA, Boeing, Lockheed Martin, ESA, Roscomos) are all expensive.  The newcomers (Sierra Nevada, SpaceX, Blue Origin, Virgin Galactic) are all pursuing different pathways to getting us into space cheaply.   One thing they all have in common, though, is re-usability.  That is key to cheap space.  SNC says that launch vehicle costs with ULA, which doesn't do re-usable, are 80% of the cost of every mission they fly.  If they switch to SpaceX or Blue Origin, those costs will fall 10-fold.

Dream Chaser approved by NASA

It tends to be good for consumers when competition in a sector hots up.  For a long time, in space, there were just the government-owned space agencies.  The cost of lifting 1 kilo into LEO (low earth orbit) was $22,000.   The government agencies all operated on a cost-plus basis, and, unsurprisingly, costs were high.  Then Elon Musk came along.  He was sure space could be done better and cheaper, especially if rockets could be re-used.  Jeff Bezos' Blue Origin also entered the race, though Spacex has been running much faster.  And Sierra NEvada Corporation started working on a re-usable space ship which could be launched on top of a re-usable booster from SpaceX or Blue Origin, thus cutting costs ten-fold.

Sierra Nevada Corporation (SNC) has been given the go ahead from NASA to begin full-scale production of its "Dream Chaser" commercial space cargo plane.

Scheduled to make its first mission in 2020, the company announced on December 18 that it had cleared the last milestone in its Commercial Resupply Services 2 contract.

Now the company is able to move ahead with the full-scale production of the carrier which will be used to deliver cargo to the International Space Station (ISS).

The Dream Chaser was originally conceptualized for NASA's commercial crew program but ultimately sidelined by NASA in favor of designs from Boeing and SpaceX.

A redesigned version of the original Dream Chaser, the cargo version includes foldable wings and is capable of carrying 5,500 kilograms (approximately 12125 lbs) of cargo to the International Space Station and return 1,850 kilograms (approximately 4078 lbs) to Earth in a runway landing.

SNC was one of three companies, alongside SpaceX and Orbital ATK (now Northrop Grumman Innovation Systems), to receive a commercial cargo contract from NASA in 2016. The contract guarantees each corporation at least six missions to the ISS.

[Read more here]

Here's a video from Sierra Nevada Corporation about the Dream Chaser.




The cost of launching to and returning from space is going to keep on falling, a combination of competition and continuing technological advances.  And it will change the world.