Showing posts with label Falcon Heavy. Show all posts
Showing posts with label Falcon Heavy. Show all posts

Thursday, February 20, 2025

Could Blue Origin offer its own rocket to the Moon, Page 2: low cost crewed lunar landers.

 Copyright 2025 Robert Clark


 In the last blog post, "Could Blue Origin offer it’s own rocket to the Moon?", I suggested that with technically feasible upgrades of the New Glenn booster engine, New Glenn might be transformed into a Saturn V-class, 100 tons to LEO, Moon rocket.

 An objection raised to the calculations I presented there was that the maximum New Glenn first stage tank size I was using did not include ullage space, i.e., the space left unfilled or filled with gas to account for boiloff. Three possible solutions: first, even with the commonly used estimate of ca. 1,150 tons propellant load it would require just a ca. 10% increase in tank size to get the prop. load in the 1,300 ton range. SpaceX has shown that additional tank rings have been swapped in and out of the Starship to get an additional propellant load increase of this size or more. 

 Second, an announcement from the Texas State Senate has indicated Blue Origin has been assigned a grant to increase the New Glenn prop.load by subcooling, i.e., densifying the propellant. Propellant subcooling typically results in an approx. 10% propellant load increase. 

 Third, New Glenn's, Moon lander uses hydrolox so it must make use of some zero-boil-off tech to not lose too much hydrogen over a mission lasting several days. This same tech might be able to be used on the New Glenn first stage to minimize the need for ullage.

 Therefore we'll work on the basis the New Glenn can be upgraded to get ca. 100 tons to LEO as expendable.

Getting a crewed lander.

 The space industry was pleasantly surprised by Blue Origin's New Glenn being able to reach orbit on its first launch. They were even more surprised by the announcement the next mission planned will take a cargo lander to the Moon as early as March, though more recently they've only said sometime in late Spring.

 The success of Blue Origin reaching orbit on the first launch with New Glenn and the rapidity at which they wish to progress to launching a lunar lander on the Moon shows the importance in having a top notch Chief Engineer such as David Limp making the technical decisions. If SpaceX had taken the route of hiring a true Chief Engineer, they would already be flying the Starship with paying customers at least in expendable mode. Moreover, they would recognize having a launcher as expendable with 250 ton capacity means they could do single launch missions to the Moon or Mars, no SLS, no multiple refueling flights required.

 As it is, SpaceX is in real danger of being lapped by Blue Origin in having a manned Moon rocket or even a Mars rocket.

  Blue Origin has stated their Blue Moon Mk1 cargo lander will have a 21,350 kg fueled mass, and payload of 3,000 kg payload to the Moon one-way.

Blue Moon Mk1 cargo lunar lander.

 Given the delta-v requirements for getting to the Moon we can make estimates of its propellant and dry mass values:

Delta-V budget.
Earth–Moon space.

https://en.wikipedia.org/wiki/Delta-v_budget#Earth%E2%80%93Moon_space%E2%80%94high_thrust

 Reports are the current version of the New Glenn has a payload to LEO of 25 tons. A 21,350 kg fueled mass of the Blue Moon Mk1 lander plus 3 tons cargo would be 24,350 kg, just under the payload capacity of the current New Glenn.

This though means Blue Moon has to provide the delta-v for trans-lunar injection(TLI) and insertion into lunar orbit as well as lunar landing. From the table the total of TLI and insertion into low lunar orbit and landing is 5.93 km/s, 5930 m/s.

 The engine on the lander is supposed to be the BE-7 hydrolox engine upgraded from the BE-3 used on the New Glenn's upper stage. We'll assume the BE-7 has about the same vacuum Isp of the BE-3, of 445 s. Then taking the propellant load of the Blue Moon as 18.35 tons and dry mass as 3 tons allows it to get 3 tons in cargo to the 5,930 m/s delta-v needed to go from LEO to the lunar surface, plus some margin:

445*9.81Ln(1 + 18.35/(3 +3)) = 6,110 m/s.

