New Mars Forums

That is very true. One individual at the last Mars Society conference told me he doesn't think the Earth's production of xenon is sufficient to supply a manned mission. If ion or hall thrusters for the cargo craft may require too much xenon. Xenon is a trace gas in Earth's atmosphere and a byproduct of liquid air production. This does raise the question of where Russia would get it for their hall effect thruster proposal.

The engines themselves have gone through some interesting developments. The NSTAR ion engine had a nominal specific impulse of 3100 seconds and a thrust of 92 milli-Newtons. The exact Isp depended on throttle setting. The XIPS ion thruster used on Boeing's model 702 satellite has Isp 3800s and thurst 165mN. Russia's D100 hall effect thruster has an Isp of 3970s and thrust of 300mN. Russia had theoretical work on paper that said a Thruster Anode Layer (TAL) hall effect thruster could produce an Isp of 8000s. A paper presented at this year's AIAA conference showed work by the Glenn Reserach Center on "High specific impulse, High power ion engine operation". The 50cm ion engine demonstrated an Isp of 5210s and they believe they can increase that to 8300s.

The VASIMR engine has the promise of Isp at 9000s. However, the VAriable Specific Impulse Magntoplasma Rocket is designed to permit lower Isp at higher thrust. Trading off efficiency for thrust was intended to permit rapid acceleration away from Earth followed by high efficiency during cruise to Mars. Princeton is working on magnetoplasmadynamic (MPD) without the specific impulse variability. The crew taxi may make the low Isp, high thrust mode of VASIMR unnecessary. One presentation from the Glenn Research Center said MPD can achieve an Isp up to 7000s at 1 megawatt, and Isp increases with power. GRC is now working on a 30 megawatt version. The advantage to VASIMR or MPD is that hydrogen is easier to obtain, both on Earth and Mars. The down side of hydrogen is that it requires a larger fuel tank.

I think it is fair to plan for electric propulsion with Isp in the 8000-9000 second range.

This is a development of the idea I posted on "Mars Direct Rethought".

To start with, keep the crew down to 4 astronauts. Apollo included 3 astronauts, only 2 of whom landed on the Moon. There are psychologists who argue for a whole town, but this is the initial manned mission to Mars so we need explorers who have the "right stuff". The "right stuff" for Mars means independence and fortitude for a 2 year mission.

The spacecraft would be assembled in Earth orbit using existing launchers. It would be better to have Energia or Shuttle-C, but it doesn't look like they will be available. Proton, Angara 5, Ariene 5, Delta IV Large, Atlas V, and the Space Shuttle will be available.

The spacecraft would travel from Low Earth Orbit into a highly elliptical, high Earth orbit. There is no need to raise the perigee, once the apogee is high enough the spacecraft will leave Earth. Since so many launch vehicles are designed to deliver payloads to Geosynchronous Transfer Orbit, we should use that. Once the spacecraft is in GTO, astronauts would be delivered via a crew taxi.

The taxi would be a capsule capable of returning all 4 astronauts and Mars samples to Earth via direct entry from interplanetary velocity. This would be larger than either the Soyuz descent module or Apollo command module, and the heat shield would have to be more robust, so the capsule would be a new design. Whether it is a cone like Apollo or "headlight and windshield" like Soyuz is a matter for the engineers to argue. In either case, the crew taxi would have a small service module with manoeuvring thrusters to dock with the Mars spacecraft, and capable of controlling its flight path back to Earth.

Once crew were onboard, the spacecraft would depart for Mars using electric propulsion. Whether the electric drive is ion, hall effect or magneto-plasma dynamic is a competition for engine designers. The Russian thruster anode layer hall effect thrusters currently have the same Isp as ion thrusters, so Russia's Energomash can compete directly with NASA's Glenn Research Center. There is current development for a nuclear reactor to power the thruster, but for now let's design for solar-electric propulsion.

The life support system would be electrolysis of water, augmented by a Sabatier reactor to conserve water. The water recycling system from the Johnson Space Center's Advanced Life Support Project had a 97% water recycling efficiency, including water from all sources. This combination has greater than 95% oxygen and water recycling.

The interplanetary habitat would be based on TransHAB and designed for zero-G, including exercise machines. Food and consumables would be sufficient for the round-trip, either a free return or both of the outbound and inbound legs of a normal mission.

Upon reaching Mars the spacecraft would use aerocapture to enter Mars orbit. During aerocapture, the solar panels must be folded and stowed. The surface habitat would be just a capsule and an inflatable habitat. There is no need for more room than one seat for each astronaut until on the surface of Mars. The surface habitat would not have the micrometeor shield because Mars has an atmosphere, so the surface hab would be lighter than TransHAB. The roof would be sturdy enough to support sand bags (regolith bags) for radiation protection. The surface hab would include a recycling life support system, food for the surface stay, and a 2-person open rover.

