Low cost commercial Mars Sample Return.

 Copyright 2023 Robert Clark

Introduction.

 Mars Sample Return is again being discussed by NASA, as it was 10 years ago. And as was the case then the chief stumbling block is the $10 billion price tag. However, if done as a fully commercial space mission, i.e., no governmental funding required, it could be done for a fraction of the amount NASA is estimating, probably for a few hundred million dollars, including the launch cost on the Falcon Heavy. 

SpaceX has shown that development costs for rockets can be done at 1/10th the cost of usual government financed rockets by following the commercial space approach. The same was proven for spacecraft in the form of capsules when SpaceX developed the Dragon at 1/10th the usual cost.

 And Planet Labs was able to produce small, highly functional imaging satellites at a fraction of the cost of usual imaging satellites.

 This plus using already existing in-space stages rather than developing entire new ones can greatly reduce the development cost of such a mission. 

 Here, I will propose a solution using a fully aerocapture approach to landing, meaning braking fully aerodynamically, at Mars to minimize the propulsive burns and therefore propellant that is needed on arrival at Mars. Below we'll discuss some possibilities for this hypersonic slowing. First, the delta-v requirements for such a mission.

Delta-V to and From Mars.

Here is a map of delta-v's for some locations in Earth-Moon-Mars space:

Delta-v's between Earth, Moon and Mars.

http://en.wikipedia.org/wiki/Delta-v_budget#Delta-vs_between_Earth.2C_Moon_and_Mars

LEO to GTO:                    2.5 km/s

GTO to Earth C3:               .7 km/s

Earth C3 to Mars transfer:   .6 km/s

Now notice for the delta-v's after this leading into Mars they all have red arrows indicating this part of the trip can be done by aerocapture/aerobraking. So this portion of the flight leaving Earth orbit headed towards Mars, and landing on the surface is only 3.8 km/s, assuming all the slowing on reaching Mars is done aerodynamically.

 After that, for the return trip:

Mars(surface) to low Mars orbit:     4.1 km/s

Low Mars orbit to Phobos transfer:    .9 km/s

Phobos transfer to Deimos transfer:  .3 km/s

Deimos transfer to Mars C3:            .2 km/s

Mars C3 to Mars transfer:               .9 km/s

Now the delta-v's after this leading from the graph into Earth all have red arrows indicating this part of the trip can be done by aerobraking. So the return part of the trip can amount to only 6.4 km/s, for a total of 10.2 km/s for the round trip, if the final part of the trip of returning to the Earth's surface is done fully by aerodynamic braking, i.e., not using propulsive burns.

 As for the heat shield for these Mars return velocities notice that the SpaceX Dragon's PICA-X heat shield was designed to withstand such velocities. It reportedly weighs only half of Apollo era heat shields which would put it at about 8% of the landed mass.

However, for the sample being returned to Earth from Mars there is concern that there may be unknown microorganisms. So current plans include the sample being returned only to Earth orbit or to lunar orbit. Thereafter, the sample would be studied in some orbiting facility only or be placed in a special canister with several redundant layers of security for return to Earth designed not to be breached even if it crashes on return to Earth's surface.

 In such case, we have two additional steps in the delta-v chart:

Mars transfer to Earth C3:  .6 km/s

Earth C3 to GTO:               .7 km/s

 For a total of 6.4 km/s +.6 km/s + .7 km/s = 7.7 km/s.

 This would be for when the sample is returned to geosynchronous transfer orbit(GTO). This is an intermediate orbit for getting to actual geosynchronous orbit. It is a highly elliptical orbit with closest point in low Earth orbit and farthest point at geosynchronous altitude of 35,700 km.

 The other possibility would be to send instead to lunar orbit. Then the additional delta-v steps would be:

Mars transfer to Earth C3:  .6 km/s

Earth C3 to lunar orbit:      .7 km/s

 The total delta-v for the return this time to lunar orbit would also be 7.7 km/s. 

