Документ взят из кэша поисковой машины. Адрес оригинального документа : http://nuclphys.sinp.msu.ru/conf/lpp14/Round%20Table%20Discussion/Spillantini.pdf Дата изменения: Wed Sep 16 16:55:25 2009 Дата индексирования: Tue Oct 2 00:47:13 2012 Кодировка: Поисковые слова: aurora

Radiation exposure and mission strategies for interplanetary manned missions and interplanetary habitats
Piero Spillantini Univ. and INFN, Firenze, Italy

Fourteenth Lomonosov Conference on Elementary Particle Physics, Moscow, August 19-25, 2009


Spectra of energetic c.rays (indicative)
15 12 9 6 3 0 -3 -6 10-4 10-3 10-2 10-1 1 101 10 Kinetic Energy (MeV)
2

Mainly protons Solar Wind (flux=1016fluxGCR)

Log intensity (p/ cm2 sr s MeV)

Dangerous

Comparison purpose Sporadic, unpredictable

SCR (fluxmax=106fluxGCR ) GCR
(ACR)

Penetrating SS from outside constant flux
10
3

104


We are protected from GCR by:

At 1 AU (Earth orbit) by solar magnetic field (solar wind)

-1 10 @ 1GeV 10-2 @ 500 MeV

Near the Earth (about 10 R

Earth

) by terrestrial magnetic field

10-1 @ 1GeV At 45є latitude

On the Earth surface by the Earth atmosphere

a further 10-2 @ all latitudes


x 10

-1

Energy (Gev/nucleon)


Showers of CR in the atmosphere 1 GeV (bulk) 1 TeV 1 PeV 1 EeV 1 ZeV
Energy of the primary CR (90% p, 9% Nuclei, <1% e,)

Outside of the atmosphere

Top of the atmosphere (ballooning 40 km) (ballooning 25 km)

bulk

(x10 of bulk)

-6

10 km on the sea level

4 km on the sea level


103 primary (p) particles/(m2 s sr) x 10 10
2 -2

20 27 10 15 Km above the sea level

4

n soft n 10
1

hard () soft (e)



soft p

1

200

400

600

800

1000

depth through atmosphere gr/cm2


Shielding in space is problematic: Passive shielding (absorbers) enough for SCR (but huge masses needed) GCR very penetrating absorbers inefficient (secondary production) Active systems are necessary for long duration manned missions


Active protection from CR: historical introduction

60s

90s

several ideas were considered, no technical projects (mainly in USA) (URSS: some work on superconductivity in space). two feasibility study of the ASTROMAG facility for CR on board of the Freedom SS.)

(1985-90


2000

review of available techniques and optimization of the working point for superconducting magnets for space applications
(INFN-Milan (L.Rossi and L.Imbasciati))

2002-2004 ESA international Topical Team on "Shielding from the cosmic radiation for interplanetary missions: active and passive methods" 2003-2004 WP "Review and development of active shielding concepts" of the contract REMSIM (Radiation Exposure and Mission Strategies for Interpl. Manned Missions) ESA-Alenia (+EADS Astrium, REM, RxTec, INFN).


electric current

Continuous cilindrical conductor Lumped conductors
B=0 outside B=0 inside B=0 outside

B 1/R
B

R1

R2

R

R

1

R

2


'She lt e r ' ( =2m , le ngth 3m ): shie ld m asses f or H20 & Tor oid H2O Tor oid R2=3m c old mas s Tor oid R2=3m env is aged total mas s Tor oid R2=3m max imum total mas s 100 mass [t]
shelter

2m 6m

10

1 0 100 200 300 400 500 600 700 800 K.E. cut [M e V ]

Hp: NbSn sc cable Al sabilized sc cable current 500 A/mm2 CFSM (cryocoolers)


Fig.6.14 - Toroidal shelter ( 2m, length 3m) integrated in the habitat scheme of the AURORA CDF concept. At the outer diameter the electric current can be supposed to be returned by a few conductors.


'Habitat' ( =4m , le ngt h 5m ): H2O & Tor oid shie ld m asses H2O s hield Tor oid R2=4m c old mas s Tor oid R2=4m env is aged total mas s 100 mass [t]
habitat

4m

8m

10

1 0 200 400 600 800 1000 K.E. cut [M e V ]

Hp: NbSn sc cable Al sabilized sc cable current 500 A/mm2 CFSM (cryocoolers)


The studies of the past must be updated for several reasons:

Realization and operation of huge volume and stored energy superconducting magnets for elementary particle physics experiments Remarkable technical developments of high temperature superconductors (in particular MgB2 material) and of the cooling technique (cryocoolers for the N2 shielding of AMS-2)

Future missions will be more and more addressed to the use of space as a `forth dimension', such as a collective property for implementing services of economical and social benefit involving more and more private investments, with the Space agencies supplying the needed technical competences, quaranties and controls in conformity with the political indications of the respective governments