This would be preceded by a Mars Ascent Vehicle. Similar to the MAV of NASA's Design Reference Mission, it would use ISPP to create propellant and just carry the astronauts and samples to Mars orbit. Unlike DRM, the MAV would be the Trans-Earth Injection stage to return the orbiting spacecraft back to Earth. The MAV would not be pressurized and would not have life support. Astronauts would ride in their space suits (with sample containers).

Waiting beside the MAV would be a cargo craft that landed by radio beacon. The cargo craft would contain an inflatable laboratory, lab equipment and supplies, as well as a backup supply of food for the surface stay. It would also have a pressurized rover. Life support for the lab would normally be provided by the habitat, but as a backup the life support system of the pressurized rover could supply the lab. This provides a complete backup for the surface habitat with minimal redundant equipment.

Upon return to Earth, the interplanetary spacecraft would aerocapture into Earth orbit. If something went wrong with the spacecraft, the crew taxi could separate and return on its own. For a normal mission, the crew taxi would separate after the interplanetary spacecraft was parked in GTO. It would be left in GTO where it could be refuelled and resupplied by a cargo spacecraft to prepare it for a second mission.

So this would use solar-electric propulsion for the Earth-Mars trip, but chemical propulsion and ISPP to return. Aerocapture and direct entry from high orbit avoids propellant use. The interplanetary spacecraft is reusable, with a new lander for each mission. Cargo and the MAV are delivered separately so a slow, fuel efficient trajectory can be used.

Eventually the MAV could be replaced with a reusable one, but it would have to carry fuel to replenish the interplanetary craft's electric thrust system. Propellant for ion or hall effect thrusters is xenon or krypton, for magneto-plasma dynamic it's hydrogen. Mars atmosphere contains 0.00003% krypton and 0.000008% xenon.

The Nerva engine was developed specifically as a Trans-Mars Injection stage for a manned mission to Mars. Ground tests were completed to the point where the next test would have been in Earth orbit. That engine was a Nuclear Thermal Rocket. It encapsulated the uranium in ceramic so strong that in the case of catastrophic failure the uranium fuel could fall all the way from space and impact the ground without splitting open. That would leave chunks of nuclear fuel all over the debris field, but each chunk of uranium would be sealed. As for radiation, I have seen video of nuclear reactor workers wearing the same plastic gloves as you get with oven cleaner to poke urnanium oxide powder into steel fuel rods. They just poked the powder in with their fingers. When nuclear fuel comes out of the reactor you don't want to be in the same room, you want a couple feet of lead between you and it, but before it goes in it is relatively safe. Since Nerva would only be turned on after it was safely in orbit, it was already as safe as any other rocket. Nerva was developed from 1950-1974. Timberwind was developed in 1990 and had a slightly higher Isp.

However, environmental and political arguments have little to do with reality.

I now hesitate to give links to web sites because I have seen NASA take down some of the web pages I referenced. For example, the web page about the X-38 and its cost justification has been taken down. But I think Russia and the Rocket Space Corporation Energia would like publicity, so you can view thier mission plan here.

I have a couple additional articles. One is in both English and Russian, and the other was only in Russian. I used translation web sites to translate it into English. The original and my translation are available on the Winnipeg chapter web site.

The Russian plan does have the great advantage of a reusable spacecraft. The plan as posted has the problem that it calls for the spacecraft to spend 3 months spiralling out from low Earth orbit to escape velocity. That much time in Earth's radiation belts is dangerous. Upon return it would spend another 3 months spiralling down. That could be solved with an idea from one variation of Semi-Direct: spiral out unmanned and use a crew taxi to deliver the crew just before departure from Earth orbit. Semi-Direct calls for the interplanetary spacecraft to be discarded upon return to Earth and a capsule return the crew. The Russian plan calls for spiralling down before it also uses a capsule to return the crew, but its spacecraft is parked in Earth orbit. You could combine these: have a capsule return the crew to Earth via direct entry while the spacecraft continues unmanned to spiral down to low Earth orbit.

For those concerned about astronauts on the International Space Station, Earth's radiation belts are in medium Earth orbit. That is why satellites are always placed either in low or high Earth orbit, they couldn't survive very long if they were parked in the radiation at medium orbit.

I have some ideas to incorporate In-Situ Propellant Production, but I'll post that on another thread.

