STEVE SANDFORD: Welcome back
for the fifth installment, the fifth lecture in our series,
for those of you who have been here the whole time of course we
started off with an overview of the future of the American Space
Program and where we are going, then we followed that up
with our two lectures about our transportation system which is
what we are working on right now, we have money to that and
funding to do that and that is happening today
across the country. And then last week we talked to
you about one of the two really tough problems, I sometimes say
miracles that have to happen for us to pull this off, and that
was landing human scale payloads on the surface of Mars through
the really poor atmosphere that Mars has. And today we are going to
hear from Dave Moore and Martha Clowdsley about how we are going
to attack the problem of the effects of
radiation on astronauts. So, it is a long trip to Mars,
and Mars doesn't have the same protections that we enjoy
here on Earth from our magnetic field. And so we have to come up with
ways to protect the astronauts on the way and while they
live on the surface of Mars. And you have got two of the best
experts here this morning and I am going to turn
it over to them. [Applause] DAVE MOORE: Thank you. Can you all hear me?
Okay, good. As Steve mentioned we are going
to give you all a briefing on the radiation protection
efforts that we are ongoing now over at NASA. As most of you are aware the
effects of radiation here on Earth, how it can
affect our power grids, our water system, our
cell phone service, the airline industry, but as
we move further away from the Earth's protective magnetic
field there are issues with protecting the
astronauts and their safety. As Steve mentioned we are
looking at missions that could go anywhere from
two to three years. So we are working on
processes to protect the astronauts going forward. Steve also hit on,
I guess this is, we are the fifth in the
installment and you guys have probably already seen kind of
our flow chart how we propose to get to Mars and what I want
you to take away here on the far right, you see our
missions two to three years, so we have a big effort ongoing
in the agency to address the top problem with space radiation. To give you kind of perspective
of what prior astronauts have seen with exposure in space,
you can see on the graph here, all the human missions, the
Mercurys and the Geminis and what I want you to focus on is
over in the right you see the Mars, little box for Mars, we
are looking at this exposure that we are expecting the
astronauts to see is a factor of 10 greater than what
anybody has ever received currently and flown. So this is a big problem for
us and we are spending a lot of effort trying to address it. To give you another perspective
and put it in context of what we see here on Earth, you
start near the line, you see over here
in the far left, if you go for an office
visit to get a chest x-ray or a mammogram, the kind
of exposure you get, and as we move
further to the right, you see commercial
airline pilot, maybe a factor of 10
or greater exposure, and then if we move one step
further over into the ISS realm, the astronauts there are seeing
like a 1000 times greater than what we see here on Earth. Then if you move away, we are
proposition to go to Mars on a three-year mission we are
seeing something like 10,000 times greater than what
we currently see on Earth. We are very blessed to have the
Earth's shielding protected with these magnetic fields. I am going to turn it over now
to Martha and she is going to give you a briefing on the
environments that the astronauts are subject to and some of the
risks that they have to endure and then she will turn it back
over to me and I will give you a briefing on some of the
mitigation efforts that we are doing here at Langley. MARTHA CLOWDSLEY: So, I am going
to try in a very few minutes to explain why we are
worried about space radiation. There are really three types
of environments we are worried about, there is galactic cosmic
rays which are heavy ions that are out there all the time,
there are solar particle events which are isolated events but
can provide a very large dose and then there is
radiation that's trapped in the earth's
geomagnetic fields. We are going to talk a little
bit more about each of those. Galactic cosmic rays are highly
charged energetic nuclei that enter our solar system from
outside the solar system. It is modulated
by the solar wind. So, we have 11-year solar cycle
and it will go from more intense to less intense, but
it is always there. It is about a factor of 2
it varies from solar max to solar min. The galactic cosmic rays, it
ranges from protons all the way up to much heavier
ions like carbon, aluminum, gold, iron, and
there is a huge range of energy, from just a few EV
to tens of GEVs. So the heavier the faster ones
are moving at speed of light and just very, very penetrating.