 The Blue Moon Mk1 is also already developed and paid for by Blue Origin on its own dime. And it is established fact at this point that spaceflight components, rockets or spacecraft, as developed by commercial space, and privately funded saves 90% off the previous governmentally financed approach that is paid for by governmental space agencies such as NASA. 

 A key fact not yet generally recognized is that we are already at the long desired point of having spaceflight being sufficiently low cost that it can be fully financed by commercial space and private funding only, no governmental financing required at all. BUT such low costs hold true only if it is privately funded.

 A majorly important example is the Mars Sample Return mission. There is much hand-wringing at NASA and among space science advocates about the $10 billion price tag estimated by NASA for MSL. But in point of fact this mission and all space science missions going forward can be paid for at 1/100th the costs estimated by NASA by following the commercial space approach. And in fact the costs as privately funded would be so low, such missions could even be mounted as privately financed at a profit. See discussion here:

Low Cost Commercial Mars Sample Return.
https://exoscientist.blogspot.com/2023/07/low-cost-commercial-mars-sample-return.html

 The argument for this is quite simple. SpaceX and now multiple other space startups have confirmed that development costs as privately funded are 1/10th the costs of governmental funded development costs. But then production costs of individual space components rockets or spacecraft are commonly 1/10th or less than their development costs. As a space company paying for a space project on your own dime, rather than paying the large development costs of a new component you would just naturally use ones that already exist, resulting in far smaller outlay on your end. Then taking into account 1/10th cheaper development cost overall as privately financed and 1/10th or lower cost using already existing components, rather than developing them from scratch, the result is 1/100th or less cost than the usual development costs estimated by NASA following the government financed approach.

 So we already have a lander in the Blue Moon Mk1. But could this serve as a crewed lander? Yes, it can because of a key fact being overlooked by NASA: Artemis is not Constellation's Apollo on steroids, It is in fact Apollo 2.0.

 Perhaps NASA didn't want to acknowledge this so that it would continue to get funding. Just saying Artemis is Apollo redone would not sound nearly as impressive or necessary. But it is important to understand this point. 

 The argument for this conclusion is quite elementary. The primary launcher of Constellation was the Ares V. It was intended to have a startling 188 tons to LEO payload capacity. But there was more to Constellation than that still. The crew were intended to be launched separately to LEO by the Ares I. This had the payload capacity to LEO of 25 tons. Then the Constellation plan with its two launchers could get ca. 210 tons to LEO. This is about twice that of Apollo, but more importantly its about twice as much as Artemis. So in point of fact in the key measure of payload mass to orbit Artemis is Apollo. It is far from Constellation was capable of.

 Once, this is understood then it is understood Artemis should not try to get a lander the size of the Altair lander of Constellation at 45 tons. It should try to get one comparable in size to Apollo. 

 Instead, NASA is seeking that Altair sized lander such as the crewed version of the Blue Origin lander, the Blue Moon Mk2 also at 45 tons, 

Blue Moon Mk2 crewed lunar lander.

or, worse seeking to get the 1,200 ton Starship HLS with multiple refuelings to fit in the Artemis architecture.

 Instead we'll show the Mk1 cargo lander can form the lunar lander for single launch crewed lunar mission format based on the New Glenn as launcher. 

Architecture 1: this will be analogous to the Early Lunar Access proposal of NASA, a proposed follow-on to Apollo.

https://web.archive.org/web/20081106190735/https://nss.org/settlement/moon/ELA.html

 The salient feature of this proposal is it used a single crew capsule for the full round trip from Earth orbit, all the way to the lunar surface, and back to Earth, thus no separate lunar module, i.e., no lunar orbit rendezvous(LOR).