How much would it cost to build just 2 Shuttle-C engine pods? The engines would be taken from a Shuttle Orbiter, so it does not require new engines. After a Shuttle-C flight the engines could be returned to the Orbiter fleet. Quoting from the X-38 web site

Shuttle-C could use the Shuttle Orbiter's static test stand. Landing would use the Shuttle Orbiter's vehicle fleet deployed at the salt flats. With only 2 operational vehicles, that should produce an inexpensive spacecraft. This is part of why I claim we can send a manned mission to Mars without any increase in NASA's budget, after the ISS is complete. Pardon me for wanting to rush completion of ISS. 

Yes, exactly. The Mobile Launch Platform has 3 holes cut in it for exhaust: 2 for the SRBs and 1 for the main engines. The holes for the SRBs also have clamps designed to support the weight of the SRBs and hold them down durring main engine ignition. The MLP also has wing supports for the Orbiter. Magnum places the engines under the ET, where the MLP does not have a hole. Ares places its engine pod at the same location as the Shuttle Orbiters main engines. Considering the weight of a HLLV, you can't just cut another hole. Moving the engine location means a whole new MLP.

I argued for a much simpler configuration because it would have a very low development cost.

I had originally argued for using the Energia launch vehicle because all infrastructure was in place, and the Energia strap-on boosters were just a Zenit first stage with a gimbal that has just 1 degree of freedom. Since RD-120 engines were in storage, all the Energia would require was restoration of production of the core module; equivalent to the ET. Another member here pointed out the safety certification of the RD-120 engines expired in 1997, but a thorough overhaul should permit them to be used. Then the vehicle assembly building collapsed. I'm not sure, but I think the RD-120 engines were stored there.

NASA now likes to talk about the Magnum. It is also a Shuttle derived vehicle, but it is a totally new design. Launch requirements are not compatible with Shuttle, so it would require new launch facilities. All this is expensive.

Robert Zubrin's Ares was designed to match the Mobile Launch Platform used for Shuttle, so it could use existing launch facilities. The external tank does not have the tear-drop top so that requires some new tooling at the factory.

Using Zenit boosters to replace SRBs does increase safety, however existing engineering is designed for the mass and thrust of an SRB, so that again means the expense of developing a new vehicle. Such a launch vehicle would also require at least a new MLP. A vehicle that uses 2 or 3 ETs, would not be compatible with existing launch pads at all. Changing engines to RS-68 or Vulcain would again require extensive engineering to develop a totally new vehicle.

For a cost and project management point of view, I argue for Shuttle-C itself rather than some other Shuttle derived vehicle. That means 2 SRBs, one external tank as it is flown on the Space Shuttle, 3 SSMEs, and 2 OMS pods. It would include all the existing fuel pumps, helium tanks, gimbals, hydraulics and auxiliary power units to support the Space Shuttle Main Engines. The thrust support structure (frame) would require very little modification from the current one. If you make the engine pod recoverable, it fits with the internal politics of NASA while providing the same reusability as the current Space Shuttle.

Getting into details, an expendable fairing would require a little structural support to prevent the engine pod from twisting on its attachment to the ET. Currently the structure of the Shuttle's cargo bay provides that torsional support. I calculated the landing mass of the engine pod to be about 14.4 tonnes and X-38 masses 11.3 tonnes, so the parafoil would have to be slightly enlarged. The onboard computer would be an off-the-shelf single board computer. Launch software would be adapted from existing Shuttle Orbiter software; while landing software would be adapted from X-38. The reaction control thrusters would be new and much smaller since they would just control re-entry of the engine pod. Notice the new stuff is just small stuff. That is one of the key points to keeping project cost down: the larger the component is the less modification you make. This design would use the exact same assembly and launch facilities, exact same launch mass, exact same thrust, exact same torsion, exact same acceleration profile, exact same orbital dynamics. Manoeuvring once inserted into orbit would be different due to different RCS thrusters, but operation of the OMS would be the same. In fact, I would use the smaller RCS thrusters only for de-orbiting the engine pod. On orbit manoeuvring of the payload I would leave to the payload itself, or rendezvous with a Shuttle Orbiter. The fairing would be jettisoned after the ET due to the structural attachment to the ET. X-38 uses landing skids instead of inflatable tires since they are so much simpler and, therefore, more reliable. I would use the same thing, but ensure there are shock absorbers to cushion the impact of landing. That only leaves the heat shield. Some people would argue for a lifting body and silica heat shield tiles like the Shuttle Orbiter, or use of the new metallic tiles, but I argue that an ablative heat shield that can be easily replaced would have a lower per-launch cost than maintenance of the tiles. An ablative heat shield permits a simpler and lower mass airframe. The airframe would not be a cone-shaped capsule like Apollo, but flat sides with the same fibreglass blankets as the white areas on the Shuttle Orbiter. That also eliminates the flap/airbrake beneath the Shuttle Orbiter's main engines.