So, that's our problem. So, you don't get enough dose
from galactic cosmic rays to worry about it
for short missions. So, it was never a problem
for the Apollo missions. You know they were
there for a few days, didn't get enough exposure. But for these longer duration
missions you are getting enough dose so we are worrying
about increased risk of cancer especially. So, it becomes a shielding
problem for the three-year Mars mission is something we just
can't actually close on it, we can't provide enough
protection right now. Question? AUDIENCE: Do the rays affect the
human DNA and if so what can you do to protect them? MARTHA: Yes, yeah, and we are
going to talk a little bit more about that in a few slides, but
the question was do the rays can they affect the human DNA
where they break the DNA strand, and the answer is yes. So solar particle events
unlike the galactic cosmic ray environment which
is always there, solar particle events
are isolated events. They correspond to coronal
mass ejections from the Sun, though the way they relate
is not always intuitive. So you can have a big coronal
mass ejection and not have a big solar particle
event or vice versa. So it is really hard to predict
and Dave is going to talk a little more about that in a bit. Really large events that would
provide significant risks to astronauts are pretty rare. We see one or two
for 11-year cycle, but a large event that
caught astronauts on EVA without protection on spacewalks
would be a challenge, it could be a real health risk. So, the one thing that's good
about solar particle events is that it is mostly protons and
they range in energy again from a few EV, this
time about 1000 MEV. So, they don't go
quite as high as the GCR. Shielding is much
more effective for them. So the point is that we have
to get astronauts in a place where they are shielded. It is a solvable problem
but we have to make sure that we address it. Entrapped radiation -- We are
not going to talk a whole lot about that because we are mostly
focusing on exploration missions that go beyond the
earth's magnetic field, mostly worried about
that mission to Mars. But I did want to mention it
because it is another source of space radiation and one that
astronauts have been exposed to. What happens is that protons and
electrons especially and a few other particles but mostly
protons and electrons get trapped in the Earth's
magnetic field lines, and basically they swirl around
the field lines and they just follow the field lines back
from pole to pole and they are always there. The space station is at a pretty
low orbit so it doesn't go through the worst of the Van
Allen's belt which is why the astronauts are relatively safe. It does sort of pass through
them on each rotation and you get a proton dose
as that happens. So they do get
some dose from this. The magnetic fields also provide
protection to us on earth and to the astronauts on ISS. The lower energy galactic cosmic
ray particles are actually, their path gets deterred
so they provide a lot of protection to Earth. Just backing up, what are these
charged ions are talking about, for those of you who remember
your high school chemistry class this picture
might look familiar. So, just remember
what an atom is, an atom is basically a
nucleus surrounded by electrons. Now this picture is
not at all to scale. The entire atom is about 10,000
times bigger than the nucleus. So, most of the volume of the
atom is the electrons rotating and the nucleus is very
small and very tightly packed. Now the electrons are negatively
charged and you have an equal number of positively
charged protons in the nucleus, and those are bound together
with neutrally charged neutrons. So the nucleus is made up of
neutrons and protons packed tightly together and then you
have got orbiting electrons. So, when we talk about
how shielding works, picture your aluminum wall
which is between the astronauts, and yeah this is a
really old graphic I know, but the astronauts are
on inside of the vehicle, the space radiation
environment starts out on the outside of the environment. You get tightly packed nucleus
of protons and neutrons which impact the wall. Now the wall, again most of the
volume is those electrons and then every so often on
a very miniature scale you have a nucleus. Mostly what happens is these
particles moving through the wall they are positively charged
because they have been stripped of all their electrons, so they
are trying to grab an electron from the atoms making
up the shielding wall, and it slows down
as they do that. So the particles coming in are
slowing down and then every so often they bump into a
nucleus of the shielding wall, aluminum or whatever it
is, and they will break up, and secondary particles
will be produced. It is possible that the
environment behind the shielding will be worse than
the environment outside the shielding. If you picture some heavy ions
here and they come through the shielding and now you have
got protons and neutrons being produced and more and more
particles being produced so we have to be really careful in how
we work shielding that we don't actually make it worse. Permissible exposure limits
-- how much radiation are the astronauts allowed to get? We have several kinds of
limits, we have 30-day limits. 30-day limits are
basically a threshold value. You don't want to get more
than this amount of radiation to avoid things like radiation
sickness and it is basically what you are worried about is
the astronaut being on a space walk when a solar
particle event happens. As long as they get the
protection before the solar particle event happens
the 30-day limits don't come into play. We also have career limits
for some specific effects, circulatory system,
central nervous system, We're not going to talk a
lot about those. The big challenge for us is
this requirement that risk of exposure induced death will be
less than 3% and that we ensure that at a 95% confidence level. We are going to talk more about
why that 95% confidence level statement is there, but what
this means is we all have a risk of dying of cancer. The astronaut's risk of dying of
cancer due to the exposure they are getting should be no
more than 3% more than average geo-Americans. The other thing is radiation
exposure should be kept as low as reasonably achievable and
this is the ALARA principle and it sounds like
really squishy words, you guys go and do
the best you can, but it is actually a
really important requirement, because what this requires
is that every time we send an astronaut in space we need to
do all of the trade studies to ensure we have done everything
we can to keep them safe. So you need to look at your
vehicle and is there a way you can redesign it and
evaluate each possible way you can redefine it. You need to look at your mission
ops plan for when they are going to be doing space walks and
basically test each one and figure out what's the best way
to keep the radiation exposure as low as reasonably achievable. It is a very important
requirement for us. So, again, why are we so worried