Now for the rocket stages for getting to Mars and returning a sample back. First, we'll use the Falcon Heavy for lofting the in-space stages first into space. Falcon Heavy has a payload capacity of 63.8 tons to LEO, but only 16.8 tons to Mars transfer orbit(MTO). This is a trajectory that sends a spacecraft to encounter Mars in its orbit about the Sun, but makes no attempt to actually enter orbit around Mars. This is the scenario we are considering where, once reaching Mars, the entire braking and landing on the surface is done aerodynamically.

So we have 16.8 tons to work with for in-space stages with capacity to lift off from Mars, fire a burn to direct the return craft back to Earth, and finally make the burn to put the craft in GTO orbit or lunar orbit.

 We'll select existing stages using storable propellant for the in-space stages for this mission that may take up to 3 years round trip duration.

For the first in-space stage we'll use the Ariane 5's EPS storable propellant stage. 

 This has about ~9.8 ton propellant load and ~1.3 ton dry mass. It uses the Aestus storable propellant, pressure-fed engine at about 324 s vacuum Isp at an 84 to 1 expansion ratio. However, an upgraded version turbopump-fed got 340 s vacuum Isp at 300 to 1 expansion ratio. Astronautix.com lists its price as $6 million.

 

 After that, we'll use two copies of the Integrated Apogee Boost Stage(IABS), at about 1.3 tons storable propellant load and about .275 ton dry mass.

 This stage had an vacuum Isp of 312 s. However, for an in-space only stage vacuum Isp is primarily a function of expansion ratio so we'll assume we can also give it a vacuum isp of 340 s with sufficiently large nozzle of ca. 300 to 1 area expansion ratio. Astronautix.com lists its price as $15 million.

 Then with these three stages we can get about .75 tons, 750 kg, payload to reach the 7.7 km/s delta-v needed for the round trip to Mars and back:

3400(Ln(1 + 1.3/(.275 + .75)) + Ln(1 + 1.3/(.275 + 1.575 + .75)) + Ln(1 + 9.8/(1.3 + 1.575 + 1.575 + .75))) = 7,760 m/s, 7.76 km/s.

 The total mass of all the stages and the payload is 15 tons, within the 16.8 ton limit of the Falcon Heavy to put into Mars Transfer Orbit(MTO).

 

Full Aerocapture/Aerobraking for Landing at Mars.

 The question of using aerocapture at Mars is a major question at NASA now for large payloads in the 15 tons to 25 tons range for landing of human habitats for manned missions to Mars. The earlier methods for landing using to a large extent propulsive landing would require a prohibitive amount of propellant (for the usual propulsion methods. However see below.) 

 On the other land using just parachutes or spherical section reentry capsules because of the thin atmosphere would also be insufficient for such large payloads. See discussion here:

The Mars Landing Approach: Getting Large Payloads to the Surface of the Red Planet.

JULY 17, 2007 BY NANCY ATKINSON

Some proponents of human missions to Mars say we have the technology today to send people to the Red Planet. But do we? Rob Manning of the Jet Propulsion Laboratory discusses the intricacies of entry, descent and landing and what needs to be done to make humans on Mars a reality.

There’s no comfort in the statistics for missions to Mars. To date over 60% of the missions have failed. The scientists and engineers of these undertakings use phrases like “Six Minutes of Terror,” and “The Great Galactic Ghoul” to illustrate their experiences, evidence of the anxiety that’s evoked by sending a robotic spacecraft to Mars — even among those who have devoted their careers to the task. But mention sending a human mission to land on the Red Planet, with payloads several factors larger than an unmanned spacecraft and the trepidation among that same group grows even larger. Why?

Nobody knows how to do it.

https://www.universetoday.com/7024/the-mars-landing-approach-getting-large-payloads-to-the-surface-of-the-red-planet/

  One possibility for how to do it is hypersonic waveriders:

Hypersonic waveriders for planetary atmospheres.