 You see from the table of delta-v's the delta-v needed from the lunar surface back to Earth is 2.74 km/s, 2,740 m/s. This would not put you in Earth orbit though but on a ballistic return trajectory to reenter Earth's atmosphere, a la the Apollo command module. 

 The total round-trip delta-v would be 2.74 km/s + 5.93 km/s = 8.67 km/s, 8,670 m/s.

 The extra delta-v could be provided by the Delta IV Heavy's upper stage, now being used for the interim upper stage of the SLS. This stage would be put atop the New Glenn as a 3rd stage performing the role of a "Earth Departure Stage" for the push to translunar injection. Carrying the Mk1 with a 3 ton crew module it could get:

465*9.81Ln(1 + 27.2/(3.5 + 24.35)) = 3,110 km/s, sufficient for translunar injection(TLI) of the 24.35 ton total mass of the Mk1 lander and crew module.

 This 3rd stage plus the Mk1 and crew module would have a total mass of 30.7 + 24.35 = 55.05 tons. The cited 45 ton payload capacity of the New Glenn to LEO was a for a partially reusable version, with the booster landing downrange. Then for an expendable use it should get ca. 60 tons to LEO, sufficient for the purpose. 

 However, the key question is of a crew capsule that would be analogous to the Apollo Command capsule or the Orion capsule or the Dragon capsule but only at ca. 3 tons dry mass. This is only half the dry mass of the Apollo Command capsule but required to play a similar role.

 A research report of Prof. David Akin of the University of Maryland aerospace department suggests this is indeed possible:


Phoenix: A Low-Cost Commercial Approach to the Crew Exploration Vehicle

Abstract: Since the announcement of President Bush’s Vision for Space Exploration (VSE) in early 2004, the architecture of Project Constellation has been selected. The system will be centered around the Crew Exploration Vehicle (CEV), which has been dubbed by NASA administrator Michael Griffin as “Apollo on steroids”. The CEV is to be launched on a new launch vehicle, derived from existing shuttle technology. The development of this new
spacecraft and launch vehicle is a very costly proposition. An alternate approach is proposed in this study. The Phoenix is a smaller spacecraft designed specifically to be launched on the Falcon 5 vehicle under development by SpaceX. Because the SpaceX vehicle will cost only a fraction of today’s launch costs, the Phoenix is estimated to cost less than half of the price of the CEV. This reusable three person capsule utilizes an innovative re-entry concept, which allows for a cylindrical spacecraft with greater interior volume. This extremely cost-effective spacecraft is an attractive option for fulfilling VSE requirements.

 Below is page 3 from this report:


 Since the Cygnus cargo capsule of Orbital Sciences, now a division of Northrop Grumman, of comparable size to the Phoenix proposal, already exits I suggest basing it on the Cygnus just given life support and heat shield. Remember our dictum is, "Use existing resources to save on costs if available."

 The proposed heat shield for the Phoenix was a "parashield", a combined parachute and heat shield:



 And a proposed heat shield of the Cygnus to make it reusable was an inflatable:



  These may indeed work. But to get to an operational system minimizing development work and cost I advise simply making the Cygnus tapered like most manned capsules and using a traditional heat shield beneath it:


 For both the Soyuz and Dragon, they have relatively small taper angle so you would lose a relatively small size in capsule interior volume by giving the Cygnus a similar side taper.

 Quite notable is with this option you can get a crewed Moon mission with only a single launch of a 60 ton to LEO launcher. Then both the New Glenn as expendable or the Falcon Heavy as expendable could do it in a single launch.

 Robert Zubrin had proposed a Moon mission architecture using the Falcon Heavy with his "Moon Direct" proposal but it would require two launches of the Falcon Heavy to do it. This alternative approach could do it in a single launch provided it is indeed possible to produce an Apollo Command module analogue of dry mass only 3 tons.

Architecture 2: an Apollo sized capsule.