about this space radiation environment and why do we have
at 95% confidence requirement. So the space
radiation as we said, it is protons but it is also
heavier ions and it is basically different than anything
humans have been exposed to. We have a very limited number
of astronauts that have had some extensive time on ISS that
have been exposed to a somewhat similar environment, but the low
energy particles are pretty much cut off at ISS because the
magnetic field protects them. So we don't have any population
of humans that have been exposed to a lot of heavy ions. There is no way for
that to happen on Earth. So, most of our risk estimates
are based on atomic bomb survivor data. So we are extrapolating from
a totally different type of radiation and a totally
different population with a totally different diet than
people were eating back then. So, there is a lot of
extrapolating going on. If you look at this picture
on the right which might be a little bit confusing, what this
is this is the path of different types of particles
through a material. Hydrogen protons
are on the left. Helium are just a little bit
heavier and then as you move to the right it gets heavier
and heavier all the over to iron ions. This is sort of the path they
carve through the material. So the ion is bigger. It is basically just
clearing a bigger path, so would be causing more damage
to DNA and shooting off more delta rays, sort of the scatter
look are delta rays coming off the particle which
also can cause damage. So, again, the problem is that
we haven't had humans exposed to this so how do we
estimate the risk? Even if we can calculate
perfectly how much radiation they are seeing how do
we estimate the risk? And the way we are working this
is by doing more and more animal testing in heavy ion
beams, but it takes time. So, your question about
DNA, these are just diagrams, here is an intact DNA
strand and up here you see, if an x-ray would come through
it might be able to do damage to one very, very small
part of that DNA strand. However, heavy ion has the
ability to break both strands of the DNA and it is shooting
off delta particles which are doing more damage. So heavy ion has the ability to
affect this DNA strand so that it can't repair itself, which
actually wouldn't be the worse thing, if you kill a few cells,
we have got lots of cells, it is when they repair
themselves in a bad way that we end up with cancer. So, there are three
things that can happen, you can have a single strand
break where a particle goes through one strand of the
DNA and those sometimes repair themselves correctly. You can have a double strand
break and this is a problem because they can come back
together the wrong way and now you have got a mutated cell and
that mutated cell propagates at some point you have got
cancer, or you can have chemical changes to the DNA. All of these are big worries but
the double strand breaks that you see with heavy ions is
really our greatest concern. So, how do we calculate
astronaut risk? There is a bunch of different
parts that go into that. We have to be able to evaluate
the space radiation environment and I showed you plots of what
the GCR environment looks like. We actually have a
pretty good fix on this. It is not perfect on any given
day but we have a pretty good fix on what types of
particles are there and what energies are there. We need a radiation transport
code to calculate how that environment changes as it goes
through aluminum shielding or whatever kind of shielding and
as it goes through human tissue, I mean your body is
providing shielding to your internal organs. We need models of the shielding,
we need models of the vehicle, we need models of
the human body. All of those things have some
error associated with them in the way we do it now. It is small, but we
don't have it perfect. Once you have done that though
and you actually know the exact radiation that is being absorbed
by your liver and by all of your internal organs we need to
be able to figure out what biological risk that poses. So we need radiation quality
factors that take into account the fact that one type of
particle is much more damaging to humans than another. We need tissue weighting factors
which take into the account the fact that one type of
tissue is much more sensitive to radiation, you are much
more likely to get one kind of cancer than another. And we need radiation
coefficient factors to convert to risk and we need dose and
dose rate reduction factors. When we test things in the lab
we give it a lot of dose really quickly whereas
the GCR environment, you know as I said, you have to
be out there for quite a while before it becomes a problem, it
is a much more slow dose that you are getting. All of these we have significant
uncertainty with those. So there is our problem, you
know if we don't know really reliably what that quality
factor is how do we tell the astronauts what their risk
is, and that's where that requirement that we ensure that
astronauts gets no more than a 3% risk of exposure
induced death is ensured at 95% confidence. This probability distribution
function may or may not be confusing looking but the red
line could represent our best guess at the astronaut's risk. So, you take the best
environment model we can come up with, you use the
best transport codes, you use the best
models for the vehicle, you calculate the organ doses,
you convert that to risk using the best quality
factors you have, however, if the quality factors
are little higher this is another estimate, the quality
factors are little lower this another, if the dose rate
factors are little higher, so all of these black lines
represent possible answers for the same exact mission, how
much risk is the astronaut is really seeing. So if we want to ensure that the
astronaut has no more than a 3% risk of exposure induced
death at a 95% confidence, we have to provide shielding
that gets us way over here on this plot, and that's where
we end up with a mission that doesn't close. We don't know how to provide
that much protection for a three-year mission to Mars and
it is something we are still all actively working on
as fast as we can. So, let's talk about
shielding materials. Most vehicles are made out of
some sort of aluminum alloy, though there are a lot of
plastics involved in current vehicles in the internal
structure and of course the things you bring food, water,
but anyway aluminum is not a great shielding material. These plots are effective dose
to the astronaut versus shield thickness, so you can see
you are getting a much greater reduction in materials
that have a hydrogen content, polyethylene, water, pure
hydrogen would be even better it is really hard to build a
vehicle out of pure hydrogen. So, anyway, one thing to note
is that materials with hydrogen provide better shielding
for the same amount of mass. So when we can we want to
use those types of materials. The other thing to note from
this plot is you know on the left you have got one for
galactic cosmic rays and on the right you have got one