So what does this require? It uses all the same guts as the Space Shuttle Orbiter's engine compartment. It is just a new airframe, small enough to fit on a truck, and a new fairing. It would use all the same launch, manufacturing and maintenance facilities as the current Shuttle. The only new landing equipment would be a flatbed medium truck with dual rear axle and a truck crane. This design uses the KISS principle: Keep It Simple Stupid.

May I make a comment without appearing to be un-American?

The United States has not paid its U.N. dues in full for decades. The federal government does this because they don't like a couple programs of the U.N. and deduct that proportion of their U.N. dues. Now tell me, how many Americans can honestly say there isn't at least one federal program they disagree with? How many Americans could get away with simply not paying their income taxes in full as a protest against the program they don't like? I must pay my Canadian taxes in full, and had to pay taxes to the IRS when I worked in Florida. If we disagree with a program we can lobby our elected officials, we cannot simply fail to pay taxes. If the United States continues to fail to pay its U.N. dues in full and on time it should be kicked off the U.N. Security Council. It could get its Security Council seat back by paying its dues in full.

The other criticism is the No Fly Zones. America requested the U.N. establish No Fly Zones after the Gulf War. The U.N. said No. America and Brittan have been enforcing the No Fly Zones anyway. Iraq could argue this is an act of aggression against Iraq; in fact, Iraq could try to claim its attempts to shoot at American war planes patrolling Iraqi air space are simply self-defence. No one could possibly defend the actions of Iraq, but two wrongs do not make a right. Could we at least see the current action against Iraq put a permanent end to the No Fly Zones?

I have a more modest suggestion. The question is how to get the powers-that-be to listen.

If the goal is to reduce launch cost, I would suggest a more modest implementation of a Crew Transfer Vehicle (CTV). The X-38 was originally called a Crew Return Vehicle (CRV), but since engineers have been working on ways to launch it on Europe's Ariane 5 or some other rocket, they now prefer the name CTV. The original proposal was for a 4-astronaut vehicle since the Russian Soyuz could carry the other 3. That would permit a fully crewed space station of 7 astronauts. Some American planners did not want to rely on Russian technology, but the Soyuz has proven itself over a third of a century so I say why not? If we return to a 4-astronaut vehicle that would make it much smaller. In fact, such a smaller CTV could be launched on an Atlas V 401. That would reduce launch cost to $77 million instead of $170 million for Delta IV Large. The Russian Soyuz FG launch vehicle is the latest upgrade to carry the Soyuz-TM spacecraft to ISS. It costs $40 million per launch in 1999 dollars. That cost doesn't include the spacecraft or mission control operations, just the launch vehicle. A small Atlas V is still significantly more expensive, but at least it's cheaper than Delta IV Large. A reusable CTV spacecraft may make the cost difference less significant.

That would create an even more cost effective alternative to the Space Shuttle. $170 million for Delta IV Large to carry cargo, plus $77 million to carry 4 astronauts in a CTV, plus whatever the servicing cost would be for the CTV, plus mission control cost. That sounds significantly cheaper than $545.5 million per shuttle launch.

Atlas V 401 is the small configuration of Atlas V. It has a 4 meter diameter fairing, and can lift 12.5t to 185km at 28?. I calculate it should be able to lift 8.25t to ISS. The 7-man configuration for X-38 with its de-orbit module would mass 14t, and Soyuz-TM with its 3-man capacity masses 7.15t, so a 4-man version of CTV should be able to fit within 8.25t.

Perhaps it would be more politically correct to argue for a space station with a 4-astronaut capacity and an all-American CTV. This would be more than the 3-astronaut capacity that some are arguing for now. Scientists complain that it takes 2.5 astronauts just to operate the station, so they are left with half an astronaut to run science experiments. Adding one more astronaut would tripple science, and politicians could still brag that the American spacecraft can carry one more astronaut than the Russian one.

Hi Shaun,

Please don't be disheartened. It may take a little research to get "up to speed" on all the various acronyms, but anyone who really cares can do it quickly. The term LV does in fact refer to Launch Vehicle. HLLV means Heavy Lift Launch Vehicle, such as Saturn V or Ares. EELV is an odd acronym; it means Evolutionary Expendable Launch Vehicle. It refers to the US program to upgrade existing launch vehicles to deliver launch capability competitive with Ariane 5 or Proton. When someone talks about an EELV they are talking about the result of a specific program, not a class of launch vehicle. That is why I never used the term until Mark S brought it up.

