VASIMR Rocket can take you to Mars in 39 days

[mheslep]

Are you saying NASA owes no responsibility to taxpayers? Or only their contractors?

No

 

[pervect]

Which ones, for instance? Could you elaborate?

I don't know much about propulsion physics but VASIMR seems to me a solution in search of a problem for now.

From what I've read, VASIMIR, with existing solar cell power sources has potential applications as the engine for a reusable "space tugs" for various orbital transfer missions. Ad Astra specifically proposed low-earth-orbit to low-lunar-orbit transfers, with an analysis supporting Vasimir's superiority over existing chemical propulsion. I'm not aware of any figures for low Earth orbit-geostationary orbit "space tugs", but it seems like a logical idea along similar lines.

 

[Monsterboy]

Zubrin said in the video that radiation levels in deep space is only twice that of low Earth orbit ,can anyone give any reference to this claim ?

 

[rollingstein]

From what I've read, VASIMIR, with existing solar cell power sources has potential applications as the engine for a reusable "space tugs"

To me, even a space tug sounds somewhat like a solution in search of a problem.

Does anyone want one? Has anyone commissioned one?

 

[Dotini]

Zubrin said in the video that radiation levels in deep space is only twice that of low Earth orbit ,can anyone give any reference to this claim ?

This is a good question. I will start with a peek at low Earth orbit.

http://www.esa.int/Our_Activities/S...ology/Space_Environment/Radiation_environment
RADIATION ENVIRONMENT
Radiation in the space environment comes from the trapped particle belts, solar particle events and cosmic rays.

Trapped Particle Belts
The radiation belts consist principally of electrons of up to a few MeV energy and protons of up to several hundred MeV energy. These are trapped in the Earth's magnetic field; their motions in the field consist of a gyration about field lines, a bouncing motion between the magnetic mirrors found near the Earth's poles, and a drift motion around Earth.

Basic motion of trapped particles in the Earth magnetic field

Radiation is an obvious concern for manned missions. In the near-term, manned activities are limited to low altitude, and mainly low-inclination missions. The International Space Station (ISS), Space Shuttle, EnviSat and other low altitude missions will therefore encounter the inner edge of the radiation belt. This region is dominated by the "South Atlantic Anomaly (SAA)" - an area of enhanced radiation caused by the offset and tilt of the geomagnetic axis with respect to the Earth's rotation axis.

Earth radiation belts with the South Atlantic Anomaly indicated
Besides the SAA, the polar horns also play a role for radiation analysis at low altitudes (e.g. ISS type orbit). Polar horns are parts of the outer radiation belts, which are close to Earth. As can be seen in the simulation below, increased radiation flux due to the polar horns can be expected between 60 and 90 degrees lattitude. The SAA is clearly visible at the South Antlantic region around 30 up to 50 degrees lattitude.

http://wrmiss.org/workshops/sixth/golightly.pdf
http://hps.org/publicinformation/ate/faqs/spaceradiation.html

The Cruise Phase poses a significant radiation problem due to the cumulative effects of isotropic Galactic Cosmic Radiation over 400 days. The occurrence during this period of a large Solar Energetic Particle (SEP) event, especially if it has a hard energy spectrum, could be catastrophic health wise to the crew. Such particle events are rare but they are not currently predictable.
http://www.sciencedirect.com/science/article/pii/S0032063311002030

Design and test of Orion capsule for radiation.
http://www.engineering.com/Educatio...-Shield-designed-by-High-School-Students.aspx

http://motherboard.vice.com/en_ca/read/orion-radiation-survival
"...radiation can corrupt data. It can turn a 1 into a 0. It can make a processor think that 2+2=5."

On the road to Mars:
http://phys.org/news/2013-05-exposure-journey-mars.html

Energetic protons constitute about 85 percent of the primary galactic cosmic ray flux and easily traverse even the most shielded paths (reds) inside the MSL spacecraft . Heavy ions tend to break up into lighter ions in thick shielding, but can survive traversal of thin shielding (blues) intact.