for solar particle events. The plot on the right,
this is a log scale, so as we said before, shielding
solar particle events is much more effective, you are getting
a significant reduction in dose here by adding a
little bit of shielding. Over here you are getting
much less reduction in dose by adding shielding. So we can pretty
much shield SPEs, we just need to
make sure it happens. Galactic cosmic rays is
a whole another issue. The other things you see about
these two plots is that the plots are leveling off. Add a little bit of shielding
you are getting a good amount of reduction, then you keep adding
more and more shielding and you are getting a lot
less bang for your buck. And I know you have heard the
previous speakers talk about how every pound, launching
every pound is a problem. The goal is absolutely to
minimize mass and here we are adding more and more
mass and getting very little reduction in dose. So that's our problem
that's our challenge. Here are some calculations
for how many safe days in space astronauts have before they
reach that 3% risk of exposure induced death,
calculated in 95% confidence. There are some assumptions
that went with this calculation. If you had different assumptions
you get slightly different numbers but it gives
you a real feel for it, in this case the astronauts were
in a 20 g per centimeter squared aluminum vehicle,
so think Mork's egg, it was just a spherical
vehicle for these calculations. Two things to note, well the
big one is that no matter what assumptions you make and
which astronauts you send we are looking at less than a year
before they reach that 3% risk of exposure induced death
with the 95% confidence. The other thing to note is that
males can stay longer before they reach it, and
the younger people, females or males, can stay
longer than older people--the other way around,
older people can stay, younger people
have greater risk, excuse me. Right now this is
the NASA model, the 2012 model. So these are the
numbers you would use. The right hand column is a new
model that people are looking at, basically our astronaut
population is a very healthy group of people. If we assume that none of them
have ever smoked which is a pretty close to real assumption
they have a lower risk of cancer, so they could
maybe stay a few more days, but none of these models are
showing that you can stay for three years, so again
this is our problem. So what are we going to
do about the problem? Well, basically we are going to
attack it from every angle we can and what's not shown on here
but was mentioned at last week's meeting for those who were here,
so I want to bring it up the absolute best thing we
can do is get there faster. Astronauts stay a
shorter amount of time, they get less
radiation exposure, they have less risk. So if there is a propulsion
breakthrough that allows us to go to the Mars and back
faster that is the best answer. And I don't have that on these
charts because those of us in the radiation community
aren't really working on that part of the problem. So, there are four ways
that we can attack it. The first is radiobiology and
biological counter measures. Reducing that uncertainty
would definitely help. You saw how much
an affect that has. And if we can find some way to
give astronaut medications or find some way to help with
that radiation that will be great too. Forecasting and detection --
we got to make sure those astronauts get into shelters the
minute the SPEs are happening. Shielding materials and
configuring vehicles better is a big part of it and there is
a possibility that active shielding will be
part of our solution. So we are just working them all
at the same time in trying to together come up with
a solution that works. I am going to talk about the
radiobiology and biological counter measures briefly and
then hand back off to Dave. So, as we showed on our
probability distribution function we have got about
450% uncertainty associated with astronaut cancer risk. So if we can reduce that
possibly they can get more dose and still stay under that 3%
risk of exposure induced death. So that is really a
big, big part of our goal. We have current models
completely rely on atomic bomb survivor data and
that's a problem, we need more data
related to heavy ions. We have some evidence that
heavy ions have a different effect on humans. We are seeing earlier tumor
growth and more aggressive tumor growth in animals that have
been exposed to heavy ions. So this is something we are
really worried about and NASA does support an extensive
biological experiment program. As far as radio protectors
and mitigators this work is really in its infancy. And if we had this all
pinned down we would have solved the cancer problem. The NIH would come to us and we
could tell them how to solve it. It is a really challenging
problem but it is being worked. Couple of focuses, they are
looking at biomarkers that would predict radiation diseases
earlier so then we could get people to treatment earlier
which might reduce the chance of dying of cancer. Hopefully this will allow us to
get earlier treatment and it may in the future allow us
to actually do personal risk assessments. So instead of talking about
female astronauts that are 35 years old as compared to female
astronauts that are 45 years old, we can talk about astronaut
Dave Moore and have a complete model of Dave Moore's body and a
complete model of Dave Moore's risks that includes all of his
risk factors from his previous life experience,
that's a long way off, but that is the goal. Just one picture, we are really
proud of our space radiation laboratory up at NSRL, it is
a laboratory at Brookhaven National Lab, so we
basically partner with them, we use their beam lines but
we have our own facility on their center. Brookhaven is a
Department of Energy Facility. So this is the beam line, you
basically accelerate particles faster and faster and then it
comes shooting down the line into our facility and we can
put cell cultures in the line, we can put small
animals in the line. Problem is it is a slow process. You saw the galactic cosmic
ray environment is all kinds of different particles at
all different energies, you got to do one particle
and one energy at a time here. So it is a big
challenging problem, but we are working it. And I am going to pass off to
Dave who is going to talk about engineering approaches. Questions? AUDIENCE: Don't we have
Chernobyl and Japanese meltdown and 3 Mile Island, or
is this different ions? MARTHA: Its different ions. You have the same type
of problem where you are extrapolating from a different,
the question was what about data from Chernobyl and the Japanese
meltdown and 3 mile island, don't we have some more
data other than just atomic bomb survivor data? The answer is you have got
the same problem with Chernobyl where it is a
different type of radiation. You also have much
smaller populations, especially with the
Japanese situation. So we don't have a whole lot
of data to build models on. You had a question...