December 1989 Journal of Spacecraft and Rockets -1(4)

DOI: 10.2514/3.26259

Anderson, John D., Jr MARK J. LEWIS, Ajay Kothari, Stephen Corda

International Hypersonic Waverider Symposium, 1st, University of Maryland, College Park, MD, Oct. 17-19, 1990, Proceedings

Article

January 1990

The concept of a hypersonic waverider for application in foreign planetary atmospheres is explored, particularly in regard to aero-assist for space vehicle trajectory modification. The overall concept of hypersonic waveriders is discussed in tutorial fashion. A review of past work is given, and the role of a new family of waveriders - the viscous optimized waveriders generated at the University of Maryland - is highlighted. The mechanics of trajectory modification by aerodynamic vehicles with high lift-to-drag ratios in planetary atmospheres is explored. Actual hypersonic waverider designs for Mars and Venus atmospheres are presented. These are the first waveriders ever presented for foreign planetary atmospheres. Moreover, they exhibit very high lift-to-drag ratios, as high as 15 in the Venus atmosphere. These results graphically demonstrate that a hypersonic waverider is a viable candidate for aero-assist maneuvers in foreign planetary atmospheres.

https://www.researchgate.net/publication/234442827_Hypersonic_waveriders_for_planetary_atmospheres

  As shown if Figure 4 from the article, the hypersonic L/D ratio with waveriders can approach 10. 

Further examination of hypersonic waveriders for reentry given here:

An overview of research on waverider design methodology

August 2017

Acta Astronautica 140

• DOI: 
• 10.1016/j.actaastro.2017.08.027

• Project: 
• Aerodynamic design theory and methodology of hypersonic waverider vehicle

• Feng Ding 
• Jun Liu 
• Chi-bing Shen et al. 

 

 

 A variation on that idea is clam-shell wings during reentry: 

Clamshell wings for hypersonic reentry of rocket stages. UPDATED, May 4, 2023.

http://exoscientist.blogspot.com/2023/02/clamshell-wings-for-hypersonic-reentry.html

 An advantage of this over usual caret-shaped hypersonic waveriders is that split in two parts and being curved they can they can more than double the underside surface area.

Falcon 9 opened up fairing as clam-shell wings.
Renders Credit Caspar Stanley 

 Research has shown that further lift can be provided by hypersonic bi-foils:

The hypersonic I Plane has a unique biplane configuration to increase its payload and reduce drag. China Science Press

  

 A key advantage of such high hypersonic L/D ratios, is that using lift we can curve the craft around the planet giving it further time to slow down in contrast to traveling in a straight-line and exiting the planets atmosphere with insufficient braking to fall below the planets escape velocity.

Possible Light Weight Propulsive Methods for Landing.

 Because of the high delta-v requirements for such a mission it was thought the propellant requirements for a propulsive landing would be prohibitive. However, at least two different methods might make it possible, both by getting all or part of the propellant from the Martian atmosphere.

1.)On Earth, oxygen is the common oxidizer for burning. However some metals in such as magnesium and aluminum burn quite well in a carbon dioxide atmosphere, especially as fine powdered particles:

The General Chemistry Demo Lab

Reaction Of Magnesium Metal With Carbon Dioxide.

http://www.ilpi.com/genchem/demo/co2mg/index.html

Original Articles

Combustion of Aluminum Particles in Carbon Dioxide

SERGIO ROSSI,EDWARD L DREIZIN &CHUNG K. LAW

Pages 209-237 | Received 05 May 2000, Accepted 30 Nov 2000, Published online: 27 Apr 2007

https://www.tandfonline.com/doi/abs/10.1080/00102200108952170

2.)Both oxygen and carbon monoxide from the Martian atmosphere. 

That Mars atmosphere is overwhelmingly carbon dioxide is well known. However, it is notable that it contains small amounts of oxygen and carbon monoxide. 

 

This is quite important because carbon monoxide can be made to combust in oxygen by the reaction:

2CO+O2​→2CO2​;ΔH=−569kJ/mol

 This is not as high energy reaction as hydrogen or methane with oxygen but may be enough to provide sufficient thrust to slow down the craft to enable a soft landing via parachutes. 