When talking about Launch Vehicle classes, definitions have become fuzzy recently. NASA used to categorize Saturn V or the Russian N1 or the proposed Ares launch vehicle as Heavy. The Space Shuttle or Titan 4B or Russian Proton were categorized as Medium. The Russians, however, categorized the Proton and Titan 4B as Heavy, and the Saturn V and N1 as Super-Heavy. Now Boeing wants to categorize Delta IV Large as "heavy" despite the fact it is in the same class as Titan 4B or Proton. The salesmen are having fun at your expense.

The article you quoted does make some good points. The heaviest versions of Atlas V and Delta IV (vehicles developed under the EELV program) have exactly the same price as the European Ariane 5, and comparable lift capacity. Does anyone believe this is a coincidence? By the way, the European Space Agency is in the process of upgrading Ariane 5. Competition lives! Add to that the Russian Angara 5 that will replace Proton, and the Chinese Long March CZ-5 that will have a core based on Europe's Ariane 5, and you have an incredible level of world competition. For those who want commercialization to replace NASA; don't worry, it is already here.

I had worried when the Delta Clipper (also known as DC-X) had worked perfectly when the US Air Force was in control, but the first launch by NASA with participation by Lockheed-Martin resulting in a crash-and-burn. It crashed because someone "accidentally forgot" to remove a pin that preventing one of the landing legs from deploying. The X-33 was mostly based on existing technology used in new ways. The only new technology was a composite cryogenic fuel tank. Lockheed-Martin made a last minute change to the tank design, and the first test resulted in failure. Lockheed-Martin refused to comply by the contract clause that required them to share the cost of that set-back, so the X-33 as cancelled. Then the X-43A (also known as Hyper-X) failed its first test flight. It was supposed to be a scale model of a SCRAM jet aircraft. It was launched on a Pegasus rocket, but that rocket mysteriously had a fin fall off. Then one month after I mentioned to an employee of Orbital Sciences (manufacturer of the Pegasus) that the Russian Energia could be reactivated relatively easily, the Russian vehicle assembly building had its roof collapse. Every possible low-cost replacement for the Space Shuttle has been lost. To those who believe in conspiracy theories, this sounds like industrial sabotage.

I should mention one mistake in that article. It mentions "NASA may soon cancel the promising VARISM plasma engine research project citing a lack of funds." I believe this is referring to the VASIMR engine. That is another acronym; it stands for VAriable Specific Impulse Magneto-plasma dynamic Rocket.

So where does that leave us now? The Atlas V and Delta IV will have to remain competitive with other launch vehicles. Their largest versions have a lift capacity comparable with the cargo bay of the Space Shuttle. Delta IV Large can lift an X38 to ISS. Replacing the Space Shuttle may take 2 launches of Delta IV Large, one for cargo and another for astronauts, but at $170 million per launch compared to $545.5 million for a single launch of Space Shuttle, you tell me which is the better deal.

The ideal would be a single stage to orbit (SSTO) reusable launch vehicle (RLV) that uses a rocket based combined cycle (RBCC) engine. An RBCC engine would operate as a RAM jet, a SCRAM jet, an air augmented rocket, and a rocket engine that uses LOX as oxidiser. This hypothetical space plane could horizontal take-off, horizontal land (HTHO). The NASA view for third generation vehicle is to use a magnetic catapult to launch the vehicle to the speed required to ignite the RAM jet. If we are going to dream, the vehicle could have a small fan jet engine added for take-off. It would only require enough thrust to lift the vehicle off the ground and accelerate to speed necessary to start the RAM jet. You could even duct fan jet exhaust into the RBCC intake so it would act as an after burner for added thrust to accelerate to RAM jet ignition speed. A fan jet could be used for powered landing; you could "windmill" the engine to air restart it upon approach to the airport. If the fan jet used the same fuel as the RBCC engine, it wouldn't require a separate fuel tank. Addition of a fan jet would increase safety, and permit the vehicle to take-off and land from any commercial airport equipped with fuel handling facilities. Unfortunately, there is no RBCC engine available.

Now back to reality. If you can launch 95 tonnes to the ISS with Shuttle-C for the same cost as 19 tonnes using the current Space Shuttle, then why not? If you can ferry astronauts to ISS on an X38 derived vehicle using Delta IV or Atlas V for $170 million per launch instead of $545.5 million for a Shuttle launch, then why not? It's just economics.