AUDIENCE: Active shielding, is that being and electronic,
impulsive type of thing? MARTHA: It means creating a
magnetic field and Dave will talk a little bit
more about that. The question was, what
is active shielding? And the answer is Dave is
going to talk about it. Question? AUDIENCE: Do we know that there
is significant bone loss during extended space travel? Will the astronauts even be
able to walk by the time they get to Mars? MARTHA: I don't know
the answer to that. We do know that there is
significant bone density loss for missions and I don't know
where we are currently with studies about three-year
missions and so I can't answer that one. Question? AUDIENCE: Would the astronauts'
medical history give us a tendency towards cancer,
en route to a place? MARTHA: Question is with the
astronauts' medical history, with his or her tendency to
get cancer enter to it at all? Right now we keep track of
all of their previous exposures because we have many astronauts
who go up more than once and that does enter into it. They use that to decide
whether they can fly again. We do not have, we do
not use specific, you know, your type of
group is more likely to get cancer than some
other group, we don't, we had some evidence that women
were more susceptible than men, we don't use that in deciding
who gets to go at this point. There is research looking at
that but we don't use that as a qualifying or a
disqualifying factor. And as far as
specifically whose risk, how much risk individuals have,
we are really not there with the science to be able to
predict, my risk being more or less than
Dave's. Question? AUDIENCE: You mentioned
this a couple of times; what is Delta-radiation? MARTHA: Delta radiation--I am
not sure I am going to do a good job explaining it. As the particle goes through,
it is basically other particles, delta rays are emitting energy,
so you are passing near nucleus and it is having interaction
that's causing that particle that is coming through
to shoot off a delta ray. AUDIENCE: A different
type radiation? MARTHA: Yes, yeah, sorry,
I am not doing a great job explaining that. [Applause] DAVE: Will see they will
clap when I am finished! All right, another area we are
working on integrated approach is forecasting and detection. If you can forecast the on
currents of the events you know that gives your astronauts
that much more warning, that much more time to go seek
shelter especially when an SPE is occurring, and then also we
are working on capabilities to improve our detection
possibilities, I will show you here. In the area of space weather
forecasting there is a lot of research and models being done
that we work on addressing the issue of forecasting and
arrival time, when the event will actually hit
you and what that dose will be and how long that
event will occur. But that has all been up
to last few years been kind of researching. We have got an effort ongoing
now at Langley to integrate that work into an operational
platform where we can have the console operators on ground or
the astronauts that are actually in space have all those
capability and knowledge right in front of the screen for them. It is a suite of software
that we put together, as you can see on the
graphic on the left, it kind of gives
them a stoplight chart, red, green, red is
bad, green is good, it can give them other features
where they can go in and check on the duration of the event,
when it is going to arrive, how it compares to other
historical events that we have recorded data on. So this is some work that
we are doing in the area of space weather. Just to dig a little deeper
in the clear forecasting area, we are hoping to increase
our warning time capability. Current state of the
art is an hour or so. We are hoping to expand that
from 4- to 24-hour window and we are doing that in
partnership with NOAA. The idea here, like
I mentioned prior, was to give the astronauts more
time to seek shelter but also this helps in the
operations planning, say you need to go outside your
habitat to do some maintenance or whatever, if you know that
that day is going to be a good day to go out and do an
EVA this is ideal for you. Operators on ground can plan
a mission for the astronauts. What you see on the
graphic on the right is an image of the Sun. We have numerous assets
circling the sun recording data, measuring activity and working
with our partners at NOAA we can identify the active regions and
then we take this data and run it through out analysis
codes and make these forecast predictions. An area of arrival times, we are
again working with NOAA in this area we are making use of
the terrestrial weather, what we currently do, everybody
here is familiar with the hurricane forecasting, we have
seen it all in the news and TV. We are following the same
type of logic in process. With modern computers you
can now do massive amounts of simulations in a short period
of time and you play with many variables and it will help you
idealize when that event will hit you and occur. And you can see in the graph
on the left there it is sort of like tracking the hurricane, as
the event gets closer to land our prediction capabilities are
better but as we extend further out our uncertainties grow, but
we are working to minimize that and I think you get the there,
I mean if we can increase that arrival time estimate that
gives that astronaut just more time to seek shelter. All right, in an area of
environmental monitoring we have got a quite a bit of work
going on there too now. What you see here is REM,
Radiation Environmental Monitor. This is actually flying on ISS. We have in a prior, I guess,
this too is new technology within the last few years,
we have been able to miniaturize it. Before it was
more breadbox size, mailbox, now we have been with
improvements in computer power been able to bring it
down to a thumb drive size. So what you see in graphics is
the thumb drive inserting into portable laptop and you see the
astronaut inside one of the US labs up in the ISS. This capability
as it progresses, we were forecasting, it will
have these embedded inside the structure of the habitat itself. So it will be
realtime monitoring. It is just another way to give
the astronaut an indication of what the exposure is he is
currently seeing and maybe some warnings, hey things
aren't going well, so you go seek shelter. In the area of particle
spectrometer it is another detector, we just recently, I
think you are probably aware we flew the Curiosity rover,
it is currently up on Mars. Well this piece of detective
equipment was embedded inside the rover. So this gives us realtime
estimates of what the radiation environment is on Mars. But also this provided us
data on transit to Mars, a flight, you are leaving earth,
taking the six to nine months it takes to get to Mars, this gave
us a good understanding of what we would see, how
many SPEs would occur, what your daily radiation
at GCR environment was. It is very low mass and
low power and it is doing a great job. We are still receiving data
daily on this that the modelers on earth can use to
help improve their models. Next, we are going to talk
about shielding materials. Use of passive shielding. Martha showed a few charts about
the different materials and which ones are better to use. So we are trying to take that
knowledge and integrate into our future habitats and how to
do a better job of providing shielding on the capsules. You can see here in this
graphic everything is in play. If we can do a better of
the shell structure material, instead of aluminum maybe some
composite would be structure, maybe the secondary structure
the same way and also the equipment that's
inside the habitat. Anything to give them more
hydrogen based shielding materials will improve the stay
of the astronauts and give them that much better protection. Another area that we are looking
at you know when we get to Mars maybe we can make use of the
regolith which is another fancy word for Mars dirt. Maybe we can make use of
the dirt that's there, the top soil and
take our habitat, you see on the right, we
encapsulate ourselves with, put large amount of this around
our habitat or seek a cave or a lava tube and embed your habitat
in there and just take use of the surface protection
that's available. Next, we talked about
the passive materials, now another area and that area
is configuration optimization. Maybe doing a better job of
laying out your equipment, your subsystems
around your habitat. This is an effort that has got
a lot of work that is done now, before--let me
back up here a bit, you can see on the