 The Apollo architecture that had the Apollo Command Module to carry the astronauts for the in space portion of the trip from LEO to lunar orbit with a separate smaller capsule for the lander, had an advantage in providing backup capability. This was quite fortunate during the Apollo 13 mission when the Apollo LEM had to sustain the crew for a part of the time on the way back to Earth.

 There is still the question of whether you can make the Apollo Command Module analogue only at 3 tons dry mass. So here we'll do the calculations for an analogous architecture to that of Apollo with a main crew capsule for the in-space portion of the flight and a smaller, separate crew module for the lander.

 I estimated above the Blue Moon Mk1 lunar lander has about a 6 to 1 propellant load to dry mass ratio, at 18.35 tons prop load to 3 tons dry mass. But the Mk1 was designed to do all the propulsion from LEO, to translunar injection(TLI), to low lunar orbit insertion, to lunar landing, with a 3 ton cargo. If the only thing required is to go from low lunar orbit to the lunar surface and back with a 3 ton crew module then a much smaller lander can be used. 

 I'll assume you can a smaller lander at 1/3rd the Mk1 size with a 6 ton prop load while maintaining the 6 to 1 prop mass to dry mass ratio, so 1 ton dry mass. First, from the Earth-Moon delta-v table, the delta-v one way from low lunar orbit to the lunar surface is 1,870 m/s. Then the round-trip delta-v is 3,740. Note now, the smaller lunar lander can provide a delta-v of:

 445*9.81Ln(1 + 6/(1 + 3)) = 4,000 m/s, sufficient for the round-trip from lunar orbit to the surface and back to lunar orbit.

 Now we need a propulsive stage to do the burn to insert the 6 ton main crew capsule and 10 ton lander into low lunar orbit, and to do the burn to bring the main capsule back to Earth, a la the Apollo architecture. For this we'll use a stage half-size to the Mk1 at 9 ton prop load and 1.5 ton dry mass.

 The burn to escape low lunar orbit is commonly estimated as 800 m/s to 900 m/s, same as that for the burn to enter into low lunar orbit. Then 2 tons of propellant is required to be left over as reserve for the return of the primary capsule to Earth, the lander being jettisoned a la the Apollo architecture:

445*9.81Ln(1 + 2/(1.5 + 6)) = 1,030 m/s.

 Then 7 tons of propellant out of 9, with the 2 tons left in reserve for the return, is sufficient to put the 6 ton primary capsule and the 10 ton lander into low lunar orbit:

445*9.81Ln(1 + 7/(1.5 + 6 +10 +2)) = 1,340 m/s.

 The rather large margin of 1,340 m/s over the maximum 900 m/s needed to insert into low lunar orbit suggests we might be able to do with a somewhat smaller stage for this purpose, perhaps 7 tons instead of 9 tons prop load.

 Now the total mass that needs to be sent to TLI is 9 + 1.5 + 6 + 10 = 26.5 tons. We'll use again the upper stage of the Delta IV Heavy to do the TLI burn:

465*9.81Ln(1 +27.2/(3.5 + 26.5)) = 2,940 m/s. 

 This is slightly less than the value commonly given for TLI in the range of 3,000 m/s to 3,100 m/s. But the propulsive stage that's used to insert into lunar orbit had so much margin that it could be used to provide the slight extra push to make TLI.

 Or as I mentioned that propulsive stage for the lunar orbit insertion, essentially reprising the role of the Apollo's Service Module, had so much margin we could make it smaller to ca. 7 tons prop load. Then the TLI total mass would be the same as the Architecture 1 case. And the Delta IV Heavy's upper stage could get the total mass to TLI on its own. 

 It's still quite notable that doing it either way we still could launch the full system to orbit on a 60 ton to LEO launcher.

Flights to the Moon at costs similar to costs of flights to the ISS. 