The solar particles of concern for astronaut safety are typically protons with kinetic energies up to a few hundred MeV (one MeV is a million electron volts). Solar events typically produce very large fluxes of these particles, as well as helium and heavier ions, but rarely produce higher-energy fluxes similar to GCRs. The comparatively low energy of typical SEPs means that spacecraft shielding is much more effective against SEPs than GCRs.

"A vehicle carrying humans into deep space would likely have a 'storm shelter' to protect against solar particles. But the GCRs are harder to stop and, even an aluminum hull a foot thick wouldn't change the dose very much," said Zeitlin.On the road to the Moon; proton backsplash hazards mentioned.
http://www.sciencedaily.com/releases/2013/11/131118133044.htm

 

[Crichigo]

I hope it'll work. We are going to experience the same emotion that people back in 1969 experienced when Neil Armstrong became the first man on the moon.

Also I hope that we (humans) don't overexplore Mars as we are doing with Earth. By the way, you might know that Europe, one of the moons of Saturn might also have oceans under its 21Km of ice. I think Europe is going to be the next objective of humanity but it won't be now or any time soon, says Stephen Hawking.

 

[mfb]

There are suggestions for unmanned probes to Europa. Manned missions ... probably not in our lifetime.
By the way: Europe is the continent on earth, Europa is a moon of Jupiter (not Saturn).

There are also some other moons that could have water below their surface.

 

[Monsterboy]

@Dotini

All that makes it look like Zubrin underestimated the radiation problem , but I didn't really get an accurate answer , there are many other things he said of which I am not sure of , like the rotating spacecraft idea to produce artificial gravity , everyone is aware of the idea but the centrifuge must have a diameter of 1km in order to prevent nausea among astronauts.

So its best if he can come up with a peer reviewed paper or something as mheslep suggested to make his points clear.

http://news.discovery.com/space/history-of-space/mission-to-mars-health-risks-1107181.htm

 

[mheslep]

The Cruise Phase poses a significant radiation problem due to the cumulative effects of isotropic Galactic Cosmic Radiation over 400 days.

Zurbrin's contention is that the concern over GCR for a Mars vorgage is overblown, as the crews on the ISS have been exposed to GCR for similar periods, and the GCR energies are such that the Earth's magnetic field provides little protection to GCR, unlike solar radiation. Extreme solar events in deep space, being directional, can be addressed by means of a water wall, as is routinely done on the ISS

 

[Dotini]

A brief NASA video on the dangers of radiation to Mars-bound astronauts. In short, they may exceed the maximum permitted lifetime limit of radiation dosage on the round trip alone. They don't rule out eventual manned flight to Mars, but do require a new set of technological solutions to be found.
http://www.space.com/21365-will-radiation-kill-mars-astronauts-video.html

 

[mheslep]

A brief NASA video ...

Credit at the end was "Space.com", not NASA.

"exceed the maximum permitted lifetime limit of radiation dosage on the round trip alone."

A maximum lifetime dose of 1 rem/yr cuts lifetime due to cancer risk by 51 days supposedly. For comparison smoking a pack/day cuts 6 years. I suspect the radiation harm would have double or triple to give pause to any serious candidates for the trip.

 

[mfb]

The lifetime radiation limits for astronauts are quite arbitrary. Compared to all the other risks of sending astronauts nearly 1000 times further away than ever before, I think an increased risk of getting cancer is not the most pressing issue. Sure, you have to consider shielding, especially against the sun. But it does not make a trip impossible.

 

[Dotini]

But it does not make a trip impossible.

Agreed.
But it makes it unlikely if you're entrusting NASA with its current standards to do the job of getting a person to Mars and back.

 

[mfb]

Well, invent new limits for trips to Mars ;).

 

[Monsterboy]

Well , Mars One doesn't appear to be depending on VASIMR but they don't seem to be doing any better either.
http://www.dailymail.co.uk/sciencet...net-colony-suffocate-months-study-claims.html

MIT study says even if their astronauts get to Mars alive , the first fatality will occur in 68 days.

 

[Dotini]

NASA has awarded prize money to five members of the public for their ideas about how to limit astronauts' radiation exposure during journeys through deep space.

http://news.yahoo.com/5-mars-mission-radiation-shield-ideas-win-nasa-112310679.html