left the habitat focus, if we just let the designers
without radiation perspective design it you would envision
that they would put it ergonomically like you would
like to setup in your office or your home, but if you have an
eccentric radiation focus you are going to see like a little
in-comb fort like you would build in your parent's living
room when you were little. So there is this dynamic that
is always going on amongst the designers and the analyst folks. So, we have got a collaborative
effort going now in the agency to work together. So they bring in Martha into the
habitat design and try to see if we can do a better way
of placing what we have as we go up. Along those lines there is an
effort I oversee at Langley for designing protection systems
for SPEs and we call this Reconfigurable Logistics. When you are in transit to Mars
there is no phone home or supply ship coming right behind
you, so you have to make use of everything you have on
that capsule at that time, that includes your
water, your food, even your trash, I mean
everything is in play, everything has to have a
secondary purpose if you are going to make use of
the total mass to give you that protection. So you see over on your
left slide there just a typical cargo bag. So we worked with the people
down at Johnson in operations and said, hey how about if we
add a few zippers here and this unfolds and turns
into a drape a curtain, so we could mount this
on one of the racks, typical rack, and hang mass
structure on there to provide shielding for the astronauts. Just something simple, but
everything you got to think outside the box. So what you see on
your right here, in our labs we did a
bunch of humans in the loop, human factor type analysis. It does us no good to come up
with shielding ideas and the astronauts say this won't
work, this is not practical. We do a lot of humans, we bring
people in into lab there and we them a set of
instructions, we time them, we ask them about
the difficulty, we do a lot of, trying to
figure if it is practical to do. I was going to say,
I am still saying, this prior to me and
Martha starting the task, this is what we
used to look like. Much younger. Another area we are looking
at is making use of water. Water is a great shield. Hydrogen content is high so we
have a lot of contingency water on our missions. So the idea is here, maybe we
can take that water and if we can move it from point A over
to point B in a relative bit of time we can provide
that much extra protection to the astronauts. So, our team we looked at
maybe we could retrofit a crew quarters, the astronauts spend
a lot of time, you now they sleep in here, this
is where they go to interact with their family, so
like a little private space. So we looked at maybe
adding some water bladders, what would be entailed for
plumbing actuators and valves to move water over and to provide
that temporary shielding but the idea of this will be temporary,
it gives them the shielding until the event passes. The event can last maybe a day
to a day and half and then we will move that water back to
where it was originally supposed to be. On the area of personal
protection we really don't have a habitat concept in place yet. Everything is going that way
but we don't have a design yet. So we were looking at what
can we do in the meantime. So this is an area where we look
at maybe this can be portable and go to any habitat design you
come up with but also just be a personal wearable. So you could see over on the
left the astronaut candidates wearing this little vest. The idea here is you pack this
full of polyurethane or maybe water or you can insert food,
anything to give you that mass, to give you that
extra protection. Sorry, was there a question?
Yes sir? AUDIENCE: Well, there seems
there to be no protection for many important
things like the brain? DAVE: Yeah, well we, this
one is designed to protect the vital organs. MARTHA: You would probably
want a helmet to go with it in protection through the lenses,
but this covers where the bone marrow is most prevalent. DAVE: We have done some work in
that area of giving them a cover and all, and we have some
pictures in our labs and it is very popular on the tour,
everybody wants to get their picture made next
to this mannequin, but yeah, we have looked at that
and it is a difficult problem. Sleeping, the astronauts when
they sleep in space they are sleeping in what a
called a sleep restraint. It is actually mounted, Velcro
mounted to their sleep area just so they won't float
around while they are asleep. So, we looked at areas where we
could retrofit a sleeping bag contraption that would wrap
around them and entomb them the same logic as the
vest, pack it full of food, water, whatever to give
them that extra protection. All right, okay I got a movie
here that I am going to show you, this kind of bring
everything into perspective what in the prior slides I
was just showing you, but I think this will
help explain a lot better. It is a, I will
tell you a few things, I will highlight a few items. [Video Presentation] DAVE: Here is an
artist rendition of warning, you see
something occurs on Sun, it gives the
astronaut a realtime, got to go seek shelter, the
event is arriving and we are transitioning here, we
are looking at retrofitting crew quarters. This one is the
water wall design. It is as simple as
turning a valve. In our lab actually we have
like iPads and we do it all automated, we can move it,
through a suite of software we can move the water into an app. This is on lines of
reconfigurable logistics, moving mass stationed in a
different part of the capsule or your habit over into where
you need it to provide that temporary shelter. Here is kind of an idea what's
involved to do that because you wouldn't want this protection
mass just sitting around, you want it to be
portable and put away. Here is a visualization
of the bags, the zipper unfolding. What you see here in these white
tiles is an effort we have going on to repurpose the trash. Currently as you each away
through the mission you have all these byproducts, the trash, so
there was an effort at Johnson and Ames to compact the trash,
burn it and reprocess it and turn it into shielding tiles, so
if you get enough of these tiles you can get added protection,
so that's the idea, you know you consume it, you
reprocess it and turn it into shielding materials. We have the astronauts here,
you can see they are in close quarters, we try to double
bunk them because you have limited amount of mass, so you
try to get him as tight as you can so you can get as much
shielding between them and the exposure as possible. So they will sit in this tomb
here for a day and day and half, they can go out as they need
to, to check vital systems, but they will spend majority
of their bunkered-down in these little mini forts. Yeah, there is no gravity. People always ask about that,
do you want to be the one in the bottom or one on the top. Is that a cue for
me to speed up? Here is the drape idea, we take
out those folding bags that can move these drapes, mount
on to where they need to, to mount for structure
and shielding. Everything has a dual purpose,
that's the takeaway here. We try to get them to
do like 30 minutes, that's one of the
rules, 30 minutes. The question was how quick
can they build these shelters? And we target 30 minutes. AUDIENCE: What about croutons,
like when you go to the store and its in something protective
and then you eat it and then you put it back? DAVE: Well we take that--have
you all ever seen space food, how it is packaged? We take that
package, we burn it, compact it and turn it
into those protection tiles. So everything is reused. All right, the last item I am
going to hit on very briefly active shielding, the question
was raised by the audience. This work is in
its very infancy. There is a lot of bang for your
buck if we could perfect it, but there are lots of
engineering issues we have to overcome to make it work. Some of the items
are, the amount of, the size of the
magnet, what's required, the power, the structure,
how much they are, the mass, how do we mount
on to our capsule structure, there are a lot of engineering
issues they have to overcome but the idea is surround yourself
and create an artificial magnetic field like Earth has
and the idea is if the radiation comes in it is repulsed, but
there is still a lot of work that needs to be
done on this right now. This is more research realm. All right, I think
that is the... AUDIENCE: These
would be electro-magnets or
permanent magnets? DAVE: They would be permanent.