 I said Artemis is really Apollo redone based on its payload size. It is not Constellation. It is not "Apollo on Steroids". Does it have any value then? I am arguing the goal of getting sustainable lunar habitation is important and doable now. It probably can't be done by Artemis though in a sustainable fashion considering that both the Orion capsule and SLS already each, separately cost $2 billion per flight. When you add on the over-large proposed landers the SpaceX HLS or the New Glenn MK2 each costing ca. $2 billion per flight, and the the Boeing EUS, advanced composite casing SRB's, and lunar Gateway, the total per flight would be in the range of $8 billion to $10 billion per flight.

 It is now becoming increasing likely that Artemis will be cancelled. The only question now is will it be cancelled before Artemis II or will Artemis II be allowed to fly and then the program would be cancelled.

 However, the most important fact is sustainable lunar habitation can be done following the commercial space approach making use of already existing space assets. As I mentioned the combined effect of both these factors can cut the costs of such missions by a factor of 1/100. For example both the Falcon Heavy and the New Glenn cost in the range of ca. $100 million. The small size of the additional in-space stages probably can be done for less than $100 million under the commercial space approach.

 And the crew capsules? An unexpected calculation suggests they can be done together for less than $100 million. For instance back in 2009, Orbital Science contracted Thales Alenia  to construct the Cygnus capsule for 180 million euros for 9 capsules, about 20 million euros each.

 A further contract Thales Alenia made with Axiom Space illustrates how low cost such modules can be while illuminating also how much more expensive space systems are when government funded compared to being privately funded. A contract Thales Alenia made to Axiom Space for two space station modules was only $110 million for two:

THALES ALENIA SPACE TO PROVIDE THE FIRST TWO PRESSURIZED MODULES FOR AXIOM SPACE STATION
14 JUL 2021
Rome 15 July, 2021 – Thales Alenia Space, Joint Venture between Thales (67%) and Leonardo (33%), and Axiom Space of Houston, Texas (USA), have signed the final contract for the development of  two key pressurized elements of Axiom Space Station - the world’s first commercial space station. Scheduled for launch in 2024 and 2025 respectively, the two elements will originally be docked to the International Space Station (ISS), marking the birth of the new Axiom Station segment. The value of the contract is 110 Million Euro.

https://www.thalesgroup.com/en/worldwide/space/press_release/thales-alenia-space-provide-first-two-pressurized-modules-axiom-space

 The individual modules have about 75 cubic meters pressurized space for four crew members, and already have life support systems.

 Now compare that to the HALO module Northrop Grumman contracted with NASA to produce at a cost of $935 million:

Northrop charges on lunar Gateway module program reach $100 million.
by Jeff Foust
January 25, 2024
Northrop received a $935 million fixed-price contract from NASA in July 2021 to build the module, which is based on the company’s Cygnus cargo spacecraft. HALO will provide initial living accommodations on the Gateway and includes several docking ports for visiting Orion spacecraft and lunar landers as well as additional modules provided by international partners. It will launch together with the Maxar-built Power and Propulsion Element (PPE) on a Falcon Heavy.



Based on the "Super" 4-Segment version of the Cygnus, it might have a volume of ca. 33.5 cubic meters:


 The Axiom Space AxH1 habitation modules at 70 cubic meters have double the space of the HALO modules but, as privately financed, cost less than 1/10th as much as government financed HALO modules.

 The needed crew module would be well cut down in size from the 70 cubic meters of the Axiom space station habitation module, with a comparable reduction in cost. Addition of a heat shield would cost a fraction of the total cost of the crew module itself.

 Then the crew modules for the main capsule or of the lander module might cost in the range of a few 10's of millions of dollars.



Sunday, March 3, 2024

SpaceX should explore a weight-optimized, expendable Starship upper stage.

