Spaceflight Vol 46 October 2004, 406
Cardiovascular complications for long space missions
Sir, I have emphasized in several publications, the cardiovascular complications of microgravity, for long missions such as interplanetary travel [1 -3]. A mission to Mars may last over two years. But even missions of 12 days, such as Apollo 15, precipitated cardiovascular complications . The complications resulted primarily from atrophy of skeletal muscle and bone with in turn, partial loss of the reservoir for two vital antioxidants –water and magnesium . Experimental animals show atrophy of heart muscle after space flights of just 18 days  and in humans, significant atrophy of skeletal muscles in only five days .
Since our genes developed at 1 G, we can't equate the environmental hazards of exploration on Earth, with those hazards stemming from exploration beyond Earth; we can equate only the required courage and ingenuity, driven by necessity. Until the protection of genetic engineering is developed, countless decades from now, it seems to me that our only alternative is to simulate 1 G during our explorations requiring several assumptions.
A sufficiently long tether (radius),
attached to a centrifuge, would be required to duplicate 1 G, and with the
angular velocity set at a comfortable level for the crew throughout the
entire mission to the planet and back. Furthermore, the size and weight of
the centrifuge would have to meet reasonable fuel and cost restrictions.
But how can the crew explore Mars and at the same time meet our requirement of 1 G, instead of that of Mars at 0.39 G? A second centrifuge would have to be delivered to the designated landing spot prior to the crew's arrival. It is conceivable that this centrifuge could be attached to a stable platform and used as a rover, propelling for example two astronauts, long distances, circumventing obstacles in transit. Surface and rock samples could be obtained from sites inaccessible to robots, with the crew leaving the centrifuge as expeditiously as possible. Prior to leaving or upon returning to the centrifuge, gradual reduction or acceleration of the angular velocity will be required, to avoid vertigo. Existence at the landing site would be entirely on a centrifuge.
After four decades of research, all the various countermeasures to prevent space-related atrophy of
the skeletal muscle and bone reservoirs have failed .The
approach I have postulated, which would avoid unremitting exercise, with its
inherent complications  may seem bizarre to some, but so did many innovations
in the medical field, which so often came to fruition.
William J. Rowe M.D.
Former Assist. Clinical Prof. of Medicine,
Med. Coll. of
Robert J. Ribando
Assoc Prof. of Mechanical
and Aerospace Engineering,
1. W.J. Rowe, Interplanetary travel and permanent injury to normal heart, Acta Astronaut, 40,1997, pp.719-722.
2. W.J. Rowe, Potential myocardial injuries to normal heart with prolonged space missions-The hypothetical key role of magnesium, Mag Bull 22, 2000, pp. 15-19.
3. W.J.Rowe, Space flight-related endothelial dysfunction with potential congestive heart failure, (abstract) Journ of heart failure, 7, 2002, p. 13.
4. W.J. Rowe, The Apollo 15 space syndrome, Circulation 97, 1998, pp. 119-120.
5. W.J.Rowe. The Reservoir, Spaceflight, 45, 2003, p.88.
6. W. Baranska, P. Skopinski and A. Kaplanski, Morphometrical evaluation of myocardium from rats flown on biosatellite Cosmos-1887, Mater Med Pol, 22, 1990, pp.255-257.
7. F.W. Booth, D.S. Criswell, Molecular events underlying skeletal muscle atrophy and the development of effective countermeasures, Int J SportsMed,18Suppl4, 1997, pp.3265-269.
8. W.J. Rowe, Extraordinary unremitting endurance exercise and permanent injury to normal heart, Lancet, 340, 1992, pp.712-714.