Are there any questions? Yes Sir... AUDIENCE: You discussed tiny
sized radiation particles. What about more
massive particles? DAVE: I will have to
turn that over to Martha. MARTHA: Micromedia
type protection, actual pieces of, that's
a whole different area. It is very important and there
is a lot of research that goes on especially at NASA Langley
about designing shields and spacing different materials so
that they slow down those types of projectiles, but
that's not our area, I guess. AUDIENCE: Does Mars have a
protective belt similar to our own here on Earth? I think there is
another belt also on Mars. DAVE: Does Mars have its own
protective belt like Earth, and the answer is no. Yes sir... AUDIENCE: This is sort
of a basic and I think it is a two part question; my experience
with the medical imaging community as in X-rays
and so on years ago, those badges, those... DAVE: The decimators? AUDIENCE: Yeah
decimators, its called radiants. That's changed now. Again, I don't know
what the terminology is... and then Dave, you
mentioned something else. You mentioned space. That's not analogous, you said
we had these energy ions which are different from
X-rays and gamma rays. What's the unit of measurement? I saw the scales there, what
is the unit of measurement? MARTHA: We still talk
about astronaut dose in terms of Sievert. Is that what you
mean by the unit? AUDIENCE: Yes, sievert.
Do you still use that? MARTHA: So, dose is measured
in gray which is just energy deposited per unit mass. However, there is another unit called dose equivalent
which is measured in Sievert which
actually has a quality factor folded into it that accounts for
the risk that these particles provide to humans. So, two different types of
particles can basically deposit the same dose but provide
very different risk to humans. So we use Sievert to be a
measure of how much risk the humans have. AUDIENCE: So even
though it's different, it's not analogous to the
gamma ray and the x-ray, it's still sievert, just a
different component in it? MARTHA: Sievert is how much
dose equivalent astronauts are getting from any
type of particle. So basically you have got x-rays
and gamma rays that you talk about here on earth, in
space we have charged protons, charged helium ions and
those which are primary concern. We measure astronaut risk
for many of them in terms of Sievert. Question? AUDIENCE: How ever do you
burn something in the capsule; talking about burning the trash? DAVE: Yes, that is one of the
issues that we are trying to overcome, the
byproducts, the gases, the out gassing, yes, we have
done this on Earth but it is like, before we could ever fly
this on a vehicle going to Mars we have to demo it in
like an ISS environment, there is no way that
they would let us do that. Yes Sir... AUDIENCE: Is there any problem
from this radiation over an extended period of time
degrading electronic equipment and stuff? DAVE: Yes, that's, I can
briefly talk about that. There is a big cost associated
of RAD hardening electronics and equipment and that would be all
considered in anything you fly that far away from earth
and for that amount of time. Yes ma'am... AUDIENCE: It
takes three years to get there? DAVE: No, ma'am, it takes six
to nine months to get there, but we just don't want to
go there and get there, we want to stay there. AUDIENCE: Three years?
DAVE: Yeah, three years, yeah. AUDIENCE: So, how long in
total; nine months to get there, nine months to get back? DAVE: And mainly a year on
the surface or around it. Yes... AUDIENCE: You talked in
terms of using water bladders and so on. And I guess I maybe
anticipate something; I don't, I think you talked
about the space vehicle itself. In some of the earlier
presentations there indicated there is water on Mars. Would there be any engineering
projections to extract some of that water? Use it in a bladder system?