 Copyright 2024 Robert Clark


 To me it’s just stunning SpaceX is ignoring that an expendable Starship could be done for 40 ton dry mass, choosing instead the current 120 tons for the reusable version: 


Probably no fairing either & just 3 Raptor Vacuum engines. Mass ratio of ~30 (1200 tons full, 40 tons empty) with Isp of 380. Then drop a few dozen modified Starlink satellites from empty engine bays with ~1600 Isp, MR 2. Spread out, see what’s there. Not impossible.
88
1.4K
17

 Keep in mind that every kilo of extra mass in an upper stage subtracts directly from the payload possible. Then that 80 tons difference in the dry mass between the reusable and expendable versions is a huge difference. 

 Now,  note because of size, that, just like with the Falcon 9, the 1st stage is 2/3rd of the cost. So for ~$90 million total for the SuperHeavy/StarShip, the SuperHeavy is $60 million of that. But as the Falcon 9 shows it is much easier to get reusable 1st stage. So assume with reuse of SuperHeavy, its cost, is now, say, $5 million per launch. Now it’s a $35 million total cost for the partially reusable SuperHeavy/StarShip. BUT now because of the radically reduced upper stage dry mass, we have ca. 300 tons payload this version!(Assume SuperHeavy lands down range if you wish to maintain the high payload.) But this is about the same cost per kilo as fully reusable 100 to 150 ton payload fully reusable version at $10 million per flight cost.

 Then the question is how realistic is it the Starship could have 40 ton dry mass as an expendable? I think it is quite realistic. 

 Consider the original Atlas rocket first used to send John Glenn to orbit:

SLV-3 Atlas / Agena B.

Family: Atlas. Country: USA. Status: Hardware. Department of Defence Designation: SLV-3.

Standardized Atlas booster with Agena B upper stage.

Specifications

Payload: 600 kg. to a: 19,500 x 103,000 km orbit at 77.5 deg

inclination trajectory.

Stage Number: 0. 1 x Atlas MA-3 Gross Mass: 3,174 kg. Empty Mass:

3,174 kg. Thrust (vac): 167,740 kgf. Isp: 290 sec. Burn time: 120 sec.

Isp(sl): 256 sec. Diameter: 4.9 m. Span: 4.9 m. Length: 0.0 m.

Propellants: Lox/Kerosene No Engines: 2. LR-89-5

Stage Number: 1. 1 x Atlas Agena SLV-3 Gross Mass: 117,026 kg.

Empty Mass: 2,326 kg. Thrust (vac): 39,400 kgf. Isp: 316 sec. Burn time: 265 sec. Isp(sl): 220 sec. Diameter: 3.1 m. Span: 4.9 m. Length:

20.7 m. Propellants: Lox/Kerosene No Engines: 1. LR-105-5

Stage Number: 2. 1 x Agena B Gross Mass: 7,167 kg. Empty Mass: 867 kg. Thrust (vac): 7,257 kgf. Isp: 285 sec. Burn time: 240 sec. Isp(sl): 0 sec. Diameter: 1.5 m. Span: 1.5 m. Length: 7.1 m. Propellants: Nitric

acid/UDMH No Engines: 1. Bell 8081

http://www.friends-partners.org/partners/mwade/lvs/slvgenab.htm


 The Atlas had an unusual design however. It dropped its main lift-off engine at altitude and continued on with what was called the “sustainer” engine. This engine due to much of the propellant mass being burned off had much lower thrust, and so much reduced required engine weight. Then looking at the specifications of this stage, note it had nearly a 50 to 1 mass ratio(!)

 The comparison of this sustainer stage to the 3-engine Starship upper stage is appropriate since an upper stage typically doesn’t need to have the thrust of a stage needing to lift off from the ground. Weight growth of the Starship now at 120 tons dry mass required adding 3 additional engines, to now have 6 engines.

 However, a key reason why the Atlas was able to achieve such a high mass ratio was that it used what was called “balloon-tank” design. This was a design that used pressurization to maintain its structure even on the ground. It would actually collapse under its own weight when not pressurized.