Signals in this direction: First instances of space tourism Successes of the SpaceShipTwo private spacecraft

Sudies for the use of Moon for extraction of useful materials (e.g.He3) Studies for the `production' of large quantity of water on the Moon `MoonBase' initiative activities Awareness of the importance of using the Lagrange points for achieving scientific results and for supporting commercial activities (e.g L1 for Moon, and Space Highways for transfer of materials)


Expected evolution of human presence in space:

Space Stations

astronauts

Space bases

astronauts and specialized personnel

Space `complexes'

astronauts, specialized personnel and common citizens


further step in GCR protection: Long permanence in `deep' space not only for a relatively small number of astronauts but also for citizens conducting `normal' activities

Minimum basic assumptions for the `habitat': Volume to be protected: 6m, L=10m Shroud of the transportation system: 10m, L>16m


B(R) =

B(R1)R1 R

L16В20m R2=5m R1=3m

B
Shielded volume

i

i

Shielded volume

B
Transverse section

i

i

longitudinal section


p flux w ith H2O and toroidal cuts
2,5 2 1,5 no c ut cut 90 MeV tor oid 'Ec ut=90 MeV '

flux [p/(m2srsMeV)]

1 0,5 0 10 100 KE cut [MeV] 1000 10000

GCR: dose reduction between absorber cut and toroid cut 28%


habitat

6m

10m

galactic proton flux in the 'habitat' (R1=3m, R2=5m)
2,5 2 1,5 1 0,5 0 10 R1=3m R1=3m R1=3m R1=3m
15%

f l u x [ p / ( cm 2srsM eV ) ]

100 R2=5m R2=5m R2=5m R2=5m B1=0T B1=2T B1=6T B1=10T
34% 59%

1000

KE [M e V ]

10000

R1=3m R2=5m B1=1T R1=3m R2=5m B1=4T R1=3m R2=5m B1=8T

75% 85% 80%

GCR dose (Gy) reduction


Technological criteria
- Cryogen Free Superconducting Magnet cryocoolers

-`ideal cable' for space applications (Turin university + Alenia) thin MgB2 cable produced by the in-situ method in a titanium sheath stabilized outside in aluminum:
Characteristic Value

- Medium operating temperature (20k) - Low density (3 g/cm3) - Small section: cables less suffering current and temperature instability, and distributing current in the surrounding cables in case of bad functioning.

Averaged density Diameter of the cable Section of MgB2 Operation temperature Critical current at 2 T

2,96 g/cm3 200 m 6,28·10-3 mm2 20 K 1,3·103 A/mm2

Ideal cable
MgB2 20 %

Ti 25 %

Al 55 %


mas s f or R1=3m 100

10 *L=6,1 T m do se r ed 0.59 * L=12.5 T m do se red 0.82 * L=20,3 T m do se red 0.87 1 0 2 4 6 8 10

Cold R2= Mass= 62 t 5m 35 t 6m 24 t 7m 19 t 8m 10m 14 t

mass (t)

B(R1) (T)

12

Cold mass for current density in sc cable 1kA/mm2 @ 2T


Minimum basic assumptions for the `habitat':

Volume to be protected: 6m, L=10m Shroud of the transportation system: 10m, L>16m However: deployment of return current circuit must be considered from the very beginning


10m 6m

>>10m 6m

L=10m

habitat

L=10m

habitat

closed configuration habitat habitat Inner conductor outer conductor shroud Inner conductor

deployed configuration

habitat

outer conductors


electric current

B=0 inside B 1/R

return of the electric current

B=0 inside B 1/R

- in a toroidal configuration the field diminishes at the increasing of the a) b) radius, making easier to support the ponderomotive forces. - the outer part of the system must be deployed or assembled in space.

return of the electric current


Basic philosophy for the `Space Complex':

All the modules linked to the protected `habitat' Protected `habitat' can be reached in a few minutes from any point of the Space Complex `Habitat' fully protected from SCR's. `Habitat' guaranties a factor 5 reduction of GCR dose @ solar minimum

Furthermore: Journeys during periods of maximum solar activity Long permanences (>1 year) during periods of maximum solar activity


Communication tunnels

Units protected only against SCR events

Cross section of the habitat protected against SCR and GCR


Shelters against SCR events


Conclusions
An adequate protection from GCR to a large human community in space is a complex problem, which can be solved in an adequate time provided that a long program of study and R&D will be set up in due time and with the due resources. It is therefore urgent a professional approach toward the study, project, realization and test of materials, mechanisms, systems, and finally `space demonstrators', and their integration in manned exploration programs. Furthermore protection from CR is - a `niche' where physicists can contribute - an occasion of collaboration between labs and space agencies - new technologies to be developped for space propulsion (magnetic lenses to control divergence and density of charged material for real-time control of thrust and direction, to concentrate it in small volume for further acceleration, magnetic bottle for suitable reactions, etc..)