That would be helpful. DAVE: The question was can we
make use of the water on the surface of Mars if there is
appreciable amount of it? And the answer is yes, we would
definitely want to use that. You saw this sketch
ahead with regolith, that could be some supplement,
you could use water plus that. AUDIENCE: I was wondering if
somebody was doing preliminary work on that now? MARTHA: Yeah, you also want
water for the astronauts for any number of reasons that don't
have to do with radiation. So there have been some
engineering efforts for how would you get that water. One thing is that
water is not everywhere, so you need to either plan your
mission to be where the water is or you can't rely on it. But there is work going on to
utilize the water on the surface of Mars. DAVE: Yes sir... AUDIENCE:
In the bladder system, in what way is that water
changed by the radiation? MARTHA: Almost not at all. So you asked about damage
to materials from radiation, that is a very slow process. The reason humans have so much
more of a risk is because if the particle comes in and damages
the DNA and then you get a mutated cell and that
mutated cell propagates you can have cancer. If a particle comes through and
damages one hydrogen atom within the water you have a
damaged hydrogen atom, but it doesn't have a way
to propagate that damage through it. So you would need way
more radiation than we are seeing in space. DAVE: And I will answer the
next question before it comes. The same answer for food.
I get asked that a lot. Yes ma'am... AUDIENCE:
Three years is a long time. What provisions are you
making in case of a failure during that time? DAVE: That's not an option.
Failure is not an option. I don't know the
answer to that one. AUDIENCE: You just burn it? DAVE: Yeah, yeah,
reuse them as shielding. You get the point. Yes Sir, in the back...
AUDIENCE: Two part question. One, are there any unusual
radiation events that you have detected from the
sensors that are on Mars now? They repeat that
information back to Earth. And the second question; what
about this medical attention I am seeing on this chart? What type of attention
are we talking about? DAVE: I can answer the first
question and I will turn the second one over. The first question was when we
flew the mission to Mars with the rover what did we see? I think we saw either
three or four SPEs, the events that we can
design and shield against. So that was great knowledge. I mean we did not, that was the
best we have had to date what an actual transit to
Mars would look like. So that was great knowledge
and about the medical question, MARTHA: I don't really
have an answer either. So the question was what can we
do in terms of providing medical attention to help astronauts who
have been exposed to radiation, and we have an ongoing research
project looking at those. Again, you are sort of
bordering on can we cure cancer, if we figure this out we will
have solved lots of problems, they are researching
antioxidants which you probably have read in any
number of magazines, might improve your risk of
getting cancer on Earth. But they are also looking at
ways to basically tell the cell it is being damaged. So basically tell the cell
to go ahead and kill itself, rather than propagating. But all of that
really is at its infancy. We are working it, but right
now we don't have good counter measures for space radiation. DAVE: Yes ma'am... AUDIENCE: To go back to
your question about dying in space, I yesterday
morning discovered a YouTube channel called Ask A Mortician,
and that was the first question that was asked on
Ask A Mortician. DAVE: Can I give
you the microphone! MARTHA: Okay,
regarding dying in space, yesterday morning I went online
and logged into a website on YouTube called Ask A Mortician. It is real, it is conducted
by licensed morticians. And that was the first question
that I encountered on there. And in essence the body could be
ejected into space and would be frozen and there is a whole
explanation as to orbiting and entering different
gravitational fields, but should you come
back to the planet Earth, the mortician said the
body will enter at 17,000 plus miles per hour and
because it doesn't have a heat shield will be super-cremated
when it hits our atmosphere. But I would advice
you to check into that, Ask A Mortician. DAVE: Thank you. AUDIENCE: I'm sorry. DAVE: Yes, next NASA employee. Yes Sir... AUDIENCE: Is there
enough known about the water on Mars to know what the
isotonic composition is? DAVE: I don't think
that we know that yet. That question was do we
know the composition of the water on Mars. MARTHA: I don't think we
know the answer to that. I think we believe that it
is similar to here on Earth. They actually have two
kinds of ice on Mars, they have CO2 ice
and they have water, H2O ice, and the H2O ice
should be similar to what we have here we think. AUDIENCE: Seems like we
could check the compound counts. MARTHA: Yeah, I don't know. AUDIENCE: I believe one of the
other presenters said the Mars water, not the CO2, was
similar to Earth water. MARTHA: I think that's
what last week's presenter said, but yeah. DAVE: Any other? Yes ma'am... AUDIENCE: Um,
one I had heard that another space craft,
Nathan, is... DAVE: MAVEN? AUDIENCE: Yes, it had
recently reached Mars? Sounded like it
was working on Mars. Um, I assume that was being
helpful for you as far as how the atmosphere? DAVE: Help me out Steve, you
know what's on MAVEN? STEVE: MAVEN is designed
to help us understand why Mars
lost its atmosphere. So it is going to study the
composition of the atmosphere that is being torn away from
Mars all the time at this point. AUDIENCE: We're all exhausted! DAVE: Is that it? Those were some
very good questions. Thank you all very much. [Applause] STEVE: Yeah, those were
great questions. I am thinking about how to get
your guys on our design team so that we can, I know a lot of
you actually worked at NASA, so of course we
want you guys back. I hope that the last five weeks
have given you a sense of the excitement of the space program
that we could have and given you sort of brought you up
to data in where we are. I also hope that it gave you a
good sense of how hard it is to do what we are trying to do. I think that, I just want
to reiterate the importance of that fact. Kennedy actually said this
when he kicked off the Apollo program, he said, "We do this
because it is hard." And it kind of sounds like a
simple statement, but because of the difficulty of
what we are trying to do we are going to reap tremendous
benefits across many different aspects of the society
from geopolitical, to economic, to social benefits
and that's the payoff of what we do in the space program. And as we talked about last
Spring that payoff is well over 100% and very low risk. We know from history that we get
that payoff when we invest in the space program. I hope that you have enjoyed it
and we really appreciated your interest and the questions and
interacting with you over the past five weeks.
Thank you. [Applause] macaroni