 However,  methanolox is at about 80% of the density of kerolox. So a corresponding methanolox version would be at 40 to 1 mass-ratio, better than the 30 to 1 mass ratio Elon suggested. But its not likely SpaceX would want to deal with the operational difficulties of having a stage be continually pressurized even when on the ground, unfueled, especially for a stage intended to have high launch rates.

 So I’ll look at another stage, the S-II hydrolox 2nd stage of the Saturn V rocket. The Saturn V launcher of the Apollo program was remarkable in the lightweight features of its upper stages, the S-II and the S-IVB. This page gives a list of the fueled weights and empty weights of the Saturn V stages:

Ground Ignition Weights

http://history.nasa.gov/SP-4029/Apollo_18-19_Ground_Ignition_Weights.htm


 The later versions of Apollo had improved weight optimization. We'll use the specifications for Apollo 14. The "Ground Ignition Weights" page gives the Apollo 14 S-II dry weight as 78,120 lbs., 35,510 kg, and gross weight as 1,075,887 lbs., 489,040 kg, for a propellant mass of 997,767 lbs., 453,530 kg, resulting in a mass ratio of 13.77 to 1. 


 Now, methanolox is 2.5 times greater density than hydrolox. Then the corresponding mass ratio for methanolox would be at 33 to 1. This comparison is particularly apt because the mass in the same size tanks would be approx. at the 1,200 propellant mass of the Starship.

 So Starship could reach ca. 30 to 1 mass ratio when using the weight optimizing methods used during the Apollo program.

 But if the price per kilo of this partially reusable version would be at about what the current version is what is the advantage? One advantage is as mentioned is you would not have the difficulty of making the upper stage reusable, no problematical heat shield tiles.

 There is another advantage not as concrete, but in my mind just as important if not more so. In my opinion the approach SpaceX is taking with the SuperHeavy/Starship is ill-conceived. It is based on the idea the SuperHeavy/Starship should be the be-all-end-all for ALL of spaceflight.

 But if you look at transport methods throughout history even going back to the horse-drawn era transports always came in different sizes. A comparison to the air traffic is most instructive. It turns our the largest air transports the jumbo-jet size aircraft actually make up a tiny percentage of air traffic. The great bulk of air traffic is carried by smaller aircraft.

 And even looking at SpaceX’s own Falcon Heavy demonstrates this. The per kilo cost is less than that of the Falcon 9. But the number of Falcon Heavy flights is tiny compared to the number of Falcon 9 flights.

 The fixation on the reusable Starship as the be-all-end-all for all spaceflight also leads to the poorly-conceived notion that a Mars or Moon mission must be carried out by multiple refuelings of the reusable Starship. The number of refueling flights for the Artemis lunar missions might be 8 to 16 flights.

But it is a basic principle of orbital mechanics that high delta-v missions such as to the Moon or Mars are more efficiently carried out by using additional stages. Simply by giving the SuperHeavy/Starship an additional 3rd stage, flights to both the Moon and to Mars could be carried out in a single launch.

 An expendable Starship would mean it being regarded as just another stage. And a 3rd stage could be set atop it as needed, such as for high delta-v missions. 

 As another illustration of the fact this approach to the SuperHeavy/Starship is ill-conceived, the payload of the SH/ST to GEO is nearly zero because that Starship dry mass is so high. This is the most lucrative satellite market, but a single SH/ST launch could not service that market. In order to just launch satellites to GEO the SH/ST would have to do multiple refuelings just to launch a satellite to GEO, just like when it had to launch manned interplanetary missions. This is an odd state of affairs for a rocket simply to launch satellites to GEO.

 Or of course it could utilize a 3rd stage. But if you are going to use a third stage then, why not just use it also for the manned interplanetary missions that would allow you to do such missions in a single flight?

 Robert Clark


Thursday, July 13, 2023

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.



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.


  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.



  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
  •  

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

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

     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:


      
     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.

    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

    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+O22CO2;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...
     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

    Could Blue Origin develop a lander for Artemis III?

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