 We have then though a similar problem as with scramjet propulsion on Earth. The craft will be moving so fast there might not be enough time for combustion to take place. The problem is made worse because there is additional time that must be taken to separate out by filtration the carbon monoxide and oxygen from the carbon dioxide.

 Still, whether or not this problem can be solved, it is extremely important that this reaction be employed for ISRU once down on Mars. A criticism of the approach of SpaceX of landing the large Starship on Mars is the high energy requirements of producing the methane propellant requiring separating oxygen and hydrogen water(ice) in the soil by electrolysis.

 For a vehicle the size of the Starship Robert Zubrin has suggested it might take  10 football fields of solar panels or even take a nuclear power plant. However, when CO can be obtained from low energy filtration from the Martian atmosphere then free hydrogen for propulsion can be obtained by the reaction:

CO + H2O → CO2 + H2,  ΔH = -41 kJ mol-1

 

 You can then get methane if that is the preferred fuel over hydrogen by reacting the free hydrogen with CO2 by the famous Sabatier reaction:

 ∆H = −165.0 kJ/mol

 

 So obtaining free O2 and CO from the Marian atmosphere by low energy filtration makes obtaining propellant for the return flight for manned missions much more feasible.

Financing a Commercial Approach to a Mars Sample Return Mission.

 If this is to be a fully commercial mission how is it to be funded?

 Recall back in 1997 the great interest over the internet from people world-wide on the Mars Pathfinder mission. The Mars Pathfinder mission actually "broke the internet", with its sites getting up to 60+ million total hits per day, to the extent some mirror sites crashed or had to have access limited:

Traffic on Mars
by Chuck Toporek
Asst. Managing Editor
Web Review
However, the most interesting and little known fact about the amount of traffic to the mirror sites comes from France, where the government actually pleaded with computer users to stop accessing the two Mars Pathfinder mirrors. You see, the phone systems in France carry all of the Internet traffic in the country, so when people started visiting the mirror sites at VisuaNet and Le Centre National D'Etudes Spatiales (CNES), they tied up the phone lines and basically disabled the country.
http://mars.jpl.nasa.gov/MPF/press/webreview/index4.html

 The web traffic to the NASA web site for the Mars Exploration Rovers was even more extraordinary, measuring in the billions of hits:

NASA’s Web Site for 2005
By Digital Trends Staff — January 7, 2005
The U.S. National Aeronautics and Space Administration Web portal continues to drive high traffic numbers — more than 17 billion hits in 2004, report both NASA and Speedera Networks, a leading global provider of on-demand distributed application hosting and content delivery services. Speedera delivers content from the space agency’s portal to visitors seeking access to the site from around the world. Popular events on the NASA Web site, including the ongoing Mars Exploration Rover mission entering its remarkable second year, as well as upcoming major projects such as the launch and comet encounter of NASA’s Deep Impact satellite mission in 2005, are expected to drive continued high levels of traffic, according to NASA officials.
http://www.digitaltrends.com/computing/nasas-web-site-for-2005/

 It was estimated there were 142 million visits to the site during this period. So the question is how much advertising could be sold for a site this well visited?

 It could be financed in the fashion of YouTube videos where the content creator is paid according to the number of views of the video:

How much do YouTubers make? 2023 facts and figures.
Edited by:
Erin Dunn • May 23, 2023
Curious about how much money YouTubers make per view? YouTubers make an average of $0.018 per ad view, according to Influencer Market Hub. Rates can range from $0.10 to $0.30 per ad view. However, the amount of money YouTube pays depends on a variety of factors, such as:

• The number of views your video receives...

https://www.creditkarma.com/income/i/how-much-do-youtubers-make

 The most successful YouTube millionaires however make even more money by partnering with advertisers on their channels. Then the financial backers of the mission could sell the rights for products to be associated with financing the mission.

  Robert Clark